bull pinion slop

[Anonymous-0]

I started to replace the drum brakes on my M, and after opening up the brake cover, found lots of grease and oil and goo underneath. The source of this goo appears to be a very trashed seal around the drum seal surface. Looking closer, I found lots of end play (.060) and lots of side play (.050) in the Bull Pinion. End play I can live with, but I think the side play is what ruined the seal. Getting the brakes working at this point meant replacing the seal and finding the cause of the side play.

It seems that the Bull Pinion is held in place on the outer end by a bearing, and on the inner end by the splines engaged in the differential bevel gear (which is inside the diff case, which is held in place by bearings on each end). The bull pinion bearing is acting as a pivot point, and the pull pinion is able to move side to side, like a seesaw moves up and down. The OD of the inner part of the bull pinion is .090 smaller than the ID of the differential case, so the only thing that could hold the inner end steady is the diff bevel gear (which it is not). So finally getting to my question, is this side play normal? Has anyone else seen it? If its not normal, what is the fix?

As it turns out there were half a dozen bad bearings on the input shaft, countershaft, and main shaft, so even if I dont get this part fixed to my satisfaction it was still worth opening the transmission up.

 

[Anonymous-0]

There are two bearings in the bull pinion cage, and inner and an outer for each of the cages. and I bet your inner bearings are as bad as the outer ones. The bolts are behind the brake drum to pull the cage. You can remove the cage by taking out all the bolts and then look for the 2 threaded holes, put 2 bolts in those and turn them out a half turn at a time. the cage will come out, but there is an "O" ring in there so it may be stiff to remove unil it comes out. When you change those "max load" bearings try to put them in so if by chance the ball retainer fails down the road the balls won't fall out and wreck the gears. If the bearings are bad on the inside, and I bet they are! check the end play slop when the new bearings are put in.

 

[Anonymous-0]

WARNING!!! DO NOT pull the bull pinion cage without removing the bull gear. The cage is slotted on the back side, and the bull gear goes into the slot to mesh with the bull pinion. If you just pull the cage, it will catch on the bull gear, and if you keep pulling on it after it catches it will break. Don't ask me how I know! Actually it was a C that I learned on, the hard way, but they are all similar. On an M you can remove the PTO and sneak in that way to unbolt the bull gear, then remove the axle, housing and all, but it still makes a tough job of replacing those bearings.

 

[Owen Aaland]

You also have to get the bull gears out of the way or you will break the bull pinion carriers when pulling them.

 

[Anonymous-0]

I actually have one side completely apart already, bull gear and axle shaft out, bull pinion and cage out. I guess my question not one of disassembly but rather where the side slop was coming from.

As Bob said, there are 2 bearings in the bull pinion cage. The outer one holds the pull pinion itself. The inner one doesnt hold the bull pinion, but rather it holds one end of the differential. The splines inside the differential, in turn, hold the inner end of the bull pinion. Now, if theres slop in the splines, or if the differential bevel gear can move inside the differential case, there ends up being slop in the other end of the bull pinion.

Regarding when bearings are considered bad, how much 'looseness' can one live with? I have measured the side slop in some bearings, and they range from .008 to .020. Im thinking that .008 in the axle shaft bearings is fine, but .020 in the pull pinion bearings is not. Bearing slop that allows a gear to pretty much move sideways, like the bull gear, shouldnt be much of an issue, as long as the gears stay aligned (shafts stay parallel) with each other.

 

[Anonymous-0]

Yep I forgot about that bullgear in the way. My gears were already out when I pulled out my cages.

 

[Anonymous-0]

How much the splines, differential gear or case is worn inside will affect the play on inside end of bull pinion shaft. They had some play when new and its usualy not a problem unless there's a lot of play. Most well used tractors have around 1/8 inch end play or more in pinion shaft.