90Q removing bolt from rear diff mount.

[John Larson]

Tom said:  "Thanks, but I did check. They are grade 8's."

That "8" 0r "8.8" on the bolt doesn't mean "grade 8".  They're closer to 5s. 
Metric bolts aren't graded like US hardware.  You need a "10.9" or better in 
this application.  They should have told you that.  But then, they're 
typical retail parts counter men, and they probably didn't know that.  BTW, 
John Deere and Caterpillar dealers are generally great places to buy metric 
hardware, and I have found the counter men  to be both knowledgeable and 
helpful.  HTH, John