Trans mount suggestions

[superstreet2055]

I'm rebuilding an older tube chassis Vega. The car was originally built with a BBC and TH 400. I'll be running a SBC with a P/G. I've relocated the motorplate and transmission crossmember and everything is sitting in place. I'd like to hear opinions/comments/suggestions on whether (or not) to use a polyurethane trans mount in conjunction with the motorplate, or just bolt the trans to the crossmmber as a hard mount.

Thanks for your thoughts.

[johnracer]

Definately use a mount! I've always used stock rubber, but many use poly.......

[kwkracing]

Yes use a flexable mount!!!! Do not hard mount it.

[itsabird]

x3 on flexable (rubber) mount.

[superstreet2055]

I'm curious... you all agree about using a trans mount, but I'm interested in "why" you feel that way.

I come from a background of 500 inch big blocks running Lenco or Liberty transmissions that are all hard mounted. I didn't design or build them, they were always that way when I started. Is it just because the P/G case is inherently weaker?

[lively]

YES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[superstreet2055]

Makes sense. Thanks.

[kwkracing]

A lenco case does not flex like stock gm cases... glide, th400 and so on. You put a solid engine and a solid gm tranny in a chassis that flex's and you will brake that small thin bell housing or tail housing right off. Something always has to give a lil, which is rubber not thin cast aluminum

[superstreet2055]

My P/G does have a Super Bell bellhousing but the tailshaft is OEM. I think the polyurethan tail mount will be the way to go.

Are any of the aftermarket cases/tailshaft housings strong enough for solid mount? Just curious.

[TopspeedLowet]

Ultimately, if your chassis is rigid enough, you can solid mount it. The chassis you had with a liberty trans were likely chassis cars? If so, that is why they were rigid mounted in addition to the case being made more rigid than the egg shell that the GM hydromatics are made of. I use a polly mount on my chassis cars using hydromatic trans to keep any stress of the case that will shorten the life of the trans. I have seen racers cantilever there entire trans off the bell housing using NO mount what so ever. I think they are foolish, but if one idiot does it and doesn't get killed, others think it is the way to go sometimes. I like to stick with (conventional) engineering whenever possible.
Bruce

[THERATTLER]

I have run powerglides with a mid plate and no cross member mount at all for over 15 years and never broken anything . however my driveshft is 6" long , if I was using a long driveshaft as in a door car , I would run a mid plate and a GM rubber mount on a crossmember ..just my two cents , for what it's worth (probally 2cents) :D

[superstreet2055]

The cars I worked on that had solid mount transmissions were all pro stock chassis (Don Ness). My current chassis is an Alston Eliminator I upgraded to Eliminator II specs. It is certified to 7.50. I suspect that it's as rigid (or more) than the Ness chassis cars I used to deal with, but I'm still going to use a polyurethane mount for the P/G. It's no trouble, I have the mount, and the only adjustment I might have to make is to raise the motorplate a half an inch to keep the geometry correct. No big deal.

I appreciate the comments. Thanks to all.