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18MM bolts for transmission mount

S

shmicah

NAXJA Forum User
Location
Texas
I have a 99 XJ automatic 4.0 (so AW-4?) and was changing the transmission mount today.

One of the 18MM bolts (driver side) that attaches transmission mount to transfer case was missing. Anyone know what the specs of that bolt are? I'd like to know before going into the local hardware store as I don't always trust them.

I checked FSM and couldn't find that info. If that info exists in FSM it would also be nice to know where it is located just for reference.

Thanks!
 
Not sure I'd really worry about it. Pull one of the others and take it to the hardware store and get a match. Can't go wrong with grade 5 or 8. If you want, go to a junk yard and pull one from a donor.
 
It's a 12 or 14 mm bolt, probably around 1.0 - 1.5 thread pitch. It's more than likley a 10.9 hardness....5-8 are SAE grades.
 
M12-1.75 grade 10.9, I can guess 40mm long (its an open ended hole so if you go too long it doesn't matter); I ended up using Allen head bolts with a washer.
 
Thanks garr.

Since I'm new to this - given that my transmission mount was hanging on by one bolt for probably many years, could this have a downstream effect and damage or strain anything else? Anything I should check on besides my motor mounts?

I'm sure the answer is "no" or "your entire transmission", but just curious. Not sure what kind of mechanical strains the transmission would be under while running like that.

Thanks for your time
 
Shouldn't really affect much because the crossmember was still there to help. You may want to check the state of your mount. If it is bad (mine was) get an OEM replacement at Rockauto or something. I think mine was $12.
 
shmicah said:
Thanks garr.

Since I'm new to this - given that my transmission mount was hanging on by one bolt for probably many years, could this have a downstream effect and damage or strain anything else? Anything I should check on besides my motor mounts?

I'm sure the answer is "no" or "your entire transmission", but just curious. Not sure what kind of mechanical strains the transmission would be under while running like that.

Thanks for your time
Click to expand...

I have an AX-5 which was missing all three bolts, because some idiot stripped them all at some point. When it came to me, it had been that way for some number of miles, and produced a significant amount of wear from all the sliding back and forth. Drilled, tapped, and helicoiled. Been fine ever since.

If your new bolt doesn't pull tight, you'll know why it fell out. I just went and bought hardened bolts to fit the helicoils which were already in my box.
 
The bolts in my 01 XJ were the same as the ones the factory used for the rear skid plate and exhaust hangers.
 
The bell housing would have taken a beating if anything did get beat up. I'd look for cracks by the dowel pins just for good measure. I'm sure they are fine. They're pretty tough.
 
Thanks for input everyone. I can't find a M12-1.75 grade 10.9 bolt to save my life, so just gonna go with a grade 8 allen and washer like garr mentioned and be sure to check on it in the coming months

amazing how worn out my motor and transmission mounts were. Can't wait to see how it drives after this.
 
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