Turning a 91 Suburban from 2WD to 4WD

How hard would it be to turn a 91 Suburban into a 4WD? As it sits, it is a stock 1500 with a 350 and a TH 700R-4 tranny. I know I'll need a new tranny and have to add a diff up front. Are there kits to do this? If so, how much would they be?

Reply to
big.drizzt
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Harder than that...there's a lot more to it. Just to point out the basics, the frame on a 4x4 is different; it's rigged for the transfer case, crossmember, etc. Suspension will need modding. And, obviously, you'll need to make sure your front axle assbly is the same ratio as the front from the

4x4 parts vehicle. Not saying it can't be done, but using a 4x4 frame to begin with is a whole lot easier.Why do you need to change out the 700R4? It would be a whole lot easier to pick up a late old body pre-92 Suburban 4x4 and use the good transmission and engine from your 2x4.
Reply to
Augustus

Yeah, found quite a bit of info after more searching. I will probably end up setting my body onto a 4x4 frame (mine is bent anyways so this kills two birds with one stone) and transferring the engine over. I still want to replace the 700R4 though as it is starting to slip a bit and this wouldn't be the first time. Also considering an auto to manual swap while I'm at it.

This is a rough idea of what I might do now that I know what would be involved.

- Swap body onto pre-92 4x4 frame (Possibly 88, seems to be the exact same frame as the 91 4x4's but might be easier to find)

- Swap over good engine

- Swap out 700R-4 for manual tranny or a rebuilt 4L80

- Install 6" - 8" lift

- 35" Mud Tires (Not sure what brand type)

Anything else you recommend? The body will be easy to swap over as this was a work vehicle. Vinyl Floormats and two bench seats, makes it nice and easy to grab a hose and wash it out.

Reply to
DJDD

I would recommend not installing a rebuilt 4L80 as this will require purchase and installation of a separate controller. Neither are cheap. The factory ECM in your existing '91 cannot run a 4L80 or 4L60 unit.. Get your

700R4 rebuilt and it will be a good reliable unit. 700R4's past the 1988 model year have had their issues fixed and are decent units. I wouldn't convert it to a manual transmission. You'll have some issues getting a TBI 350 with what is most likely factory 3.73 or max 4.10 gears to turn 35" mud tires. I owned a '94 K1500 Suburban with 350 TBI and 3.73's brand new.....it was not exactly a torque generator, even chipped and moderately tweaked with bigger throttle body and K&N.
Reply to
Augustus

I beleive this is the one case where that is not true.

Chad

Reply to
Chad Fernandez

Many of the mounting hole and bracket positions are different. The rear spring hangers are longer. Can you use a 2wd frame? Yes. Should you? The basic size and dimensions of the 2wd and 4wd frame are the same. But if you start with a 4wd frame, you'll have a whole lot less modding and work to do. This is one guy who did it (it's a '73-87 body even though it's posted on the 69-72 forums)

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Reply to
Augustus

I didn't read the whole thread, you pointed to, but the first page shows a guy with a truck and a Blazer...... not a Suburban. Normally, I'd agree with you. But this specific case is about a Suburban which, from what I've always heard do actually use the same frame between the

2wd and 4wd.
Reply to
Chad Fernandez

This is the frame spec sheet for 73-87 Chev/GMC chassis. Suburban isn't listed. But the differences are at the rear. Note the differences between ALL K series and C series for the front of the frame. In other words, they are not the same for 2WD and 4WD. You are correct that Suburban frames are different, the frame stays dropped all the way to the rear axle, but the 2WD frame and the 4WD frame are not the same. The 2WD frame does not have holes in the same position as the 4WD frame.

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Reply to
Augustus

I'm just repeating what I've always heard about the Suburban. I wouldn't consider holes a big deal on a 4x4 conversion since in most other cases you'd have to do a lot fabrication. I don't have any experience with the 70's/80's/ early 90's trucks or Suburbans, so I can't speak about frame difference, first hand. It sounds like you've at least looked, for yourself.

Chad

Reply to
Chad Fernandez

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