Rear Diff Drain PLug [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: Rear Diff Drain PLug


Vince
08-25-2005, 10:29 AM
I was poking around under my TB a couple weeks ago and I didn't notice a drain plug on the rear diff. Is there one on the '04 models? I may have just missed it. Hopefully I am going to change the fluid in the front and rear diff's this weekend and it will be much easier if there is one.

04TBEXT
08-25-2005, 10:55 AM
Vince, I have an '04 T/B extended with an I-6. My rear differential does not have a drain plug...earlier models do. Draining on my vehicle required removal of the rear cover; the gasket is reuseable. The front differential has a fill and drain plug which is located in the left half of the front differential case, to the front of the axle shaft.

bmm354
08-25-2005, 11:25 AM
I'll post this here just as an FYI for earlier years...

On my '02 Envoy with the 3.73 limited-slip diff the drain plug is on the underside of the differential / "pumpkin." It's about right at the spot where you'd position a floor jack on the pumpkin.

Vince
08-25-2005, 11:47 AM
Vince, I have an '04 T/B extended with an I-6. My rear differential does not have a drain plug...earlier models do. Draining on my vehicle required removal of the rear cover; the gasket is reuseable. The front differential has a fill and drain plug which is located in the left half of the front differential case, to the front of the axle shaft.

I had a feeling they got rid of it. Thanks for the info. Is there any chance I might not be able to reuse the gasket? I may buy a new one just in case. They should only be a few bucks.

Windy City
08-25-2005, 12:58 PM
Is there any chance I might not be able to reuse the gasket?

I highly doubt you'll be able to reuse it and I never have. I've had real good luck using black RTV to seal the cover and no gasket.

04TBEXT
08-25-2005, 02:31 PM
Vince...some gaskets on today's vehicles are of the reuseable design. The differential cover gasket we discuss and the transmission pan gasket are some on our vehicle which can be successfully reused. I changed to Mobil-1 differential fluid @ 3000 miles and reused the rear cover gasket...almost a year later and still "bone dry". I see gaskets/seals reused (as specificed) in the repair field quite often. The GM service manual states to inspect the gasket for nicks and cuts and to replace as necessary or clean both contacts surface and reinstall the existing gasket. There are also seals and gaskets which are deemed not reusuable requiring replacement each time.
If you are performing your fluid changes as a weekend or evening project where a needed part is required, i.e. "not open on Saturday" and/or the vehicle must be repaired, I can understand purchasing the "just in case" part(s). If you want a gasket and you want GM, the part number is 12479020 with a list price of $17.88. Good luck...

Vince
08-25-2005, 03:57 PM
Vince...some gaskets on today's vehicles are of the reuseable design. The differential cover gasket we discuss and the transmission pan gasket are some on our vehicle which can be successfully reused. I changed to Mobil-1 differential fluid @ 3000 miles and reused the rear cover gasket...almost a year later and still "bone dry". I see gaskets/seals reused (as specificed) in the repair field quite often. The GM service manual states to inspect the gasket for nicks and cuts and to replace as necessary or clean both contacts surface and reinstall the existing gasket. There are also seals and gaskets which are deemed not reusuable requiring replacement each time.
If you are performing your fluid changes as a weekend or evening project where a needed part is required, i.e. "not open on Saturday" and/or the vehicle must be repaired, I can understand purchasing the "just in case" part(s). If you want a gasket and you want GM, the part number is 12479020 with a list price of $17.88. Good luck...

Again, thanks for the great info. I think I will try to reuse the gasket. I'll probably have some black RTV on hand just in case. That gasket is 9.26 on gmpartsdirect, but they kill you with the shipping so it ends up costing more than it would at the dealer.

Vince
08-25-2005, 06:05 PM
Anybody know the transfer case capacity? It's not in the manual.

04TBEXT
08-25-2005, 06:40 PM
Vince,
Fluid capacity is 2.0 quarts. GM recommends use of their transfer case lubricant, called AUTO-TRAK II (GM P.N.# 12378508). This is one fluid that I recommend to obtain from GM and would not substitute.

ScarabEpic22
08-25-2005, 09:50 PM
Vince,
Fluid capacity is 2.0 quarts. GM recommends use of their transfer case lubricant, called AUTO-TRAK II (GM P.N.# 12378508). This is one fluid that I recommend to obtain from GM and would not substitute.


Yea, there is no other compatibly fluid as of now to put in there as far as I know. I looked into at 2500mi ago when I changed all the fluids, and that was the one part I went to the dealership for (besides the fuel filter because the auto parts store was out of them and would have to special order one for me). On gmpartsdirect.com, it says the fluid comes in 4pks, which it doesnt. You have to buy two of them to fill your TB/Voy with. (I woldnt recommend buying it online, too much of a hassle. Just go to the dealership for it.)

envoy62
08-25-2005, 10:53 PM
On my Envoy 2002 (45000 miles)the dealership proposed to change the differential oil, for draining it the mechanic removed the cover and replaced the gasket by a new one (it didn;t look bad could have been reused, but i prefer a new one instaed of taking chances). After bolting down the cover he refilled the differential through the plug that is on the upper rear towards front side of vehicle. He used the GM oil thats mentioned in above posts.
pointed out howdirty the oil is (i like to watch when they work on my car). Well i wonder how necessary it is to change the oil.
What is GM maintenance requirement for this, i don't thinh that it should be changed before 60 70 k miles.

On the other hand sometimes its better to spend 70 bucks and feel better about the condition of the vehicle.

04TBEXT
08-26-2005, 07:51 PM
envoy62...I think you made a good move changing you differential fluid(s). I do agree that lubricant technology has advanced itself a great extent. I also feel that the manufacturer uses the long-interval fluid changes as a marketing tool advising a prospective owner about care-free, low-to-no maintenance costs. GM's basic warranty is not that long of a period (3 years or 36,000 miles...). GM has planned obsolecense,...I don't thing they would want there vehicles to last too long. How does GM then sell you another vehicle???
I have worked at GM dealer service deaprtments quite a long time. I have customers whos' vehicles go for 130, 150, 170, 210K. I guarantee that the service histories to these vehicles, as far as maintenance goes, are extensive and includes repairs as needed and the "religious" changing of all lubricants at specified times.
From what I see in the field, I will be one of those who keeps a close watch on the levels and performs prudent, periodic fluid changes as I see fit.

lt2000
08-26-2005, 10:10 PM
I have a 04 LS that didn't have a drain plug on the rear axle,so I drilled and taped for a 1/4" pipe plug ,that has a magnet on the end of it,so now it is very easy to drain.The truck had around 5000 mi. on it when I installed it.Didn't go with synth.fluid,just 80w90 dino.
gary

rcam81
08-26-2005, 10:15 PM
I have locking diffs on my TB. Do I have to put the additive in if I use synthetic lube?

ScarabEpic22
08-27-2005, 04:01 AM
It depends on the fluid. I know for my Amsoil Severe Gear lube, I didnt need it, and no problems after ~2000mi. Check the bottle or with the manufacture if you are unsure.

Good luck!!

bmm354
08-29-2005, 12:27 PM
It depends on the fluid. I know for my Amsoil Severe Gear lube, I didnt need it, and no problems after ~2000mi. Check the bottle or with the manufacture if you are unsure.

Good luck!!

I used Amsoil as well and did not need any additive. It's probably been almost 3,000 mi. for me and no problems--and trust me I would've noticed. If you notice any binding you can always add some. It's only about $5 for a tube.