Tightening up studs

[lostagain]

I am just about to install a new differential on my bus.

It is mentionned in RV Safetyman's thread about rear end synthetic lube that the studs that hold the two halves of the pumkin together should be tight. There is also studs to hold the drop box to the diff case.

That gets me wondering: how do you tighten them up? They go in coarse thread first. How do you get a hold of them to tighten them? Can I use 2 nuts on the fine thread side to torque them down?

Thank you,

JC

[luvrbus]

I double nut the studs and tighten to 60 ft lbs, fwiw you need to remove the flange and check to be sure the washer is behind the flange if not order one from Jefferson 55 bucks if you need one, that washer is a must to get get the right torque on the input shaft and some manuals do not show it

good luck

[bobofthenorth]

I'll be watching to see what advice you get but my personal opinion is that if you need to torque the stud in then its already too late. You need to clean the seat with a bottom tap & clean the stud on a wire wheel. It should go all the way to the bottom with your fingers. But that's just my opinion and I'm sure as hell no mechanic.

[bevans6]

Studs are designed to be installed finger tight in class 3 interference fit female threaded holes, which effectively lock them in place.  Use loctite if the hole is worn or just not threaded correctly with the interference fit.  Torquing the stud in creates stress that encourages premature failure.  Sorry to disagree with the experts, but this is based on two decades of studying threaded joint design and use in high performance applications.  Keeping the cover on a differential isn't exactly a high performance application and you can probably nail it on, but the principles still apply.

Brian

[luvrbus]

If he has the correct studs they have a shoulder that seats into the drop-box finger tight won't get it my Rockwell bible calls for 58 foot lbs ,the self locking nut torque I think is wrong 52-58 ft lbs,fwiw every rocker arm stud I ever installed on Chev V8 torqued to 22 ft lbs a example  

good luck

[lostagain]

Clifford, there is a washer behind the flange on the input shaft.

There is no shoulder on the studs. They are just a coarse thread on the side that screws into the drop box, and fine thread for the nuts. The studs that stayed into the drop box are tight. 3 of them came out with the nuts. That is why I was asking about how tight to put them back in. All the threads are in good shape.

The MCI maintenance manual says: "Torque the nuts and studs or cap screws that attach the drop box to the differential cover to 160 to 205 foot pounds."

JC

[lostagain]

Brian, "you can probably nail it on". I got a good laugh out of this one. I used to be a horse shoer, (still shoe a few regularly), and in this 21st century, we still nail them on, and they stay on real good, most of the time. So I should look deeper into the use of nails (simple technology), in bus maintenance, lol.

JC

[Oonrahnjay]

(snip)  The MCI maintenance manual says: "Torque the nuts and studs or cap screws that attach the drop box to the differential cover to 160 to 205 foot pounds."  

  That torque is only for the final fitting, housing/stud/housing/nut combo but I agree with Brian here (the studs should be a snug but easy fit all the way in) and Clifford (that they should be seated into their threads and if it takes a firm push or a torque wrench on a double-nut, then that's what it takes) but I also don't trust studs not to leak oil.  Threads have a very small but perceptible clearance and oil can often get through that clearance.  Even if the thread doesn't require Loc-Tite, I still like putting a little soft sealer (and by little I mean about a single thread's worth) in there to seal the oil.

   And, also agreed, if the studs don't go in because the threads are distorted, or the housing is warped, or the threads are rusty or for whatever reason, that's a problem that needs to be fixed properly (tap and die, cleaning, rust removal) before you do anything else.  If that kind of problem is "fixed" with torque, it ain't fixed and it's really likely to turn around and bite you later.

    I'm a little worried about the idea that three studs came out with the nuts.  Are you sure that the fine threads between the nuts and the studs are clean and not distorted?  If they're OK, the studs shouldn't come out with them (OK, it sometimes happens that there's dirt on the end of the stud that gets jammed down in the thread as the nut is coming off but that's different).  Once there's no locking force jamming those threads, if the studs came out with the nuts, there should be so little drag on the nuts that they come off easily with finger pressure.  If not, either the coarse threads are too loose or the fine threads are too tight.  This is another "fix it - don't just jam it on" thing.  Of course, if there's rust or other corrosion that's occurred in those fine threads, all bets are off but I'd be careful with them.

BH NC USA

[lostagain]

Bruce, I think the nuts made the studs turn out because, like you point out, the end of the studs had rust and dirt on them that made the nuts hard to come out. The nuts came off the studs quite easily later. The threads do look good otherwise. I'm thinking I will probably get new nuts as the old ones are quite rusty.

Thanks,

JC

[Oonrahnjay]

Bruce, I think the nuts made the studs turn out because, like you point out, the end of the studs had rust and dirt on them that made the nuts hard to come out. The nuts came off the studs quite easily later. The threads do look good otherwise. I'm thinking I will probably get new nuts as the old ones are quite rusty.     Thanks,    JC   

    Yeah, new ones are probably a good idea.  But check the fit in the housing with the coarse threads - they shouldn't be loose and they shouldn't bind going in.  Sounds like you're being careful and that's good.  Let us know what you find.

[luvrbus]

That is the same torque JC it calls for in the Eagle manual I have no Idea where they come up with 52-58 lbs in the Rockwell manual and I just pulled a stud from a Eagle box and it does have a seat with a taper on the stud 58ft lbs torque but I am looking at a drop box from a 1994-1995 model 15

good luck

[bevans6]

If you have a stud with a taper seat, then that should be torqued in.  If you have installation instructions for the studs, then you should follow those.  I was referring to generic plain studs that simply thread in.  If you torque those you are either binding the end of the thread at the top or the bottom and creating incorrect stress. 

Brian

[artvonne]

  Big difference in experience between salt-belt northern climate and salt free southern climate. I been watching all my life, its just not the same. Things you see in the north just dont happen down here very often, they barely know what rust is. Studs coming off with the nut is quite common on vehicles run in salt, its so corrosive to vehicles its hard to imagine if you havnt seen it/lived in it. The salt permeates between the threads and can lock the nut to the stud so hard you can often throw both away. even worse is studs threaded into aluminum, they can bond so hard you have to drill the stud out, or give up and throw the whole works away. Ive had studs in the vise that came out with the nut, all the torque in the world would only serve to mangle it and twist in half.

  Clean out the threads, put some brown permatex on them and thread them in. If Clifford says 60 lbs torque on them, crank em in. The permatex will seal them from oil and salt and youll still be able to get them out years from now.