'Red' - '89 RC, 6BT/518 - (...at home in Virginia...)

[jungle]

Sam,
This 6BT has the stock injectors right & did you crank up the VE before? Hows the power feel with it in Red? I can't wait till spring to get going on mine.
Jim

[Mad Max]

affirm - the engine is basically stock.  The only mods are the 366 rpm spring and a bit of timing.  Stock sticks and (currently) turbo/collar.  However, very soon (maybe this weekend) I'll be adding on the '99 12cm collar/HX-35 combo that Nacho was running, and that should glean a bit more airflow down low where the engine is always running.
The DTT converter is borderline on stall speed - it does its job in fine fashion and stalls out low, almost too low, but after the new rubber goes on today that should be a non-issue.
- M2

[Mad Max]

cool - got the ATZ's on, and the smaller size made just the right difference.  It feels real good off the line and still has all the top end I'll ever need, tho there is some driveline vibration under it coming from somewhere...could still be a tranny issue.  This 518 is the one from nacho and it never really was 100% 'right'.  I may have to find another core and get it rebuilt later on.  But for now, drive on.



Fuel mileage is down from before, which is unexpected, but then again I haven't been into this pump to see what's been done, and the tire size change may make it better too.  The DTT converter definitely does its job - jury is still out on wether or not I'll swap it out for one that stalls a bit higher.  Red don't need much converter just to push itself along, and a bit higher stall would help it off the line, but again with the smaller tires it definitely feels better. 

The 727 converter that was under Red felt actually pretty dern'd good - I'd compare it to a TCI unit - and maybe I'll swap it in one of these days just to see how much difference it makes...when I have 5 hours to burn up one snowy day later this winter/spring.  I'm just about a pro at converter swaps now...

[Mad Max]

well...I'm still having tranny issues.  The overdrive , no matter how many times it gets rebuilt, can't lose this 'whine' coming from it, and at high speed some sort of vibration.  Sounds like a bearing whining, and even though it's been apart several times now it seems like it may just be a bad unit.  The tranny came from a crashed donor truck and who knows what life the tranny lead up until I got it.  I have the other 518 core and I think I'm going to scope the od unit on it and swap them out.

Soon as the od engages an immediate 'whine' comes from the unit...from somewhere.  My other truck with a 2wd 518 makes absolutely no noise at all and has brite pink fluid, wheras this one...well doesn't.

Another thing is, when I was installing it over Christmas I happened to be looking at the output shaft and cleaning the back area out, and as I was wiping out the back side of the rear bearing I noticed the outer race...moved.  I checked it again and sure enough the outer race can in fact rotate around inside the case housing.  My tranny guy said 'it is supposed to do that', but I'd like to offer it up to y'all for a second opinion.  Thoughts?

I want to scope the od myself and swap them myself, both of which I've never done, but I can read.  Meanwhile, the fuel mileage comparo continues as does the pump tuning etc for max fuel mileage.  My goal is 25 mpg, and I think I can get there with this RC.

I think this RC is earning a new name - the 'Mule' - as in a factory test/demo vehicle.  I'm trying a lot of practical stuff with this rig in an attempt to both learn and apply some theory to the road.

So long as it gets me to work it's all good

- Sam

[blueduster]

hey sam, does your manual talk about opening up the oiling holes in the overdrive? a book i read about 5-6 years ago talked about it, saying the factory specs were flawed. also mentioned that some rebuilt units may have already had it fixed. i tried to find it on the web before posting this but i can't remember the name to save my life. anyway, that is something you might ask around about if you hadn't heard that before. the money and time needed to sort out those 46/47/48 trannies are a big reason i went to the NV4500. that and the 5.61 first gear.  

well...I'm still having tranny issues.  The overdrive , no matter how many times it gets rebuilt, can't lose this 'whine' coming from it, and at high speed some sort of vibration.  Sounds like a bearing whining, and even though it's been apart several times now it seems like it may just be a bad unit.  The tranny came from a crashed donor truck and who knows what life the tranny lead up until I got it.  I have the other 518 core and I think I'm going to scope the od unit on it and swap them out.

Soon as the od engages an immediate 'whine' comes from the unit...from somewhere.  My other truck with a 2wd 518 makes absolutely no noise at all and has brite pink fluid, wheras this one...well doesn't.

Another thing is, when I was installing it over Christmas I happened to be looking at the output shaft and cleaning the back area out, and as I was wiping out the back side of the rear bearing I noticed the outer race...moved.  I checked it again and sure enough the outer race can in fact rotate around inside the case housing.  My tranny guy said 'it is supposed to do that', but I'd like to offer it up to y'all for a second opinion.  Thoughts?

I want to scope the od myself and swap them myself, both of which I've never done, but I can read.  Meanwhile, the fuel mileage comparo continues as does the pump tuning etc for max fuel mileage.  My goal is 25 mpg, and I think I can get there with this RC.

I think this RC is earning a new name - the 'Mule' - as in a factory test/demo vehicle.  I'm trying a lot of practical stuff with this rig in an attempt to both learn and apply some theory to the road.

So long as it gets me to work it's all good

- Sam

[Mad Max]

not sure Dave, I haven't really looked in any books yet - just haven't got 'there'.

Well crap - after the second fill up...my fuel mileage is down between 2-3 mpg .  Weird - add an overdrive, decrease mileage.   Hmmph....gotta be something goin' on here.....

So there's a couple factors to consider.  First, there's also a whole different, though near identical, engine in there...and with that an entirely 'new' injection pump.  And while the IP is 'the same' as the one on the other engine i don't really have any idea what kind of 'tune' it has.  It doesn't pump hardly any smoke out the pipe so I think the fuel tune is pretty standard.

My thoughts are two-fold.  First, the tranny does need some work - it's making noises that it shouldn't, so another rebuild from another shop is upcomming.  Second, with the deeeep airplane gears under there the converter pulls the engine down pretty hard, and I'm pretty certain I'll not re-use the DTT unit in this truck - I'll reinstall the one that was behind the 727.  It has a bit higher stall speed and I think that'll actually help the truck out a bunch around town.

Plus, I've been in 4wd a lot lately, and it's been really cold, both of which of course don't do fuel mileage any favors.

So, the plan is to get the tranny rebuilt, install a bit higher stall converter, and maybe bump the timing a bit.  I just can't think of any reason why this overdrive combo should get worse mileage than the non-od setup.

Anyone have any ideas?  I'd appreciate any feedback

[blueduster]

is the 727 t/c a lock up unit?

not sure Dave, I haven't really looked in any books yet - just haven't got 'there'.

Well crap - after the second fill up...my fuel mileage is down between 2-3 mpg .  Weird - add an overdrive, decrease mileage.   Hmmph....gotta be something goin' on here.....

So there's a couple factors to consider.  First, there's also a whole different, though near identical, engine in there...and with that an entirely 'new' injection pump.  And while the IP is 'the same' as the one on the other engine i don't really have any idea what kind of 'tune' it has.  It doesn't pump hardly any smoke out the pipe so I think the fuel tune is pretty standard.

My thoughts are two-fold.  First, the tranny does need some work - it's making noises that it shouldn't, so another rebuild from another shop is upcomming.  Second, with the deeeep airplane gears under there the converter pulls the engine down pretty hard, and I'm pretty certain I'll not re-use the DTT unit in this truck - I'll reinstall the one that was behind the 727.  It has a bit higher stall speed and I think that'll actually help the truck out a bunch around town.

Plus, I've been in 4wd a lot lately, and it's been really cold, both of which of course don't do fuel mileage any favors.

So, the plan is to get the tranny rebuilt, install a bit higher stall converter, and maybe bump the timing a bit.  I just can't think of any reason why this overdrive combo should get worse mileage than the non-od setup.

Anyone have any ideas?  I'd appreciate any feedback

[Mad Max]

no the 727 is a '91 unit and the 518 is a '93 unit, both non-lockup, both use the same converter.

One other piece of the puzzle is I am going about 10 mph faster than before, on the highway at least.  Maybe I'll try to do the same speed as I was doing before and get some numbers that way - might be a good baseline.

[Killerbee]

Similar to an engine's HP and Torque curve having peaks, the efficiency curve does too.  Throw in boost, and it's quite a bit more complicated...  So you might have it too low RPM to get good efficiency.  THe peak efficiency curve is usually close to the peak torque curve.

Mroe boost might help   It'd increase the fuel combustion's power output.  How much boost do you have when cruzing?

Ben

[Mad Max]

don't know - no gauges before or after the swap.  I know, bad Sambo.  But the turbo and collar are stock for a '91 non-IC rig, which will be upgraded to the '99 IC combo I had on Nacho one of these days.  The biggest major difference is the converter and the overdrive.  I'm going to play with the turbo/collar combo and the timing. 
The 93 engine has smaller injectors than the 91 engine does, and with the DTT converter the thing is pretty lethargic down low and has a bit of a hard time revving up - which makes sense because that's what this converter is supposed to do - pull hard on the engine.  But it may be too low considering the airplane gearing this thing has now.  So swapping converters will likely happen when I have the tranny re-ovehauled, and that means I'll likely have a DTT converter for sale.  Bud won't need it for similar reasons as the Mule, but Big Mack can't live without it's converter (an identical DTT unit) because it's a serious tug boat...and I'll be selling that whole 518 with the converter when that dude get's the 6-speed.  The gears are always a'turnin'!

[blueduster]

must be a diesel thing, the no lock up i mean. or maybe they just hadn't started it yet. my 95 1500 was a lock up version. the A-999(904 w/lock up conv) started in the late 80's in the M cars so i assumed the trucks were then too. that's what i get i guess. i don't need to finish that saying...

no the 727 is a '91 unit and the 518 is a '93 unit, both non-lockup, both use the same converter.

One other piece of the puzzle is I am going about 10 mph faster than before, on the highway at least.  Maybe I'll try to do the same speed as I was doing before and get some numbers that way - might be a good baseline.

[Mad Max]

must be a diesel thing, the no lock up i mean -

It was only for a very short timeframe.  The '1st gen' Dodge Cummins rigs are the 89-93 trucks, and from 89-91 the trucks had the non-intercooled engine and the standard 727 3-speed auto.  The 91-93 trucks had the intercooled engine and the 518 (46RH) overdrive auto.  Neither of those era diesel auto's had a lock-up converter, not until the '2nd gen' body came out in 94 - those autos were called the 618 (47RH) auto, and those had factory lock-up.  The gasser trucks, however, did have the lockup converters.  Why the diesel's didn't is anybody's guess, but mine is because the converter technology wasn't up to snuff yet to handle the Cummins torque.

What us 1st genners have been dealing with is a high HP Cummins without a lock-up converter.  The converter is the achieles heel for the whole truck, and the aftermarket units (DTT, Suncoast, Goerands, TCI) make very good units, and depending on the engine's power level the stall speeds will vary a bit, but for certain the stall speed is much lower than the stock clams.  

For my issues with the Mule, I have been talking wtih several of my diesel brothers and I've decided that when the tranny gets rebuilt I will not be re-using the DTT clam and I will be reinstalling the one that was in front of the 727 that Andy put in.  That 727 converter has a bit higher stall speed than the DTT unit, and I need a bit more stall speed for the around-town driving that I do a lot of.  Once up to highway speeds this truck won't need much 'converter' to maintain speed - it's getting up top speed and getting going off the line that the engine is wanting for a bit more rpm.  
Funny too, because I'm always preaching about how important the converter is for a truck to pull the weight and keep the tranny from getting too hot, and that is 100% true for a tug boat like Big Mack, but what I’ve discovered is with a truck with this much gearing (the 3.07 “airplane” gears), the big dawg clams stall too much for a ‘city’ daily-driver truck like this.

My next thought was…well can I use the DTT clam in Bud?  And I’ve decided that I won’t – I’ll get a TCI clam for Bud for the same reason as the Mule.  Bud is going to be a slow crawler, and I’m going to want a bit more stall speed for that kind of crawling as I do for driving the Mule around town.

With the 3.07 gears, 30” tire, and overdrive, the Mule cruises 75 mph @ 1800 rpm.  Just right.
Bud, with its 4.56’s, a 36” tire, and overdrive, it’ll cruise 65 mph @ 1900 rpm.  When I go up to 38’s, it’ll cruise 65 mph @ 1800 rpm.  Again, just right.  And 65 mph will be plenty for Bud.  And if I ever get a wild hair to go to 44’s , well then it’d do 75 mph @ 1800 rpm, but I’m doubting I’ll go there.
So, since I’m having the tranny rebuilt very soon, I’ll go ahead and post up that my DTT converter is for sale.  It’s an $800+ unit new, and I’d sell it for $500 plus shipping.  If’n anyone’s interested lemme know.

I’ll get the Mule dialed in, and I’ll hit my magical 20-25 mpg fuel mileage.  I just gotta work the chassis, and I’m working on some weight-savings things too.  Since I know I’m going to have this truck for a long time I’m using it as a test bed for efficiency ideas, just like the factory did with it’s fiurst line vehicles, hence the new nickname, the ‘Mule’  .

- M2

[DevilzTower]

MM - thinking about the converter ... yes it's wound a little tighter than the stock 727 ... but it should also have a higher overall efficiency than the stock 727 unit ... from what I know ... the 727s are good at making lots of heat, not a lot transmitting power.

Changing the turbo collar from the "lagmaster," is what I believe that housing is on these trucks - 21cm, to the '99 12cm unit (I think it's 12 or 14?) should let you put a little more fuel to her down low and spool up the turbo significantly faster, throw in a little more timing and be right where you need to be mpg-wise.

I understand the logic however, the transmission already has to come out so why not swap the TC ... just food for thought.

Efficiency: I also have been thinking about some projects to increase efficiency on these old dogs ... I'm sure you'll actually get to it before I ever could (can't even get my truck together much less do improvements, so I'll throw it out there. 

1.  Louver unit that works on a thermal switch to block off and open up the grille opening - when closed, completely blocks off airflow to the radiator - great for cold mornings - when open, opens airflow to the rad allowing full cooling.  The mechanism could look something similar to window blinds - sort of like that.

This would allow you to reduce the overall aerodynamic impact ...

[jungle]

Sam,
Was the DTT converter for the 518 or 727 or are they the same?
Thanks, Jim

[Mad Max]

That's some cool thoughts DT - I'll have to think about that'n  .  And yeah I agree that the turbo swap will indeed 'wake up' the engine, and I'll likely get that done before pulling the tranny so that'll be a good comparo.

On the converter, I agree with you that the efficiency will help the heat issue, and if it were a bigger heavier rig then I'd definitely keep the DTT unit.  But since this is just the RC by iteslf, and since the previous clam felt really good in the 727, it should feel the same in the 518.  I doubt the DTT clam will 'sell' before I get some miles on the rebuilt tranny gig, so I guess I could toss it back in...but I doubt it.

Jim, yup the DTT clam is the same for the diesel 727 and 518 - both non-lockup.  Whyyyy??   ya wanna trade for some of yer hardware???

[jungle]

I will be needing a good converter for the gold RC. How much HP/Torque is that one good for?
Jim

[Mad Max]

how much 'ya got?    The DTT unit is, IMO, the best 1st gen clam on the market.  I routinely crank over 300 hp and 600 tq through the DTT clam in Mack (306/630 to the tires on a dyno up at 6800 ft) - no problem, and never any heat issues.  I've never seen Mack's tranny go over 235*, and that has only ever been towing Nacho back from Moab coming back up the east side of the Rockies - steeeep.  Of course Mack has the factory aux bed cooler and a deep pan, etc, to handle the big numbers, but that tranny is good to go.  This DTT clam from Nacho is the same unit.  Nacho's tranny had a gauge on it and it never got any hotter than the engine (the heat exchanger was installed), including crawling over Moab with no airflow.  
Actually, now that I think about it, I don't know of a stronger or better 1st gen conveter on the market, however the folks that have the Suncoast and Goerands 1st gen clams have all reported the same results.

I'll drop you a line if you want - PM me a good day number for you

[jungle]

Sam,
I'm thinking at least 350 on the hp but hopefully more . I'll send you a PM with my phone # & date. Are you around this weekend?
Jim

[Mad Max]

yup yer definitely going to want something thick and meaty in there.  Yah this weekend's good - I'll holler at ya  
Cool - thanks Jim

[RVA RC]

Hey man, what calculator do you use to figure your rpm at certain speeds? I've seen a few online, but none that I've liked too much.

[RVA RC]

Is it the one I found on this website right after I asked the question?

[Mad Max]

not sure - the one I use is a mega sweet excel spreadsheet I've used for years.  I honestly don't know how to upload a non-photo to a website.  Anyone??  I can e-mail the thing, but not sure how to upload it.  It's bitchin tho - is has several Mopar transmissions available and just about every gear/tire combo you can think of, and thus far it has been 100% accurate compared to the real world.

[Mad Max]

kewl - I just e-mailed my GSC to Joe S, he's gonna try to git it up on the calculator thread.  stand-by

[DevilzTower]

I'll keep a look out for that calculator spreadsheet, I've had one for the last few years and it's loaded with with all modern dodge transmissions - read 89 - present.  It didn't have the G360 in it, but I fixed that 

[jungle]

Sam,
PM sent.
Jim

[jungle]

Sam,
I just wanted to say it was great talking to you today & looking forward to doing some business together in the future.
Thanks, Jim

[Mad Max]

Likewise Jim.  When we get all of our respective 'stuff' lined up and rolling we'll definitely have to work a joint wheelin' meet-n-greet gig somewhere mid-US and put away a few cold ones afterwards.
Talk later,
- Sam

[KansasCrewCab76]

Likewise Jim.  When we get all of our respective 'stuff' lined up and rolling we'll definitely have to work a joint wheelin' meet-n-greet gig somewhere mid-US and put away a few cold ones afterwards.
Talk later,
- Sam

Ya know....RamJam is going to be Mid-US this year......(hint hint)

[jungle]

Sam that sounds like a good plan!! I don't think this summer is going to be OK because we are trying to get a BIG addition going for the house. But with that said I DO want to do a road trip & meet some of the guys. Moab is one of my most favorite places to get back to & with a 6BT under the hood the cost of the trip would be cut in 1/2!!!!
Jim

[Mad Max]

Ya know....RamJam is going to be Mid-US this year......(hint hint)

Sam that sounds like a good plan!! I don't think this summer is going to be OK because we are trying to get a BIG addition going for the house. But with that said I DO want to do a road trip & meet some of the guys. Moab is one of my most favorite places to get back to & with a 6BT under the hood the cost of the trip would be cut in 1/2!!!!
Jim

copy all .  With us getting settled into our home we too have everything else on the back burners.  It'll very likely be summer 2011 before Bud is built and ready to take anywhere, but it's all just a matter of time .

- Sam

[s ǝoɾ]

kewl - I just e-mailed my GSC to Joe S, he's gonna try to git it up on the calculator thread.  stand-by

Sam (Sam Simpson) has received the sweet spreadsheet.

Thanks guys.  I put it up on google docs, seems the only way to make it available online.  However I could code it up like our other calculators.  All the formula's are right there in the spread sheet.  When I get some free time I may give it a try.

www.docs.google.com

http://en.wikipedia.org/wiki/Google_Docs

This may totally change the way we exchange info, as I and many others have a lot of files that could be exchanged, some of which are too large for email or other normal uploading.

[KThaxton]

Hey man, what calculator do you use to figure your rpm at certain speeds? I've seen a few online, but none that I've liked too much.

The formula is:

Gear ratio (ring and pinion) X Speed X 336 /actual tire diameter. If you have an OD, multiply the OD ratio before you divide.
Also, Adding about 200 rpm is pretty close to account for torque converter slip without lockup.

[blueduster]

novack's is my favorite for 4x4s, followed by kiesler.

http://www.novak-adapt.com/knowledge/gearing.htm

http://www.keislerauto.com/speedanalyzer.html

The formula is:

Gear ratio (ring and pinion) X Speed X 336 /actual tire diameter. If you have an OD, multiply the OD ratio before you divide.
Also, Adding about 200 rpm is pretty close to account for torque converter slip without lockup.

[Mad Max]

   - cool (literally) -

If you can smell antifreeze...well that's a bad sign.  In the Mule's case, with 300,000 miles on the truck, and the radiator, it was starting to literally come apart, and it was sweating from several places.  So, time for some preventative maintenance. 
Pulled the radiator, took it to my rad guy, he tanked it, disected it, cleaned it out, soldered it all back together, slapped some shiny black paint on it - all for $100.  Today, back in the truck it went.  I also took the liberty of replacing the seriously old rad cap.  Test drive - up to temp - good to go.  Yay - one less thing to worry about .

[blueduster]

i wish there was a good radiator guy here. the one we had retired, sold the business. it was run into the ground in 2 years and is now closed. all the rest are a bunch of hacks.

[jungle]

Looks good & cheaper than a new one!!

[rob904x4]

well...I'm still having tranny issues.  The overdrive , no matter how many times it gets rebuilt, can't lose this 'whine' coming from it, and at high speed some sort of vibration.  Sounds like a bearing whining, and even though it's been apart several times now it seems like it may just be a bad unit.  The tranny came from a crashed donor truck and who knows what life the tranny lead up until I got it.  I have the other 518 core and I think I'm going to scope the od unit on it and swap them out.

Soon as the od engages an immediate 'whine' comes from the unit...from somewhere.  My other truck with a 2wd 518 makes absolutely no noise at all and has brite pink fluid, wheras this one...well doesn't.

Another thing is, when I was installing it over Christmas I happened to be looking at the output shaft and cleaning the back area out, and as I was wiping out the back side of the rear bearing I noticed the outer race...moved.  I checked it again and sure enough the outer race can in fact rotate around inside the case housing.  My tranny guy said 'it is supposed to do that', but I'd like to offer it up to y'all for a second opinion.  Thoughts?

I want to scope the od myself and swap them myself, both of which I've never done, but I can read.  Meanwhile, the fuel mileage comparo continues as does the pump tuning etc for max fuel mileage.  My goal is 25 mpg, and I think I can get there with this RC.

I think this RC is earning a new name - the 'Mule' - as in a factory test/demo vehicle.  I'm trying a lot of practical stuff with this rig in an attempt to both learn and apply some theory to the road.

So long as it gets me to work it's all good :)e it out

- Sam

hey sam did you figure out that tranny wine im haveing the same problems and cant figure it out as soon as i put it in fifth gear its starts to wine but when it was in the donar truck i had no problems it a get rag 360 that works perfect i didnt know if it was in the driveshaft or if the tranny is to straight and maybe it needs to be a bit to the left or right i know the tranny is good for sure but i cant figure this stuff out

[Mad Max]

well when this one gets ripped apart again and inspected i'm going to make sure the guy looks at the internals with the mindset that something may be bad to start with.  Fortunately I have another core 518 to use if needs be.  Hopefully I'll be taking it in in a couple weeks...

[Mad Max]

so last fill up calculated to 18 mpg - not bad to begin with but there's more to be had.  Tranny's going in to the shop in a week or so, after that I'll swap the stock turbo/collar for the HX-35/12cm, and I'm going to crank up the pump a bit because it seems a bit weak.

I'm also realizing that this 6BT is fairly under-utilized in this little RC - way more engine than it 'needs', and in that light I'm working a possible long-term plan to downgrade to a 4BT.  But I'm also thinking when 4BT time comes I'll likely try to find a clean '92-93 RC with all the bells and whistles and a bad engine, and very simply convert it to a diesel. 

In the end, I'm looking at a clean 93 RC/LE with a 4BT/518, 1/2-ton driveline (D44/9-1/4, 3.21s).  That's down the road a ways, but driving this little diesel RC has been and continues to be a pleasure.  The diesel just hums along effortlessly, and I'm hoping to break into the low 20's for fuel mileage.  I'm certain a 4BT will have all the power I'll need or want, and when it's just puttering along having 2 less cylinders to feed should net some pretty great fuel mileage.

Gotta have something to look forward to 

[jungle]

Sounds like a really sweet plan!!!! I'm not in a hurry but when do you think the converter will be available?
Jim

[Mad Max]

...probably in about 2-3 weeks?  Should be taking the truck in this week, and after that it should be good to go.  Sound good?

[jungle]

Sounds good to me.
Jim

[blueduster]

that's what i've been thinking all along too. that's among a few reasons why i didn't hang on to that 6bt i had last year. still putting the magnum in for now but long term the plan is definitely a 4bt. just gonna add a lot of sound deadner.  i  i like the idea of keeping the 1/2 ton axles. less wieght, more mpg.

so last fill up calculated to 18 mpg - not bad to begin with but there's more to be had.  Tranny's going in to the shop in a week or so, after that I'll swap the stock turbo/collar for the HX-35/12cm, and I'm going to crank up the pump a bit because it seems a bit weak.

I'm also realizing that this 6BT is fairly under-utilized in this little RC - way more engine than it 'needs', and in that light I'm working a possible long-term plan to downgrade to a 4BT.  But I'm also thinking when 4BT time comes I'll likely try to find a clean '92-93 RC with all the bells and whistles and a bad engine, and very simply convert it to a diesel. 

In the end, I'm looking at a clean 93 RC/LE with a 4BT/518, 1/2-ton driveline (D44/9-1/4, 3.21s).  That's down the road a ways, but driving this little diesel RC has been and continues to be a pleasure.  The diesel just hums along effortlessly, and I'm hoping to break into the low 20's for fuel mileage.  I'm certain a 4BT will have all the power I'll need or want, and when it's just puttering along having 2 less cylinders to feed should net some pretty great fuel mileage.

Gotta have something to look forward to 

[Mad Max]

some interesting notes: 

Red has 3.07 gears and 31" tires.  At 74 mph it turns 1700 rpm.  It gets 18 mpg.

Mack has 3.54 gears and 35" tires.  At 74 mph it turns 1700 rpm.  It gets 20 mpg.

Mack has ~double the (available) power as Red.

So, that begs the question, are 3.07s too deep to efficiently move a big heavy SUV?  And my answer to that is, 'maybe'. 

Mack has taller gears and WAY taller/heavier tires, and it gets better fuel mileage.  Hmmm .  So, the natural conclusions are that maybe there is something wrong with Red's tune (I think likely), and maybe I should turn up Red's pump more along the lines of Mack's pump and see if there is a fueling issue (or lack of it).

Red is essentially stock, but, Mack is getting the same fuel mileage as it did bone stock - 20 mpg. 

So, what is the difference between Red and Mack?  Well, Mack is 2wd so it rides lower, has LOTS more fueling potential, is a bit heavier, has 100,000-less miles on it, has way better breathing (turbo/exhaust manifold), and as far as I can tell has a perfect transmission.  Whereas Red is taller (less aerodynamic), has airplane gears, has lots lighter and shorter tires, has a stock turbo/collar (which equals horrible turbo lag), and has a bad tranny.

Now, Red is getting the turbo/collar upgrade pretty soon, as well as a fresh tranny, and after the first fill-up I'll see if those two things make any appreciable difference in mileage.

One other thing Red's tranny is still doing (did it when under Nacho too) is this:  When I have the overdrive 'disabled' (kill switch disengaged), when under very light throttle, and warmed up, the tranny will 'engage' the overdrive.  Apply a bit of throttle/load and it immediately disengages back into third (and if it's manually in 2nd it'll engane the od then too).  That's with the kill switch disabled.  It's almost like the tranny is trying to save fuel or something.....but in Mack, with the factory overdrive circuitry and PCM, the od will not engage, under any circumstances, unless the [on-off] button is 'on'.

So, in the back of my mind I'm wondering about the effects of too low of a gear .  This is however all a very fun experiment.  Meanwhile Red continues to be a fun daily-driver - gives me stuff to ponder and mull over - the "what if" stuff.  I LOVE the "what if" stuff!

.....I'm just thinking out loud..... 

- Sam

[440 4spd Power Ram]

There is something very wrong with your 518 Sam, going into overdrive with the kill switch off is bad enough but doing so in second gear means there is a hydraulic malfunction in the valve body allowing the overdrive to engage whenever it likes.

Should the overdrive engage while moving in reverse very bad things will happen, either the output shaft will twist in two or the overdrive unit itself will explode..

[Mad Max]

yeah that's what we're thinking too.  Well hopefully the new shop that's getting the tranny will do a better job than the last.  S'all I can do... 

[440 4spd Power Ram]

Just be very careful when backing up, if you feel the truck act like the rear brakes are locked don't give it any fuel, the overdrive can't rotate in reverse do to the one way clutch in the overdrive.

[jungle]

 



Interesting!

[KThaxton]

Maybe a dumb question, but are you sure it's not just the torque converter locking and unlocking? It feels almost like another gear.

[blueduster]

not a lock up trans.

no the 727 is a '91 unit and the 518 is a '93 unit, both non-lockup, both use the same converter.

One other piece of the puzzle is I am going about 10 mph faster than before, on the highway at least.  Maybe I'll try to do the same speed as I was doing before and get some numbers that way - might be a good baseline.