at what mileage should i change my differential fluid? i jsut hit 77k miles on my trans am

 

Hopefully, you have already changed it a few times already. I change mine every 15K.

 

I took a peek at your owner's manual for the 97 TA. It has two different schedules for diff lube changes, Severe and Highway.

Severe - Change at 6000 mi and every 6000 mi there after. This is for limited slip with short trips, taxi svc, cop cars, and pulling trailers.

Highway - Change at 7500 miles (for limited slip), and it doesn't show it again.


I have the 98 Z28 with an Auburn L-S. Conventional fluid and 4oz L-S additive is indicated. Don't know about yours. If you use the search in the forum you could find a lot of opinions on how often to change and what to use.

Hope this helps.

 

I change mine once a year. But it is a 99 with 20K miles if that tells ya anything. Lots of track time as well.

 

this is kinda a stupid question but how do i change the diff fluid?

 

Here's how I do it... All this presumes you have a limited slip diff and basic tool proficiency.

Legal Disclaimer - Check your local listings and void where prohibited. If there are others with exactly the kind of vehicle and rear end as this gentleman and you see a flaw in the procedure, please speak up.

Purchase two quarts of your favorite 80-90wt gear lube (G5 compliant), 4 oz of GM Limited Slip friction modifier, gasket sealer (Gask-a-Cinch or equivalent), and a gasket.

Grab your oil catch tub, your metric socket or wrench (15mm I think...maybe smaller).

I've just started using those latex gloves to keep my hands clean. I love 'em to death now.

Drive for a while and heat up your differential. Warm lube drains better than cold.

Jack up the car and put it on jack stands.

Loosen all the bolts holding your diff cover. Leave in the bottom and two top bolts and take out the rest. Break loose your cover and let the lube drain into the pan.

When your lube is drained out take the rest of the bolts out and take off your cover.

Clean off all the old gasket material from the cover and the housing. It's gotta be real clean. I use my 4 inch grinder with a wire brush for the cover. Use a gasket scraper or sharp putty knife for the big bits and for the housing.

Nows a good time to wire brush your cover and paint it the color of your choice. Before you paint, though, give it a good scrub in the sink with Dawn dish soap and HOT water.

Wipe out as much lube as you can from the housing so it doesn't drain into the gasket surface.

Per instructions on the gasket sealer, put sealer on both sides of the gasket. Put gasket sealer on the cover where the gasket goes. Put sealer on the housing gasket surfaces. Don't use a lot, just enough to lightly cover. Be careful 'cause now everything will want to stick to something it shouldn't. Especially those latex gloves.

Put a couple of those bolts through the holes and use them to guide you as you set the gasket on the cover. Likewise with the cover on the housing.

Once you've got that done, replace all the bolts. Tighten the bolts in a criss-cross fashion like you would your lug nuts. Tighten to 22 ft lbs.

Clean all the dirt and grime away from the filler plug and remove the plug. A stiff bristled brush or a wire brush is recommended.

Add the 4 oz of GM friction modifier, then your quarts of 80-90w lube. Add until it starts running out the hole. It shouldn't take the entire two quarts. Don't get carried away and have a lot gushing back out. Some folks would have you jack up both ends of the vehicle so it's all EXACTLY level and the lube depth is PRECISELY correct. I didn't bother.

Replace your filler plug and torque to 26 ft lbs.

Remove your tools and drain pan, clean up your mess, return your car to its normal, upright position, and give it a test drive.

I hope this is good enough, with the ten million technically proficient proofreaders out there. If it leaks you must not have been holding your mouth right...

 

mr incredible thanks for the instructions im gonna probably change the fluid this weekend

 

what differental fluid should i use. around how much will it cost for diff fluid, gasket, sealer and limited slip fluid

 

Use a good name brand 80/90W gear lube ~ 3.50/QT. Gasket ~ 4.00. Gasket Sealer ~ 4.00. LS Fluid from GM ~ 8.00.

Knowing you have clean fluid and the gears look good = Priceless.

Good luck.

 

i changed my differental fluid this weekend everything went good except wen i was bolting the diff cover back on the very top bolt just snapped in half. so half the bolt is stuck the other half just broke off. will it be ok driving around like that. all the other bolts on in and i also got a new diff cover gasket

 

Owie! That always sucks!

An Expedient Combat Fix (or lazy fix, or "it's my only car") would be to leave it like it is until it starts leaking. This is the least desirable action.

If you didn't use a torque wrench, I suggest you go get one before trying any more fixes. The tighter-is-better method doesn't always work best. Also, always check your fasteners/parts/bits for damage while you are working with them. It can save time in the long run. Taking a wire brush to threads can work wonders.

If you did use a torque wrench, I suggest taking it back or buying a new one if it's old.

If the bolt is sticking out far enough to get purchase with a pair of vise grips you might try easing it out that way. Likewise, you could hacksaw a keyway and try to back it out with a screwdriver.

If you have room for a regular drill or have a 90-degree drillhead you could drill a hole in what's left of the bolt and back it out with an extractor.

If you are unable to do any of these things without tearing things up a lot worse than it already is you may have to get a reputable shop/mechanic to a$$i$t you.

And, of course, some of my best learning came from fixing my screw-ups.

 

ROYAL PURPLE---the only way to go!

 

id upgrade to a better cover for some added strength.

 

Call around to find Royal Purple. Worth it if you can find it.

 

Redline is what i am using and it should be good.
75w90 full syn

 

Would anyone be able to tell what limited slip 97Lt1TA would have?

My 98 Z28 has the Auburn, and the guys at Auburn told me that the recommend conventional 80-90w with 4oz of the GM L-S additive. They were adamant that synthetic not be used in their L-S's.

 

85w140 royal purple

 

Anyone know if you need to use the GM Limited Slip additive w/ Royal Purple Max Gear 75w90 fluid?

Thanks

 

im probably gonna changed the diff fluid again because im changing the gear in my car. i used valvoline 80w90 and i was wondering if i can upgrade to 75w90. my car is at 77 k miles now and i was told that with that mileage i shouldnt change to 75w90 synthetic

 

In my eaton posi from strange they also say not to use synthetic. Be sure to find out if its ok before you put it in.