L3940D FRONT WHEELS LOCKED !! RIDDLE ME THIS??

[Renman]

Tractor: L3940D hydrostatic 4 wheel drive.

Problem: Reversing tractor in 2 wheel drive. Will reverse in 4 wheel drive.

HERE IS WHAT HAPPENED IN SEQUENCE.

1. Running into town about 1.5 miles to pickup an old motor. I was traveling at full speed along the shoulder. WITHOUT ME REALIZING THAT I WAS IN 4 WHEEL DRIVE.

2. Half way into town the machine literally skidded to a stop along the shoulder. I mean 13.4 mph to -0- in the blink of an eye, almost throwing me over the top of the steering wheel.

3. This is when I determined to check my underwear for staining and look over the machine, which is at this point I found out I was in 4 wheel drive..... I attempted to gingerly inch forward and backward in 2 wheel drive and 4 wheel drive. Lots of grinding and very little movement. The front wheels where locked up for the most part. Called a tow truck and loaded it by skidding up the tow truck bed using my forks to lift the front of the tractor.

4. Got the tractor into the barn and up on stands. Removed the wheels and began disassembly of the drivers side wheel hub. The outer wheel bearing and seal where trashed.

5. Thinking that the bearings and seals where all worse for wear I replaced all of the bearings and seals in both wheel housings after cleaning every part thoroughly, reassembled the axle hubs, and replaced the axle lubricant.

6. Yesterday evening I drove slowly forward out of the barn in 2 wheel drive and then tried to reverse. The front wheels locked up and would not turn. I then flipped the machine into 4 wheel drive and was successful in reversing, but I could hear and feel protesting trying to go forward in 4 wheel drive. Back into 2 wheel drive I motored around for a few minutes with no grinding, vibration, or noise.

I have a suspicion of what is now wrong. What do you think?

 

[crashz]

My WAG is that you have similar damage to the ring and pinion gears and bearings as you had with the wheel hub assemblies. In 4wd there is a slight lead of the front axle (which is highly stressed at high speed) and with worn or damaged bearings, maybe causing a bind under power. Under no load, it may just be floating.

Good luck and let us know what you find.

 

[rbargeron]

The ring and pinion are pretty strong - but a kingpin bevel gear (40 or 80 on .pdf)
may have broken a tooth when the bearing locked up.

 

[Renman]

The ring and pinion are pretty strong - but a kingpin bevel gear (40 or 80 on .pdf)
may have broken a tooth when the bearing locked up.

Thanks for the reply. Not the ring and pinion gear for sure. I totally rebuilt the wheel hubs with new bearings, and seals, and of course cleaned and inspected everything.

 

[crashz]

Were the bevel gears that rbargeron mentioned in good shape?

 

[Renman]

My WAG is that you have similar damage to the ring and pinion gears and bearings as you had with the wheel hub assemblies. In 4wd there is a slight lead of the front axle (which is highly stressed at high speed) and with worn or damaged bearings, maybe causing a bind under power. Under no load, it may just be floating.

Good luck and let us know what you find.

We have a winner!!!! I removed the front axle last night and quit at that point to figure out how to move the axle and work on it. Ending up buying a harbor freight transmission jack to lower the axle and then rigged a hoist in my barn from the rafters. The pinion gear (which I thought) is fine upon inspection looks good. The bearing closest to the gear was destroyed to the point where the roller bearings where welded together. Whats left over is a collar welded to the pinion gear shaft that will barely move (1/8") which I presume is part of the bearing assembly. Tomorrow I will try to get an actual picture of the pinion gear shaft.

 

[rbargeron]

The bearing is common to a lot of models (Kub part 34070-12200) NTN's part number is 332/28PX1 - available here for around $22 (2 req'd). To cut an old bearing race off the shaft a dremmel & abrasive disk should do. Dick B

 

[Alan W.]

Yeah it appears the pinion has been very hot. Replacing it also would be money well spent.
Was the differential oil level ok when you started tearing it down?

 

[Renman]

Well I finally was able to remove the old bearing race collar by cutting it on opposite side with a Foredom tool, soaking it with lube oil, beating on it, and finally used a gear puller to pull it off the shaft. Believe it or not the shaft looks alright, as does the ring gear.

I ordered all new collars, bearings, etc for the pinion shaft. What is now my concern is I believe the collar #30 is stuck in the bottom of the barrel as shown the illustration. Does anyone know if the collar rests on a ridge to keep it from dropping onto the ring gear. I haven't tried to remove it yet and would welcome advice.View attachment 614515 Thanks.

 

[rbargeron]

.......I ordered all new collars, bearings, etc for the pinion shaft. What is now my concern is I believe the collar #30 is stuck in the bottom of the barrel as shown the illustration. Does anyone know if the collar rests on a ridge to keep it from dropping onto the ring gear. I haven't tried to remove it yet and would welcome advice.View attachment 614515 Thanks.

Attachment 614515 doesn't open but in the .pdf below, parts 30 and 40 are select-thickness shims used to set up gear clearance. Often new bearings are consistent enough to use the existing shims when reinstalling the original gears. If approx .005 to .015" backlash can be felt the setup is ok.