"BANG" on launch

[Pathogen]

Had the car out Friday night and had a problem that seemed to just get worse with each run; it sounds/feels like something is actually hitting the bottom of the car.

By the final run of the night, the 'hitting' was bad enough to actually stop my CD - I say stop because it took it SECONDS to start playing again.

We were uping the launch RPM with each pass and the higher I went, the worse the "hitting" got. Last pass was at 4500. (Until then it was almost tolerable.)

Has anyone else had this problem? If so I'm looking for suggestions.

[Nachius]

sounds like Tranny mount!

[Pathogen]

it's a brand new mount. :(

[Nachius]

I'd still check it is it stock or poly.

Other things off the top of my head is it only on launch? If it increases with RPM check your driveshaft, if not shake your exhaust and see if you can move it a lot by hand [img]smile.gif[/img]

[Pathogen]

I am noticing a clunking noise when the car starts moving (cold) .. like exhaust. Maybe I broke something loose. (grrr)

Mount is stock.

[1DangerousV6]

yup..i went through 3 stock rubber tranny mounts before i finally went poly and never had a problem since..only thing i could think of would be that or exhaust..maybe you broke a hanger or it just came off of one..or maybe something with your intercooler setup?

[Pathogen]

The bang is from the back, so it couldn't be intercooler. I haven't had a chance to get under the car and look, but I'm pretty sure it's exhaust or drive train/shaft/transmission.

When I brake (say at the end of a run) and the car pitches, you can hear something hitting something else, like the driveshaft rubbing on the tailshaft/exhaust... Wednesday I'm going back north, might find something out then.

[Tru2Chevy]

Was it just a single bang right off the line?

- Justin

[Pathogen]

yep, just one big "BANG!" ... I think it actually shows up on the log. (laugh)

[WickEdSix9838]

Sounds like a transmission mount to me also. Something else to look at, do you have an aftermarket torque arm? Might check that out also.

[foff667]

sounds like tranny mount.

[wasjo6431]

tranny mount or your torque arm aint bolted up to the trans no more. But i got 20 bux that says its the mount snapped on you. dont use stock mounts. They blow.

[Pathogen]

stock torque arm .... going to take a look at everything next time I get a chance ... side note, my entire rear exhaust section has come loose .. just hanging on by two rubber hanger right now. [img]tongue.gif[/img]

[shenanigans]

Originally posted by wasjo6431:
tranny mount or your torque arm aint bolted up to the trans no more. But i got 20 bux that says its the mount snapped on you. dont use stock mounts. They blow.

Don't laugh that **** happened to me on my 3.4L.


I snapped the bolts that connected the torque arm bushing to the tranny. But when I accelerated it hit the tranny tunnel when I slowed down it hit the ground.

Things I'd check...(in order) ;)

-tranny mount
-torque arm front mount to tail of tranny
-Rear bumpstops
-check all your rear suspension(sway, lcas, panhard) you will have the wheels off checking the bumpstops.
-exhaust
-motor mounts

[Pathogen]

Got a call late last night from (undisclosed shop) - we're going to be working late tonight.

Various adjustments
Shift light hook up attempt (someone help me with this, I've tapped every wire on the poor car twice)
Wire Boost & Fuel gauge to light up (ground fuel gauge)
Change trany fluid (It's been two weeks on the road)
Check motor & trans mounts, torque arm, all lower bolts
Check rear suspension (this was the first time out with this suspension)/bump stops
move/adjust/reweld exhaust
Install new rear
New tune, still having fuel issues ... this may wait until Friday night

[ June 21, 2005, 12:13 PM: Message edited by: Pathogen ]