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Transplanting a Duramax into a '71 Jimmy

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texinxin

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Hi Everyone,

I'm new to this site but I've been reading on and off for a long time. What I've learned is that many of you have either seen it or done it so I here is what I could really use your advice on.

I have a '71 GMC Jimmy w/ 350/350, 2in lift and 33" MT's. I plan on going radical and putting in a 6.6L Duramax engine with a Allison-1000 5 speed tranny. I have Three questions I have to answer before I'm successful.

First: What parts do I need to make this happen?
Second: what alterations will I need to make to my vehicle to make it fit?
Third: Given the expense of buying the components am I better off buying a wrecked vehicle? How do I find one and how much should I expect to pay?

I have a few thought on the first but no idea yet on the second so any info you can provide would be helpful.

The parts I know I need:
Engine with wiring harness, ECU, sensors, and accessories such as alternator, water pump, and fuel pump. I'll also need an adapter from the tranny to the NP205(unless you have a better suggestion)

What else? Some reading I've done suggests I need the fuel tank and the instrument panel as well.

Now how do I fit it into my truck? The allison is a big tranny so I figure I'll have to cut the hump out of the cab and reshape. What about the motor mounts? The firewall?


Thanks for your input!

71 Jimmy1.JPG
 
Ok, first things first *not trying to be a d!ck*, but are you financially capable of handling this kind of project? That means do you crazy money to finish a very rare conversion like this? If yes...then I think we'll all start throwing our suggestions at you...
 
The Duramax is a really tall engine which is why the swap isn't so popular, why not a Cummins with a nv4500 or whatever auto they put behind them? Look around in the diesel forum or try a quick search. Good luck, that is a sweet looking 1st gen
 
don't get me wrong, I'd love to see a Duramax in a jimmy or Blazer in this body style, but you just need to be realistic $ wise...it's not going to be cheap. Last month's Diesel Power had a very sweet '70 shortbed with a Duramax running insane quarter mile times...might want to look for that one.
 
just do a 4bt or 6bt cummins all mechanical diesel swap. better motors and much more realistic swap. I've seen a small hand full of duramax swaps and there complex computers and wiring makes it a tough task. plus fitment issues with your k5, how ever I have seen cummins in k5s, suburbans and k30 trucks.
 
I guess I'll be the first to not piss in your cheerios - I say go for it.

Why? Cuz it'd be more unique. It certainly won't be the first custom job that costs alot of money and turns out really cool in the end. If people only did things cuz they were easy, where would we be?

Unfortunately, I have no help to offer regarding the swap - just encouragement. Oh, yeah, and SWEET TRUCK!
 
The duramax swap is going to be insanely expensive (I wouldn't be surprised if you dropped $15k w/o breaking a sweat)...

Also what is the reason for doing this swap? Is it a performance aspect or is it just so you can have a one-off truck? Reason I ask is for a small truck on 33's like yours I just don't understand...maybe if you had rocks on 50"+ military tires and you needed the torque but for your setup you could do a BUILT gas engine for MUCH less and have more power than you'll know what to do with... 512cid Caddy Engine swap... built 454... shoot you could even do a vortec big block swap for probably much less than a duramax swap...

Again not trying to be a downer but just wondering why you're doing this...there may be better options...
 
Nice Jimmy. How about some info on it and more pics? Good luckm on the swap if that is really what you want.
 
might just be easier to fit a blazer body onto a rolled truck that still has a straight frame.:thinking: i'm kidding....mostly. frame would be too long, anyway. either way, you're getting into a big project. one i'd love to see
 
I'm doing one in an '85 Chevy truck as we speak.
I think it will be a cool setup, but I just spent all day trying to make mine run. I'm hoping to use the complete wiring harness & all the new truck bells & whistles, but I am still not sure everything will fit.

You can eliminate the body wiring & use just the engine/trans wiring. You better have a lot of wiring experience as it is not for the person that has trouble with circuitry.

It gets very expensive in a hurry... plan on $10K or more before you are done. I would try to get everything: engine & trans computers, airbox, wiring etc. or the misc parts will eat up a lot of cash. I got a complete setup including dash, every wire, master cylinder, all accessories & transfer case for $6500.

Now I have to spend about $600 for custom computer reprogramming to eliminate the unnecessary codes.

If you would like to boost the output. Along with this comes the trans & converter mods to withstand the power increase for another $2-3000.

The trans is huge... almost the same size as the bellhousing. The floor will likely be an issue. I'm not sure if a bodylift will provide enough clearance on your year.

Adapters are available for the 205 for about $1500 to mate the allison.

There is a CD available on e-bay that gives a lot of engine & conversion details. Check it out.... I got one relatively cheap. It has hundreds of photos & a lot of wiring info.

If you would like to discuss this in more detail, please e-mail me your phone# & a good time to call (including time zone).
[email protected]


Lonnie
 
You really think you'll have to drop $2k-$3k on the trans to "withstand the power increase"? I think we've all seen stock allisons handle an insane amount of power in stock form and thats in a HUGE (in comparison to a standard cab k10 for instance) 2500hd or 3500 dually...

You obviously have done your h.w. and have more experience w/ this than I do but I just doubt you'll need to touch the trans...

Also... are the stock transfer cases they stuff behind the allisons all that bad? Just seems like it'd be worth it to just leave it in place compared to spending $1500 on an adapter to slap your 205 behind it...even if it doesn't have as low a gear (not like a stock 205 is all that low) you'll have so much torque I doubt it'll be an issue...
 
Around 80-100 additional HP is all the Allisons can withstand without long term clutch damage. That is still around 800ftlb torque, which is a very considerable amount.

Torque is what causes breakage & because diesels run at such a low rpm, they nearly have double the torque than the HP rating.

As for the NVG263 transfer case, they are pretty strong, but also have their own problems. I'm using one in my conversion, but it is a DS drop which will require a Ford front axle.

Lonnie
 
i see $10K being REALLLLLLLLLLL easy to hit with that swap. Expect to spend 15K IMO. I have 5500$ in to my 5.3 vortec/4l80e swap in my blazer and i picked up the motor for 500$ with harness, pcm, accys, etc. I know the wiring is EXTREMELY simple on the vortec swaps, but i doubt it is so easy on the diesels. Like the others have said, you will probably encounter problems with trans tunnel, etc. From what it looks like, the going rate on pull out motor/trans/tcase is 6K or better...and unless you get a 100% complete, unmolested truck, you will have a few parts here and there that you will have to pick up from the general...I had about 500$ in misc stuff for my motor and trans swap that i ended up having to get from GM...and that was just basic 3rd gen vortec/80e stuff. Allison and d-max parts are that much more. Even little stuff like running new exhaust will eat up a couple/few hundred dollars quick. Shafts will have to be altered, typically running 2-300$ for both to be cut/lengthened and rebalanced. Its just stupid little crap like that you may not realize at first that will come to bite you in the ass in the end.

Do more research...and when you think you have read everything you need to know, READ MORE! Buy as many manuals concerning those motors and transmissions as you can. Find all the wiring and other misc diagrams you can online for both the doner truck/motor and your current rig...and print out multiple copies AND store all the addresses. wiring should be simple in your truck, but its VERY involved in the newer trucks I thought i had a good grasp on everything going into it, but there was still SO much i had to learn and teach myself. I ended up "rushing" myself so the current result (wiring and all that) looks like poo...it works, but its just ugly.

One more thing you will need to consider...it may not take A LOT to get the motor to physically fit in there...but what about the extreme extra weight up there? Your frame will hate life without some major strengthening/reconstruction in that area.

i say go for it, but just be prepared, both with adequate knowledge and resources, and financially...also make sure work/family/other responsibilities will allow you to work on the truck adequately during the swap. Its real easy to get deep into something and forget what goes where, what does what, etc, when you haven't had to mess with it for weeks or months instead of just days...
 
shesh... almost sounds like it'd be easier to get a wrecked early year 2500hd and pull everything you need from it (since you can see how it all originally went together you can map it out before you yank it all apart) then just sell the rest of the truck when you're done... I mean if we're talking over $10k for the swap I've seen wrecked d-max trucks for around or less than $10k...


Here is an extreme example but check it out... COMPLETE 2006 1 ton extended cab dually with the duramax/allison/transfer case with only 12k miles... $18k

http://www.dealsonwheels.com/search/detail.aspx?id=001087-200708-000003


Or here is another...

2004 K2500 again... same drivetrain for only $14,900

http://www.dealsonwheels.com/search/detail.aspx?id=000001-200710-000010
 
Avery4jc said:
shesh... almost sounds like it'd be easier to get a wrecked early year 2500hd and pull everything you need from it (since you can see how it all originally went together you can map it out before you yank it all apart) then just sell the rest of the truck when you're done... I mean if we're talking over $10k for the swap I've seen wrecked d-max trucks for around or less than $10k...
Click to expand...

Thats exactly what I want to do. I'll steal the dash board and do that cool interior swap to. Maybe just maybe might steal the rear end to. There is a guy on ebay selling a CD with all the info he used to complete his swap.

http://cgi.ebay.com/ebaymotors/ws/e...STRK:MEDW:IT&viewitem=&item=200160714306&rd=1
he usually has one for sale all the time.
 
Dude, I say go for it! It won't be easy, but it's definitely doable. Take a lot of pictures to share too!
 
vortec said:
might just be easier to fit a blazer body onto a rolled truck that still has a straight frame.:thinking: i'm kidding....mostly. frame would be too long, anyway. either way, you're getting into a big project. one i'd love to see
Click to expand...

Actually in 4WOR they dropped a new JK Unlimited body onto a Dodge 3500 frame that had been shortened. They did have to remove part of the firewall and hump, as well as channel the body to clear the frames.

It's hard to say which would be easier. Would his frame properly support the weight of the Duramax?
 
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