alright, I got this car about 2mo ago. it had been sitting for 17yrs in a garage. Original owner had replaced the engine and trans back in in 92' but never completed the install. I finished it up and was shocked on how much power it had. was and 305tpi car with a 700r4, now?? I thought it to be a 30 over 305, all i know is that when you mash the gas it light up the tires almost all the way thru 1st and when it hits 2nd it slides sidways agian would have never thought that from a 305. anyways the loud thump, when you get on it there is what sounds like a hammer hitting the floor board comming from the passangers side rear seat area. any ideas? I thought broken shock or mount but everything looks fine.

 

You need to be more specific, is it under certain conditions or is it all the time. You stated that it was making sounds on the passenger side right? Look to see if the cat is hitting the floor board during suspension jounce and rebound. More inportantly, look at the transmission mount. The owner may have never tightened(or there may not be one at all) the mount,causing the tranny to hit the foorboard of the car.

Cheers!!!

 

could be tranny mount or could be the torque arm springin up and hittin the cage that surrounds the front of it. when i shift gears, it'll load and hit that cage. it soudns like metal on metal like a hammer hittin somethin tin.

 

310 - best suggestion is to jack the car up, put jackstands to support the car, and crawl underneath and look at the tranny mount, t/a bushings, or anything out of the ordinary. Lots of times the tranny mount will crap out and tear away from the metal. It should be an easy fix, just got to get under the car and take a look.

 

Thanks guys. Thats the thing, jacking it up and checking all mounts was the 1st thing i did. everything looks fine. I will check it one more time to make sure, that must be what it is.

 

looking forward to what you find. I've got the same exact thing going on and no time to really investigate. I figured i just wore out another bushing and something had too much play in the rear and was doing metal on metal now.

my car is in serious need of a total suspension overhaul.

 

I remember a few years ago, I had a customer come into the shop and describe the exact same thing. He and a few of his friends had put a motor in his car. The car was a chevy truck. I know it is a different vehicle but what your describing sounds the same. They had forgot to put the long bolt in the motor mount of the drivers side. When you got on the gas the motor lifted up and when you let off it came back around the motor mount and made a thump. might want to check the motor mount bolts. The transmission bolts would be another thing to check as well as the TA bushing.

Let us know what you find.

 

My issue is that my trans shifts firm and hard. When i go any higher than half throttle, off a stop and first to second shifts throw you back a bit, it'll even sometimes chirp the shift to second. Only recently in the last month or so has this resulted in the loud thump. I thought it was due to my rear springs being so weak and close to bottoming out that the jerk due to shifting caused it to actually bottom out. That or a bushing is gone. It doesn't feel like it's coming from anywhere but the rear passenger. No other effect it felt related to it.

 

I'm thinking it's that rear tranny mount. It's kind of hard to see when it's torn loose, since it just sits right back down on that metal plate, and is usually covered in grime.

 

same thing happens to my RS but it is due to not having adequate suspension (it's all worn out) and when hitting large bumps or potholes on the freeway, my pass. side rear tire is getting scratches on the sidewall because the wheel well gets that low to scratch it, so my suggestion is to see if you have pretty good springs and shocks!