1978 suburban rear end

stanaslos · May 12, 2019

I have a 1978 suburban rwd 454 with a 12 bolt 3.07 rear end with a locking differential. The rear end blew up and I'm looking to get a new one, what year rear ends can I swap in?

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Darksky · May 13, 2019

IIRC all the dimensions from that era trucks are the same, as far as spring saddles and shock mounts go. Most any of them will “fit”.

But that’s where you’ve got to make a few decisions. Junkyards are loaded with rear ends that will work. A big block suburban could merit a 2500 series rear end. That may get you better gearing and ensure a locking diff. A fourteen bolt rear end is also a possibility. Going to much heavier rear diffs can mean brake changes as well. If you go up a lot, you may need to swap out the metering valve below the master cylinder, if not the master cylinder and power assist.

it will definitely be cheaper to buy a junkyard diff than to have yours rebuilt, but it’s more complex. I would get an estimate to rebuild an existing one, just for reference. You might consider trying to get an entire parts truck, if you’re going to be swapping things around. You can guess the rear end gear ratios by spinning and counting (you tube that, it’s been too many years for me to recall off the top of my head), if you don’t want to remove the cover at the yard and inspect it. If you change gear ratios, fixing the speedo is literally a little plastic gear swap at the back of the cluster. Heavier rear diffs may mean a different U joint size as well. A heavier diff might come with a sway bar as well. On that Suburban a big rear sway bar might be a welcome addition.

That era truck is so cool. I had a 1980 single cab shortbed stepside with 10 inches of lift 40 inch Gumbo Mudders on 15 x10 chromed steelies. a top loader granny + 123 transmission with a ridiculously heavily springed pressure plate on the heaviest flywheel we could find. We built a .030 over 4bolt main 350 with a 400 crank, Chevy black rods and 10.5-1 pistons. Double hump fuelie heads with 63 cc chambers, worked over to accommodate 202 valves and a three angle valve job with huge double springs mated to a big ole loped hydraulic cam. A single plane aluminum intake and a Holley 650 double pumper carburetor that had all the internals polished and or swapped out.

a set of Doug Thorley headers and dual 2.5 inch exhaust with an H pipe crossover. That ruck was a monster, a rolling death trap and I loved it more than life itself.

Edited May 13, 2019 by Darksky