BX-22 4WD Driveshaft Coupling Problem

DOC4444 · May 3, 2015

The other day, I saw the driveshaft that is connected to the front differential hanging down at the aft end. Inspection revealed that the coupling had become disconnected from the driveshaft that goes forward from the transmission at the center support bearing.

It appears to me that the coupling is normally kept from slipping off the splines by a roll pin. If I am correct, both ends of the roll pin have broken off. I initially tried to drive it out and replace it with a new one. However, that did not work, at least working from below with a hammer and punch. I then tried drilling it out and only succeeded in making the hole a little bigger in the roll pin. (It is VERY hard material and I dulled several larger drill bits.)

My question is why the roll pin broke. On closer inspection, there seems to be a fair amount of slop between the splines of the driveshaft and coupling, though wear marks are not obvious. (I have never looked at these parts before, so I have no idea how much slop is normal, though it does seems similar to the splined coupling that connects the drive to the belly mower.) I am guessing the slop caused side loads to be delivered to the roll pin that it was never intended to sustain, breaking off the ends.

Do I have to replace the splined coupling on the front driveshaft and/or the rear driveshaft? Or, assuming I can finally successfully drill out the remains of the roll pin, could I simply install a 3/16", or there abouts, grade 8 bolt in place of the roll pin and have it last a while?

Thanks as always for all your help,

DOC

repete · May 3, 2015

DOC4444 said:
The other day, I saw the driveshaft that is connected to the front differential hanging down at the aft end. Inspection revealed that the coupling had become disconnected from the driveshaft that goes forward from the transmission at the center support bearing.

It appears to me that the coupling is normally kept from slipping off the splines by a roll pin. If I am correct, both ends of the roll pin have broken off. I initially tried to drive it out and replace it with a new one. However, that did not work, at least working from below with a hammer and punch. I then tried drilling it out and only succeeded in making the hole a little bigger in the roll pin. (It is VERY hard material and I dulled several larger drill bits.)

My question is why the roll pin broke. On closer inspection, there seems to be a fair amount of slop between the splines of the driveshaft and coupling, though wear marks are not obvious. (I have never even looked at these parts before, so I have no idea how much slop is normal, though it does seems similar to the splined coupling that connects the drive to the belly mower.) I am guessing the slop caused side loads to be delivered to the roll pin that it was never intended to sustain, breaking off the ends.

Do I have to replace the splined coupling on the front driveshaft and/or the rear driveshaft? Or, assuming I can finally successfully drill out the remains of the roll pin, could I simply install a 3/16", or there abouts, grade 8 bolt in place of the roll pin and have it last a while?

Thanks as always for all your help,

DOC

On mine the roll pin is there only to locate the splined coupling. It carries no load. I would recommend putting grease on the shafts and make sure the coupling slides easily.

Can you visually examine both splines?

I just lost the input spline on the pinion gear on my 2550. The spline stripped out. New ring and pinion and coupling. The proper pin can be ordered.

SeymourBota · May 4, 2015

The same thing happened to my BX2200 a couple of years ago. The front driveshaft dropped on to the top of the mower (a convenient way to avoid further damage!!)

I reinstalled with a new roll pin and have had no issues since.

At the time, I remember thinking I must have turned too sharply in 4WD while mowing, without enough give in the ground below.

Not sure I would use a grade 8 bolt. That might result in a more expensive component breaking next time.

RaydaKub · May 4, 2015

I had mine break a year ago last winter. Found a comparable one at the local (former) JD shop (now an ATV / boat dealer). I figured I must have had the front axle tipped very high on the right side some time, then it took a while before it finally slipped off. My spines were decently snug. I was able to get mine out with a punch though.

DOC4444 · May 10, 2015

Had to remove center support bearing carrier in order to remove driveshaft. Then, I put it in a big bench vise and wailed on it to get the roll pin out. It was obvious I would NEVER be able to drive the new one in from below with the shaft in the tractor. I drilled the hole out a couple of letter drill sizes. On installation, I squeezed the roll pin with vice grips to be able to get it started in the hole. Then, I used a huge pair of vice grips to put a lot of load on the pin and then hit the jaw with a hammer to drive it home. (I considered using an air chisel type tool, but was afraid it would shatter the pin and I would have to start all over again.) I packed the splines with grease, but there is still a fair amount of slop, so it is unclear how long it will take before the pin shatters again.

Thanks as always for all the help,

DOC