RTH lower trunnion bearing stud torque spec (1 Viewer)

[rc51kid]

Quick question. I am replacing my lower trunnion bearing studs with new OEM hardware. Plan is to install STUDS with red loctite. Any idea of the torque spec on the STUDS themselves? The original ones were not very tight. Should i just use red loctite and tighten down to a reasonable torque such as 20ish or just by feel?

 

[Tools R Us]

There is no torque spec, they only need to be tightened enough to not spin, snug. We never use Loc-Tite on them, it only makes later removal more difficult.

 

[Wayne]

I'm looking at the '96 FSM and it doesn't show the installation of those studs. When I replaced mine I screwed them until end of the stud started to enter the knuckle ball. I also used red Locktite.

 

[rc51kid]

I figured loctite was a sure thing on these. But i guess if one broke on the trail drilling it and removing it would be a LOT harder if it had red loctite on it. Is that the consensus? Why do these simple things become dilemmas when i over think EVERYTHING on these trucks.

 

[inkpot]

I'm looking at the '96 FSM and it doesn't show the installation of those studs. When I replaced mine I screwed them until end of the stud started to enter the knuckle ball. I also used red Locktite.

IIRC when you run an OEM stud into the knuckle housing it should go in until it is threaded up to the smooth area in the middle of the stud?

 

[Tools R Us]

The only benefit I see to Loc-Tite is making a broken stud just about impossible to remove.

 

[ccslider]

A little heat will melt the loctite in a jiffy

 

[bloc]

Or.. don't use it in the first place, per FSM knuckle assembly procedure. I'm firmly in @Tools R Us camp that with proper prep and assembly of the stud holes and arm to knuckle face loctite isn't needed.

As to why applying anything more than hand-tight torque to the stud is a bad thing.. ALL of the force will be applied to the first thread in the knuckle face, and mating with where the threads end on the flat section in the middle of the stud. The only thing stopping that stud from turning further is deformation of these two small areas. Basically, it'll beat the piss out of that first thread.

This is different than torquing a normal bolt or nut, where the clamping force applied by the flat face of that bolt head or nut is what is pulling back against the threads.

I'm not doing a good job of explaining this, but generally it is a bad idea to torque a straight stud into a hole, especially where it can't bottom out. There are exceptions to this out there but if the FSM doesn't list a torque spec understand it's not supposed to be torqued.

 

[Tools R Us]

A little heat will melt the loctite in a jiffy

Agree, ~350F at the glue joint will release it. So, your out in the middle of the desert, 3 of the studs are broken, the wheel is fixing to fall off, birf soup/slop is puking out, have many rocky miles to make it out before mama calls S&R on you. What are you going to do, build a fire under it? Been there, passed on the t-shirt!

Both cases were relatively recent purchases, with fresh knuckle seal jobs (from the PO). The owners did the right things, checked/replenished grease level, torque checked the nuts, didn't move (of course they didn't, they were glued in place).

In this application, glue is much more likely to cause harm than good. Removes the only warning clue that you have before failure, the torque check.

 

[rc51kid]

Well i skipped the loctite. But i did put a little torque into them. i did it before reading blocs post. Screwed them down with a 3/8 drive.Then gave them just a little more. Hopefully it didnt mess anything up. I did understand that it was just the end of the threads starting to hit the threads on the birfeikd housing. So i knew better than to really tighten them. I just gave them a good snug chocking up on the small ratchet.

 

[bloc]

Should be fine unless you are particularly hard on steering arms and knuckle studs. Any damage will most likely be confined to the first thread and -probably- won't contribute significantly to the strength of the joint. Also can be fixed easily with a tap next time you have it apart (hopefully a long time). And for anyone else reading this the stud has a different thread pitch where it runs into the knuckle vs the nut on the end. DON'T use a tap that matches the nut.

Where guys screw up is when they assume the stud needs 71lb-ft like the nut.