airborne1942

I have a 1970 Rallye 350, factory 4spd, with a anti -spin, 391 gear rear end. I drove it about 30 miles the other day and the rear end was acting funny, like it was low on oil, later I checked the oil level and it was full, its been about 14 years since I changed the rear end oil, so I went ahead and changed it, I put the correct 85-90 weight gear oil and the posi additive and filled it all the way up to the filler plug, I finished it up and drove it to see how it does, and it still was hot enough you can't hold your hand on the rear end for very long. the rear end is the original type O. I don't know what is wrong if any thing is wrong. when I drive it I get it up to around 65-70 mph. any help would be greatly appreciated. thank you! Brian

monzaz

Well depends on where you are in the USA / World... with climate. Hotter climate will tax the rear and other components into running hotter. I would say after that many miles the rear should be running fairly cool IF things are in goo shape.
I would have to say you need to go in to the and have a look see. Check your backlash for being too tight .005 and tighter... remember you need to clean the gear faces your checking completely from oil .

Questions - are there any unusual noises that started whining, whirling etc?

Check your axle bearings for drag - may cause the posi unit clutches to excessively work and will create more heat. Jack up rear off the ground and just spin the rear in neutral and see how easy it is to spin...should be pretty darn easy with that many miles on the rear.

Lastly...you may just be overreacting and the heat range could be normal if you have never felt the diff cover before ...it will be as hot as a oil pan after hitting the freeway for good 30 40 minutes.

Jim
J D

airborne1942

I jacked the car up and put it in neutral, the drivers side tire spins reasonably free with the yoke turning, but only the drivers side tire turns. the passenger side spins both back wheels and the yoke but is a little stiffer.

Koda

I think your limited slip has issues and is probably hating life on corners.

monzaz

yES IF YOUhave limited slip / posi it sure appears to be having issues. UNLESS you have a true trac posi which that wheel spin is normal for the worm gear unit. '



Jim