Rear diff fluid

[MN6WS6]

What weight is ok to run in the rearends in our cars? Mine is a 3.42 limited slip, 1996 WS6. I'm going to be taking the car on vacation and will be pulling a trailer with a motorcycle, so I was thinking of converting to 75/140, but wanted to get you guys' input on it first. I think stock is 75/90 but not 100% sure...

[96FirebirdFormula]

What weight is ok to run in the rearends in our cars? Mine is a 3.42 limited slip, 1996 WS6. I'm going to be taking the car on vacation and will be pulling a trailer with a motorcycle, so I was thinking of converting to 75/140, but wanted to get you guys' input on it first. I think stock is 75/90 but not 100% sure...

Pulling Trailer with F-body?? eww

[MN6WS6]

I've had a trailer hitch on it since I bought the car, and I've pulled with it before, it doesn't hurt anything as long as you keep the weight under 1,000 pounds.

Anyway, it's time to change out the diff fluid so that's why I'm wondering if you can step up to 75w140 and not hurt anything.

[BrdWAtti2d]

The owners manual on my 97 says 80w90 with 4 oz. of the Limited Slip Additive for stock. No mention of changing for towing other than you should do it more often if you tow frequently.

[MN6WS6]

Thanks. I got the additive today and we have 80-90 GL5 here in the shop in bulk Mobil, so that's what I'll be going with.

[BrdWAtti2d]

If you could let me know how much it takes that would be great. I want to do mine this weekend and I don't want to get caught with my pants down, so to speak, once I drain it. (Nothing worse than having to run out to the parts store once you're in the middle of doing something). The owners manual or haynes book doesn't say how much it holds other than "fill it up", well duh, thanks I was going to run it half full, lol.

[MN6WS6]

It's 1.5-1.7 quarts plus the little bottle of GM additive. 2 quarts will leave you plenty of extra, but you will need to buy that hose add-on for filling it up, as it is near impossible to fill it with a funnel or anything of that nature. There's just no room. The good thing for me is that our bulk setup has a pump on the barrel, so you just roll it up and pump away until it spills out. Nice and simple.

[BrdWAtti2d]

Cool, thanks for the info. Lol, why should this be easy, like anything on these cars is? I found that a large vacuum tube slipped over the spout on the lube bottles works well for pretty much any car. Seems like I always have some sitting around. You just have to make sure to hold it onto the bottle or else you end up with a face full of lube like I did once. My brother got a good laugh at my expense.

[Injuneer]

A lot of this info is in the Owner's Manual. If you don't have one, Shoebox has the links to the GM website manuals:

http://shbox.com/pdf/manuals.html