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Installing '91 Suburban Drivetrain into '71 Blazer

clay1937

clay1937

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American Fork, UT
We have a '91 Suburban that we've been driving for the last 4 years, that is rusting badly, but runs beautifully, so I'm interested in moving the engine (small block 350), and transmission (700R4), and if need be, the transfer case, over to our '71 Blazer that currently has the stock 350/350. It would be nice to have TBI and an overdrive gear for the freeway, in the old Blazer. I never offroad the Blazer, so the 700R4 hold up just fine (plus it's a rebuilt Jasper transmission).

I've done engine and tranny swaps in cars before, but never with a 4x4. I've read several postings on this topic on this website, but am still fuzzy on some things.

I know I'll need to move over the computer and wiring harness for the TBI, and have the Suburban driveline shortened, but...

1. Do I need to move the '91 Suburban transfer case to the '71 Blazer? Unfortunately, I don't know much of anything about transfer cases
2. Will the '91 700R4 tranmission and transfer case crossmember bolt directly to the '71? Or will the '91 transmission and transfer case bolt directly to the '71's crossmember? If not, is there someone out there that makes the crossmember I will need?
3. Will adapters be needed?
4. Will it be a problem to try to move everything over as a single unit? For example, if I pull the radiator supports out first. I assume that this would only work for the engine/transmission, and that I'd probably have to unblolt the transfer case before trying this. Right?
5. What about hooking the transmission up to the steering column shift lever linkage?
6. What about speedometer cabling?

The only other thing that comes to mind is cooling lines, but that should be easy to adapt.

Any suggestions, articles, links, etc., will be greatly appreciated.

Thanks!

Clay
 
clay1937 said:
1. Do I need to move the '91 Suburban transfer case to the '71 Blazer?

you dont' HAVE to, but it'd probably be easier and cheaper because you could you use the same d-shafts...as well as not having to get a spacer to run the 700R4 to the 205...also you could also probably use the same x-members from the '91.

2. Will the '91 700R4 tranmission and transfer case crossmember bolt directly to the '71? Or will the '91 transmission and transfer case bolt directly to the '71's crossmember? If not, is there someone out there that makes the crossmember I will need?

not sure

3. Will adapters be needed?

see question 1...unless you decide to run the 700r4 to the 205, then yes...

4. Will it be a problem to try to move everything over as a single unit? For example, if I pull the radiator supports out first. I assume that this would only work for the engine/transmission, and that I'd probably have to unblolt the transfer case before trying this. Right?
5. What about hooking the transmission up to the steering column shift lever linkage?
6. What about speedometer cabling?
Click to expand...

4-6 not sure on...so maybe some of the real gurus can answer these :D
 
You can use the 241 from the 'burb if you want but I would get a spacer and run your existing 205.

If you use the 205 you can reuse the stock adapter and will be able to reuse your crossmember, you will have to move the crossmember back 2-3 inches though.

No adapters needed, just a spacer if you want to use the 205, or a shorter output shaft for the 700r4.

It's easiest to remove and install motor/trans/t-case in one chunk.

Shift linkage will bolt right up with minor tweaking.

The 241 uses a speed sensor doesn't use a speedo gear and isn't the best choice for your stock speedometer unless you change to a slip yoke eliminator with speedo gear provisions. If you use the 205 you'll likely need a longer speedo cable.

This is a straight forward swap. I have the same setup in my Blazer and can help with all the little gremlins that will creep up.
 
Sounds good.

Where would I get the needed spacer for the '71's transfer case?

What's the easiest way to move the crossmember back the needed 2"-3"?

With moving things back, how does this affect the 4x4 shifter?

Thanks!

Clay
 
As far as the wiring harness goes. Does everything including the fuse-box need to be moved over?

Since you live in A.F., I wonder if I could maybe come and see what you did sometime.

Thanks!

Clay
 
The Computer harness is pretty much a stand alone deal. Unhook everything from the motor and trans, unbolt the computer from behind the glove box, unplug wiring from computer, unplug 8 pin connector that's kinda by the computer, pull the harness through the firewall. Then unbolt the bulkhead connector on the driver's side, unplug any small connectors and joila you're done. It shouldn't take more than a half hour or so to do. I can usually get a harness out of one at the wrecking yard in about 15 minutes.

You'll also need the ALDL form under the dash, just unbolt and cut the wires as far up as you can. It's easiest to reuse the 'burb fuel lines as well, make sure you leave about a foot of steel on the frame side.


You're more than welcome to come over whenever you want, I work out of the house so I'm almost always here.

Let me know if you have any questions on any of this stuff. I can modify the harness so you only have to splice 4 or 5 wires which will save a lot of time and frustration.
 
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