Loose bolts on J.Deere

My good neighbor has a small J.D. 3320 tractor with loader and he cannot keep the mounting bolts of the loader tight. The first time it happened he had several bolts on each side snap while others had only loosened. They (all 16)were all replaced on each side with new J.Deere bolts. I am suspecting that those bolts that loosened the first time rattled around long enough to leave the holes eggshaped, hence nothing will ever tighten, even with Locktite until the holes are retapped and threaded with oversize bolts. Any ideas on what causes them to loosen? Any ideas on how to remedy the issue?
Thanks for any help on this.
Cal

Checking the threads that still exist is the key to success. Put a new bolt into the hole about a bolt diameter deep. wiggle it. if it is not tight, it will be necessary to use a next size larger bolt. The size chosen should have a tap drill size at or a whisker bigger than the major diameter of the original bolt. This allows all old threads to be removed. Grade 8 bolts should be used. If metric bolts are used the 12.9 property class bolt should be used. Drilling the holes in the mount bracket (loader part) should be held very close to the shank size of the new bolts to provide locational stability. The threads of the new bolts should not extend more than 2 threads into the bracket (this is also part of positional accuracy) a heavy flat washer and locktite should be used. No lock washers, they break and fall out. Jim

Dads new Holland is the same way I?ve got to get some new bolts and get them a little longer and use some green loctite and put a nut on the back will hold it tight

Use grade 8 or equivalent all thread, run the all-thread into the bottom of the holes with Loctite and cut them off to the needed length. Use harden washers and nuts (grade 8 or equivalent) and torque them to 90% of proof load (there are online tables with this info). This will get the maximum thread into the tractor frame and get maximum stretch on the studs.

Good luck
Rich

There is a similar topic on this over on Restoration and Repair.

As said, the holes are probably wallowed. They can be drilled over to the next size, or if not enough room, repaired with a Recoil kit, or thread insert bushings.

How ever it is done, it is necessary the holes be drilled straight using a mag base drill or a drill guide block. Attempting to hand drill without a guide will always result in a crooked, wallowed hole causing more harm than good!

Another problem is the mating surfaces are no longer flat. You can try to clean them up with a file or a grinder, but it is very easy to make the situation worse. If it is impossible to remachine the surface, best to leave it and just debur the holes, be sure there is no paint or grit between the surfaces.

Then go back with grade 8 bolts and heavy grade 8 washers. The washers are as critical as the bolts. If they crush, the bolts will be left loose.

If you choose to use Locktite, clean the holes with carb cleaner, get rid of all traces of oil. Red Locktite the bolts, use primer for the best results. Torque the bolts per the recommended torque found on torque charts.

But, one of the drawbacks to using Locktite, it is difficult to get a good retorque on them after the first use. If the surfaces are less than perfect, real good chance it will settle in and loose the torque on the bolts. You may want to run it without Locktite for a while, retorqing them several times until there is no more loss of torque, then take them out one at a time, clean the oil out of the hole and off the bolt, then apply the Locktite.

Still, keep a close watch on them. If they come loose again there may not be anything to work with next time!

I found over the last 50 or so years if the bolts work loose they are not big enough in the first place. Dad had a tongue on a chopper that had 5/8 bolts and they worked loose. He drilled them out for 3/4 never a problem after that for over 30 years.

Don't know if this would matter, but the threads on today's bolts are microscopically thinner than they were back in the day. Way to save some material and money, I guess.

How I found out was I was working on a 1940 JD B and we were replacing the manifold. I think it's just one bolt hole that connects straight into the coolant chamber on the block, but we used a copper washer, modern bolts & every type of thread compound known to man and after draining the thing 12 times because of leaks I called a JD specific restoration company and had a talk with them. There explanation was modern bolt threads are thinner and it is almost impossible to seal up correctly with out an old style bolt. A few bucks and days later and it sealed up like a charm and never had a problem since then. Just my 2 cents.