Like the title says, whats the specs of these (pitch/lenth/nominal dia. etc) or the GM part number if you have it. I need to get another pair of them.

 

you're talking about the tranny crossmember to frame bolts?

I'm guessing you just broke off your old bolts? I'm trying in vain to get this fixed on my car too, apparently stock was M10*1.5*32mm bolts, but I removed 3 3/8" bolts, and tried drilling that out to tap for 7/16", but there isn't nearly enough meat for threads.... I think i'll end up with a 1/2" bolt going in there..Or a threaded insert.

are we talking about the same part ? I didn't think they were self tapping...

 

Yes. Same bolts. I have the spohn crossmember for my TKO and it has provisions for three bolts on each side. The stock four bolt holes are in poor condition from all the years of people removing the xmember to get the trans pan off. I relocated two of the bolts to the fresh unused holes, but Id like to have an extra set of bolts to help give some saftey since there isnt much left for them to grab into on the four holes that the stock xmember was bolted into.

 

If you look at the bolts head-on, they have a triangular profile. Basically all you do is stick them into a blank, and they cut their own threads as you bolt them in.

 

oh ok, I guess the stock ones are self tapping then... Like I said, I don't have stock ones any more, I have 3/8"NC bolts in there.... which are stripped out...
I may try a giant oversized bolt.
are you going to try stock type bolts again, if you holes are stripped out?

 

Just out of curiosity, have you ever seen the actual size of the steel blanks that where used for the xmember bolts? I was always curious just how big a bolt could be used in place of the stock ones.

They arnt stripped yet. Theres still threads there, bujt theyre sort of f'd. Im going to add an extra set of bolts for now. The threads that are there held up the 700-R4 for years like that, so those four plus two good ones should hopefully hold up the TKO until I get around to fixing it. I may try a standard bolt of the same size as well, but I seem to remember that a standard bolt didnt quite fit as well in place of one of the self tapping bolts.

 

no, I haven't seen the plate in there. I searched last night and some members thought it was ok to drill up a size, and some thought the plate wasn't large enough go to up much bigger. I felt around up there, through the access hole, but it's hard to tell. I can use a magnet to drop a bolt down from the top, but I wouldn't be able to get a wrench in to hold it. I was thinking of using a socket capscrew, since i've got some, but it's very hard to line up my allen key into the bolt head....

 

Im going back under the car tonight. Ill see if I can squeeze an inspection mirror in there and see something. Im curious myself. Drilling up to the next appropriate standard or metric size and retappiing would be the easiest solution if there is enough metal there.

 

It's basically a nut-sized bushing tack-welded inside the frame section. It's softer than the typical nut so it will self-thread more easily.

 

Thats what it was. Not only that, but from what I saw, the center part is conically shaped to give more thread engagement, so it doesnt look like overdrilling/re-tapping would work as a repair.

 

crap.

ok, bolt from the inside then...

 

When I built my crossmember and torque arm I drilled the crossmember to use three bolts per side instead of two. The original bolts weren't stripped yet but they were getting very soft when i put a wrench on them. I measured the diameter of the stock bolts and decided that the 25/64 drill bit(drill size for 7/16-20 tap) would just cut out the old threads. Tapped them out and have never had a problem with them.

 

I ended up taking the easy way out by cutting a 1" dia hole through the floor on each side and running a bolt in place of the old stripped one. Gotta say it didnt take much to strip those old threads. Didnt even have to drill them out. Just turned the bolt with a ratchet and all the threads came away with the old bolts. Im amazed the xmember never tore away from the underside of the car.

 

whoa wait, you drilled up into the passenger compartment? or do you mean you drilled into that frame rail from the side to put in a bolt and nut?

 

Yep, straight down through the floorpan on each side, ground the raised area on each of the bushings flat, and dropped a bolt in. I dont have to worry, though, the hole should blend in nicely with all the other rust holes in my floor.