Neglected Differential Service

[dollman0]

I just bought a 97 Chevy Tahoe truck with 190K on the clock, much like in the brakes video Eric just posted. I wanted to service the rear Differential because that is one of the most neglected things on a car/truck. The pinion seal is seeping a little and I twisted the vent cap as a possible restriction allowing pressure to build.

The fluid was low and there is a dark black coating above the oil level. My question is: can someone recommend a way to clean the crud out of the differential without disassembly?

In the past, I have added a pint of diesel to rinse some of the crap out of the axle and allowed it to run on stands for a few minutes (or drive it a mile) before draining. I filled it with 2 qts new oil and 8 oz Marvels Mystery oil to help dissolve some of the sludge in the pumpkin… I am just looking for a perspective from other techs out there.

I am wanting to run synthetic oil due to the heat coefficient and prefer it to be cleaned up first, and yes I think a new seal should be installed & a gasket used to seal it up for good.

Topic

[3SheetsDiesel]

I’ve never personally cleaned out the inside of a differential, although it does sound like a good idea. What you’re describing sounds like it would work. Obviously make sure that the fill plug will come out before you remove the diff cover, since you don’t want to let the fluid out if you can’t put it back in. As for the gasket around the cover, I’ve always just used black RTV silicone and have never had a problem with it. If a gasket exists and you feel like using it, more power to you, I just never have. I also have a tendency to spray paint the diff cover with gray primer so I can more easily see any future leaks. I do that to valve covers and oil pans too.

[dollman0]

Just an update:
I had burnt oil in the differential from the previous owner running it low on fluid. The vent tube was cut and I fixed that with some 3/8 fuel line.

I tore this down to replace the axle seals I suspected of leaking. The Marvels Mystery Oil I added to the gear oil did a great job of cleaning up the burnt oil deposits. The truck was only driven 1,500 miles and most of that was towing.

I filled this differential with a high quality synthetic gear oil and it should not need any service for a long time. Just wanted to share my experience and opinion of cleaning out a rear end and using a premium 75W90 gear oil.

[dollman0]

Just an update:
I had burnt oil in the differential from the previous owner running it low on fluid. The vent tube was cut and I fixed that with some 3/8 fuel line.

I tore this down to replace the axle seals I suspected of leaking. The Marvels Mystery Oil I added to the gear oil did a great job of cleaning up the burnt oil deposits. The truck was only driven 1,500 miles and most of that was towing.

I filled this differential with a high quality synthetic gear oil and it should not need any service for a long time. Just wanted to share my experience and opinion of cleaning out a rear end and using a premium 75W90 gear oil.

[Bill]

It seems like you did a thorough job there. The synthetic i feel should protect your diff. for a long time. I have never flushed a diff but it sounds like a great idea.

Only problem i have with synthetic fluid is i find it can leak through RTV silicone sometimes. I use Permatex “right stuff” and my leak problems stopped.

[Bill]

It seems like you did a thorough job there. The synthetic i feel should protect your diff. for a long time. I have never flushed a diff but it sounds like a great idea.

Only problem i have with synthetic fluid is i find it can leak through RTV silicone sometimes. I use Permatex “right stuff” and my leak problems stopped.

[Author]

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