Chatter when shifting

[gamblingman]

So I decided it was time to change the transmission and rear end fluids. No issues, just time for a change. The rear diff fluid was changed at about 60 k. Now at 125k. Once it was changed, got the car back and noticed some chatter when it was shifting. (Or about to). The shop said that people say it all the time and to drive it for awhile. Well a month went by and the chatter really started getting to me so I took it back. They changed the rear again and now it is worse! If I accelerate slowly it really doesn't happen, but up inclines and over about 2000rpm, it is very noticeable I'm taking it to the dealer, but I really could use some guidance here before I get a 3k bill. Help.

 

[ccclarke]

Was the supplemental friction modifier added?

CC

 

[James Landi]

Could it be that your rear and struts are worn out and that's setting up the chatter? If you have the rear end lifted and the wheels off the ground, you can test for front and back looseness of these rear struts that attach on the upper section of your transmission/differential. My car had 28K miles, and they needed to be replaced. You could move those rear wheels back and forth! James

 

[gamblingman]

Called my guy who replaced it he said that he absolutely added it. He also said it's the clutches chattering. And he thinks it needs a rebuild. Could be my shocks I guess. They are all shot. However the noise is very specific leading up to when it shifts.

 

[BeardBros]

I just had the transmission service and rear end fluid done. My car has 87K miles on it and had never had either done. The transmission got a full service and the new fluid was dexron 6 which replaced the dexron 3 it came with, it is working better than ever. The rear end was drained and the new GM LS rear gear oil was used, no additional friction modifier. My rear end was chattering, clutches sticking, before the change. Now it is smooth with no issues with just the LS gear oil in it.

 

[rexster314]

I changed out the differential lube last year with this: [h=1]Mobil 1 104361 75W-90 Synthetic Gear Lube It's an LS alternative[/h]
Did a world of improvement to our 06

 

[James Landi]

rear end lubricant.

I changed out the differential lube last year with this: Mobil 1 104361 75W-90 Synthetic Gear Lube It's an LS alternative


Did a world of improvement to our 06

Sorry-- what is "LS" -- in following the various posts, there's clearly agreement about the need for an "up grade" rear end gear oil....are you suggesting a much better alternative??? Appreciate the clarification. James

 

[rexster314]

Sorry-- what is "LS" -- in following the various posts, there's clearly agreement about the need for an "up grade" rear end gear oil....are you suggesting a much better alternative??? Appreciate the clarification. James

LS=Limited Slip The Mobil 1 gear oil is a synthetic.

 

[gamblingman]

So I took it to a chevy dealer. I think they really don't see XLR's at all. Told them what i think it is, but they seem to think its a torque tube bearing that is going bad.
Want to charge 7 hours to diagnose. Not sure what to do. Said the sound is coming from the front of the car, not rear.

 

[James Landi]

So I took it to a chevy dealer. I think they really don't see XLR's at all. Told them what i think it is, but they seem to think its a torque tube bearing that is going bad.
Want to charge 7 hours to diagnose. Not sure what to do. Said the sound is coming from the front of the car, not rear.

-- I feel bad for you! A chatter between first and second can occur if there is an internal crack in the transmission case, so that when torque is applied, there is loss of hydraulic oil pressure. Can you get the car to shift without the chatter by permitting it to shift from first to second without pressing on the gas at all-- allowing the momentum of the car to "carry" you through the shift point? ANother point I feel you might consider raising, what other GM cars have the same transmission? Broadening your "search" on the internet for cars with the same transmission might get you to the point that you can locate some one who is familiar with the issue and had the repair made without spending hundreds on dollars on what might be an inconclusive result... so sorry.

 

[gamblingman]

It shifts OK throughout the gears, If you apply light acceleration it doesn't make much noise at all.
The more research I do on the Torque Tube bearings, the less I think that is the problem. Seems that if the bearings have gone, I would have alot of vibration. I don't have any vibration that I can feel at all. Just a sound that really resembles a loose heat shield on the catalytic converter to me....
Is the Torque tube the same for all model years? I have seen ones for sale that do not specify 2004-2005???

 

[James Landi]

Transmission

I am feeling your pain... As you likely know, there are many elements to the underside of these cars that are dynamically aligned, any one of which, if bent or shifted can cause an awful vibration that is synchronous to the torque/ aka movement of the engine, the drive shaft, constant velocity joints transmission/differential and exhaust elements. The best diagnostics for SYMPATHETIC VIBRATION of dynamically mounted parts is to have the car on the lift, have a driver in the car applying the brakes and (gently) apply the accelerator, and then having an savvy technician with good hearing under the car to locate POSSIBLE metal to metal rattles. THe best case scenario is the your transmission problem is simply a bent and vibrating exhaust pipe. .. God willing.

 

[gamblingman]

Well another dealership down and still no idea what is wrong with my XLR. It has developed a whine and a grinding noise at very slow speeds around 15 miles an hour.

 

[James Landi]

Well another dealership down and still no idea what is wrong with my XLR. It has developed a whine and a grinding noise at very slow speeds around 15 miles an hour.

I suspect you've tried new transmission fluid... There are "labs" that perform a chemical analysis on motor oil, and I suspect, transmissions and differentials as well... basically, aside from checking on the chemical mix, they often times provide the owner with an analysis of suspended metals --- usually particulate, that can provide you with some understanding of what, if anything, as wearing. Just thinking you searching and researching for additional information... James