Anyone install a 1974? leaf spring rear end in their 1967 GMC/Chevy

[sduckworth13]

I bought a 1974? Chevy 1/2 ton truck suspension with 5 lug, front disc and rear drums , actually I believe the correct year is a 1976 Chevy 1/2 ton. I am planning on swapping the rear end in my 1967 GMC 3/4 that has a 14 bolt with 8 lugs, drum brakes and leaf springs on it and installing the later year 12 bolt, 5 lug and it has the 3.40 ratio rear end. Has anyone done this swap before. I just had the 1974 suspension sandblasted and I believe I'm going to need to get the perches moved in 3/4 of a inch so I'm waiting to paint it. I'm using the leaf springs from my 1967 3/4 ton for now or will I want to change them too because I'm doing a 4/6 drop. I read that the 3.40 ratio 12 bolt was the first year for the 3.40 ratio rear end in Chevy trucks. I'm wondering if someone has some pointers on the swap.

[a.c.ward]

if they are both leaf spring, it should be a direct swap. I did a swap on a 72 frame with a 84 rear differential, bolted directly in. By the way, if you want to drop the rear stance, you can do a differential over axle while you have it apart. the parts will cost about $75 or so from just about every suspension place. I did mine on the cheap, got some trailer axle locator pads from tractor supply for $14, ground the size up to the size of the differential, new U bolts from O Reiley's for $10, mocked up the perch to differential, bolted the whole affair together, set pinion angle to 4 degrees (it just happened to be 4 degrees, same as it was before) then welded the perches to the differnential, and gained about a 4 inch drop for $25 bucks or so. The only thing that has to be addressed is the shock location. The "newer" differential has differnet shock mount points. I cut off the "old" olds from the 72 rear, the "new" ones from the 82 rear, and mocked them at the same time. Welded everything up, and good to go. This set up has been in my LWB 72 GMC "junk" truck for about 8 years with no issues, other than when loaded with 2000 pounds of gravel... cut 1.5 coils off the front, and she sits level......

post some pics of you set up when finished... I am currently in Afghanistan, and dont have any pics of mine.

Thanks

[sduckworth13]

Thanks lot, I am glad you told me that about the rear end perches matching up with no mods. I am doing a 4/6 drop and using the flip kit on rear end. I will post my picture as soon as I get it all bolted up.
Thanks for the help

[N2TRUX]

Originally Posted by a.c.ward

........ I am currently in Afghanistan....

Thank you for the very informative answer. More importantly a BIG thank you for your service to our country....

[sduckworth13]

I got my rearend installed along with flip kit installed. I haven't had the shock mounts welded on yet though. I'm definitely glad to have all the help I get from you guys and other board members.

[mcm1209]

Bumping this for people looking!
This answered my quiestion

[Whiteboy]

So it was a direct bolt in before you did the axle flip? I just blew out the rear end of my 72 1/2 ton gmc on wednesday morning on my way to work and from what I have found so far its not the origional rear end.. so 73-87? Should bolt right in correct??

[sduckworth13]

Yes, it should as long as both are leaf spring rearends.

[Whiteboy]

Thank you for the swift reply!!! That info helps alot!! Truck looks good man!!!

[sduckworth13]

Thank you