Gear Oil and Backlash Question

[MGD72Monte]

Any recommendations for Gear Oil brand and specs for a stock 2.73 used gear set. The owner's manual says GL5 - SAE 80. Also, what is the backlash I should be looking for? This is an 8.2" open, used gears with new bearings. The specs I found say 0.006" - 0.0010". It had just under 0.0011" before disassembly. Am I better on the low end of the range or doesn't matter?

 

Thanks

[footballubet]

I always try to go with a popular name brand. You could actually go with synthetic with no problem. Backlash between 0.006 - 0.011. No difference if it's on the high or low side. Take your readings at 8 points around the ring gear. You want to be within 0.002 of the highest and lowest readings.

[FASTSS454]

I would shoot for a middle of the spec total backlash. Pinion depth is important too so make sure to check the contact pattern before calling everything good.

[geartech]

Yeah, as long as its in the range, even .012 or a little more is ok if its a used gearset. If you want to get exact about it, drag racers will generally go tighter, even .004, as they are only going 1/4 mile at a time, and want maximum gear contact. But then something like a one-way moving van should be at the looser end of the scale for the most gear oil between the gears, as they get very hot for a long time. .011 is perfect for what you are doing, or what I imagine anyway (some highway). Something set up too tight and driven on the highway won't last. Ideally, since you are using a used gearset, I would go for what it had (within a thousandth or two) when you took it apart (assuming no major problems when you measured that) so that its set up into the same pattern. But that's getting picky really...as long as its in the range.

For what its worth, the gearsets I've re-used in the same housing like that, generally don't require any shim changes from what you took out. Not always, but most of the time.

 

For the brand, I usually look for valvoline, but it really doesn't matter. 80W90 is the good ol' normal gear oil. 75W90 is synthetic, would also work. 75W140 is synthetic too but isn't necessary unless its a truck with some weight involved or towing.

[MGD72Monte]

Great info, thanks for the quick and detailed responses guys, more questions to come. Mike, I am hoping as you said that since it is the same gear set, the same shims will work.