Differential fluid change
 

How hard and what do I need to get to change the Differential fluid. First time doing this so any advice will do.

thanks

Our moderator has you covered. :)

http://www.bfranker.badz28.com/fbody/lubeoil.htm

Its actually really easy but is a little messy.

You will need 2 quarts of gear oil and the little bottle of additive since the Z28 has a limited slip rear end. Just go to any auto parts store and they should have it. While you are there, get a new gasket for the differential.

A large catch pan, basic set of sockets w/ratchet, putty knife (scrape off old gasket), RTV gasket maker and a torque wrench (not necessary, just don't over tighten the bolts....12-15ft-lbs is all they need) A hand pump will come in handy also for putting new oil back in Diff.

1. Remove bolts with catch pan under diff.
2. Remove cover. Sometime it sticks and will need to pried off. Don't put gouges in the metal though. Try a block of wood and a hammer.
3. Completely Remove old gasket from cover and Diff.
4. Wipe out all old oil and inspect gears for damage.
5. Put a thing layer of RTV on cover and then place gasket on cover
6. Put cover on the Diff. and tighten the bolts in a criss-cross pattern. Tighten to 12 ft-lbs
7. Remove fill plug. Just use a ratchet with nothing on it. Be sure to clean out all the junk inside the hole so you don't round it off.
8. Put in additive bottle and then gear oil until it starts to run out the fill hole.
9. Put fill plug back in and tighten. (I like to add a little RTV to the threads to ensure leak free plug)
10. Go ask girl friend to smell your hands. :) That old gear lube will stink.

For the next couple of days, check the diff. for leaking but I doubt you will have any problems.
Repeat process every 15k miles.

I think I covered everything. Someone else jump in here and add something if need be.


EDIT: Or you could just follow the link above. I just wasted 10 min of my work day.......oh well its still better than working. :D

If you want to save a little work you can use a pump to draw the fluid out so you don't have to take off the cover. Can't do an inspection though.

Two things to add to Joe's instructions:
Synthetic gear lube is not recommended for stock differentials
Add 1 bottle of GM limited slip additive, available from your Chevy dealer for about $7.

Yeah, one thing to do is to take it to a quick lube place and they have the pumps to suck that crap out and normally do it real cheap if you bring your own fluid and additive. I wouldnt trust their limited slip additive as it is universal.

Which one is better.... Sucking out the fluid or removing the diff cover to drain the fluid

If you are confident there is no nothing wrong with the diff., just suck out the fluid. I prefer to remove the cover just ensure everything looks ok and there isn't any metal shavings in the bottom. You also get a chance to almost completely wipe out all the old fluid.

Why do you say synthetic is not reccommended. I just bought some synthetic to put in mine this weekend because i read on here that it was better. :confused:

Bill

Synthetic is not recommended for stock (auburn type) differentials. Use regular gear lube and GM limited slip additive.

I just changed the fluid in my rear and followed this sites procedures, http://www.bfranker.badz28.com/fbody/lubeoil.htm . My 02 Z28's owner's manual recomends using 75W-90 Synthetic Axle Lubricant (I'm using Mobil One) and GM's Limited-Slip Axle Lubricant Additive. Is the use of Synthetic gear oil only recomened for certain years? All4Chevy, I would check your owners manual and follow it's recomendation's for which type of gear oil to use.

Also, per the above web site, I tightened the differential cover to 22 ft lbs. Was that too much?

Re: Differential fluid change
 

Bringing this thread back from the dead to ask a quick question. Is it cool to try and change the rear diff fluid while the rear end is either jacked up and put on stands or rolled up onto ramps while the front end remains on ground? I was planning to buy some ramps at at the auto shop, back up onto them, and chock the front wheels. I don't know if having the rear end up in the air will prevent the old fluid from draining or not.

Re: Differential fluid change
 

Since the rear cover will be off, you can coax out any fluid that might not readily drain.

Re: Differential fluid change
 

Just finished with it. Took about 3hrs start to finish, mostly because I didn't know what I was doing and I've never worked under the car like that before except to change the fuel filter. The oil that drained out didn't look anything like the oil I put in it. Anyone know what I'm supposed to do with the old stuff?

Oh, and prices have changed a bit since the 2004. I paid $8.99x2 for 2qts Mobil Synthetic, $5.99 for Posi-trac limited slip additive, and $6.99 for RTV Red High Temp Silicone.

Re: Differential fluid change
 

Do you need to move the sway bar in order to remove the bottom two nuts from the cover?