I have a 85 chevy one ton with a 350 ci and have a 06 duramax alli combo out of my buddies wrecked truck... the question how hard is it to make the swap and what kinda cost should i be looking at?

Did you happen to get the ECM?

IF you got the ECM and all the wiring it should be pretty easy. There is lots of room in those old trucks.

You also need the TCM because the ECU and TCM talk to each other and they are matched to the ViN of the vehicle. Plan on a lift kit, exhaust modification, and drive line mods. Not major dollars but they at up! Did you get the radiator and intercooler??? More money!

i have the whole truck. The truck was hauling a 4 horse trailer and was t-boned on the trailer by a Lexus and rolled the trailer on its side and resulted in the frame being bent...

That would be a cool setup! Sleeper for sure! Please post updates as it happens!

PM thefurmanator,
he did a late 90s GMT400 series down here in Fl, that would be simular in mounting, the intercooler/radiator he said was tough but he could shed some lite on it for you. You can set it up to run stand alone, just shut down theftlock. The ECU-EDU-TCM all talk on a dedicated 2 wire buss, (a twist pair you'll find looking through the harness) the serial class II is for talking to the truck but it doesn't need the truck to run, you just won't have tow/haul. I'm working with an Allison group in Iowa to get around that right now.

Good luck sounds fun, just remember "Its an adventure" don't let it get the best of you and you'll be shocked at what you'll learn in the end.

You also need the TCM because the ECU and TCM talk to each other and they are matched to the ViN of the vehicle. Plan on a lift kit, exhaust modification, and drive line mods. Not major dollars but they at up! Did you get the radiator and intercooler??? More money!


other than a body lift and exhaust i dont think he will need much else the th400 is the same length

It is ALOT of work. I know pussow here did his 87 with a 06 VAN engine and then flashed it with an LBZ and swapped in a 6 speed ALLISON. For the 85 a body lift would be in order or a custom oil pan. I can PM you some more stuff on this swap into the older body style that I can't put into the post. I swapped in an 01 LB7 simply due to the fact that it is more basic electrically than the LLY or LBZ. I've also come to the conclusion that the ECM,TCM, BCM, and cluster are required to make this swap work to it's full potential. My swap only has the ECM and TCM, but I don't have tow/haul mode. I'm still hoping I can find somebody or someway to get it to work with the fewest parts swapping as possible, but tow/haul is my only hang-up. EFILIVE or a PPE is also required if you don't transfer the BCM due to PASSLOCK.

other than a body lift and exhaust i dont think he will need much else the th400 is the same length

Are you saying that the Allison transmission is the same length as the TH400? That would be great, because I feel bad about cutting apart my nice drive shaft.

timoloco, I am swapping a Duramax LB7/Allison 6 speed into the '87 1500 in my signature. Maybe you could help me out, or maybe this is a question you too have. What do the engine mounts look like on the Duramax's?

Keep us posted on your project. We've seen swaps in older trucks, chevelles, camaros, and a grand national. Should be cool.

Are you saying that the Allison transmission is the same length as the TH400? That would be great, because I feel bad about cutting apart my nice drive shaft.

timoloco, I am swapping a Duramax LB7/Allison 6 speed into the '87 1500 in my signature. Maybe you could help me out, or maybe this is a question you too have. What do the engine mounts look like on the Duramax's?


should be i know it will fit against the np205 transfercase and is the same length as a 4l80 which if im not mistaken so the th400 is its just taller around the bellhousing which is why we need the body lift.

with a 1/2 ton you will need to mod the drive shaft though

should be i know it will fit against the np205 transfercase and is the same length as a 4l80 which if im not mistaken so the th400 is its just taller around the bellhousing which is why we need the body lift.

with a 1/2 ton you will need to mod the drive shaft though

Thanks for that info :) and I have a custom drive shaft
(very strong) but I assume I will have to change the yoke (no big deal). So since it fits against the NP205, does that mean that it has the same size output shaft and spline count?

you're also gonna need to think out which transfer case you want to run... the older trucks have pass. side drop front axle whereas the new stuff with the dmax has driver's side axle in the front. That can be a problem if you want to run the allison with the same xcase behind it as was in the donor truck. If you do that (use the allison with GM 261/263 transfer case) then you'll need to swap the front axle to one that is driver's side drop. Such as from a Ford. The recommended ones are the 78-79 HP D60 - same as what's recommended/used in the SFA conversions for the GMT800-900 trucks. ;)

IF you DO want to run the alli but do NOT want to use a 261/263 transfer case and swap the front axle, there are a few options:

- get an adaptor and bolt up the xcase of your choice that is pass. side drop. i.e. a GM NP205.
- Atlas makes a transfer case that will bolt up to an Allison and can be pass. or drivers drop.
- you might even be able to get a 2wd allison setup with a divorced transfer case (again, the NP205 would be real popular) that is pass. side drop.

Either way, I think you will have to put the VSS (speed sensor) on the output of the transfer case just like it is on a 261/263 so that the Allison will know how to shift correctly when in 4wd. Something else to consider if you want to keep the allison, are the controls for it. Not sure how handy you are but if you aren't real good with car elec. and custom fabrication it might not be easy to control all the features of the allison. Meaning the T/H button and Tap Shift +/- buttons are built into the gear selector in the GMT800 trucks. Unless you can take them out and mount them on your own somewhere in the cab of the old truck, you'll have to find a way to fit the steering column et al from the donor into the cab of the old truck. Don't imagine that will be the least bit easy. Fun? if you like fabbing stuff. But easy? doubt it. LOL There again, some custom stuff has been done with this stuff in other conversions so depending on your ability or $$$ available, there are options. PPE has done some cool things to incorporate those functions by means other than retrofitting the GMT800 steering column into the vehicle. i.e paddle shifters on the steering wheel like race cars, push button controls to go into P R N D M (or whatever it is on the 6-spd alli), etc.


IF you aren't hung up on running the allison, there are almost endless combinations of transmissions and transfer cases that can and have been mated up to a Dmax since they are reg. ol; GM bolt pattern. That means ZF6 (like the GMT800 trucks) manual trans., GM NV4500 5-spd manual trans., 4L80E/85E auto trans. either setup to be stand alone or full manual VB, etc. etc. and any number of transfer cases that can be bolted on to them.

Obviously, if you run a manual transmission, or some other auto besides the allison, you should NOT need the TCM or any assoc. wiring.

You will need the accelerator pedal, bracketry and associated wires also.

If you can't do your own harness modifying, PPE can do it for you. For a fee, of course. Once they are done, the wiring is a 5-wire deal from my understanding to make it run. Either their own custom tuning or EFI Live will then make it run.




Shoo, that was a mouth full. There's more and actually, fabbing up the engine mounts might be the easiest part. :D



C-ya

Thanks for that info :) and I have a custom drive shaft
(very strong) but I assume I will have to change the yoke (no big deal). So since it fits against the NP205, does that mean that it has the same size output shaft and spline count?


same spline count is what i was told on www.67-72chevytrucks.com for the 4l80e and the th 400 so the ally should be the same also

same spline count is what i was told on www.67-72chevytrucks.com (http://www.67-72chevytrucks.com) for the 4l80e and the th 400 so the ally should be the same also
the 4l80e and th400 share alot of similar parts because the 4l80e is basically an electronic version of the th400 but with an overdrive planetary tacked onto the end, which is why the overall length is ~2.5 inches longer than the th400. It also shares the same spline count(32) as the th400.

The allison trans whether 5 or 6 spd, is a completely different animal. Will not bolt up, nor does it have the same spline count or shaft diameter. I have seen pics of them side by side and there is a big difference. There is a company that makes an adapter kit to mate the two together, but havent seen it in a while.

For a duramax swap on a budget, I would bolt up an nv4500 and get a np205 that will bolt up to it. Easy and still a very tough setup.

the allison is way longer than a th400, it makes the 400 look like something out of a honda civic! you do not need the gauge cluster, definitely the tcm, ecm, tcm, efilive for passlock removeal, dash harness, adapter to mount transfercase a/c your pumpkin is on the opposite side. this is will get you going.

should be i know it will fit against the np205 transfercase and is the same length as a 4l80 which if im not mistaken so the th400 is its just taller around the bellhousing which is why we need the body lift.

with a 1/2 ton you will need to mod the drive shaft though

this is not correct, the allison is longer than a the 4l80e, been there done that

you're also gonna need to think out which transfer case you want to run... the older trucks have pass. side drop front axle whereas the new stuff with the dmax has driver's side axle in the front. That can be a problem if you want to run the allison with the same xcase behind it as was in the donor truck. If you do that (use the allison with GM 261/263 transfer case) then you'll need to swap the front axle to one that is driver's side drop. Such as from a Ford. The recommended ones are the 78-79 HP D60 - same as what's recommended/used in the SFA conversions for the GMT800-900 trucks. ;)

IF you DO want to run the alli but do NOT want to use a 261/263 transfer case and swap the front axle, there are a few options:

- get an adaptor and bolt up the xcase of your choice that is pass. side drop. i.e. a GM NP205.
- Atlas makes a transfer case that will bolt up to an Allison and can be pass. or drivers drop.
- you might even be able to get a 2wd allison setup with a divorced transfer case (again, the NP205 would be real popular) that is pass. side drop.

Either way, I think you will have to put the VSS (speed sensor) on the output of the transfer case just like it is on a 261/263 so that the Allison will know how to shift correctly when in 4wd. Something else to consider if you want to keep the allison, are the controls for it. Not sure how handy you are but if you aren't real good with car elec. and custom fabrication it might not be easy to control all the features of the allison. Meaning the T/H button and Tap Shift +/- buttons are built into the gear selector in the GMT800 trucks. Unless you can take them out and mount them on your own somewhere in the cab of the old truck, you'll have to find a way to fit the steering column et al from the donor into the cab of the old truck. Don't imagine that will be the least bit easy. Fun? if you like fabbing stuff. But easy? doubt it. LOL There again, some custom stuff has been done with this stuff in other conversions so depending on your ability or $$$ available, there are options. PPE has done some cool things to incorporate those functions by means other than retrofitting the GMT800 steering column into the vehicle. i.e paddle shifters on the steering wheel like race cars, push button controls to go into P R N D M (or whatever it is on the 6-spd alli), etc.


IF you aren't hung up on running the allison, there are almost endless combinations of transmissions and transfer cases that can and have been mated up to a Dmax since they are reg. ol; GM bolt pattern. That means ZF6 (like the GMT800 trucks) manual trans., GM NV4500 5-spd manual trans., 4L80E/85E auto trans. either setup to be stand alone or full manual VB, etc. etc. and any number of transfer cases that can be bolted on to them.

Obviously, if you run a manual transmission, or some other auto besides the allison, you should NOT need the TCM or any assoc. wiring.

You will need the accelerator pedal, bracketry and associated wires also.

If you can't do your own harness modifying, PPE can do it for you. For a fee, of course. Once they are done, the wiring is a 5-wire deal from my understanding to make it run. Either their own custom tuning or EFI Live will then make it run.




Shoo, that was a mouth full. There's more and actually, fabbing up the engine mounts might be the easiest part. :D



C-ya

Now this fella knows what he is talking about because i lived through exactly all of the above. there is more details to the vss but he is on the right track.

I'm glad you all gave your input... time to think it over.

this is not correct, the allison is longer than a the 4l80e, been there done that

My 95 4L80E and 01 ALLY 1000 were within a 1/4" of each other in length when I set them side by side, both of them were 4X4's as well. The rear adapter housing though is oriented differently and the rear mount sits about 1 3/4" furthur back on the ALLY though. The VSS can go on the output of the transmission in front of the transfer case and the trans will shift, check the DURAMAX BUGGY thread as that is how his is set-up. The problem withthat set-up I see is that it will mess up your adaptives when your in 4 low, so when you go back to 4 high it will shift funky and vice versa. You could always go in and hook-up the 4 low wire, but use EFILIVE to set your transfer case ratio to 1:1 so that you wouldn't mess up your adaptives and get banging shifts. Of course though if you put the VSS in front of the T-case your speedo wil be way off and would mess up your ABS if you had it. As for tow/haul and tapshift, I can't really help you much there. I'm still working on tow/haul on mine, and my 01 doesn't have tap shift in it.

not sure what your measuring but if you take two 4x4 trannys less the transfercase and measure from the bell housing bolt face to the transfercase flange bolt face then the ally is 3.75" longer, as for your 1/4" not sure where you got this figure.


allison transmission = 29.750" flange to flange

4L80e transmission = 26" flange to flange

I just walked out and measured my 4L80E sitting in the shop and it is within an 1/8" of being 29" bellhousing to transfer case adapter face, 26" roughly if you measure it without the transfer case adapter.

I just walked out and measured my 4L80E sitting in the shop and it is within an 1/8" of being 29" bellhousing to transfer case adapter face, 26" roughly if you measure it without the transfer case adapter.


ok now i see where you get the extra inches, by adding the adapter to the 4l80e. problem is if he is going to use the ally tranny then it will require a custom adapter and op side transfercase for his front diff. this all adds inches and will require a shorter rear drive shaft. already been and done in my truck, np205 bolted to a ally

Yep custome adapter or a custom SUNCOAST rear C5 housing would do it. They can build theres to whatever transfer case you want, and it is a beefy piece(but REALLY $$$). I doubt you would have to worry about the rear housing ever breaking with the SUNCOAST part though.

autocad my own adapter and had it machined 4340, the other manufactures are way overpriced. did mine for a case of beer.

here is a link

http://www.dieselplace.com/forum/showthread.php?t=297428

Ok, so here's a few new questions:

1. if you are modifying the ECU to bypass the theft-lock and to add an idiot / SES light, why would you need the under-dash harness?

2. why would you need the pedal assembly?

the pedal assembly is needed because it's a drive by wire system (I think that's what its called anyways) where the computer gets input on yout throttle % from sensors on the pedal. Not mechanical linkages, all elec.

Under dash comp. may or may not be needed. I think you are referring to the BCM or body control module. It may be needed because some of the alli controls work through it. T/H for sure and maybe the elec. shift transfer case goes through it I *think*. Not positive on the later or any others that might go through it.

I'm pretty sure theft lock is just disabled. Not sure if any of the conversions still retain it or not. I'd say not but might be wrong. I'm pretty sure disarming it is a simple Enable/Disable function with EFI Live.



C-ya

the pedal assembly is needed because it's a drive by wire system (I think that's what its called anyways) where the computer gets input on yout throttle % from sensors on the pedal. Not mechanical linkages, all elec.

Under dash comp. may or may not be needed. I think you are referring to the BCM or body control module. It may be needed because some of the alli controls work through it. T/H for sure and maybe the elec. shift transfer case goes through it I *think*. Not positive on the later or any others that might go through it.

I'm pretty sure theft lock is just disabled. Not sure if any of the conversions still retain it or not. I'd say not but might be wrong. I'm pretty sure disarming it is a simple Enable/Disable function with EFI Live.



C-ya


Ah, that makes more sense with the drive-by-wire. I'm an old wire & linkage guy ;) Guess I'll pick one of those up. The under-dash computer & wiring, I'm guessing if I bypass those items in the PCM I won't need them (other than possibly the T/H switch). I will be towing occasionally, but the rig I'm hoping to slap this in is a 1991 GMC Suburban that is 2wd. Would only be towing to and from the trail heads, so no real 4wd needed (plus I have enough 4wd's to maintain as it is) :)

Get a throttle pedal out of a 6.5 drive by wire truck for your 91 as it will be easier to fit in. If this is a 2WD then I wouldn't worry about a BCM at all. Get EFILIVE to bypass the theft system and whatever engine tuning you may want. Then flash your TCM to an 01 or 02 OS, then set the transfer case ratio to 1:1 and hook the wire upo that would normally go to the 4X4 to tell the TCM your in low up to a toggle switch to ground. Then you have tow/haul mode the same way that ALLISON would normally do it in other applications. The factory TOW/HAUL is done through the BCM. If you want the push button transfer case though, you will need the BCM to make it work.

the 4l80e and th400 share alot of similar parts because the 4l80e is basically an electronic version of the th400 but with an overdrive planetary tacked onto the end, which is why the overall length is ~2.5 inches longer than the th400. It also shares the same spline count(32) as the th400.

The allison trans whether 5 or 6 spd, is a completely different animal. Will not bolt up, nor does it have the same spline count or shaft diameter. I have seen pics of them side by side and there is a big difference. There is a company that makes an adapter kit to mate the two together, but havent seen it in a while.

For a duramax swap on a budget, I would bolt up an nv4500 and get a np205 that will bolt up to it. Easy and still a very tough setup.

question how does gm offer the allison and 80e in the same truck is there oem adapter

well ive dug for a hour on the net and found the allison is 29 spline the input on the 205 is 32

but there is a simple swap just get a 205 from a cummins or 29 spline input shaft replacement for a dodge and swap in your 205

also to pussow are you going to sell those adapters?

http://www.makcotransmissionparts.com/NP205.html lookie for 196 bucks

and the coupler is 123 so for under 400 bucks you could do what advance and all would charger over 6 for

seems cool, keep us updated

bcm is required for t/h mode, if your going to do the np205 conversion your going to need 2ea speed sensor, one for an aftermarket speedo (autometer) and the other for final output speed.

question how does gm offer the allison and 80e in the same truck is there oem adapter


programming of the ecm, wiring changes to the hslan network, serial data, and hard wiring to the tranny. allison is different. the hardest part of my conversion was not the engine but the tranny upgrade from 4l85e to 6spd ally.

need to purchase the output gear for the np205 and coupler to match the 29spline allison male shaft. forgot to mention, will need efilive to change the low range ratio so your tranny doesn't go into limp mode. i hardwired a switch to ground for low range, when i pull the stick for low it hits a the switch which triggers the signal for the ecm so it knows to recalculate the output speed for low range. as for my adapter, it is a beautifull pce of work, never thought of marketing it. machining costs are not cheap so it would be best to put on cnc machine so many can be fabricated.

bcm is required for t/h mode, if your going to do the np205 conversion your going to need 2ea speed sensor, one for an aftermarket speedo (autometer) and the other for final output speed.

The BCM is required for tow/haul mode in factory form or if it is a 4X4. 2WD apps though can change the low range to 1:1 and hook-up a switch to ground similiar to what you did for your 4Low and have a secondary shift mode, or actually have 3 shift modes if they installed the BCM with it. I talked with an ALLISON programmer and the switch to ground for pin 10 was what he said to do for tow/haul until he found out that the GM app uses that for 4 low.

programming of the ecm, wiring changes to the hslan network, serial data, and hard wiring to the tranny. allison is different. the hardest part of my conversion was not the engine but the tranny upgrade from 4l85e to 6spd ally.

i meant do they use different input shafts on the transfer case or a adapter or a different transfer case cause the 4l85 is 32 spline and the alli is 29

i meant do they use different input shafts on the transfer case or a adapter or a different transfer case cause the 4l85 is 32 spline and the alli is 29

gm doesn't make a duramax 4x4 with 4l80e tranny, my original 91 truck was gaser and it had a 4l80e c/w np205 transfer case as original equipment.

gm doesn't make a duramax 4x4 with 4l80e tranny, my original 91 truck was gaser and it had a 4l80e c/w np205 transfer case as original equipment.


i get that thats not what im asking the 2500hd is the same truck if it is a 6.0 8.1 or 6.6. ok gm offers both the 4l85e and a1000 in the 2500hd. the a1000 is 29 spline 4l85e is 32. how does gm mount them both in the same kind of truck. are there 2 different transfer cases they use or do they change input shafts or use some type of oem adapter that us swap guys can use.

also do you have any pics of your truck id like to see a under the hood see how it looks and all

There are in fact 2 different transfer cases. The regular 261/263 that comes behind the gassers in either a 27 or 32 spline input, and then the XHD series that comes behind the 8.1L and diesel models. They look similiar from the outside, but internally they are different. There are options out there for different transfer cases, but I would say choose wisely. The 205 is a heavy SOB and even with a light tune the ALLISON tail housings can break with the stock case that weighs in around 70 pounds. Whatever route you go proper bracing will be very important to keep the tail housing from breaking.

i get that thats not what im asking the 2500hd is the same truck if it is a 6.0 8.1 or 6.6. ok gm offers both the 4l85e and a1000 in the 2500hd. the a1000 is 29 spline 4l85e is 32. how does gm mount them both in the same kind of truck. are there 2 different transfer cases they use or do they change input shafts or use some type of oem adapter that us swap guys can use.

i believe they are all np261/263 cases just use a different input. pm me and i will send a pic

The 205 is a heavy SOB and even with a light tune the ALLISON tail housings can break with the stock case that weighs in around 70 pounds. Whatever route you go proper bracing will be very important to keep the tail housing from breaking.[/quote]

i have a bracket designed but just needs to be fabricated and installed. been running without the bracket and have not experienced problems to date (6 months). will do this winter though.

i believe they are all np261/263 cases just use a different input. pm me and i will send a pic

The ones behind the 4.3L-6.0L are quite a bit different from those behind the 6.6L/8.1L combos. There is roughly a 1/4-3/8" difference in the diameter of the mainshafts as well as the dramatic difference in the size of the input shaft. The 261/263's are pretty compareable to the older 241's that GM used, but when you see them side by side you can clearly see that the 261/263XHD models like those behind the ALLISON and ZF6 are bigger and stronger in many regards. I also believe the housings are thicker with extra ribbing material in the XHD's.

you gots a pm

I need someone who knows more about the 6 speed wiring than me and my tech. We just finished an 06 avalanche 2500 with a 06 dmax and 6 speed ally. Its done everything works except the indicator lights on dash. The tech 2 is seeing it shift, tow haul etc, but NO LIGHTS on dash. HELP. The wiring scematics are vague on the neutral saftey switch to column.

Hey wood,
I think we are hyjacking a thread here but real quick, the PND indicaor is driven off the classII buss so there is a comunication problem between the TCM and the buss. I'll check my notes Monday and PM you.

although quite old, any updates on this build?

The 06 Duramax was sold off to another individual for a good price :)

gotcha. I had a '91 burb that I was going to plop one in, but realized how much work the truck needed so I sold it. One day I'll get a better platform to do a build from.