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Discussion Starter #1
I'm planning a 6bt Allison np205 swap in my 85 m1008. I'm trying to figure out how I'm going to mate the Allison to the t/c.

Can I swap a dodge 29 spline input shaft into a chevy np205?

Is the dodge input shaft the same diameter as the Allison output shaft?

If the input shaft can be changed or I can find a dodge 29 spline t/c, I'm planning to use the 29 spline nv4500 to 205 coupler and use an adapter similar to this: http://www.pirate4x4.com/forum/moto...ts-replaces-stock-full-spline-engagement.html
 

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blatant asshole
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yes they are the same providing you got the allison form a diesel not a gas.


idk how long that adapter setup is but it may work. the key is that the dodge is a male input and will need length to fit the coupler. ask them to make it extra long so you can cut it down to fit if needed.
 

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The 29 spline Dodge input will work in a GM 205 but it does need to have the larger 90mm input bearing bore.
 

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Discussion Starter #4
The plan is to get it set up out of the truck and measure for the adapter and get it a little longer than needed. I have a machine shop at work and can cut the tube portion down and mill it flat to whatever proportion I need.

Will probably get a newer 6 bolt np205 from a th400 to use. Thanks
 

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blatant asshole
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if you get a round pattern 205 then the adapter you posted wont work.


since you have a machine shop handy and you want a round pattern tcase. give the machinest a tcase gasket and tell him you want 2 cut out 1" thick steel. have them cut a relief for the snap ring and brg on one plate and a relief for the tubing on the other side and other plate. tubing od only concern is the bolt heads for the flanges.
 

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Discussion Starter #6
if you get a round pattern 205 then the adapter you posted wont work.


since you have a machine shop handy and you want a round pattern tcase. give the machinest a tcase gasket and tell him you want 2 cut out 1" thick steel. have them cut a relief for the snap ring and brg on one plate and a relief for the tubing on the other side and other plate. tubing od only concern is the bolt heads for the flanges.
The one in the picture is just an example. They will make it for the round pattern. I could have the machinist make the whole thing but he's kinda cranky...
 

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Discussion Starter #8
what are your plans for vss and controlling the allison? ive got the destroked controller with modified ford tcase for now. would love to swap over to a 205 or hero case if it was direct fit.
My thoughts right now are to put the tone ring/vss somewhere between the trans and t/c in the adapter. I will probably use a gm tcm and harness. Not for sure on that yet though.
 

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what about divorce mount? why the 205?
 

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Discussion Starter #10 (Edited)
g-[CENTER said:
wizz;29147042]what about divorce mount? why the 205?
I already have an allison with the 4x4 tail housing.

As far as the 205, I would like to have something with better gearing but its the easiest to adapt to the allison. The truck has a 6.2 700r4 241 now. I'm open to new ideas, just has to stay pass. side drop. Everything else I've looked at I would have to have a conversion shaft made to go from the trans to the t/c. The 205 I can do with off the shelf parts
 

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LLY Escalade
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When you install the 205 do not hang it off the back of the Allison without supporting it at the adapter and at the back of the t-case near the output. Its a heavy old beast and you stand a pretty good chance of breaking the aluminum housing on the Allison if you are doing any real wheeling with it just hanging off the transmission. You need to make sure it can move with the engine and transmission as well, don't solid mount it.
 

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I already have an allison with the 4x4 tail housing.

As far as the 205, I would like to have something with better gearing but its the easiest to adapt to the allison. The truck has a 6.2 700r4 241 now. I'm open to new ideas, just has to stay pass. side drop. Everything else I've looked at I would have to have a conversion shaft made to go from the trans to the t/c. The 205 I can do with off the shelf parts
If you get a wide bearing 29 spline input gear for your 241 you would be able to bolt it directly to the Ally.

If you really want to use the 205 then you are on track with the 29 spline Dodge input gear and coupler. Scoring a complete assembly, including adapter, from a first gen Cummins truck would be ideal, but they're like hen's teeth. Do you have a friendly machine shop around? Machining a spacer for a round pattern 205 is pretty easy:

 

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you can either find a 205 output with a VVS, but since you have a machine shop access, piece of cake to just add on to any np205 output housing. Would have to search, but there is a thread here on doing just that. or just mount a tone ring to the drive shaft

I bought the ORD magnum box so I could use a 205. The 205 with 1 1/2 wide gear is what I needed for my heavy beast.

X2 on support. I used the stock NP205 cross member and modified it to fit.
Used the stock rubber mounts too. From there I made a cradle to hold the 205 and the rear of the trans. Keeping the mounts to 3. 2 motor mounts and one trans/transfer mount. I also made a rod that goes from the side of the NP205 back to the bell housing of the trans, just like the OEMs did.
 

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you can either find a 205 output with a VVS, but since you have a machine shop access, piece of cake to just add on to any np205 output housing.
Forgot about that. Yeah, you can machine a flat and drill and thread a hole to fit a 241 VSS sensor in the cable speedo housing. The reluctor from a 241 fits the 205's splines, but it needs to be narrowed. Turn down both sides evenly until it is the same width as the 205 speedo gear. IIRC a bit of grinding for reluctor clearance was needed on that protrusion seen in the lower left of the first pic. You need .005"-.010" clearance between the sensor and the reluctor. Then either weld the speedo nut closed, or tap it for pipe and plug it. Lotsa guys have done this with no issues.





If you put the speed sensor here you need a switch on the rear shifter to signal the TCM when you are in low range. You also need to change the low range ratio in the TCM from 2.72 to 1.96. If you don't do these two things the TCM will throw a code and refuse to shift.
 

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Discussion Starter #15
If you get a wide bearing 29 spline input gear for your 241 you would be able to bolt it directly to the Ally.QUOTE]

Will an early dodge Input shaft fit the chevy 241? JB conversions has this one listed for the dodge:
Input Gear (29 spline - Long - 1987-1994)
Part #1458
 

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Discussion Starter #16
Forgot about that. Yeah, you can machine a flat and drill and thread a hole to fit a 241 VSS sensor in the cable speedo housing. The reluctor from a 241 fits the 205's splines, but it needs to be narrowed. Turn down both sides evenly until it is the same width as the 205 speedo gear. IIRC a bit of grinding for reluctor clearance was needed on that protrusion seen in the lower left of the first pic. You need .005"-.010" clearance between the sensor and the reluctor. Then either weld the speedo nut closed, or tap it for pipe and plug it. Lotsa guys have done this with no issues.

If you put the speed sensor here you need a switch on the rear shifter to signal the TCM when you are in low range. You also need to change the low range ratio in the TCM from 2.72 to 1.96. If you don't do these two things the TCM will throw a code and refuse to shift.
Is there an issue with keeping it in front of the t-case? The trans will not know its in low gear so no tcm issues but will it shift normally? My speedo is mechanical so I need to keep the cable output if I can.

If I do put it in the t-case tail housing, can I send the tcm out to have it programmed (regeared)? Who would be capable of doing this? Otherwise I'll have to rig up an obd2 port on the truck to use a programmer correct? This is assuming I use a gm tcm.
 

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If you get a wide bearing 29 spline input gear for your 241 you would be able to bolt it directly to the Ally.QUOTE]

Will an early dodge Input shaft fit the chevy 241? JB conversions has this one listed for the dodge:
Input Gear (29 spline - Long - 1987-1994)
Part #1458
Not sure what "long" means on that. Hopefully not "longer than the 32 spline GM shaft" :confused: Otherwise, yes that is the correct one. In 1995 New Process changed the input bearing and helix angle of the gear, so '95 and later gears are not useable in your case. The 87-94 gear will have the correct bearing journal and helix angle.

Is there an issue with keeping it in front of the t-case? The trans will not know its in low gear so no tcm issues but will it shift normally? My speedo is mechanical so I need to keep the cable output if I can.

If I do put it in the t-case tail housing, can I send the tcm out to have it programmed (regeared)? Who would be capable of doing this? Otherwise I'll have to rig up an obd2 port on the truck to use a programmer correct? This is assuming I use a gm tcm.
You can put it on the input if you want. IF you want to use the alternate shift schedule, program the TCM for a 1:1 t-case ratio and add the low range switch.

As for programming the TCM, that is pretty much a given. You do know a DMax TCM won't work behind a 6BT, right? You need an A40 or A46 TCM flashed for an 8.1 gas motor, and you will need the shift points and other parameters altered. It ain't a trivial swap.

im not so sure about running the vss post gear reduction. i was told when looking into standalone allison controllers to keep the vss in the stock location to keep things working properly.
The VSS on the t-case output IS the stock location in 4WD trucks. There is a switch that tells the TCM the case is in low range, and since the TCM is programmed with the low range ratio it can make the proper adjustments.
 

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If you have a 5 spd allison, and since you are going to need a tcm flashed, you can make it a 6 speed trans just by adding the solenoid and a cal flash.
 

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Discussion Starter #20
Not sure what "long" means on that. Hopefully not "longer than the 32 spline GM shaft" :confused: Otherwise, yes that is the correct one. In 1995 New Process changed the input bearing and helix angle of the gear, so '95 and later gears are not useable in your case. The 87-94 gear will have the correct bearing journal and helix angle.



You can put it on the input if you want. IF you want to use the alternate shift schedule, program the TCM for a 1:1 t-case ratio and add the low range switch.

As for programming the TCM, that is pretty much a given. You do know a DMax TCM won't work behind a 6BT, right? You need an A40 or A46 TCM flashed for an 8.1 gas motor, and you will need the shift points and other parameters altered. It ain't a trivial swap.
That's the only early 241 29 spline shaft I can find listed anywhere. He said that he "might have one left." So hopefully he can find it.

As far as the tcm goes I really haven't done much research on it. I didn't know the dmax tcm couldn't be used. Why is that? The only input the tcm should need from the motor is tps. I'm not real concerned with it at the moment. I know it can be done so I'll look into it more when I get to that point.
 
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