A thunk from the rear

[dipolley]

Hi everyone. Hope someone can help me on this one, since Saturn can't.

When I am decelerating I feel and hear a thud and a sudden shudder that seems to be comming from the rear end. It happens everyday when I turn into my sub. I am traveling at 40 mph, slow down, turn right and if I don't hit the gas it feels like a hard down shift. If you aren't paying attention you will actually lurch forward in your seat. I have saturn look at the problem every time I take it in and I get the same responce. "Cannot duplicate problem". I myself have trouble duplicating it but it only seems to happen to me and hav't been able to consistantly reprouce the problem except turning into my subdivision.

Any ideas? Any help? Thanks

[Bogie]

I think your thunk is the diff, but I would shudder if I had a shudder after the thunk because I don't recall ever felling a shudder after the thunk.

What year is you vehicle? Trans type...yada yada.

[dipolley]

Bogie,

08 Sky Redline, Automatic. I noticed the problem around 5k miles and I'm at 18k now. I have taken it in once specifically for this (They had the car for 3 weeks while I was in Germany and they said they found nothing wrong) Then an overnighter, and a cusory inspection 2 other times. So 4 total with No trouble found. I even said "It sounds like it's coming from the rear diff".

Let me rephrase to "a thunk and then a sudden deceleration durring low speed deceleration and turning". Almost like if you downshifted in a manual trani and dropped the clutch hard. But mine is an automatic.

[Bogie]

I also have an 08 RL automatic. I do occassionally get the thunk. It is my understanding the thunk is normal.

The problem is how do you tell the difference between a normal thunk and an abnormal thunk?

It supposedly occurs on a low engine speed downshift from second to first, so I think the best way to try and duplicate it is to be traveling in 2nd gear...coasting on a level surface. As you slow down in the coast, the auto will decide to downshift, and you might be able to initiate a clunk. It might also be a function of the speed you are in when in 2nd gear and the slow-down profile.

The times I remember it happening are in parking lots...and on occasion when approaching a stop light in coast.

While I believe GM when they say the thunk is normal, I also know that some folks have had the thunk and come to find out the thunk they have isn't the normal thunk, but something was wrong. The problem is when they tell Saturn they have a thunk, Saturn goes "The thunk is normal", because there is a normal thunk.