99 Expy Rear Diff Question

Reply Subscribe

Thread Tools

Search this Thread

Oct 12, 2003 | 04:55 AM

BigMan69

Thread Starter

Senior User

Joined: Jun 2003

Posts: 261

Likes: 0

From: Long Island, NY

99 Expy Rear Diff Question

In my owners manual, it says the rear diff is filled with synthetic fluid and should NOT be changed unless it is submersed in water. You guys buy that or should it be changed? If so, when?

Thanks

Oct 12, 2003 | 11:30 AM

PaulC

Posting Guru

Joined: Sep 2002

Posts: 2,297

Likes: 0

I've never bought into the lifetime-fill philosophy. Your truck is approximately five years old. That fluid, along with loose metal particles from the manufacturing process and normal wear and tear, has been circulating in the diff for a long time. Even if the lubricating qualities are intact, it's probably contaminated to some extent.

I have changed mine every 30k. A bit **** for the rear diff, but I had an unpleasant experience with ring gear failure on another vehicle, so it buys me peace of mind.

Oct 12, 2003 | 11:57 AM

BigMattXXL

Postmaster

Joined: May 2002

Posts: 3,028

Likes: 1

From: Annapolis, Maryland

I agree 100% with PaulC - I think the "lifetime fill" idea is that the differential will continue to function (keep in mind I say "function", not "function well") to 200,000 miles on the same fluid. Most people get rid of their cars long before that.

I never liked the idea of all that crap floating around in there.

XXL

Oct 12, 2003 | 12:04 PM

BigMattXXL

Postmaster

Joined: May 2002

Posts: 3,028

Likes: 1

From: Annapolis, Maryland

Also, when you do change it, don't buy the Ford stuff. Ford wants around $30/Qt for it, whereas you can buy Redline 75w140 GL for $8/Qt, and Redline is super high-end fluid.

XXL

Oct 12, 2003 | 04:32 PM

pounder90

Senior User

Joined: Sep 2003

Posts: 268

Likes: 3

From: Florida

Matt,

Does the Redline fluid require the friction modifier? If so, is it available other than from the dealer? What brand of silicone sealer did you use on the cover? Is it difficult to get a good seal on the cover?

Sorry for all the questions.
Thanks in advance for your response.

Oct 12, 2003 | 04:58 PM

BigMattXXL

Postmaster

Joined: May 2002

Posts: 3,028

Likes: 1

From: Annapolis, Maryland

Quote:

Originally posted by pounder90
Matt,

Does the Redline fluid require the friction modifier? If so, is it available other than from the dealer? What brand of silicone sealer did you use on the cover? Is it difficult to get a good seal on the cover?

Sorry for all the questions.
Thanks in advance for your response.

I don't know - the website says it's got a friction mod for LS differentials, but I sent them an email yesterday asking whether or not I should add the Ford stuff. The Ford friction mod is only like $8, so I wouldn't spend too much effort looking for alternate sources. I used black silicon in a pressurized tube - just put it on the cover, let it skin over, stick it on there. Pretty easy.

XXL