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Old 03-13-2011, 07:46 PM   #1
Duramax605
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Lightbulb 1971-1972 2wd to 4wd Conversion

I am looking to convert a 1971 longhorn to 4wd. Now i know most people will say to switch out the frame for a 4x4 frame but cant do that. Chevy NEVER made a 4x4 longhorn from the factory. (Actually called GM and cost me $75 for them to research all vins in that year). How difficult is this and what will i need other than the obvious 4x4 parts (transfer case, i have np205 already bolted to a np203 drive, new transmission, front leaves). This will be my first project and i'm already working on it as you can see with the transfer case. I also have a motor which should feel at home in the truck (motor that came out was a 400 sbc) I have a 406 to go in with dual predator carbs and about 3000 into the bottom end. Any help would be greatly appreciated thanks in advance guys!!! CHEVY POWER
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Old 03-14-2011, 10:17 AM   #2
YBNORML
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Re: 1971-1972 2wd to 4wd Conversion

Hopefully one of the mods will move this over to the 4x4 section for you. Lots of info over there for this kinda swap.
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Old 03-17-2011, 10:27 PM   #3
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Re: 1971-1972 2wd to 4wd Conversion

there's one being built... look in the 4x4 build section..

find a donor truck to steal parts (axles, crossmembers, spring hanger etc..) off of
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Old 03-22-2011, 09:39 AM   #4
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Re: 1971-1972 2wd to 4wd Conversion

Dieselwrencher is building one ask him
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Old 03-22-2011, 09:52 AM   #5
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Re: 1971-1972 2wd to 4wd Conversion

I bought an 85 blazer for $500, and took it apart. Most of the parts "almost" bolt right in. I used everything but the 2 frame rails, and 1 crossmember. You will HATE rivets when you are done! Just bolt it back together with a bunch of 7/16" grade 8 bolts. The biggest PITA is smashing the 2wd E-brake cable pockets, where the front shackles mount.

Do a search for "Legacy build", that is my build (just a longbed, not a longhorn). Any questions, just ask, I'll try to answer, possibly with pictures.

Last edited by Dunenutt; 03-22-2011 at 09:53 AM.
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Old 03-23-2011, 12:18 PM   #6
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Re: 1971-1972 2wd to 4wd Conversion

The Longhorn already has 2 1/2" rear springs which helps. Not sure if all the brackets are same height as the 4x4 ones, but the other 2x4 trucks have 2 1/4" rears which make lift springs almost impossible for the back. The Longhorn frame is the same 40" width as the 4x4 trucks and not the 42.5" of the 2x4 trucks.

In the front you should be able to use spring mounts off a 4x4, just cut the rivets, and bolt onto your frame. I would tack weld the nuts to the bolts after torquing them down to act more like rivets. You will need the crossmember and braces from a 4x4 as well since the motor is mounted significantly further back in order to have a reasonable length and angle to the front driveshaft.

Sometime in the future I'll peer at my parts Longhorn frame and make sure all of the holes are already in it, but if not, they could be drilled pretty easily. Rear shackle hanger shouldn't be that much work.

A donor 4x4 truck seems the best (read fastest and most economical way) to do this. This would give you rear spring mounts as well if it turns out the 2x4 Longhorn front hangers are different than the 4x4 longbed hangers.
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Last edited by Mike C; 03-23-2011 at 12:23 PM. Reason: Added frame rail info
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Old 03-23-2011, 12:22 PM   #7
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Re: 1971-1972 2wd to 4wd Conversion

Quote:
Originally Posted by Dunenutt View Post
You will HATE rivets when you are done! Just bolt it back together with a bunch of 7/16" grade 8 bolts. The biggest PITA is smashing the 2wd E-brake cable pockets, where the front shackles mount.
LOL, Plasma Cutter. I will NOT grind another rivet. This will also make eliminating the parking brake cable brackets pretty straightforward.
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85 FJ1100 & 01 XR400
86 Kawasaki X2 & 89 SX650 w/PJS cylinder and dual carbs
02 GMC 2500HD 4x4 Duramax
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