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Discussion Starter · #1 ·
Hey guys , I had a couple of posts about a drivetrain swap I am starting on my 75 ramcharger, the project has taken a different turn, I was planning to swap the 360 for a 440, that fell through but I just purchased a 92 diesel 4x4 that has everything I need to swap in the 5.9 and the Dana 70/60 axles. I'll have lots of questions as I go along but I am still going with the 42" tires and I'm wondering how much lift I will need to clear the stock fenders, this truck is in beautiful shape for a 75 and has the SE trim so I don't want to cut the fenders out. I can radius the bottom edges a bit but that's about all. I currently have a skyjacker 8" suspension lift, I was planning on installing a three inch body lift and just wondered if that will be enough or will I need a bit more suspension as well. I have measured up the new axels and I think they will give me about an 1-1/2" of lift on there own.
Also if I do lift it more with a shackle flip etc. How do you get the driveline angles to work, I already had to drop the transfer case and hog out the joints as it is?
 

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Here's an 87 RC I built for a friend - it's got 40s, 4" lift springs (48" Dodge fronts, 56" Chevy rears), and a 3" body lift. Had to trim the front fenders to allow for turning and articulation (this truck is built for on and off-road), but the rear quarters are untouched.







I highly recommend either 56 or 63" rear leafs, and 52" front leafs - doing so will give you a better ride, with the same weight-carrying capacity. Naturally you'll relocate the leaf spring mounts. If you are looking for the best aftermarket spring mounts look at Jungle Jim's hardware in the vendors section - if you get his mounts you likely won't need the body lift, or at least not as tall of a body lift.

On the rear axle rotation, you will need to cut/separate the leaf spring perches on rear axle, rotate the axle to aim straight at the t-case, and have a custom double cardan driveshaft made - dc joint at the t-case.

42's are a big tire without trimming fenders, but if you do it nicely you can make it look like it came that way.

- Sam
 

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I'm quite sure the older fenders have smaller wheel-well openings...
 

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Discussion Starter · #5 ·
Mad Max said:
Here's an 87 RC I built for a friend - it's got 40s, 4" lift springs (48" Dodge fronts, 56" Chevy rears), and a 3" body lift. Had to trim the front fenders to allow for turning and articulation (this truck is built for on and off-road), but the rear quarters are untouched.







I highly recommend either 56 or 63" rear leafs, and 52" front leafs - doing so will give you a better ride, with the same weight-carrying capacity. Naturally you'll relocate the leaf spring mounts. If you are looking for the best aftermarket spring mounts look at Jungle Jim's hardware in the vendors section - if you get his mounts you likely won't need the body lift, or at least not as tall of a body lift.

On the rear axle rotation, you will need to cut/separate the leaf spring perches on rear axle, rotate the axle to aim straight at the t-case, and have a custom double cardan driveshaft made - dc joint at the t-case.

42's are a big tire without trimming fenders, but if you do it nicely you can make it look like it came that way.

- Sam

Thanks Sam, a fellow below commented on the wheel openings being bigger on the later trucks like yours, and I don't think that is the case, I measured the ones on this 92 truck that I bought and they are the same as my 75. You didn't mention the front driveshaft, and that is the one I had real problems with already , hopefully I won't have to go any higher with the suspension
 

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"clocking the C's" (rotating the front pinion up) on a front axle is a lot lot lot more complicated (and difficult) than a rear, especially when using leaf springs, but it certainly can be done, and depending on your situation it may be 100% necessary, and then there's potential input bearing oiling problems but one problem at a time.

What are you intended plans for the truck - presumably serious off-roading, but mud wheeling? rock crawling...?
 

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Mad Max said:
"clocking the C's" (rotating the front pinion up) on a front axle is a lot lot lot more complicated (and difficult) than a rear, especially when using leaf springs, but it certainly can be done, and depending on your situation it may be 100% necessary, and then there's potential input bearing oiling problems but one problem at a time.

What are you intended plans for the truck - presumably serious off-roading, but mud wheeling? rock crawling...?
I agree...what are your plans. 42s are one thing on a buggy or a purpose built off roader but what are your plans for a fullsize truck with 42" tires and purty sheetmetal. Trails that require 42s generally require far less sheetmetal.
 

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not to mention you'll need really deep gears too - the RC I posted runs 5.86's.  Also, tires that big and diesel torque can easily snap stock axle shafts... :-\
 

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A W600 will fit 42" with room to spare.  ;D ;D

Bucky
 

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Discussion Starter · #10 ·
Mad Max said:
"clocking the C's" (rotating the front pinion up) on a front axle is a lot lot lot more complicated (and difficult) than a rear, especially when using leaf springs, but it certainly can be done, and depending on your situation it may be 100% necessary, and then there's potential input bearing oiling problems but one problem at a time.

What are you intended plans for the truck - presumably serious off-roading, but mud wheeling? rock crawling...?
I do plan to off-road the truck but nothing too crazy, the body is too nice to get wrecked
 

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well what I was getting at is if you're not doing serious rock crawling - which places the belly and hardware in mortal danger - then you could consider clocking your t-case down to reduce the front driveshaft angle.  Some OE t-cases all for this and some don't - just depends on your transmission rear mating flange, etc.

Also, while this probably won't sound like too good of advice, try not to worry too much about wrecking the body and instead just go enjoy the truck.  If you go off road even once then you sign up for body damage, but unless you're going where there's BIG rocks and/or lots of trees then you likely won't have much to worry about. 

Plus, the old adage still applies regarding off-roading and body damage:  "There are those that have...and those that will".  Once you accept it, the whole thing gets a lot more fun ;) ;D

- Sam
 

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I agree, offroad body damage up to and including a complete write off is possible. If your not mentally prepared to write off your vehicle every time you hit the trails you have no business offroad. My rule for body damage is as long as it doesn't take out the glass,lights, or prevent the doors from opening I don't care. I've had one vehicle where I tried to preserve the body because it was "pristine", which was a 1990 Geo tracker 2 door. I wheeled everywhere with that little creature with 235/75/15 tires at stock height with a spool, with no real body damage to speak of. Then I installed a 2" lift and some 31x10.5x15 tires. The very next weekend while playing in a rocky creek bed I smashed both rocker panels to where I needed to kick the doors open and hammer the door sills back down. That same day, I removed both mirrors and the passenger taillight trying to squeeze through two trees that just happened to be tracker width apart. The next day a buddy was riding shotgun for some night wheeling and he didnt say anything about the 4ft boulder I was about to come down on until I caved in the passenger door and pivoted around the rock. On that trip I stopped caring about body damage 30 minutes in on day one after I realized how much better it wheeled after the rockers self clearanced. I would also like to point out that on day 2 there was a rocky obstacle that the bigger vehicles were having trouble with. I posted the "high water mark" and lost my driver side tail light in the process. My record stood until a tube buggy on 40's got through it with some difficulty. Now I'm not saying a wheeling rig has to look like a crumpled up beer can, its just that body damage is kinda to be expected...
 

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Anything is possible, but you're gonna have to make some serious compromises. The combination of big lift, and short wheelbase is going to be hard to reconcile. The one good thing is you won't need really low gears with a Cummins. If built right, they can produce more than enough torque to turn big tires with taller gears. I'm personally running 4:56 and 42s and my Cummins pulls it just fine.

The issue is drivetrain and lots of lift. You need lots of lift to avoid cutting fenders, but that means your driveshafts will have to run at steeper angles. The problem is the greater the angle, the more the u-joints will have to take. At higher angles, they will not last very long. There are several options to reduce driveshaft angles and you'll probably have to combine them and it still might not fully resolve the issues.

So your compromises will be as follows;

Live with the short u-joint life, no or little daily driving
Reduced ground clearance for the tire size chosen (thru lowered t-case, clocked t-case)
Choose a smaller tire and a smaller lift
or cut the fenders

Ed
 

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They make industrial CV joints, If you insist on a silly lift with a short wheelbase you could use some of those for driveshafts. If you have a slip yoke in the driveshaft you can use CV joints with a 45* max operating angle which blows a U joint's max operating angle of 3* out of the water.
 

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Seems likely you'll ruin a nice body.  Might as well thoughtfully and tastefully ruin it in advance by massively trimming the fenders, go with minimal lift for belly clearance, keep low center of gravity.  Might even consider some M715 style fenderwell inserts from a 55 gal drum.
 

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RedneckInTraining said:
They make industrial CV joints........... If you have a slip yoke in the driveshaft you can use CV joints with a 45* max operating angle which blows a U joint's max operating angle of 3* out of the water.
There are several companies offering high angle CVs now for some time, but none of them are designed for constant use. When a CV has to run at high angles, those little crosses have to see-saw, back and forth, within the yokes at very high speed. There isn't very much grease in those trunnions to begin with, and the heat thats created from rapid rocking turns that grease into liquid that will eventually burn, losing it's lubricity in the process. At that stage, it's not long before the trunnion bearings fail and the CV fails.

Believe me, I've extensively researched this for years, trying to find a solution. I spent several hours on the phone with several manufacturers including Tom Woods on their high angle CVs. Even looked into agriculture CV joints, and no one would recommend a CV at high angle to handle constant use. Sure they could be used and some ag joints could run at nearly 90*, but they couldn't do it for very long.

To give you a bit of back story, I'll admit I was building something a bit more extreme than our OP's build. My RC was lifted 13 inches (10 suspension, 3 body) to clear 46" Michelin military tires. I stuck a Cummins in it, Dana 60/70s, and I was running a 727 with a divorced 205. That made for a really short rear shaft with a really steep angle. I did drop the tailshaft about three inches, and a further two inches on the t-case, and still the angle was rather steep. I talked to a local driveshaft shop who was building custom shafts for high rollers, and decided to try an experiment. We went with a Rzeppa style CV joint that was designed for a 70s era Eldorado. They were the largest joint we could find of this type, and the idea for using was, these joints carry a lot more grease to help keep them cool, but of course, there was no guarantee that it was going to work.

I never got to try it out, The project stalled and never got restarted. Eventually, my Dakota needed some serious attention and I had to address that, and then we found some beautiful property and decided to move. So, long story short, I combined the RC project with my Dakota, dropped tire size, went with a more conventional drivetrain configuration, a longer wheel base, and now I have virtually zero rear d-shaft angle.

Ed
 

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...while pretty extreme, another option...and I know it works because I have done it...is using rockwell axles, which have the massive benefit of the pinion being 7 inches higher than a Dana axle, dramatically reducing the driveline angles. The catch is...everything about rockwells is "huge" - "massive" - "need more shop equipment to move them around" -...and, "custom" (if you want to do it right and still be fairly safe,...and reliable).

I put rockwells and 46's under a 70's crewcab - a truck I wish I could have kept, but wow did that machine crawl over...well...everything. With the tire size and chassis mods you're considering...well rockwells might just be legit for your build...just be prepared to have built a monster truck in the end before buying anything, oh and you'll need a BIG tow truck and BIG trailer to haul it anywhere not 'local'.

This truck had about 12 inches of lift (4 in the suspension, ~8 in the custom body mounts), which ended up being perfect for both the tire size and wheel base, AND...yes I clocked both the front and rear axles up to zero out the driveline angle(s) into the diffs.







If you haven't seen this thread, with the tire size you're considering this might glean a lot of helpful info -

https://ramchargercentral.com/mopar-trucks/b-u-d-'78-m-350-(-need-some-shoes-)/1500/

- Sam
 

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Rockwell = Big deep pockets too.

Been there.

But oh how they work.

Bucky
 

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Rockwells could be a possible option (so can Portals) but to run Rocks, you almost have to run tires over 44s and you'll need overdrive because those axles came with a very short 6:72 ratio. Most 12V engines came from the factory governed at about 2600-2800 rpm and with those 6:72s you'll be against the redline if you try to run it on the highway. You can change the gov spring and get more rpms, but these engines pull much better at lower rpm. The sweet spot is around 1800 rpm even with higher gov speed

With 40s and a 6:72 ratio if you're doing 55 mph, the engine will be spinning at 2772 rpm in 3rd and 1913 rpms in OD....At 70 mph the engine will be spinning at 3528 rpms and 2434 rpms in OD. I can tell you that the engine is going to sound very unhappy and fuel economy will plummet.

I read somewhere about a 4:30 ratio being made available for the Rockwell top loaders, but I can't tell you if they were ever offered or if they exist at all, but it would open up the option to run 40s with a low rpm engine, like the 6BT

Ed
 

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I think he's looking to run a big block, but yes Ed you're def right about the rpm's and a diesel.  I ran a 6BT Cummins and a 47RH and it topped out right around 65 mph, and that was with a fairly stock pump and 46" tires...
 
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