Anyone out there breaking motor mount bolts? Twice now I have sheared of the bolts going into the motor on the left side. Just a little tweaked 3.4 v6, 1.6 roller rocker arms, 4.3 tbi, 4 speed auto. Factory bolts first time and grade 8 bolts the second time. When the bolts shear off the engine falls and breaks off the oil pressure sender, spewing Mobil one out the left fender. The bolts hold up to nearly a year of daily driving, but go offroading on harder trails and .....


I do have low profile rear crossmember that is reinforced. I doesn't seem that the rear tranny mount controls torque very much anyway. Here is a picture of the sheared off bolts <img src="/forums/images/graemlins/evil.gif" alt="" />



Thinking about building a new mount that catches another hole in the engine block. Or chaining / cabling the motor down to contain my awesome torquey motor <img src="/forums/images/graemlins/nana.gif" alt="" />

I have broken a couple of the same bolts. I have long felt that the correct solution would be a new mount that incorporated the use of all three holes in the block, but I haven't gotten around to doing anything about it.

Seems like a real pain, especially getting in there to extract them. <img src="/forums/images/graemlins/angry.gif" alt="" /> They are metric right? Have you tried class 10.9 hardware?

Yes a real pain to fix .... Small chisel and hammer spun one out. The other required drilling and a not so easy out <img src="/forums/images/graemlins/evil.gif" alt="" />

10mm metric bolts, nope not tried 10.9 hardware yet. < EDIT I think maybe Jeff da Marmot may have given me grade 10 bolts now that I think about it. At the time I just happy they wre bolts that fit. end EDIT > Finished up replacing them again this afternoon, grade 8.8 again.

Also thought about giving the transfer case some kinda of arm. To limit how much it torques back there.

The thing is, Metric class 8.8 is like an SAE grade 5. So you need to use a Metric class 10.9 to get the strong stuff.

Broken motor mount bolts a third time. My mechanic came up with this simple mod.



Angle iron drill to catch two upper holes. And one hole drilled and tapped into the factory mount. Plus a small brace to keep the angle iron from folding. Three weeks and still holding <img src="/forums/images/graemlins/smile.gif" alt="" /> .