Hey all, 87 firebird, just started this afternoon. When I accelerate from a standstill, I'm getting a thunk coming from the right front side. Almost sounds to me like something hitting the floor boards on the right side. Handling is still the same, cornering is fine too, just an audible thunk now...

 

tranny mount. you can get an energy suspension one at autozone for ~$20

 

yep i'd be looking at the trans mount. i'll second the ES poly mount. bullet proof for the same money as stock.

 

a good gm mount (rubber) will be fine for your stock car and won't have nearly the vibration or noise that is generated from the poly mount.

i'm running a poly mount which works well but even they can fail as i've broken a few with my motor. however for a stock car i would much rather have the rubber piece.

 

thanks guys, I'll head out and pick one up tomorrow. On a side note, I'm planning on dropping in a stout 350 as well as doing suspension and drivetrain upgrades - should I go with a stock mount, or would it behoove me to go for one thats a bit stronger?

 

over 300 rwhp i'd go with the poly....

 

i'd go with a poly mount period. your factory rubber mount broke it didn't wear out. why would you want to replace it with something that you know had failed once before.

 

I've seen broken OEM rubber mounts on 3.1's, LG4's, and L03's... Not to mention LB9's, and L98's. Go poly and don't ever worry about it again... Lets see $15 (rubber OEM mount) or $25 (Energy Suspension)... $10 buys a lot of insurance but only a third of a tank of gas.

Your choice.

 

PROTHANE.

 

the rubber mounts will tear when they are beat on, especially under heavy abuse like so many thirdgen owners do. however unless your running a good amount of power having to spend $15 every couple of years isn't that bad to keep the annoying vibration and road noise out that is common with poly. even still poly will tear and break just like the rubber will if you have enough power.


do as you wish, if i could get away with running a rubber mount once every few months i'd do it just to keep the noise out. poly pieces work great and they are perfect for race/road cars but the rubber is fine for street and much more liveable.

 

You might want to inspect the tranny mount before you go out and buy one. I'd inspect the engine mounts too. They are probably kind of old too.

 

I've used the Energy Suspension mounts on 3 cars now, two L98's and an L03 and haven't run into any noise or vibration issues... nothing I'd consider objectionable at least.

 

when i switched to my energy one, i hardly noticed anymore vibration. my buddy with a 2k SS w/exhaust and gears has gone through like 4 rubber mounts

 

I'm running a Poly mount now after my stock one failed. I didnt notice any difference after the install, no new vibrations or noise!

 

then you have other things in your driveline or your going deaf.....

there is quite a difference between the two. only a loud radio, poor suspension or loud exhaust will cover it. there are so many things to mask it but if your car is in great running shape it's very noticeable and not pleasant.

 

i've never noticed a differance in interior noise nor has anyone complined about noise that i put a poly mount in.

 

I'm with ede and company on this one. Sorry Kandied I too did not notice enough of a difference to bother me with the Prothane trans mount. But like Kandied said, there IS a difference. If anyone tells you otherwise, they're still running original everything else on the car, too, which after 20 years or so is not exactly vibration-free. If you notice a BIG difference, there's something wrong with your drivetrain that should be addressed.

 

it's ok to disagree you know.




all i'm saying is if you have a good tire, well balanced rim combo as well as properly working suspension and drivetrain it's noticeable and it isn't quiet when compared to rubber.

however because of this reason even on my suspension and motor mounts i've kept the stock setup of rubber so it's more pronounced....or at least it was until i added the 388 and 4" where it doesn't matter any more. it's just one opinion but i wouldn't do it unless the car called for it. if your someone who drives your car like you could care less then go with the poly as it will hold up longer which outweighs the other side effects.

 

Went and bought a rubber OEM mount last night (8 bucks at O'reillys) and not only that, but found a complete rebuilt 400ci GM motor for sale by the guy that sold the mount to me for 300 bucks so.... I'm glad I didn't wait for responses

 

400 ci motor that works for 300....

o'boy...

 

hush, obviously gonna need a rebuild

 

Dapht Punk gets possession, he moves infield, the clock's almost out... he shoots.... HE SCORES!!!!

So what engine is it?

 

... darn double post.

 

The motor is out of a 78 suburban if I recall - I'm getting a few of my GM club friends together here soon and we're going to go over the block from top to bottom and make sure its good. I'll let you know. Of course, the best part is, the wife signed off on it

 

check your ujoints out too, and yes go with something like prothane or polyurethane, dont go back to rubber.
i prefer solids myself but they arent for the daily driver.

 

Hey folks, new mount in (just went rubber) and no more thunk! 1 hour job (that took 5 hours because 2 rusty bolts snapped and I had to tap the damn things out, not easy in 14 inches of space)

 

 

Good find on the 400. Hopefully it's a 2 bolt main but those are getting harder to find.
As for the rubber vs poly, well I've done both and been in cars that have also done the swap. My conclusion is that poly introduces no more noise into the car so long as the engine mounts are strong. I've also found that the only time the poly has been an issue with noise is when it's installed with that stupid pressure preload plate. My car hated it because it altered the driveshaft angle and everybody knows the stock steel driveshaft is a POS.
When (not if) the rubber mount breaks I would invest in a poly unit and forget about it.

 

When its time for the 400 to go in (probably not til this winter, gonna garage it and build it up for power ) I'll most likely replace all of the mounts again anyway. Then I'll revisit the poly vs. rubber argument again

 

I broke a stock tranny mount with a 2.8 and a T-5, they suck.