changing diff fluid
 

After break in I changed out the diff fluid if my 24 SS 1LE and the question I have are you guys changing the hydraulic (ATF) fluid also or just the gear oil. It's my understanding there is a special procedure when doing the control module, is it even needed.

Just the gear oil. The hydraulic fluid change is not needed.

Where is anyone getting the idea there is a "break in" period for the differential? The only info I have seen on recommendation for changing the fluid is normal maintenance (45k) or for track cars the recommendation is dependent on TRACK HOURS. There is not even a recommended "break in" engine oil change after 500miles but most think there is :noidea:

My 2016 I waited until 10k miles and it was nasty. Even this one changed at 700 miles it was pretty bad and had quit a bid of material on the magnet. I am not one to waste money but after reading these forums for 7 years I would suggest everyone changes out the diff fluid at the first oil change.

500 mile change in here:

https://www.chevrolet.com/content/da...ackPREP-R3.pdf

Attachment 1143472

As for the diff, recommended change is after first track day then every 24 hours of track time. Break in is indeed 1500 miles. But realistically, a fluid change after any "break in" is a smart thing. Especially a diff where high speeds equal high temps. I change mine every year even though I never hit 24 hours

Attachment 1143471

1st couple changes the diff oil is very dirty! I'd do it with the engine oil the 1st 2 changes, so 500 and 3000 miles.

45K for the first gear oil change is ridiculous. New diffs produce a lot of fine metal that should be drained out. I did mine at 500 (was nasty black) and again at 1500 (much better). But I do all my services myself so it's only the cost of materials.

I wouldn't think the dealer would change the differential fluid before selling me my car with 2400miles on it but the fluid came out clear as new when I changed it at 5k. It did strike me as odd being so clear :twitch:
FWIW I don't have the ELSD. I don't track my car other than roughly 10 1/4 mile passes and rowdy street fun.
The engine oil looks good, they claim to have changed that. I'll change it again in the spring. Car has about 7k on it now and is in winter hibernation :smiling1:
Can't wait for spring for the strip to open. I think I can get an 11.7 before the modding starts :cool:

In my mind when you transfer 400+ hp with an abrupt 90° to the wheels on 2 sides at the same time, that component deserves royal treatment above the rest. 2 quarts and 10 minutes of your time.

Gear lube is just as important for drag racing as it is for road course use. Gear lube needs to help with the intense shock loading of drag racing. Heat isn't really an issue. But for road course driving heat is the issue.




Spot on!

:happy0180:

I haven’t tracked her yet, but I did change out my diff fluid at 31,840 miles. I was performing normal maintenance and wanted to change it. I put in Royal Purple MaxGear w/SynerLec (75w - 90) with friction modifier designed for limited slip differentials.

I apologize for the lengthy explanation, but it was important to my point.

In my experience most manufacturers put cheap fluids in their vehicles. I guess to save a dollar or whatever. I believe Dodge is the worst. I bought a 2001 Dodge Dakota R/T, extra cab new. At a little over 10,000 miles, I took a short trip to Santa Cruz, about 400 miles from my house. A friend and I started driving at about 11 PM. We ended up driving with a chevy 454 truck. We took turns leading and following. We were, however, rolling at around 110 mph for about 2 hours. It was fun and safe given we didn’t come across any other vehicles and at least my truck had equipment rated for those speeds. Or so I thought. When we arrived in the Aptos mountains and were unloading our stuff, I heard a very loud boiling sound coming from under the bed of the truck. I figured it wasn’t fuel because we’d have been dead. It was the diff fluid boiling. Non-synthetic diff gear oil has a boiling point of approximately 600 degrees. A few days later, when we drained the fluid, it had the consistency of black water. I put in a full synthetic gear oil with a limited slip additive and never had another issue. Thank heaven they built the heck out of their differentials. A diff cooler would have helped quite a bit as well.

Given this experience, I didn’t want to take any chances, so I changed the fluid before I had any issues. Also, think about their choice of ATF fluid and the A8 shudder that choice created. Running the best fluids possible seems like cheap insurance.
This is simply one man’s opinion. Take it or leave it. I offer it for your consideration only.

I don't agree with the 500 miles diff oil change.

1500 miles is for the break in of the Axles CV joints.

Fine metal particles are found in any oil bath system. As long as the fine metal parts are smaller than the gap or the thickness of the oil films this is acceptable.
The transmission also has a lot of gears inside and nobody changes the ATF at 500 miles.

The "dirt" might be attributed to the Limided slip clutches wear. This material is compatible with gears and bearing and won't damage them. 45k interval sound reasonable for realtible cheap part that's easily replaceable.

I'd probably do mine at 20k or 25k with transmission flush.

Also 24hs of competitive driving @ 80mph average speed its 1,920 miles. Almost 2k miles between changes.

I was surprised that the owners manual would suggest even for normal driving the rear diff service doesn’t need to be done for the first 45k miles. These aren’t your basic, old fashioned 10 bolt 7 1/2” open diffs that could probably go infinitely without a single fluid change. They generated little heat and the machining tolerances were probably “good enough to work”. This is some high tech (ie expensive) stuff, precise machining tolerances and can get warm if you like to have fun. Doesn’t hurt to change the fluid within the first 10k miles.