Solid trans mount?

[2yellow69]

Hopefully someone is up reading this tonight! I need some info on tranny mounts. I can solve a clearance issue if I run a solid mount at the back of my trans. A friend is telling me I shouldn't do it but I'm already running Moroso solid engine mounts and he has no reason for not doing it. He heard somewhere that it's bad news. Breaks the tail housing or something like that. If I need to run a non-solid mount I need to know so I can have the welder at work modify my crossmember tomorrow. My engine/tranny combo is a 396/T5.
Thanks!!
Matt

[dhardison]

You can easily crack a tailhousing and even the bellhousing if you run a solid trans mount WITH rubber/poly motor mounts. The rule of thumb is either run all solid or all rubber/poly, never mix the two unless you like welding aluminum (don't ask me how I know this).

[TA219]

He is correct, i have also heard of 4th gen f-bodies wearing out their engine mounts and the stress of the engine setting crooked w/ the solid trans mount is enough to crack the tail housing with time & use

[6'9"Witha69]

Solid trans mounts are never a good idea in a street car. I run Solid motor poly trans mounts. The rule of thumb has always been that the trans should be the same or softer than the motor mounts. Solid trans mounts are mot good even with solid motor mounts, the shock from hard shifting WILL lead to a case failure over time.

[JEFFTATE]

I've got rubber motor mounts and a Poly trans mount on my '69 camaro.
No problems yet.

[GetMore]

Solid trans mounts aren't a good idea on a street car, even if you've got solid motor mounts. The frame/chassis can flex under hard acceleration.

[dhardison]

I've never had a problem running solid motor with solid trans mounts, but that was always with an automatic. I could see where speed-shifting a manual trans would put more stress on everything.

If you need to raise the tailshaft just a bit then just install a piece or two of drilled 2" flatbar between the trans and mount to raise it.

[2yellow69]

Thanks for the info everyone. I think I'll run a non-solid trans mount. Hey Dhardison, any good ideas on how to lower the trans about an inch? 69 camaro with the same trans mount you probably had in the Nova. Not the T400 trans crossmember but the other one. I'm thinking I'm gonna have to cut the upper center section out and then try to rebrace it.
Thanks,
Matt

[dhardison]

Thanks for the info everyone. I think I'll run a non-solid trans mount. Hey Dhardison, any good ideas on how to lower the trans about an inch? 69 camaro with the same trans mount you probably had in the Nova. Not the T400 trans crossmember but the other one. I'm thinking I'm gonna have to cut the upper center section out and then try to rebrace it.
Thanks,
Matt

It's going to be tough to cut and try to keep any strength in that stamped steel crossmember (assuming I'm thinking of the same crossmember as you). You'd probably be better off picking up a tubular cm for a th400 or maybe the one that CC5S sells, then cutting and re-fabbing your own trans mount pad. Either that or Summit/Jeg's sell numerous universal trans crossmember mount kits.

[LS6 Tommy]

You can easily crack a tailhousing and even the bellhousing if you run a solid trans mount WITH rubber/poly motor mounts. The rule of thumb is either run all solid or all rubber/poly, never mix the two unless you like welding aluminum (don't ask me how I know this).

The rule of thumb is NEVER run a solid tranny mount, period. The trans is NOT designed to be a stressed member.

You should run poly or rubber trans mounts with solid engine mounts, or all rubber/poly.

If you need to secure that end of the engine that much, something's wrong or you need to get a mid plate.

Tommy