Mystique

iTrader: (3)

1998 V6 3.8 Firebird. Car vibrates at park in neutral. Vibrates at park in gear, vibration smoothes out while driving at 50mph. While laying under the car if you put your hand on the oil pan and the transmission pan, the vibration is significantly stronger in the transmission.
While sitting park we shifted from park, to drive, to neutral, while the transimssion shifts gears there is a pause in the vibration and then the vibration continues when it gets into and out of gear.

Car has a new OEM transmission mount
New oem motor mounts
Car has a new harmonic balancer
Double checked to be sure the converter was seated
Ive rotated the flexplate on the coverter a few times to see if that would help.
Bolt holes on the flexplate do not appear stretched.
Car shifts fine while driving


This isnt a tire or driveshaft related vibration. As mentioned above the car vibrates while in park and in neutral at a stop.
One last thing.. I've had this vibration for 25k miles. It hasn't gotten worse or better. Its taken all this time of trouble shooting.

This vibration is so heavy it rattles the dash and console.

Thanks for your input guys.

askkmb

iTrader: (3)

If its not the engine, most likely its the converter. Very few things besides the converter is turning or moving in the transmission while in park. I've had a converter vibrating but mine only did when lock-up engaged.

mrvedit

The heaviest part in the trans which sometimes get out of balance is the sun shell. It is locked motionless by the band in 2nd and 4th gear, but spins rapidly in 1st and 3rd gear.
With that in mind, by driving at different speeds in either [D3] or [OD], you might be able to determine if the vibration is RPM or Speed related, or whether the sun shell is spinning.

Obviously when the trans shifts from 3rd to 4th the sunshell stops spinning, but the engine also drops in RPM. You might want to compare e.g. 40mph in [D3] with 70mph in [OD] as that will give you similar RPM, but with and without the sunshell spinning.

I also recall a thread where the replacement OEM trans mount was defective and the two metal halves were almost touching each other.

ybaslo1

iTrader: (10)

I've had a similar issue for the last 5-6 years. I think it started after I installed my yank converter and tci flex plate. I really think it's one of those components. It's annoying, but it seems to pretty much go away when hot. It either goes away, or I forget about it. Mine happens in park and neutral too, the only things turning are the flex plate, converter and pump. I just live with it as no one else who drives my car even notices, so it must not be that bad. Plus it's been like that for so long and over 15k miles, so whatever.

ybaslo1

iTrader: (10)

Also, if you really want to know for sure if it's in the trans or engine, you can remove the tq converter and run the engine. If the vibration is gone, it's the tq converter or pump, most likely the tq converter.