Whenever I start from a dead stop there is a nasty clunk coming from under the car like something is hitting the floor HARD. I can feel it through the seat and steering wheel. only happens from a dead stop with half throttle or more. Does anybody have any ideas about what this is or how to fix it? It just started doing this yesterday. It feels like it's coming from just behind the seats uhnder the center console.



1990 pontiac firebird formula 305tbi 700r4

Probably a broken transmission mount. It takes about 30 minutes to fix and will cost you about $10 if you do it yourself. Couldn't cost more than $60 bucks for a shop to replace it.

Edit. Some people will tell you to put a polyurethane one in so it doesn't break in the future. Do a search to find out about it.

I agree, possible broken transmission mount.

I have to say tranny mount as well I have replaced one on every thirdgen I have owned but all of them had well over 100k and it was the original round mount not the square replacemnts that I removed.

ur not an official thirdgen owner until u have the tranny mount go out and wonder what the heck that sound is, and replace it with an Energy Suspension mount only to be pissed off at the vibration.

welcome to the club! and Thirdgen.org

sounds like a tranny mount

http://www.slponline.com/view_produc...RTNUMBER=60005

It's a quick easy job. If I can do it, you can too

That happened to me too a few months ago, after I was...uh... Anyway, is this a recurring problem, I mean, does it happen alot, or was it an age thing? (mostly newbie)

julie, yes it's a problem that is going to happen over and over untill you replace it with a poly mount from ES. gm did everything they could to make sure the mounts break from time to time.

That's not a BAD clunk, that's a GOOD clunk.

That stupid blob of spooge mount with no reinforcement always breaks. It's probably been broken for a long time, it just wasn't completely into 2 pieces like it is now, to where the trans and drive shaft hit the botom of the car.

Get an Energy Suspension poly one and never worry about it again.

believe or not autozone now stocks alot of ES stuff. ie tranny mounts, motors mounts, and sway bar bushings.

lol sucks hu just went through that on my car a week ago. i went and got the new mounts but when i brought it to the shop they where fine, its just the bolts where like half out thats holding the tranny, i would check that first.

yeah tranny mount, had the same prob about 3 weeks ago

I had the same problem with my 305 5 speed.
Took some friends for a ride and got on it and loud CLUNK from the bottom of the car and the shifter would move up and down about 2-4 inches.
Stock replacement from Advance Auto tore in half less than 500ft from my house.
Motor died shortly after.

A problem I had was a cracked torque arm and it was flexing and hitting the driveshaft tunnel.

Craig