Duramax / 6.2 swap

[Mike in KY]

Hello everyone. I'm new on this forum and sure the subject of this post has been discussed and cussed many times before, so please excuse the redundancy.

I have just purchased an '86 Chevy military 1-ton in excellent condition with 62,000 miles. It has the 14-bolt locker rear and Dana 60 front, but has the pitiful 6.2 and less-than-desireable chain-drive NP208 case. I currently own an '05 GMC Duramax / Allison and am extremely happy with it. So I am curious to know the feasibility of obtaining a salvage Duramax drive train to replace the 6.2 and 208 in the '86. Yea, I know many of you will probably say that it is an expensive deal, however I just cashed in my 201K (it used to be a 401K) and I am now cash strong and ready to embark on the project. Heck, I even got permission from the 'ol lady to spend the funds.

So here are the questions - Should I obtain a Duramax engine on Ebay or somewhere and try to piece the thing together, or should I simply purchase an entire wrecked truck to get all the fittings and accessories? Will the new engine & drivetrain fit into the '86 without modifications? Will the motor mounts align? What are the surprises that I will encounter? I am not a mechanic, so I will hire out this work. Are there reputable firms out there that specialize in this sort of project?

I want to convey my gratitude in advance to everyone who can help me with this project. Here's a photo of the truck -

 

[Mike in KY]

Stupid me

I apologize. I believe I have posted the above in the wrong place. Maybe the Administrator can move it for me.

 

[KEVINL]

Nice truck

I have always wanted one

 

[Kat]

moved to hard parts

 

[Mike in KY]

Thanks KAT.

 

[dmaxvaz]

As much as i like the dmax, it would be easier/cheaper to put in a 12 valve cummins in there. There are no motor mounts, you would have to fab your own for the dmax. The cummins swap parts are readily available and are cheap. Check out www.autoworldmt.com

 

[SmokeShow]

It can and has been done. There is a thread on here about this with pictures outlining the process.

PPE can make you a wiring harness to make engine wiring a minute problem no moreso than the current 6.2.

You will have to fab engine mounts/front cross member. If you keep the Allison and corrosponding allison trans n 261/263 xcase you'll need a front diff that is drivers side drop like in the older fords as opposed to the pass drop d60 currently in it. An alt to that is using a 4l80/85e or nv4500 manual behind the Dmax that opens up some xcase options that let you use the gm front d60.

IMO a complete donor would be best. Not totally necessary but advantagious IMO.

Where you at in ky?

 

[Mike in KY]

Okay, here's a follow-up question. Will the Duramax mate to a TH400? Or will the Allison mate to a NP205? I need help guys. I really want to put this project together.

 

[dmaxvaz]

okay, here's a follow-up question. Will the duramax mate to a th400? Or will the allison mate to a np205? I need help guys. I really want to put this project together.

duramax will mate to the th400, but will not work properly. The np205 will not just bolt up to the allison.

 

[SmokeShow]

The np205 would either need to be a divorced or you'd need one of the billet allison tailhousings from suncoast setup to mate up to the Np205. If you want to turn up the power of the Dmax though, the np205 will not love you if you use the power much. Outputs won't hold up.

 

[Mike in KY]

Well, what about this - Will a 4L80E mate to a Duramax? If so, would these units be compatible with each other? Will a NP205 mate to the 4L80E? Would that put the output on the correct side for the dana 60? I'm new at this guys, and really need and appreciate your help.

 

[Mike in KY]

If the NP205 is not strong enough for all this power, then what TC would be?

 

[mytmousemalibu]

Im no 4x4 expert or anything but with this being a sizeable invesment on your part, might consider somthing like a, Pro-Fab, Atlas II,

Depending on the power your after and vehicle usage, other trans options might not hold up well. You might be able to use a 2wd allison with a divorced Atlas or other?

http://www.advanceadapters.com/ <---- They make the Atlas II

 

[SmokeShow]

They make an atlas that will drop on the pass side AND bolt to a 4wd Allison just like the 261/263 in the hd trucks.

Yes, a 4l80/85 will bolt up behind a Dmax. In fact, the vans with a Dmax have the 85 behind them. And yes, im 99% sure theres adaptors available to bolt an np205 up to one. You'd probably have to either get a full manual 4l80 or a stand alone elec harness to get it to work. They won't stand up very well to a hot Dmax either according to some well respected trans builder on here. At least not in a heavy truck application.

What's your planned use of this truck?

 

[RodZZilla]

If you find a donor truck, I would use the whole tranny and xfer case. Then source a Ford D60. They had the high pinon. That will help w/driveline agnles.

 

[SmokeShow]

^ what he said.

 

[THEFERMANATOR]

It's possible, but not neccesarily feasible. I have one dropped into my 95 SUB, and it was a BIG job that I am STILL working on geting the bugs worked out of. The harness isn't that bad of a job to modify yourself if you can read wiring diagrams and make good solders. The only big hurdles I ran into with the harness was that ALLDATA and GM have some of the info incorrect and can be time consuming to work out. The 205 can be bolted up to an ALLISON, there's a guy at the place who did one(but he is having some issues with it in 4 low). Strength is a concern though with it in the output shaft, and the ATLAS has been said to not be up to the task either. Also remember that the fuel system will have to be re-plumbed front to back. The actual fitting of the engine and tranny is the easy part of this swap IMHO, the little details of this swap will drive you NUCKING FUTS though.

 

[Mike in KY]

Mitch, I'm not really wanting a "hot" Duramax, just more engine than the 6.2. A standard Duramax will be just fine. And I prefer an automatic. The truck currently has a TH400 mated behind the 6.2, with a NP208 TC. Heck, if there was some way to supercharge the 6.2, I would probably leave the train alone. But from everything I have heard and read, there's no way to improve the 6.2 performance without spending megabucks, so if I am going to spend money, I might as well go whole hog and opt for the Duramax. If you or anyone else knows a secret to super-tune the 6.2, I would like to know. If not, I am ready to go forward with the Duramax strategy. I guess my main questions would be thus - What would the ideal automatic transmission and transfer case be for the Duramax to provide correct-side output for the Dana 60 front axle?

And to answer your question regarding my planned use of the truck - I intend to use it to haul moonshine out of North Carolina (HA!).

 

[Mike in KY]

Well, I will have to say that you folks have all but talked me out of trying the swap. Unless someone can provide details for a system that will bolt in and work properly, I guess I will need to start thinking about pumping-up the 6.2.

I would still like to continue receiving your comments and opinions. I have the desire and financial means to do this project, and find it hard to believe it can't be done. I am a big fan of the Duramax, and I love that Dana 60 front axle. I just need to figure out how to connect the two parts.

 

[Big Block 88]

If you have the time and monsy this can be done. If your money is not up to par then a 12 Valve cummins would be the way to go. Alot less of a headache. I would love to put a D-Max in my old 88 but the time and money is just not there for me. So a cummins will take the place of the old gas hogg. The 6.2 will never be a power house, the sidewinder kits from Banks can wake it up, but it will still be up to par with modern diesels.