1975 K-20 rear axle & springs under 1986 1500 Suburban?

[Ravenshurst]

Not sure where this should go, it's a suspension question but not about lifts. Mod, feel free to move this if this is the wrong spot.

We blew the tranny in one of our trucks, and it makes more sense financially to replace than repair, so we are just going to cannibalize the 1975 for spare parts. The K-20 has the 14bff that I want under my 1986 GMC 1500 Suburban. Will the springs bolt up, or are we talking major surgery? I am in the "ok" class of auto mechanics, just wondering if this is something I want to tackle or pay a professional. I would rather not pay, lol.

Any advise would be greatly appreciated. Thanks.

 

[austinado16]

Can you throw a tape measure under both and see if the distance between spring mounts is the same, as well as spring to spring width?

 

[77_Jimmy]

It will bolt in. However sometime around 84 gm changed the backing plates , so the 75 axle parking brakes won't work with the setup on the burb. Some states require a working parking brake. The easiest thing to do is look for a 84-86 14bff and put that in.

 

[Ravenshurst]

Austinado, Jimmy, thanks for the input. Sorry to take so long, but I was down south, and there is no cell reception where I was. Jimmy, The '75 is what I have, so I will have to make it work. I can probably figure something out. Austinado, I feel kinda foolish not having already crawled under the truck with a tape measure, lol.

 

[bucket]

It will bolt in. The springs may or may not be longer than what you currently have (most 1/2 tons have 52" leaves and most 3/4 tons have 56" leaves), but the holes are already in the frame to move the spring hanger if needed. You will need a conversion u-joint (Precision #447) for the drive shaft or have a 1350 yoke and u-joint installed on your shaft. Depending on the 75's trans and t-case, the shaft from it MIGHT fit the Burb. Is the Burb a 4x4?

 

[Ravenshurst]

thanks Bucket. Yes the Suburban is 4x4, but the truck is not. No transfer case, so the drive shaft will probably need to be shortened. My friend tells me that I will need to rotate the diff. Is that correct?

 

[bucket]

thanks Bucket. Yes the Suburban is 4x4, but the truck is not. No transfer case, so the drive shaft will probably need to be shortened. My friend tells me that I will need to rotate the diff. Is that correct?

No, you don't need to rotate anything. You're just mixing and matching factory parts and when it goes together it will still all be in factory specs. If your '75 is 2wd, that makes it a "C20". With it being 2wd, the shock mounts might be the lower hanging design so there's a chance you might need longer shocks.

 

[Ravenshurst]

...and this morning, while I was pulling the engine, some guy just drove by, stopped, and offered me a silly amount of money for a truck with no engine. So, I won't be swapping axles soon, lol. But, when I do get axles, at least I will know how to install the rear. Thanks for all your help anyway, gentlemen.

 

[bucket]

Out of curiosity, got a pic of the truck? If I had the money, I might have offered a silly amount too. Some guys see a lot in old trucks.