Breaking engine mounting bolts

Usually when i see this it happens because mounts are damaged or something is not lining up properly i dont know if you have tried to change all 3 mounts at once it should take care of the issue.

 

First question i have is how hard is the truck being used in the lower gears?

Second is this, what are you using for bolts?

Grade 8 or some grade 3 stuff.

Many times when I see a mechanic crank down on MM bolts beyond their torque specs, it leads to being sheered off under stress.

So use grade 8 or if you can afford them grade 9.

And torque them to spec.

 

I’ve had all types of applications do this you have something going on with one of the other mounts or they r worn I’ve been here and changed bolts and one mount multiple time to the point I got pissed off of the truck coming back with same issue and changed all 3 with new screw and never had an issue since mine was a Volvo and we found that the front mount was damaged must have been putting extra stress on rears

 

Yup.

I have some documents with updated part numbers and procedure for this exact issue. Please PM me your direct email and I will shoot it to you when I get to work tomorrow.

See attached for engine mount revisions- I have yet to see the upgraded 4 bolt mounts break when correctly installed.

 

Grade 10.9 are roughly equal to a grade 8 imperial bolt. Grade 8.8 metric are equal to grade 5 imperial.

 

When I had my transmission rebuild, I told the shop to replace both motor mounts regardless. The passenger side was bad and the drivers side was fine. Regardless, they replaced BOTH. The mounts aren’t cheap but why pay for the labor later when it’s easier to get it done with the transmission out already.

 

Ether need to update the mounts to the 4 bolt per side style or drill out your 2 bolt mounts to take 3/4 bolts. It was an issue on the first series of the trelleborg mounts