The ol' bait & switch
 

Hey guys, just a quick ?? I'm needing to replace my tranny mount (AT) and going to get the part this weekend. Not my first rodeo, and I remember from years back on my 85 T/A that the listed replacement part was a circular mount, but what I removed was the rectangle style. Are these two interchangable? I shop O'Reilly Auto Parts, and they list the round one for all third-gens. But all the aftermarkets show the poly rectangle, and even some OEM manufacturers online show the rectangle as stock replacement. Can someone shed some light on this for me? And before it's said, I plan to visually verify the style I have in the 87 GTA before purchasing, or at the least buy both and return the unused. I'm just curious as to the opposing information out there.

Re: The ol' bait & switch
 

Look at what u have. The different mounts are kinda random in their application so its hard to guess what u have. They all use different crewmembers so they are not interchangeable without changing the trans crossmember. You most likely have the typical small rectangular block mount thats used on most cars, but you really should check.

Re: The ol' bait & switch
 

Info and types below:

https://www.thirdgen.org/forums/hist...ss-member.html

JamesC

Re: The ol' bait & switch
 

If you have the 2 piece type, before you fork over cash to replace the "donuts" between the upper and lower the (if you're doing that)….take it apart first….they rust out pretty badly. Mine was stuck on both sides, and when I pulled them apart, metal came off with it. It was crusty.

So I went to the boneyard and just replaced it with the 1 piece type with the square mount. I know the 2 piece probably absorbs vibs better…but I felt zero difference between the two.

Re: The ol' bait & switch
 

Great info, gentlemen! I figured I'd have to get under there to verify, not a problem. Sounds like it's a crap-shoot as to what got put in where at what time. Secretly I'm hoping I don't have the secondary! I will post up next weekend with my findings!

Re: The ol' bait & switch
 

As 86 said, they're kind of randomly assigned; but seems like, 6-cyl cars got the $$$"fluid filled" aka "hydraulic"$$$$ mount, the most. The round one.

Most of the V8 cars got the normal $15 one.

By no means a hard-and-fast rule or anything; just; the odds.

The thread JamesC posted has lots of pics and info on it, will tell you exactly what you've got.

All the same, if you've got the $$$one$$$$, get the crossmember that will support the normal one, and put yourself out of its misery.

The ones that came with the "secondary" mounts, the ones that are really just yerbasic body biscuits, aren't a problem. If you've got that, just get the "normal" mount and move on. Swap out the biscuits if they're toast which they sometimes are but not all that often.

Re: The ol' bait & switch
 

Confirmed, I have the round style tranny mount, no secondary mount. Thanks, guys!

1987 GTA L98 a/t

Re: The ol' bait & switch
 

UPDATE Please look! I just crawled out from under the car, and wouldn't you know...the mount appears to be fine, but get this....NO BOLTS MOUNTING IT TO THE TRANSMISSION!!!! What the heck??? Can anyone give me any specs as to the lenth and size of these bolts?

Re: The ol' bait & switch
 

Posting for future searches....

700R4 transmission mount bolts are M10x1.5 20mm

and remember....lockwashers are our friends! lol

Re: The ol' bait & switch
 

I was thinking M10x1.5 30mm, but you may be right.

JamesC

Re: The ol' bait & switch
 

And you're probably right, James...I went to the short side because I only had one shot at a ride to the parts store and I didn't want to be too long (with my luck, that would have happened). Happy ending to the story is that there are now bolts where there once was not! yay!

sidenote: The grade 8 bolts I got from O'reilly's have a 17mm head on them.