The Stovebolt Site Forums The Shop Area Driveline Rear diff, what years are the same?

My buddy has a 61 Chev 4wd panel and the rear end is making funny noises.

Will the rear diff from my 59 GMC 1/2 ton parts truck be the same?

We believe both at 3.90:1.

The measurement that is used to determine fit is called WMS to WMS. Wheel Mounting Surface to Wheel Mounting Surface. Measure this on both rear ends. This dimension is from one side to the other from where the wheel bolts against the drum. That will tell you the first important item. Next: the spring perches must be the same and then the shock mounts. You can cut off and weld these last two so as to modify one rear to fit. The best thing to do is get a 60-62 rear from a donor and bolt it on. I think 63-66 went to coil springs. But the 59 may work.

4x4 needs identical ratios front and back, and I believe the GMC had other than 3.90 in 59, confirm ratio first .... also might investigate if the 'funny noise' isn't just that it needs pinion bearing and resetting

Bill

I looked on the internet and some info is conflicting but the measurement is about 60"-62" on your two trucks. The width can be a little off and it will still fit and look OK. The perches have to be the same from center to center. As squeeze said, check the ratio, it is stamped on the ring gear (example 41 11) divide 11 into 41 = 3.73. If no stamp, count the teeth, don't try the rotate tire/count the revolutions bit. No good. If you take it into a shop to redo the pinion it can be expensive. You can buy rear ends for small money. Many times a rear end noise is not the rear end at all. Just changed to knarly knobby Tires, ujoints, something loose in the brakes, REAR WHEEL BEARINGS!!!!!!!! If he needs to drive it to work and it really makes too much noise, remove rear drive shaft and drive it in 4WD. Been there, done that. It may still make noise, but it may not because you have relieved the torque/load on the gear train, but of course, they are still turning, so....

OK a couple of things.

My 59 GMC is Canadian and has the same drivetrain as a Chevrolet.

We both believe our trucks to have 3.90:1.

The trucks are 1400 kms apart so I guess we will have to take measurements and pictures to compare.

His diff is making noise and with the tires off the left axle turns freely but the right axle is very stiff to turn.

Pictures, measurements and count the gears. Believing they are the same is not good enough. You mean you are running the drive train up on jack stands with the wheels off? the freely/stiff part could be posi. I said could be. Maybe you can run it and feel the axle tube/axle end to see if that area on one side is real hot compared to the other. ALSO very important: use a stethoscope if you have one or a broomstick or conduit pipe and place one end near the axle tube end and listen at the other end of the stick/pipe for noise. Listen at both sides to hear the difference. Also place the stick on the differential cover. You are lucky that it makes noise up on jackstand. Being strapped under the truck while being driven down the road and listening for noise is a nightmare! and muddy and fumes and...

Well we tore the K10 rear diff apart last night. We found one real bad axle bearing on the right side and the left wasn't great. He ordered new axle bearings and seals.

His rear diff has seen a few miles and we still may need to swap diffs.

Here is a link to a very old post. I knew someone had wrote it down for me.
https://www.stovebolt.com/ubbthread...amp;Main=9997&Number=64488#Post64488
Look for the short answer. This thread has some dates for punkin's and axle splines.
Hope it is helpfull
Cave bulll