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Discussion Starter · #1 ·
I really really want to put one of these behind my 410 small block. The 4.69 1st gear and close ratios vs the 727's 2.45 and wide spread would just be too cool in my clapped out old 4x4. Things I'm not sure of yet is the engine/converter interface. Given that these are bolted to the 5.7 Hemi and a 727 can be made to fit that, that doesn't seem too much of a stretch, but I've never seen the flexplate/converter setup on one of these transmissions in person. These 5.7 transmissions are readily available in boneyards for a little less than a grand and be found with relatively low mileage, 50,000 miles or so.

Axis Industries makes a 6 bolt tailhousing to accept the 241D t-case, and the 8HP70 supposedly has the common 23 spline output. That in turn makes me wonder if my existing 208 passenger side drop would bolt up.


On to the electronics/shifting. HTG makes a standalone, fully user programmable controller. According to their site you can control every aspect of this transmission. Clutch apply pressures, converter, shift points and firmness. Full auto or manual shifting, hell it even has a transbrake option. Not sure whether it has a VSS output. Downside to it is it's made in the UK and it's not exactly cheap. Keeping a spare in case it ever crapped out would be a good idea given it's origin, being down in the middle of nowhere for a week or two waiting on a replacement TCM would suck. That of course doubles the price. In for a penny in for a pound I guess.

Let's hear your thoughts or shoot holes in the idea.
 

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I know I have one in my 5.7 charger and it is something to behold, first gear is basically useless in a car. Most of the time the car actually takes off in 2nd unless you are in sport mode or you punch the throttle. First will burn tires through into 2nd and 3rd from a dead stop even in the 5.7 if you have the guts to hold it. I nearly got to the end of 2nd gear and about crapped my pants since she was sliding all over the place with the tires spinning at 50 mph or so.

With your 408 I am sure it would be a hoot. They probably will become cheaper over time. The electronics is what scares me. Does the kit from HTG allow you to program shift points based off RPM signal or does it go off of some other sensor or just your hand control of the stick? Are the HTG units warrantied?

You would probably have to figure that all out, but in theory it could be done and I believe has been done several times.

Not sure on compatibility with transfers, do some google searching and you may find something. You may need a special adapter (probably pricey) if you rig is passenger side drop since all these new things are driver side drops. Now in theory you could run it to a divorced 205 setup as long as you have the real estate under your rig. I know those 8hp's are long as hell. Keep me updated and I am sure others will chime int. I have thought about doing this when prices drop in 15 years or so if ever.

Neil
 

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The 208, and 241 have different noses. a 241 will fit on a 46RH, but a 208 not so well. But pass drop 241's are not that hard to find.

My 17 Gas Pacifica had a 9 speed trans, was crazy to feel it shift three times going through an intersection. After the fun wore off, the constant shifting started to work on me. The 2020 Hybrid Pacifica is more fun to drive, with the electronically continuously variable transmission. An 8 speed in a truck/RC, could be fun, I will keep an eye on this thread.

I am not well versed on the 8HP trans, but many of the newer engine/ trans combinations the gas pedal is electronic, and the computer controls the throttle, and trans, allowing the engine power to be cut back when shifting, to ease the shift load on the trans.
 
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Discussion Starter · #4 ·
The 208, and 241 have different noses. a 241 will fit on a 46RH, but a 208 not so well. But pass drop 241's are not that hard to find.

My 17 Gas Pacifica had a 9 speed trans, was crazy to feel it shift three times going through an intersection. After the fun wore off, the constant shifting started to work on me. The 2020 Hybrid Pacifica is more fun to drive, with the electronically continuously variable transmission. An 8 speed in a truck/RC, could be fun, I will keep an eye on this thread.

I am not well versed on the 8HP trans, but many of the newer engine/ trans combinations the gas pedal is electronic, and the computer controls the throttle, and trans, allowing the engine power to be cut back when shifting, to ease the shift load on the trans.
There's a guy who made his own manual solenoid control and adapter and stuck a stock 8HP70 behind a turbo'd big block Chevy in a Chevelle and it lasted a long time. He used a simple circuit board, some mosfets, a pmw and a switch. Threw the factory tcm in the trash and hard wired the solenoid pack to his controller. Not too concerned about my 450lbft stroker roasting the clutches due to lack of engine management. From what I've read the trans uses a pressure bleed solenoid to control apply pressures/shift firmness. The aftermarket HTC controller supposedly has the ability to operate that as well. It uses a TPS and tach signal to calculate shifts based on how you program it. You can create and switch between programs. Race, street, tow, take off in 2nd or even 3rd and skip shift to whatever gears you want etc. But it's been my experience that aftermarket stuff rarely performs as advertised or dependably and flawlessly.

Any pass drop t-case is a bit hard to find in this area, and Mopar stuff even more so. I'd probably have to buy one online and have it shipped in. Was reading up on them last night and it seems there are 40+ different inputs for the 241. That could either help or complicate matters.

At some point my conjecture will have to stop. The only way to answer these questions is to put my hands on the trans and Axis adapter and figure out if there's some way to mate something to it.

I guess the first step would be to call and discuss the controller, then if satisfied a trip to the boneyard with a tape measure and see what it'll take to make it mate to a small block and fit in the chassis.
 

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I guess the first step would be to call and discuss the controller, then if satisfied a trip to the boneyard with a tape measure and see what it'll take to make it mate to a small block and fit in the chassis.
It will fit to the small block no problem as the mounting to all new hemis, magnum small blocks, and small block la's are identical. Chrysler, dodge, and all its variants never changed that thus far. You could bolt up a truck 4 speed manual with small block bell to a hellcat if ya wanted too.

I agree with your thoughts sort out the controller and length first then go from there....you can make anything work but how much time and money and skill development/fabbing do you want to sink into your idea. I am all for the time and fabbing, but money is where things get tight for me...keep us updated in this post.

Neil
 

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I would not worry so much about the transfercase mating either, there is a few ways that can be done.
 
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Discussion Starter · #7 ·
What exactly is the difference between the 208 and Dodge 241 23 spline t-cases? The input depth is different I know, but which direction? Are the locating bosses the same od? The Axis adapter has three sets of holes for angle in degrees.
 

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The 241 is supposed to be a bit stronger. Has the synchronizers for shift on the fly, like the later 208's did. Otherwise, I think the main difference is in the extra ribbing in the case. I never thought of looking up parts, to see if there is any commonality of parts.

IIRC, its the 208 that has the longer snout. I'll look again later, to see if I can find my pics, or will run down, and take some more.
 

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Discussion Starter · #9 ·
The 241 is supposed to be a bit stronger. Has the synchronizers for shift on the fly, like the later 208's did. Otherwise, I think the main difference is in the extra ribbing in the case. I never thought of looking up parts, to see if there is any commonality of parts.

IIRC, its the 208 that has the longer snout. I'll look again later, to see if I can find my pics, or will run down, and take some more.
That'd be a big help and much appreciated. If the 208 is indeed longer Axis offers a .300" spacer ring so their tailhousing can be used on the ecodiesel 8spd, which for some reason has a slightly longer output shaft. Whether or not that spacer would solve the problem as an off the shelf piece for people installing the 208 would remain to be seen. But it's possible a correct spacer could be made provided long enough studs were installed. Main reason I'd like to keep the 208 is that I have one lol. Used to have two spare 208's and a 205 but I got rid of them.
 

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Ok, I will overload you with info.

This one is the 208.

IMG_2607.jpg

This is the 241

IMG_2606.jpg
 

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The 208 has the extra piece. Otherwise it looks like the input shaft casing. I forgot to bring a ruler, but the metal piece is a 2" square chunk.

617360


617361


617362
 

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Here is the 241
617363


617364
 

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I could not find my 46RE tail section, I believe it has a bearing that the 241 input shaft fits into. I have doubts about a spacer doing the trick. Depending on how the bearing is, you might be able to cut some of the aluminum case off. Need to find some pics of the back end of the 8 speed.
 

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Discussion Starter · #14 ·
I could not find my 46RE tail section, I believe it has a bearing that the 241 input shaft fits into. I have doubts about a spacer doing the trick. Depending on how the bearing is, you might be able to cut some of the aluminum case off. Need to find some pics of the back end of the 8 speed.
Thanks for the pics.
 

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Discussion Starter · #15 ·
Just to clarify I misread and Axis does not offer a .300" spacer. Clearly says it would need to be a custom piece but I have the reading comprehension skills of a knat.
 

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Discussion Starter · #16 ·
What's the starter ring tooth counts on small block 727 converters?
 

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looking forward to seeing how this works out for you Joel {popcorn}
 

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Discussion Starter · #19 ·
looking forward to seeing how this works out for you Joel {popcorn}
IF this works out. The correct word is IF. :) Found HTG on Facebook, looks like they've sold about a thousand of these controllers so far and are still working the bugs out of the software. Faster data logging refresh rates etc. Appears to be a bunch of fuzzy faced 20 somethings with hotrod BMW's and Mercedes. But......Bill Gates was a 20 something that started in his garage so..... Still, might be wise to give them some more time and learn to speak Polish for tech assistance. I wish companies in this country would get the stick out of heir arse and offer something besides GM crap.

From what I can tell you can control every aspect of the trans. Clutch prefill rates, apply pressures etc. From butt smooth daily driver to hardcore race box with the push of a button. You chunk the factory TCM in the trash and connect theirs directly to the solenoid pack, no piggybacks or work arounds. Whether the controller is hard wired or uses CANBUS, or can do either I can't say yet.
 

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You got me interested, that trans is something. I wonder how the HTC controller interfaces with the 8HP, at the end of this video, he says the TCM is built into the valve body. A great watch, when you have time.

 
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