Engine mounts are tired...

[LMP]

Just recently, my '93 transport 3800 has started making weird sounds when engaging transmission , forward...and specially reverse. THis is not a transmisison problem. It sounds like there is increased torsional movement of the engine/transmission unit and it made me take a look at the engine while a helper would shift in drive and reverse....it does lean much..impressive ..but in fact I do not remember having tried looking for that before...so I cannot compare.
I'll take a video soon and post it but I'd like to hear from others who might have changed the engine mounts for similar reasons...I have not seriously investigated yet for their number and varieties ..Rock Auto shows one type only and they do not have the dog bone....

[500hpgtx]

It did not take long before the dog bone motor mounts failed in my GTX. With the amount of mods performed, including a firm shift kit for the trans, the engine began rocking on its mounts. This caused the headers and exhaust to make some noises. I replaced the dog bone mounts with a solid plastic material type. You can remove the internal rubber and replace it with the solid neoprene like material mounts. I feel some vibration from the steering wheel at idle, but I had the same feel with my 68 Firebird and turnbuckles to hold the engine down from the big torgue of the 421S.D.
The performance sites should carry the neoprene mounts.

[LMP]

Yes..dog bone AND I think of the other mounts too. Will take a look soon. You surprised me with the 421SD....not sure this ever came around my place in Canada...never heard of. THis has driven me into other forums to feed my knowledge about this.....as I understand, it might have been a rebore/restroke of the 389...???..

[500hpgtx]

In the mid 70's I bought a 1962 421S.D. from an original owner. It was a special NASCAR engine that came with dual 4 barrel carter carbs. It had 4 bolt mains, a forged crank, and a special harmonic balancer.

THe engine was bored to .120 over, wihich is the max for this special high nickel content block. He O-ringed the block with copper wire around the cylinders. He had 12.5 to 1 pistons and a oval track racing cam with crane roller rockers. I bought a rare Mickey Thompson Cross-Ram intake manifold from him as well. I put on 2 holley 660 double pump racing carbs on and a mallory Unilite electronic distributor and Mallory coil.

THe engine spun a bearing, and I got 455S.D. H-beam type rods and had it re-balanced. In put it back together and put a mellings oil pump and a Mildon pan in it.

I drove it on the street and never lost a race, including motor cycles.

I broke the turn buckle on the passenger side holding the engine from rocking once. Tremendous torque. I had a 456 rear end gear and a turbo 400 automatic.

[500hpgtx]

Hopefully, the photo shows up of the 68 Firebird

[Jeffrv]

LMP. I changed the dog bone last year on my 95, simple to do and was dirt cheap at UAP NAPA, under $10 tax in for a decent looking unit Maybe start there to see if that helps before the really ugly job has to be done
Jeff

[LMP]

Thanks jeffrv..I have a UAP NAPA at a few minutes bike ride distance...

[Jrs3800]

Its possible to have a broken front trans mount as well... Those are really common to fail.. as well because I went to the Series III engine with the series II intake and TB, I was smacking the master cylinder due to the amount of movement as the dog bone allowed for a lot of stretch if that makes any sense.. I went to a shorter W body dog bone and used the 96 U van radiator header panel bracket.. I installed poly bushings on both ends to keep the motor from moving.. It works.. I do feel a tad more for vibration but it keeps the engine from jumping back when I hit the gas..

[LMP]

A bit busy on other items at this time ..like restarting the swimming pool ..chipmunks like building trails under the liner.....but I have the dogbone ..new at C$7.75 local... and start with that then look for the rest...

[500hpgtx]

I remember the Pontiac trans mechanic friend changed out the front trans mount on our 1995 3.8L when he rebuilt the trans. I remember the engine used to rock quite a bit before he changed it out. The engine dog bone mounts are still original.
Probably likely LMP that you will have to change out that front trans mount like Jrs3800 said...cheers KEV