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Old 10-09-2017, 12:42 PM   #1
72kool
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New 4x4 conversion questions

I have gotten alot of good info from this forum but need help still.
Every year around this time I get the itch to have my truck 4x4 so I could is it more. It's a 1972 GMC C20.

Ideally I would find a 67-72 frame and swap, but I can't find any.

So I'm trying to find a complete plan on the best way to do a conversion. It has coil rear springs currently. Can I keep those? What is the best donor vehicle to get every part from that I need to swap? What is the best transfer case and front axle to use? ( I can't afford a d60 around here)
Aside from changing cross members, and installing spring hangers, any other frame modifications needed?

I have found lots of info on this subject in this forum. Seen it done numerous different ways and different parts . Looking to find the best,most proven plan to accomplish my goal. Thanks alot!
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Old 10-09-2017, 03:15 PM   #2
jjzepplin
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Re: New 4x4 conversion questions

I would get the same or close to year of your truck but 4x4. A doner is the only way to go.
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Old 10-09-2017, 03:33 PM   #3
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Re: New 4x4 conversion questions

Try to find a '71 or '72 rusted out 3/4 ton 4x4 with a bad motor for cheap, it will have the axles, spring hangers, tranny/t-case, cross members, steering parts and drivelines you will need. If you're looking at a '71 make sure it has the front disc brakes. These years will have the 205 t-case which is preferred. Buying the complete truck will ensure you get matching gear ratios in the axles too, unless it was pieced together...
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Old 10-09-2017, 03:45 PM   #4
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Re: New 4x4 conversion questions

I know you said you can't find a frame, but if you really love your truck but want 4X4 that's going to be the best route. Maybe look for a complete truck with a bad body. Piecing it together is going to be a pain and could end up being far more expensive.
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Old 10-09-2017, 06:16 PM   #5
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Re: New 4x4 conversion questions

There was a complete rolling frame in the trucks for sale section about 2 months ago. Your body and engine looked to be all you would need. Back to converting your frame it can be done, but by time you round up and buy everything you need you will be money and time ahead to find a donor.
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Old 10-09-2017, 09:22 PM   #6
72kool
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Re: New 4x4 conversion questions

Would something like this work, and just swap everything to my frame and then buy the correct cross members needed ?
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Old 10-09-2017, 09:37 PM   #7
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Re: New 4x4 conversion questions

The front diff and springs should bolt in as will the engine crossmember most likely.
The frame width is the same at ~32" but the rear spring perches were wider, and I think the WMS is a bit more. The WMS isn't much of an issue, but you'd need to remove your frame spring perches and mount the square's perches. Most people just bolt new ones on, and that's going to get dangerous when the springs fall off. Also the shocks are staggered on squares so you'll beed to move one frame shock mount at least.
Finally, it looks the the trans crossmember, trans, TC and driveshafts are all missing.

The NP205 is the big boy in stock GM transfer cases, there's also the NP208 and the NP241 is slight improvement over the 208.
Then there's the trans question. Since it bolts to the TC, its a good idea to buy as a pair bolted together. Don't beat on it in low range with an automatic in drive. Its easy to burn them up. You can get a TH350, 700R4, TH400 or 4L60 in automatics. In a manual SM465 or NV4500 are your best bets, but then you need clutch parts, which is a whole discussion.

You also convert to K10 from C20 with that setup.

Last edited by franken; 10-09-2017 at 09:50 PM.
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Old 10-09-2017, 11:08 PM   #8
KSCHEVYUP
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Re: New 4x4 conversion questions

I have 1972 4x4 frame in Trucks For Sale section and 200 miles from you.
Ron
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