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What weight of gear oil should i use in my 3.73s after my break in period? I'll be driving 65 fairly often and don't want it to get too hot. It doesn't get hot at all right now though, I have a T/A Performance diff cover to try and dissipate all the heat it can. I still have about 200-300 miles until I feel safe doing anything other than cruising around for a bit then stopping to let it cool off. Its starting to get cold here in Kansas so hopefully that will help keep it cool
Why so slow? I hope not TOO often? I just HATE IT when people do that in front of me, except of course in school zones. At such low speeds, very little stress is applied to anything in the drive train, beyond the weight of the car and the mere fact of rolling.
I live in a minor city (2 or 2½ million people; quite small and quaint really) and people do that down the 1½ lane wide street in front of my house. They go AT LEAST 85 or 90 on the freeway; gotta be careful ya know, can't get too carried away, it's curvy and hilly and there's entrance & exit ramps all over the place, not to mention Grandma white-knuckling it down the middle lane in her minivan at whatever laughable speed limit they post. Which about the only vehicles that go THAT slow are 18-wheelers when it's icy. Good thing I don't live out West or on the Great Plains like you, I'd get RUN OVER if I was doing only 65 on just about any public road.
Seriously though, Mobil 75W-90. Then, if you have a clutch-type posi, a unit of the GM "whale c**" additive before the lube. It'll be fine. If you have a 9-bolt, it's got cast-iron clutches and the additive has no effect; or, if you have a stock (Auburn) posi, it's a total POS and doesn't really do anything anyway because it's a POS and has already failed and wore out, and it doesn't matter what you put in it. Or, if you have a Torsen or True-Track, it's all gears (no clutches at all of any kind), and doesn't need the additive either. Or, if you have a Gov-Bomb aka Grenade-Lock, it won't matter what you put in it, it'll EXPLODE SPECTACULARLY when you least expect it, and hopefully the red-hot shrapnel it produces when it does, won't penetrate all the way through the diff cover AND the gas tank and make your car explode. But if you have a REAL ACTUAL posi with composition clutches, such as an Eaton or Yukon, the additive will help it work smoothly without chattering or groaning or wheel-hopping around sharp turns or any of the rest of that.
