2002 Tahoe 5.3, 4wd with locking rear axle option, has 120,000 miles. I bought it new and it's never had a differential leak or rear end noise. Seems I read somewhere the locking rear axle requires some sort of additive? Approximate cost from a dealer or established shop?

I don't think a locking rear requires anything different. Limited slip rear should use gear oil with a LS designation. I recently did my 4runner (front, rear and transfer case) and it was not that hard of a job. Bought synthetic gear oil cheap online. If I had to guess I would say a dealer would charge around 350, maybe more. Call your dealer first then start asking around.

You would need either oil that has that additive added or plain differential oil and the additive.

I had my Tacoma Rear(its differential fluid already has the additive added) ,Front differential, xfer case and 6 speed transmission done for 200 dollars at the Toyota dealer.

Very close. Dealer charged me $300 for front and rear on a 4 Runner. After looking at the manual it was only recommended for a vehicle used in dusty conditions. Which mine has seen little.

If your locking rear axle option is a clutch plate type of diff, you'll need to add the LSD additive. If it's like the newer worm gear type of diff, you don't need to add any LSD additive.

I use synthetic diff fluid in my trucks. Both came with it from the factory. Just had the front and rear diff fluid changed in my new truck, IIRC it was about $200. Had the dealer change it because I have the lifetime powertrain warranty. If anything go's wrong, it's their problem, not mine.

NYH1.

Some shops use pneumatic pumps to suck out the oil through the fill hole, while others remove the cover to drain the fluid and clean the internals. There is no way to get all of the fluid and junk out with a pump, but it's probably not an end-of-the-world thing. It may be worth asking which method they use. Independent off-road shops are worth considering.

No big deal if they don't get every last drop...the bulk of it and clean the metal shavings on the magnetic plug and it is good. As long as everything is done on the schedule and the proper lube is used that is all that matters.

I paid $149 art the dealer for my F150. Thats with removing the cover.

$167 on my 98 Dodge Ram this past summer

I do both pumpkins, standard transmission, and transfer case in my Dodge 2500 diesel every two years. It gets a lot of use on the dusty plains and up in the hills in the mud and snow. Cheap and easy to do.

I change drive-train fluids whenever I buy a used vehicle regardless of how many miles are on the clock and every 50K miles thereafter; differentials, transfer case, and transmission. New, clean, fluids are cheap insurance against routine wear and tear. Full synthetic if it is applicable.

Full synthetic and you are good to go, the Tahoe locker has no clutches.

Thanks to all for the info. Paid $354 for the front & rear differential and transfer case fluid changes. 75w90 synthetic in the differentials and Auto Trak II in the transfer case.

Missed it by 4 bucks.

You can do it yourself next time for under 100 bucks easy with new washers. BTW, washers should never be reused.

Wow, this thread makes me glad that I mostly do my own work. You could do the front and rear and transfer case on most vehicles for $80 an about an hours time.

Pull, flush, inspect.