Thread: Engine movement

I've made plenty of threads on this topic and so have others, but I haven't found a solution for engine movement yet. My GS has more power than my LS but at the slightest gas applied(or maybe a lil more) in reverse in the GS the more will move and make a knocking sound(LS doesn't do this, in fast usually doesn't make any sound at any speed in drive or reverse).


All the mounts on the GS are new with no damage. In park doing a Torque break the motor barely moves(a good thing, thanks to the ZZP poly trans mount, GM engine mount, Intense poly dogbone round mounts and the radiator square poly support mounts). This knocking sound happens only in reverse while parking with a slight or should I say firm press of the gas.

only in reverse guys, not forward/drive. Again while torque breaking it the motor is solid in reverse and drive. I know the tranny makes a lil noise while changing gears but this noise is much louder and only in reverse while backing up.

only thing I can think of is while im backing up(slightly or firmly) the motor/tranny is naturally gonna want to move in the opposite direction possibly affecting one of the mounts(probably the damn tranny mount as always).


just a lil weird because while torque breaking it(aggressively up to like 4k RPMs give or take) the motor and tranny was pretty solid with minimum movement. A lil lost of where this movement/knocking sound is coming from(only in reverse, gotta be from motor/tranny)

Do you have headers on this?

if your seeing the tach hit 4,000 rpm's torque braking it, your trans is shot to hell.

if you got sd headers, thats the o2 hitting the fire wall. or the lca's are f ed up.

Solution = stop going in reverse.

I get a clunk or knock or something if I hit the pedal hard enough in reverse. I figure it's my headers hitting or everything shifting at once in the front end. I have new struts/mounts and new lca's and I just stopped caring.

Originally Posted by Fivefingerdeathpunch

I figure it's my headers hitting or everything shifting at once in the front end. I have new struts/mounts and new lca's and I just stopped caring.

As mentioned above. My 3 bolt flange on my collector has one of the ears at 12 o'clock. Every time I hit the gas in reverse, that flange hits the bottom of the floor tunnel.

sc cars should hit 2,000, n/a cars 2500. thats your stall speed of the converter, any higher, the trans is slipping. or you changed the converter to a higher stall speed.

Originally Posted by Scottydoggs

sc cars should hit 2,000, n/a cars 2500. thats your stall speed of the converter, any higher, the trans is slipping. or you changed the converter to a higher stall speed.

Hm, didn't know the NA cars were higher. No wonder my topswap car seems like it can launch harder than a SC car haha.

Conveter is also small/lighter

I think your best bet is to bring a buddy with you to a parking lot, open up the hood, and try to recreate it while he or she watches and listens to the engine bay.

In the end if you can't find it, I'd just do your best to ignore it, it most likely isn't doing any damage.

Originally Posted by BillBoost37

Conveter is also small/lighter

Is that good or bad? Like will it end up being to small in a high power build?

Originally Posted by SnowTh1ef

Hm, didn't know the NA cars were higher. No wonder my topswap car seems like it can launch harder than a SC car haha.

a bunch of us were all wondering the difference, so a few of us s/c and n/a guys did a test.

maybe part of why a top swapped car is faster then a stock sc car.

I have TOG headers and I may have exaggerated on the torque brake RPMs. This clunk/engine noise in reverse doesn't make sense bc while torque breaking it theres no noise or clunking at all(in reverse or drive) and engine movement is very solid

Maybe I missed it but who's square mounts do you have? Zzps 2 piece of Intenses one piece?

Did you ever get around to changing subframe bushings? If you haven't and they are in deed shot there might be slight cradle movement causing the thunk.

Originally Posted by Fivefingerdeathpunch

Solution = stop going in reverse.

I get a clunk or knock or something if I hit the pedal hard enough in reverse. I figure it's my headers hitting or everything shifting at once in the front end. I have new struts/mounts and new lca's and I just stopped caring.

Makes me glad to know other guys have this problem. I thought my problem was severe, but that sounds just like my issue. Only under heavy enough throttle in reverse do I get this weird noise.

Originally Posted by ILoveGM

Makes me glad to know other guys have this problem. I thought my problem was severe, but that sounds just like my issue. Only under heavy enough throttle in reverse do I get this weird noise.

Same here. I was wondering if it was the ABS self test or something.