The Stovebolt Site Forums The Shop Area Driveline Lubricants for rear end/transmission

I hate to be the one to start a thread on anything oil related but here goes. I have a 1949 GMC 1 ton with original 4spd and 302 and did the rear end swap. An old local mechanic stopped by and told me he always mixed 90W gear oil with equal amount STP to quiet the gear whine. He also added "some" STP to the tranny. I'm hoping to do some long distance trips with my truck and would like to reduce noise for driving pleasure. Any consensus on alternate lubricants that aren't snake oil?
I've already used rattletrap on the interior of the cab and topped that with glued on reflectix to help with noise and heat. I'm very happy overall with all the mods but since I will be draining the gear box and diff again soon I thought I'd ask.

What is the rear end swap?

Did you put in any new bearings in rear end and axles?

I don't think I would put more then just a little STP in the rear end. Rear end lube is specially designed for Hypoid gears which require extreme pressure lubes. Use a GL -5 gear lube. I don't think it will cut down on noise anyhow. I have tried different lubs to fight gear whine & none have been sucsesful.

Lube manufacturers do a great deal of research and put additives in their products based on facts, not guesswork or "old mechanics' tales". Messing with the hypoid lubricants in rear end grease would be unwise at best, and possibly a disastrous mistake. We used to use straight mineral oil without hypoid additives in Fuller Roadranger transmissions in the big rigs to avoid getting carbon deposits and early failure of synchronizer rings on the air-shifted range selector synchros. I don't think that would be a concern on a stovebolt transmission. Just use the same hypoid lube in the transmission and the rear end.

I've even seen some shade tree wrench jockeys add a couple of handfuls of sawdust to a rear end to try to quiet down gear noises- - - - -that didn't work, either!
Jerry

I replaced wheel bearings all the way around but the rear end swap was a pumpkin swap from a 1972 3/4 ton pick-up with automatic transmission. It gave me a 20% speed increase. This is covered pretty well in the one ton forum. That project was only 1/2 days work and the results were immediate and pretty dramatic. I now can cruise at 50-55 and pass at 60 if I need to (can't wait for someone slow enough that I can pass)! Overall this makes my truck pretty balanced between the power (302 with Stromberg 2 bbl), braking (one ton disc conversion in front) and handling ( rebuilt knee action shocks), and safety (55 mph). I can live with the gear whine but hoped there might be something else that makes it more enjoyable to use.

What does the 1972 manual recommend for gear oil? With this lower ratio, the noise should be less, due to lower rpms, so use what is recommend for '72 trucks and you should be fine.

This is what I plan to try in my HO52, 4.11 geared rearend.

Would already have given it a shot but have had the agony of helping my baby brother deal with his 21 year daughters death in an auto accident. Other driver crossed the center line, hit her head-on. No Chance.