I have a 69 3/4 ton chevy. the differential is Gm ho72 . I jacked it up to check the gear ratio. because the engine is rev high (no tach) on the highway. I turned the driver side rear wheel about 8-9 times for the drive shaft to turn once. the other wheel was turning the opposite direction.what is wrong?the calls i maded said no parts availibe for gm h072 and it only came with 4.11 and 4.56? what is the easy swap for the 3/4 ton differential.I only haul, REARLY tow , would like to go to 3.42.
Yes it is a HO52 produced by Eaton not GM. I have the same in my 64 Chevy C20 3 Door Crew Cab truck.I too haul but not tow. The ratio is like 5.42. No ring and pinion parts available for this bullit proof rear end for many years. However you can swap out using a later model GM 12 bolt rearend but will have to cut off the mounts, weld new spring seats and so on. Not too bad if ya can find a rear end with a 3.73 or better. On my last 64 C10, I swapped out the 4:11 rearend for full rearend out of a 67 chevy with 3.07. It kept my stroked SB400 revin down the highway at bout 28k.In order to the rpm down on my C20 I had to run a taller tire to keep rpms down to bout 38k @ 65-70 mph. I'm still killing my motor so I plan a 7004r tranny and 12 bolt swap rearend soon. Good Luck on your swap!!
CORRECTION: the H052 i have is running 4:56... there are no part avail for the 52 or 72.
I have a 3/4 ton rearend in my 95 GMC extended cab that I'm taking out to change to dually rearend. It has a 3.73 gear in it. It's for sale if you're interested. Reasonable! I can be reached at 1-330-549-5134. If I don't pick up, leave your name and number and I'll call you back
Thanks but i picked up 69-70 rearend recently. However I am still hunting for a 60-66 rearend in SoCal if possible.