Duramax in K5

[lak2004]

Hello all, I have just recently started debating about what engine to swap into my 85 K5 and I am pretty set on a Duramax. I have been reading all that I can but I cant find very much trans/tcase info. I want an automatic and a good low geared tcase. Any ideas? What tranny would hold up to the hp and torque of the Duramax? This is going to be my DD and wheeling rig. It will be linked front and rear with a Dana 60 front and 14bolt full floater rear. Thanks!

[More Power]

If you want to tone down the Dmax, you could run a TH400/4L80-E. This would allow you to use your existing transfer case (or those that work for the 80's drivetrain). If you want the Allison and HD 261/263 transfer case, you could swap in a Dana 50/60 Ford or Dodge front axle, which has the pumpkin on the correct side for the new style transfer cases. :)

Jim

[lak2004]

Awesome thanks for the info! Now I just need to figure the rest of the build out!

[lak2004]

So the strongest option will be the Alison combo? Anyway to mount up say a Lomax 205 to it?

[TenBucks]

Do you have a set budget for the whole swap?

Scott

[lak2004]

Well since I am going as far as this swap I plan on going ahead with linking the front with a nice set of coilovers at the same time and doing a Dana 60 front with xover and high steer if its still possible and an ARB locker.

So with all that at once, I imagine I will spend roughly anywhere from $8000-$13000? Just depends on what all I end up with and how much I can complete myself.

I will probably have to box the frame too so that will be a little more, plus buy some more tools :D

[lak2004]

If you want to tone down the Dmax, you could run a TH400/4L80-E. This would allow you to use your existing transfer case (or those that work for the 80's drivetrain). If you want the Allison and HD 261/263 transfer case, you could swap in a Dana 50/60 Ford or Dodge front axle, which has the pumpkin on the correct side for the new style transfer cases. :)

Jim


How about shifting those tcases? Arent they both electronic? Anyway to convert them to manual? Or do you just mount the stock button inside for ease?

[More Power]

The NVG-261 is a manual-shift t-case. The NVG-263 is electric-shift.

While I haven't tried it, I'd bet the 263 could be converted.... The electric servo package bolts on over the shift selector shaft. When the servo package has been removed, it looks very much like a 261. :)

Jim

[lak2004]

Thanks a bunch for the quick response, so now after more reading here is my next question:
Is that drivetrain combo going to be too long for my frame?
I will be leaving the engine stock, so would I be better off running a 4l80e w/205 or something? THanks

[mhagie]

I don't see how it can be too long, driveshaft lengths are adjustable.
there was a Blue 85 3/4 ton a while back that was converted, posibly do a search and you might find some onfo.
If I remember corectly he had to cut the frame to clear the mainfolds, I do believe it was a straight shift.

Merle

[lak2004]

I don't see how it can be too long, driveshaft lengths are adjustable.
there was a Blue 85 3/4 ton a while back that was converted, posibly do a search and you might find some onfo.
If I remember corectly he had to cut the frame to clear the mainfolds, I do believe it was a straight shift.

Merle

I do have 6" of lift in the rear but I can move my axle back a little if I need to as well. I think the blue truck was a crew cab IIRC. I am going to get some measurements from a friend who has a couple of DMAXs

[More Power]

Thanks a bunch for the quick response, so now after more reading here is my next question:
Is that drivetrain combo going to be too long for my frame?
I will be leaving the engine stock, so would I be better off running a 4l80e w/205 or something? THanks

I doubt your wheelbase is much shorter than that of Lil Red... ;)

Jim

[lak2004]

I doubt your wheelbase is much shorter than that of Lil Red... ;)

Jim

Ahhhhhh good call! ;) Forgot I just read all about that build, thank you very much for all your help! I will continue to post questions after I think about them more thoroughly ;) .

[Lonnie P]

I'm currently doing this on a similar year pickup.

There are a lot of options.

The easiest would be the 4L80E, but I'm not sure how the durability is with that trans if you really wheel it hard. They are strong & I believe the vans used this setup. Your driveline/axles could remain almost the same as it is now.

Swapping the Allison trans & xfer case will be about 7" longer from my initial measurements. I'm still in the mock-up stages. There will be floor to trans issues.

[lak2004]

Im not gonna leave the stock 10 bolt axles cuz they are not HD enough for the wheeling I want to continue doing :D . I planned on just making a custom tranny tunnel anyway, possibly incorporating a center console into it depending on how tall it will need to be. Plus I would like to clock the tcase up so I can have a nice flat belly to slide over rocks with. :cool: