Discussion in 'Differential & Driveline' started by Iowan, Sep 13, 2017.
I crawled all over the axle and have no idea what I found
Can this be upside down? I found the GM21 too which I've never heard of. Thanks guys!
That looks like a casting number for the rear end itself. Now Im not a rear guru, but, the rear ends used to be tagged on one of the cover bolts, but it being 37 years old, thats not there. I think the only way you will be able to know is to count the ring and pinion gear teeth.
The ratio should be stamped on the edge of the ring gear. If you're going to open it to count teeth, I'd look for that instead.
see.... I knew someone would know more than I do.
Calvin, is it a posi rear end or an open rear end? If posi, put truck
In neutral gear, block front wheels. Then jack up truck so both back wheels are off ground. Now make chalk mark on either tire
Facing ground. Also make mark on driveshaft facing ground.
Rotate back wheel one complete revolution while counting
Driveshaft revs. Example: if it's a little over 3 revs it's a 3:08 .
If it's less maybe a 2:73 etc. if open rear end drop Opposite wheel to ground , then do same wheel/driveshaft procedure. Done.
Thanks and I have one more picture too
It took 1 and then some
Not much just about maybe an 3/8 more of a turn
You have to double the amt of turns. I may have forgotten
Yo mention that. It looks like a 2:73 gear.
Thanks @Jerry phillion
Haha, Im glad this got solved b/c Im about to count mine. I was wondering if Iowan had counted correctly. Hahaha.
I wondered too, I even did both sides but that's also how you find out if you have a posi, I do not.
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