gears fluids

[viper1]

what would be the recomended time to change the trans and rear end fluids with 3.73 gears?

[daveg]

Depends if your tracking vs. not tracking.

[viper1]

not tracking, really babying it

[daveg]

If your not putting on tons of miles, every 2 to 3 years. Don't forget the additive in the rear!

[viper1]

thx cuz

[C.J]

What year Viper?

How do you like the 3.73 setup?

[Tom, F&L GoR]

Transmission and gear fluids are not exposed to combustion gases like engine oils are, so the chemical stress from exhaust byproducts (acidic) is much lower. The external attacks come mostly from water into the vent or condensation. Water is unfortunately pretty good at binding with performance additives and keeping them from doing their job. Transmission and gear fluids have durable viscosity control additives, again unlike engine oils. So for moderate use the change interval can be quite long - in fact most passenger cars these are likely to be fill-for-life.

The differential and transmission have helical or hypoid gears so the tooth face is ideally rolling contact, but in reality is it "smear." The additives are therefore very tenacious and work in conjunction with the metallurgy. This is why you should not put gear oil additives (or any of the circus show miracle additives) into an engine - the additive technology is so aggressive it will corrode engine parts. For the same reason, do not put gear oil into the transmission - the aggressive gear oil additives will corrode the "yellow metals" like bronze bushings or synchronizers. Manual transmission fluids are usually GL-4 with a milder additive system, gear oils are GL-5 with a more aggressive system. Yes, there are GL-4/GL-5 fluids and those formulations have found a middle ground. Using automatic transmission fluid is also recommended in manuals and the lower viscosity will make it easier to shift, run smoother when cold, better fuel economy, and probably rattle in neutral more.

You may think when you do run hard and smell the sulfur odor that you've used up the fluid. This is not really true, what it means is that you've activated the sulfur-containing chemistry and it's doing it's job. Everything considered, it's hard to know when to change these fluids, but a 50K mile interval for a car with minimal track time would be reasonable. Keep it full, keep it dry and use full synthetic, top quality transmission or gear oil.