z28_n_tx

iTrader: (7)

well i noticed this a few months ago...its not much just 3-4 drops every time i look under the car...car has 70k on it don know if the previous owner ever had it serviced...but ball park extimate , how much am i looking at to get the leaking to stop... the dealer ship quoted me $200 to service the rear diff. ( taking it apart and actually cleaning it, not just taking the old fluid and replacing it with new fluid..)

pentavolvo

pull rear diff cover off

scrape off old gasket material

clean diff

get some gasket sealent put diff cover on trq to spec, and fill back up

2001NBMZ28

Hard to tell what's going on without getting under there and checking everything - pinion seal, diff cover, is vent clogged, etc. My pinion seal leaks and need to get it taken care of, but doesn't drip on the driveway yet so haven't bothered. If it's been dripping a few drops overnight for several months hope you've kept it topped off.

tennz28

Changing the fluid can be a messy job but its easy. Like pentavolvo said remove the diff cover, clean it up, use a new gasket, bolt it back in an fill her up. Im pretty sure install university has a write up on it, but dont quote me on that.

DVS99TRANS

iTrader: (7)

Is the leak coming from the front of the pumkin or the diff cover??? Hopefully the diff cover.

z28_n_tx

iTrader: (7)

have not really out the car up.. but if you stand at the back of the car you can see the the diff. cover and the fluid that has leaked out...(has the wet look to it)

DVS99TRANS

iTrader: (7)

Most likely means it's coming from the cover. Still a chance it could be the pinion seal. Best to get it taken care of as soon as practical. When you get a chance under there, see if it's wet or see any kind of dampness near the from of the pumpkin. If so, and the dealer is saying $200 to disassemble, clean, and put back together isn't really that bad. Plus if anything goes wrong, you can point the finger at the dealer If the cover, then a half hour job. Just like pentavolvo said, get the RTV gasket maker and use that instead of a gasket. Creates a much better seal than paper.

slayer_taunu

iTrader: (3)

if its leaking from the diff cover, then you can just do a fluid change and replace the gasket. no need to do anything on the inside.

z28_n_tx

iTrader: (7)

im the second onwner, i dont know if the orevious owner did any kind of maintenance to the diff... i thought it would have to be taken apart in order to do a PROPER CLEANING, i could be wrong..

slayer_taunu

iTrader: (3)

i'm no professional mechanic, but i've never heard of the inside of a differential needing to be cleaned... just drain and fill. just like oil changes, make sure its warmed up first so it flows out better... gear oil is thick!

SladeX

lift it up and check carefully, pinion seals are notorious on our cars to leak. My 88 did it, my 98 did it. Damn 10 bolt.

Parts & tools

2 Jack stands
1 jack
13 mm socket (I think the bolts are 13 or 14...)
3/8 drive ratchet wrench and 3/8 torque wrench
2 quarts gear fluid 80w90 or 70w90 for synthetic, I've noticed no difference in noise or performance, only if yours makes some noise like rusty nails, GM has a differential additive which can fix that
A hose or pump of sorts to get the fluid in

The cover can easily be serviced by you. 2 Jack stands and a jack. Any new 10 bolt gasket from autozone, napa or dealer. Lift by differential pumpkin, place jack stands at frame before the lower control arms, lower the jack to give access to the rear differential cover.

To change fluid, have a pan ready to catch the fluid, prepare for a nasty smell and start loosening and removing all the bolts. Leave 1 or 2 on the top partially threaded and pry the cover with a screwdriver. Let fluid spill into pan. Go for a bit of a walk, catch breath, you will get used to the smell...sorta.

Once most of it is drained, get the cover out. Hopefully the gasket removes fine and you won't have to do any serious scraping of gasket material. If you want to, use some clean rags and scoop out the remnants of the fluid from the lower differential area.

Clean the mating surfaces and prep the gasket. A little bit of gear fluid on both sides of the gasket will help seal well. Place gasket in between and bolt up the cover to 22 ft/lb of torque using a crisscross pattern.

On the passenger side of the differential pumpkin is a plug for a 3/8 drive. Open it and use your jury rig pump to fill. The goal is fill till spill. Simply keep pumping until it doesn't hold anymore then re-cap it.

If it's the pinion seal that's leaking, it's a bit more involved. You need a new pinion seal and crush washer or crush bearing. Note if you've done this before or know someone extremely familiar with these rears, you can get away with simply changing the pinion seal. I did that on both my 88 and 98. New mechanics of today usually mess up the old one when trying to keep the old crush bearing.

z28_n_tx

iTrader: (7)

iwas going to post pics but i cant find my damn usb connector or what ever its called...well i got under the car and the drops seem to be falling from the end of the 2 bolts after the diff. dont know if it makes much sence w/out pics.... let see if i can explain ti better ..ok im at the back at the car i get down look under and see the diff move just past it and i see a buch of grease with the two bolts that i mention that the diff fluid is leaking from,....

kny3twalker

iTrader: (31)

for 200 dollars, they are not doing anything but taking off the cover, removing the old gasket material, sealing it back up, and putting in new fluid

huge rip off

if the leak is coming from the cover, which does happen, mine is leaking now cause I did a shitting job(needs to be redone soon)

follow the instructions above, there were a few
its easy, only slightly messy