So this is probably a really noob question... how do you check the differential oil? Would it be a good idea to change it? I got a 98 OBW with close to 200k on it. Doubt the previous owner(s) were as maintenance inclined as I am. And what kind of fluid would I fill it with? It is just ATF?

Diff oil is 75w90 gear oil, if you use ATF you'll destroy it in a heartbeat.

 

Dead center under the front differential (I assume it's the front you're asking about since the rear is pretty straight forward) there is a large drain plug. It is pretty much right between where the exhaust pipes Y together from the heads. I don't recall the size but you can figure it out. Get a new aluminum washer for it from the dealer (it's like $1) before you go draining it.

Anyway, remove the drain plug, let the oil drain out. Should only be about 1.5 - 2 quarts. Fill with 75 or 80w90 gear oil through the dipstick hole on the passenger side of the transmission. The dipstick is short and yellow. (probably dirty as hell but it's there) You'll need a transmission fluid funnel, or funnel with a long hose.

 

Dipstick has marks on it or the fluid level, anywhere in the middle is fine.

 

Pic of the dipstick location.

Thanks for the pic! Gonna go look for it later today. About the rear, should I replace the washer there as well? I haven't looked around there yet, but does it have dipstick as well? And I assume the whole thing is much like transmission fluid change, drain from below, fill through dipstick hole?

Thanks for the pic! Gonna go look for it later today. About the rear, should I replace the washer there as well? I haven't looked around there yet, but does it have dipstick as well? And I assume the whole thing is much like transmission fluid change, drain from below, fill through dipstick hole?

 

the rear has 2 plugs. a low one for draining and a higher one for filling. they can be difficult to remove because there isn't a lot of clearance for a breaker bar and or a pipe extension which will probably be needed to remove the plugs.

 

i had mine topped off at a shop once, it was leaking, and the tech used a 4 ft. bar to torque it back in. i busted several cheap tools trying to remove it the next time. i finally gave up.

 

always remove the upper fill plug first. that way you are garranteed to have oil in it even if the lower one will not come out. if you do it the other way around, you could end up with no oil in the diff and no way to fill it.

i didn't see you mention auto or manual but auto's have front diff gear oil, manual trans gear oil is shared by the trans and front diff. so auto trans has two fluids - ATF and front diff oil, manual trans only has one - gear oil.

 

find one of the owners manuals for your car on ebay or in a parts car or something, or ask in the parts wanted forum. they're quite helpful for where fluids are, what kind to replace with, and other specific info to your car.

Edited May 28, 201015 yr by grossgary

always remove the upper fill plug first. that way you are garranteed to have oil in it even if the lower one will not come out. if you do it the other way around, you could end up with no oil in the diff and no way to fill it.

 

Great advice.

 

i didn't see you mention auto or manual but auto's have front diff gear oil, manual trans gear oil is shared by the trans and front diff. so auto trans has two fluids - ATF and front diff oil, manual trans only has one - gear oil.

 

If you have an automatic, the dipstick on the driver's side is for the transmission, and the passenger side dipstick is for the differential.

That is a great advice to loosen the fill plug first... wouldn't have thought of this myself.

 

About the front diff, I just checked the dipstick, and I noticed that it doesn't sit in the hole very tight. It took me no effort to pull it up, at all. Is it supposed to be like that or am I missing something there? the o-ring was on it and and all, but it really feels like it's just sitting on top of the hole, not really plugging it.

Thats about right, mine is sitting in the hole. Not much force to remove it

The O ring may just be a little dried out (old). As long as it keeps most of the dirt out its fine. It's not gonna fall out or anything.