PDA

View Full Version : Allison Lockup Noise


TxDoc
09-02-2002, 20:52
Passing this question on to see if anyone may have a comment:

"Have the 8.1 with the Allison; 12K miles on it. Lately when the engine's spinning around 1500-2000 RPM and the torque converter locks up, there's a vibration/low-pitched growl that comes from the tranny hump and passenger side footwell. It lasts for only about a second, and then goes away when the TC's fully locked. And it only does it when the tranny's fully warmed up.

Has anyone else encountered this problem? If so, could you get it fixed? The only reason I'm even slightly concerned is I know about early Allisons having valve problems, etc.-"

Thanks
DmaxMaverick
09-02-2002, 21:23
Definitely get this checked out. Could be loose converter bolts. Sure doesn't sound right. The converter lockup should be silent and seemless.
saphauler
09-03-2002, 15:44
My 01 8.1/A does the same exact thing.Bought it used w/ 10000 miles. Now has 15000 miles and does it to some degree on 3out of 4 lockups.I dont think its normal. Its absolutely the tcc system making the noise. If you put it in t/h mode it will make the noise and vibrate right after the 1-2 shift which is when the tcc locks up.
I can feel the vibration/buzzing noise on the gas pedal and cab floor. By the way where is the tcm located? I wonder if its making the noise.
Have changed both tranny filters and checked wiring for loose connection on solenoids.
Took to dealer but could not get it to do it that day-figures.They said there were no codes and have current tcm/pcm updates.NOt sure what to do.
TxDoc
09-05-2002, 21:22
The fellow with the problem posted back:

Got my ex-GM engineer father-in-law to listen to it on Monday-he says that it sounds like maybe the TCC locks-up through an engine exhaust harmonic. He says that shift points are programmed to avoid shifting through harmonics, but that some come pretty close, and a no-load 45 mph TCC lockup may shift through one.

Wouldn't loose torque-converter bolts rattle like crazy? I thought that bad torque converters rattle and vibrate like crazy . . . I mean, the rest of the time, this tranny is seamless. . .

Any other thoughts?

Thanks-Fitz