changing rear diff fluid

[akvette]

Spent too much time today staring at the differential trying to find the fill plug till my neck gave out. Where is it located? Found the drain plug which is a 3/8 allen plug with tag stating posi-trac lube needed. My manual does not show or refernce the fill plug. Any help would be greatly appreciated.

Thanks, Akvette

[Stryker_78]

Hi, my fill plug on my 78 is on the passenger side towards the top above the yoke. It is hard to get to. It is easier if your rear end is jacked up so that the rear axle is hanging.
Good luck. Oh make sure you use the GM additive. It works wonderful.



Scott

[Scott81]

Akvette,

On the 81 diff the drain and fill plug are the same thing, that's all you get. Get yourself one of those fairly cheap vacuum pumps from the local auto parts store and suck out the old fluid with that. When you refill don't forget the posi-lube.

If I ever take mine out again I'm going to drill/tap for a drain plug before it goes back in.

[Yoda]

I take Rare into the "Local" Chevrolet garage for her rearend oil change ;) Once I showed them where it was :eyerole it only cost $24.50 with fluid and the proper GM Posi-Lube additive. No mess, no stuff to dispose of and on the road in 20 minutes :D

Plus I got to get another good luck at Rare's bottom side :D

Bud

[jon81]

Theres not a fill plu on the 81. You have to put the fluid back in the same hole it came out of (the one with the tag attached). Make sure you add enough fluid that it runs back out of the hole...let it drain until it stops...it's full when this happens.

If you can't find a vacuum pump at a local auto parts store try a marine (boat) dealer with a parts dept. Be prepared to spend a while getting the old fluid out with one of these hand pumps as the fluid is really thick. Use the Mobil One gear lube in the correct viscosity as the replacement fluid and MAKE SURE you use the Positrac additive. I ususally add a little fluid and then mix the posiirac additive in the bottle so I know it's blended well. Synthetic Mobil One is just a little extra cheap insurance. If you want the "real stuff" positrac additive it's a dealer only item but any parts store will have the same item but non GM.

It's easier to take it to a quick change place but I'd rather do it myself so I know it has enough fluid, etc..

[Don&Kelly]

I do what Rare81 does - it's in and out quickly & I don't have to figure out what to do with the old fluid ... no mess either .. most dealerships have a speedy lube or quick lube area to compete with the fast change oil change places..

[akvette]

Well that explains it then. Damn near went blind looking for that non-existant fill plug. Thanks everyone for passing on your knowledge i sure do appreciate it.
Akvette

[Dave L.]

Akvette - If you are going to do it yourself here is a little tip...
jack up your car and remove the spare tire assy...take the car for a little drive to warm up the rear axle oil...use your suction gun and suck out all the old oil... (that oil sucks out much easier when its warm)...use suction gun to insert the new oil in the rear.I usually set the bottles of oil I am going to install out in the sun for a bit. It's much more fun doing it yourself!!!

Happy Motoring...........Dave

[Vette81]

I changed my own rear end fluid. I found that it is easier to jack up the right rear side and to remove the right rear wheel. As previously stated above, the filler plug is on the passenger side towards the top. There is no drain plug. I Use a ratchet with a universal adapter and a HEX head wrench to remove the plug. Be careful not to cross thread the plug when you reinstall it. You can purchase a hand suction pump at Auto Zone and suck out all the fluid. As everyone else said : " Use the GM Positracyion additive".


This can be a messy job and If I was not so stubborn I would take my Vette to a garage like Bud recommended and have the rearend oil changed.

;shrug

Grizz

[Dave L.]

Thanks Grizz. that beats removing the spare. I'll try that when I change my fluid in the next several weeks.
GM# for additive is 1052358 GM# for the oil is 1052271
When I do mine I put in 2 additives and fill the rest with oil. It might be overkill but I have never had any rear end problems or noise of any kind.

Dave