Need Silverado differential fluid advice

[Jim 5]

CBODY provides some useful information. Here's the confirmation from the manufacturer of the diff that confirms what he is saying about clutch discs.

Here's my email to Eaton performance products from the link provided above:
-----------------------------------------------------------
1. Does G-80 Locker have clutch packs that wear out?

2. Is a normal 75w-90 synthetic gear oil (like Mobil 1 75w-90)acceptable? Subject to your answer above, does this gear oil need a friction modifier?

I have this rear end option in my 2004 Chevrolet Avalanche and do not want to use the factory specified synthetic gear lube because it costs $28/qt.

----------------------------------------------------------

Response from Eaton:

"Jim,

Yes, the G80 locker has clutch disks in them that may eventually ware out over time. As for as the fluid recommendations, please reference an owners maintenance manual to verify, but I have always used the straight
80w90, GL5 mineral axle oil with no issues.

I hope this helps.

Regards,

Barney Gwozdz
Sales Administrator
Eaton Performance Products
Phone# (248)226-****
Fax# (248)226-****"

[I will provide his phone number to anyone who PM's me. I just don't want him to start getting phone calls from telemarketers and such.]

 

[rspoden]

Thanks for all the information. I think I'm ready to proceed with the job now. The picture Bill posted of his drain plug looks just like mine. I have a black vent hose in the front that I believe will need to be changed to be compatible with synthetic fluid. I would never have known that if it weren't for this site. Thanks again.

 

[bmwtechguy]

As Bill said earlier, take out the fill plug first to make sure you will be able to refill ok. I always liked being able to see the gears and any potential problems by taking off the cover when draining the axle oil, but it sure is convenient and quick when you can just open up the drain plug, and then refill so easily. Why has it taken GM so long to see the light?

 

[Rhymingmechanic]

GM apparently saw the light but then shut it off again right quick regarding differential and auto trans drain plugs.

 

[Bill in Utah]

My moms 2002 Silverado 4x4 has drain plugs on both diffs and a drain plug on the auto trans.

What GM model are you talking about?

Bill

 

[Steelers]

My F150 does not have a drain plug either. I used my hand pump through the fill hole to pull the old fluid out, in this case 2.5 quarts. Never opened the rear differential cover. Installed Amsoil 80w-90 about 25K ago. Plan on changing every 50K or so.

 

[Rhymingmechanic]

Bill,

I'm talking about Silverados in particular, but probably the SUV's as well. I'm not sure on the exact years, but the new body style trucks had trans and diff drain plugs up until about 2002. My 2001 has them, and they are super convenient--one of the things I really like about the truck. But I gather from posters here and on other sites that the plugs disappeared around the 2003 model year.

 

[crashz]

I've checked with my dealer and still can't find any more info besides this thread on problems using syn in the frontend. Anybody have the TSB on this? I've already been running M1 75w-90 in the front for a couple of months now without issue, but really don't want one to pop up this winter.

 

[rspoden]

Allow me to clarify my last post and answer crashz's question. It's not the vent hose on the front differential that you need to look at, it's the hard plastic vent hose connector that screws into the differential. If yours is black, the O-ring inside the connector is not compatible with synthetic fluid, and may leak. If yours is white, you're all set. Any truck manufactured after 4/1/04 should have come from the factory with a white connector. If you need one, the part number for the synthetic compatible connector is 12479390. GM dealers have them for $24.85. Sure adds to the cost of switching over to synthetic!

 

[rspoden]

An update... I changed the fluids in my differentials over the weekend. Pretty easy job. Thanks to a 15/16" deep socket and some extensions, changing the front differential vent hose connector cap wasn't too difficult. The fluid that came out of the front differential was nasty and there were quite a few metal flakes stuck to the drain plug. I thought for sure that the truck would handle much better in 4-wheel drive thanks to the new fluid. However, I found the opposite to be true. The truck doesn't seem to hardly want to move now when I put it in 4-wheel drive. When I turn, my front tires slip and jump. It's almost as though my front differential is locked or something. Has anyone else experienced this problem?