Is the stock type transmission mount strong?

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Jay Anderson

Jay Anderson

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Installing my 408 and 727 w/transbrake in my '68 Valliant. The transmission mount looks to be held in the crossmember with just a small 5/16" stud inside the mount to the crossmember, held with a nut. This just does not seem to be a very stout setup. The poly mount does not even fit snug into the crossmember. This is a steet/strip car leaving on a transbrake. I'm more used to the GM type held in with large bolts. Am I missing something here?
 
I never used a poly mount back there so I can't speak to that one, but I have never broken that style mount in a heavy B body with slicks and tons of 1/4 mile passes on the strip. Most of the load is actually rotational and is controlled by the two engine mounts. Trans mount is just picking up the slack. I should also note that I use cheap parts store rubber mounts back there too, nothing fancy.
 
Ditch that and get the later style trans cross-member that features a captured thru bolt.
 
jos51700 said:
Ditch that and get the later style trans cross-member that features a captured thru bolt.
Click to expand...
Like off of a later Duster? Is this a spool type? I can see where the captured bolt would be a stronger design. Is it just a bolt in swap? Here's the Valiant it's going in. 543 hp with a 150 shot. I may be overthinking this, but the more I look at, leaving off a transbrake at about 4000 rpm, that syle of mounting looks like a weak link to me. I appreciate the help and input from all!

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If you do want to go to the later style spool mount, it is an easy bolt in swap. Just need the crossmember and then the spool mount and associated through bolt. Everything else stays the same. If you get a complete crossmember and old mount together, you can buy just the polyurethane inserts and then you don't have to buy a cheap replacment spool mount. I run that way on my Dart.
 
Been using the same OEM transmission mount 71 Dart for 10 yrs now....using a transbrake....ran some low 10s with a 360....But.....

this one is available for your transmission mount

Search Results for 5.1112g
 
Last edited:
70aarcuda said:
Been using the same OEM transmission mount 71 Dart for 10 yrs now....using a transbrake....ran some low 10s with a 360....But.....

this one is available for your transmission mount

Search Results for 5.1112g
Click to expand...
That's the new mount I put in. It just seems that the little 5/16" stud wouldn't secure it very well to the crossmember. The mount isn't even snug in the crossmember. The mount itself is secure to the transmission. It looks like the little stud is the only thing holding it in.
 
I've rip trans mounts in half street racing. Small block 4spd. And not the weak style you have in the older car. Grab a Poly mount at the min. or the solid mount so you never do it again.

By the way, sweet lookin car you got there.
 
My memory is a little fuzzy, but i recall a tab you have to bend over the new mount.
 
Mark2205 said:
My memory is a little fuzzy, but i recall a tab you have to bend over the new mount.
Click to expand...
This may be exactly right. When I was removing the old 48 year old mount from the crossmember, it fit so tight, I had to work to get that thing out. The new poly just dropped right in. I'm going to try this! Thanks! I appreciate all the help. I'm new to Mopar stuff. Man, have I had to learn alot.
 
rumblefish360 said:
I've rip trans mounts in half street racing. Small block 4spd. And not the weak style you have in the older car. Grab a Poly mount at the min. or the solid mount so you never do it again.

By the way, sweet lookin car you got there.
Click to expand...
Thanks, been a long 4 year project, finally wrapping it up.
 
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