Transmission Crossmember

[kp72]

I've been crawling under the car ('70 GTX, 440, 727) quite a bit wiring in new gauges senders. I noticed something strange: my transmission crossmember only has two of four bolts in place. The crossmember looks like it is bent a little on the driver's side, so the hole isn't perfectly lined up. I think I can bend it back in place, though.

What size bolts are those supposed to be? Do you use hardened? Grade 8?

 

[69HEMICORONETR/TCONV]

Off the top of my head I think these are 3/8, ......On a restoration I would use stock bolts only and nothing else,..... On a Street Fighter or a Driver It wouldn't hurt to upgrade to grade 8, .....I would check to make sure you have the correct cross member for the car, these get changed out often just so people can go with different style transmission mount.

 

[rumblefish360]

I've used grade 5 to replacew these bolts before. Never had an issue. Since theres 4 of them, the hold everything in place very well.

 

[daredevil]

i think yhey are 3/8 also but seems head end is shouldered thicker to fit the crossmember holes securely. Seems there isnt a lot of force against the crossmember if your motor mounts are good or the crossmember to mount bolt would be way undersized being a measly 5/16 i believe

 

[detmatt1]

Not sure, but didn't they use a smaller diameter bolt in 1970 than they did in previous years?

 

[Meep-Meep]

They are special bolts with interference fit nuts http://rtspecialties.net/proddetail.asp?prod=1000292 but a grade 5 (minimum) with heavy washers will do the trick.