Rumble Strips

[eqppwqqep]

Hi there. I tried searching for an answer to this one and couldn't find anything similar. I bet I missed it somewhere...

I have an 07 LT2. Just recently it started doing this thing at 10-15mph, whether coasting or braking, the car almost has an idle stumble or shudders, like driving over rumble strips...no noise accompanies the vibration. I have had the transmission fluid and filter replaced and shudder fix added. I am not sure if it is TCC or not. Here's what I have done to the truck so far:

Mileage 140K

New cats
New tires
New rotors/pads
Tx filter & fluid R&R
Brake Light switch replaced for Cruise Control issues

I did run a stall speed test which showed the RPM hit about 1600 and stop, which was telling me the converter appears to be fine. It locks up fine on the highway, it just seems like it might be sticking.

It feels like a manual coasting to a stop in 4th gear, at some point the engine lugs and the car feels like it could stall, but just like with a manual, the engine frees up and the car idles fine and smooth. If I put it in tow mode, it does not do this at all. Any help would be greatly appreciated!

 

[thzpcs]

Were the tires balanced properly? That's about the only thing I can think of

 

[Vista Cruiser 69]

Hi Rumble,
what made you choose the other name...?
Anyway, fact that he's fine in towing mode leads you to the gear box. Not too familiar with 07 models but towing mode makes him shift at higher revs and generally engaging the converter clutch far "later" than without. A defective converter clutch (guess you know about what it is - the device that bridges the converter slippage saving fuel) is often caused by wrong ATF. Reason for different ATF types (GM, Mopar, Ford,etc.) is different friction charcteristics for different clutcjh amterisl. Make sure the right fluid was used and keep your fingers of any "shudder fix" with mostly cocks friction characteristics up. Always stick to OEM recomms with ATFs!!!

good luck

 

[Vista Cruiser 69]

...as mentioned, the ATF you got or in combination with "Shudder Fu..s" may have lead to friction characteristics causing this extra shudder. Especially Mopar designed ATF (Type 4 etc.) put into GM boxes can cause real hassle.
So check out what went in, because the longer you bother your trannie under this condition the more severe gets the resident damage by this NVH issue. Should you find out the wrong ATF has been used then try to get most of it out or even flush again as all friction modifiers in Gear Oils plus your famous booster (aarghh..) stick to friction plate surfaces and need some time to get washed away. Patience pays off here.