slow_90firebird

Well, yesterday I finally got around to changing my rear diff oil. And guess what ... the pinion seal has not leaked at all today in my driveway!!

I am so happy that this worked. I remembered that when I was still at college, and it started leaking really bad, I bought the last bottle of gear oil walmart had (85w140) and squirted over 1/2 of it in right in the parking lot with the back wheels on curb. After that, it didnt leak for a month, and then started leaving spots under the car again. I kept filling it up with 75w90 after that, and it never stopped leaking again.

Yesterday, I actually got a new gasket so I could remove the cover. I bought 2 quarts of 85w140 again instead of the 90w ****. When I took off the cover, it came out really watery and like graphite colored. Everything inside had a black coating of sludge, except were there was contact on the teeth. I tried to wipe as much out as I could reach, which wasnt alot. Also, the magnet in the cover had about 1/4" of shavings all around. I wiped most of those off, and cleaned the cover real good. Cleaned the old gasket off, and coated the new one with some blue RTV to keep it in place while I put the bolts back on.

Filled it up with all the 140w I bought. On the 2nd quart, it got a little low so I had to add a little extra 90w into it to keep squirting, and I overfilled it just a tad.

So far so good. I made 4 trips on the highway today about 25miles each, up to 90mph once, with no problems so I think I am all set untill I can afford to build a new rear end for the car!

samiam91RS

well thats good! i got a better rear end and im looking to do this as well. as far an diff and trans i dont know much at all. what kind of oil are you supposed to use? and is it specific gear oil? i was hoping to just take off the cover and get a new gasket from kragen to put on and change the oil out. do you just pour it in and slap the cover back on?

red92firebird

why you guy use gasket for the cover ? why not just grey rtv ?

slow_90firebird

you could probably get away with RTV, but the gasket is only like 3 bucks so it really doesent matter.

92RS702

Using a gasket with just a bit of RTV to hold it in place seems to seal better IMO.

punkdude908

didn't think it was safe to use 85W140 on the stock rear ends. i always used 80W90. glad to hear it solved your problems. what brand oil did you use and was it synthetic or conventional? i've been thinking about trying either Mobil 1 or Royal Purple gear oil in my stock open 10-bolt but wasn't sure of what grade to use.

slow_90firebird

Personally I wouldnt try the 140w oil unless you need it. I figured, as long as it keeps the gears wet, it will be better than the alternative (having all of it **** out the pinion seal)
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Oh, and I used "Super Tech" GL-5 conventional from wal mart. It is real cheap, so I always go there to get gear oil. Either that or the valucraft stuff from autozone is good too.

samiam91RS

grey? more like blue...grey is for motorcycles..but I dont think it really matters. i bought the blue stuff anyways..
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oh ok. cuz im going to drain mine all out and check out whats inside. whats a regular viscosity of rear end gear oil?

92RS702

For our cars I think it's 80W90.

samiam91RS

80w90? sounds good. how much does it take? i never dealt with rear ends and diff. so im kinda new to this..so bear with me guys. do i pour it in with the cover open? then seal it up with the rtv?

red92firebird

No, unbolt all the bolt and take out the cover, clean it then use razer to scruff all the old gasket out off the cover and rear, drain all the fluid, get paper tower and clean inside the gear, try get much fluid out possible, use half tube of grey rtv or more on the cover, put the cover on the rear, hand tight he cover, do not over tight the cover now to make the rtv sqeeze out the cover, wait few hours or over night to let the rtv dry up, then tight the bolt down, fill 80w/90 thru the filler hole until it coming out, tight the filler hole and test drive, try to drive low speed first few min then get on high way, check for leak before and after drive. check for leak again after a few day. I dont know these rear need the posi addictive add on or not ?.

92RS702

Well red92firebird pretty much said it all,the biggest mistake guys make is they over tighten the bolts,just take your time and you'll be fine.

samiam91RS

why dont cha just pull out a rear from another 3rd gen? like a posi disc set up
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sounds good to me, is there a difference between grey and blue RTV? other than grey is supposedly for motorcycles so it says..i got the blue stuff anyways. and, using RTV i dont need a gasket at all?

slow_90firebird

Because I dont want to pay high dollar for another POS rear end. I would rather drive on this one, untill I can afford another 10-bolt housing, and then I will build it using a nice new posi, nice axles, 3.42 gears, a girdle cover, welded axle tubes, and then powdercoat it all. I would pay a tranny shop to set it up for me too, because I have no knowledge or skill in shimming a rear end to work right. And I would use all new bearings, seals, and royal purple.