My manual says I should torque my trans to the clutch housing at 120-150ftlbs for a 5/8 bolt???!!!! Ive stripped 7/8 nuts at 140ftlbs!!! There's NO WAY that can be right. Whats the actual torque spec???

 

or is the ford manual going by thread size, cause I could see 40-50ft-lbs for a 7/16 thread size, and 120-140 for a 5/8 thread size.?

 

That seems to be a bit high. However it is possible.

Torque values are given for the nominal shank size and thread pitch...NOT the size of the hex-head. Torque specs are also given for NEW bolts. A bolt with a shank diamenter of over a half inch should (if its a good bolt) be able to take this torque without trouble (and its into steel). Some manuals give reduced torques for reused bolts. Some just expand the lower range.


Torquing is done to put ONE stress cycle on the bolt at its first installation adn removal. The bolt is only going to adequately survive a given number of stress cycles. So if a particualr bolt has been uninstalled and reinstalled a number of times, it begins to weaken. Stress cycles change the actual molecular grain structure of the material the bolt is made out of.

The problems arrise when people try to torque a bolt that has seen several stress cycles and fail to see/feel when a bolt begins to stretch. Using a "Beam" style torque wrench will allow one to notice that they are turning the bolt, but that torque is not increasing rapidly.

A good, strong bolt, when torqued, will start torquing slowly and increase in torque at a higher rate as the value gets higher at the same time, the relative movement of the bolt is reduced. The platauing of the torque indicates stretching. Any stretching indicates a need for a new bolt.

If one insists on reusing a bolt, it should be torqued to the lowest value in the range and stretching should NEVER be allowed. A bolt that streches before the min torque is reached is a likely candidate for failure.

I'm sure you knew all this, but it is for those who may not.

Happy torquing!

 

Sounds like way too much torque to me. The reason being is I think it might crack the ears, they are only cast iron. I had a few bolts fall out (at the top), what I did is put washers/lock washers under them and then torque the bolts down until they felt good. Maybe 1/8 turn past when they seated after compressing the washer.

 

I just tighten these with a standard 1/2" drive rachet until they are moderatly tight.

 

As they used to tell us when I worked in a Nulear Safety Related Switchgear Refurbishment shop, use good craft practices. Neveer did explain what that really meant though. I tighten them with a 1/2" ratchet until gooduntight.LOL
Clint

 

Man! Just snug them down with your hand hear the socket end of the ratchet. If they get loose later retighten them. Lot easier than digging out a busted bolt. True fact about bolts wearing out after many torque cycles. Makes a case for my rule of never reusing fasteners on anything important.