REAR DIF FLUID SERVICE - DO 8 FIGURE 8's TSB - CHATTER

[Dimitrim]

My 2014 ZL1 has 9,000 miles on it. I get 2 years free engine oil/filter service from dealership. Change engine oil light soon came on yesterday. Today I dropped it off at the dealership. Since it will be racked I asked if they can service the rear diff fluid also. The reason to service rear diff was to get out all that metal shavings out of the rear diff, other than that it worked great.

Service manager told me about a TSB rear diff fibrous clutch chatter. After replacing the rear diff fluid to drive the car in 8 figure 8's or 8 circles to the right and left right a way. If you do not do this it causes a dry spots on the clutch surfaces causing the chatter.

I thought this was very interesting.

Dimitri

[Stingr69]

I would not worry about that. If you assemble a new differential or if you need to add the limited slip additive, you need to do some figure 8's after you add the additive. If you don't have "crunching" or "snapping" when turning, you are fine.

[Dimitrim]

When you drain the fluid it leaves dry spots in between the fibre clutch packs. The dry spots causes slippage causing chatter. Doing a figure 8 or eight circles to the left and eight circles to the right gets the fluid in-between the clutch plates.

[el ess A]

If you drain and refill right away, I'd challenge the "dry spot" theory. The ZL1 fluid already has the additive in it, and the fluid that's still on the parts has additive in it, so no...not buying that.

If you don't have chatter, you won't have to do this.

Note what it says in red below.

But here's the TSB that's being discussed for reference.

#PIP5097A: ZL1 Rear Differential Moan Noise On Turns – (May 19, 2015)

Model Years :2012-2015 Chevrolet Camaro ZL1

This PI was superseded to update Model Years. Please discard PIP5097.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern

Some customers may comment on a moan noise from the rear axle during cold start turning maneuvers. In some instances the noise has been described as coming from the front of the vehicle. The noise may start to be noticed as the vehicle accumulates over 3,000 miles.

Recommendation/Instructions

Note: Steps 2 – 9 MUST be performed two (2) times for a total drain and fill of three (3) times to have this procedure be effective.

1. With original lube in axle, conduct Freeway Speeds for 10 miles to warm up lube.
2. Immediately drain original lube and refill with fresh lube
3. In parking lot lock steering to the right, and then execute 5 Full Circles at (5-10 mph).
4. . In parking lot lock steering to the left, and then execute 5 Full Circles at (5-10 mph).
5. Perform 4 Figure 8’s at (5-10 mph).
6. Freeway Speeds for 20 miles until operating temperature is achieved.
7. In parking lot lock steering to the right, and then execute 5 Full Circles at (5-10 mph).
8. In parking lot lock steering to the left, and then execute 5 Full Circles at (5-10 mph).
9. Perform 4 Figure 8’s at (5-10 mph).
10. Immediately drain current lube in axle and refill with fresh lube
11. Perform Steps 3 thru 9 again.
12. Immediately drain current lube in axle and refill with fresh lube.

This procedure is only to be used for the condition listed above. During regular maintenance, the fluid only needs to be changed one time. The maintenance schedule can be found in the owner’s manual on pages 11-5 and 11-7. For regular service the fluid is changed at 45,000 miles or 72,000 Km and for severe service the fluid needs to be changed every 15,000 miles or 24,000 KM.

[Dimitrim]

Originally Posted by el ess A

If you drain and refill right away, I'd challenge the "dry spot" theory. The ZL1 fluid already has the additive in it, and the fluid that's still on the parts has additive in it, so no...not buying that.

If you don't have chatter, you won't have to do this.

Note what it says in red below.

But here's the TSB that's being discussed for reference.

This is a different TSB. This refers to vehicles already experiencing chatter. I did not have chatter when the dealership replaced my fluid. So all they had to do is replace my fluid one time and then do the figure 8's.

[el ess A]

Now I'm interested in seeing that TSB. Got a number for it?

I've had all sorts of positraction GM cars in my lifetime and never saw a drain/refil/figure 8 and circle drive/repeat in a procedure unless you had chatter.

If you drive it around town after a regular fluid change, you'll do plenty of turns and accomplish the same thing.

[Dimitrim]

Originally Posted by el ess A

Now I'm interested in seeing that TSB. Got a number for it?

I've had all sorts of positraction GM cars in my lifetime and never saw a drain/refil/figure 8 and circle drive/repeat in a procedure unless you had chatter.

If you drive it around town after a regular fluid change, you'll do plenty of turns and accomplish the same thing.

I do not. It is what the service manager at Novato Chevrolet told me.

[Jasper]

I visited my Service Managers house where he has a lift so I could do my tranny and diff fluid. He just told me to drain the old fluid out, push in half of the new fluid, put the additive into the half bottle of fluid and shake it up. Then push that into the diff. Did that and left. It's been a week and I don't have any problems and didn't do any figure 8's.

J

[Avenging Orange]

Changed fluid in many a differential.......never done anything but drain, fill and drive. Never an issue.

[Tenring]

Originally Posted by Avenging Orange

Changed fluid in many a differential.......never done anything but drain, fill and drive. Never an issue.

Just did my sons 4th gen again today, for the third time and we just drain, fill and drive.