L35 Left Brake Drag, Damaged

I have a 1994 TLB35 with 2800 hrs. Like most others I use it for variety of things, from logging (sawmill), to earth works and plowing snow. Rear tires filled with calcium.

I have a bad habit (memory is 2nd thing to go as we age) of forgetting to unlock the parking brake when backing up- yes I am human. Last week that habit finally caught up to me. Had a pile of logs on the forks and the noticed left wheel dragging as I tried to crawl along. When I used the brakes, felt like the left side would not release. Parked it and came here looking for help.

Am an infrequent visitor and like most dont use OTT unless there is a problem. Found a lot of good general info but nothing detailed. I have been fuddling with wrenches for a number of decades, but this is my first venture into the world of WET BRAKES.

To gain an understanding of how these brakes work, found this:

Cat® Wet Disk Brakes | How Oil Cooled Hydraulic Brakes Work

https://www.youtube.com/watch?v=dvCYBUOtKrk

Though its not a Kubota tractor, it is a really good representation of HOW they work. From here I had a better understanding of the problem, and have now dove into tearing apart the left side of tractor. Though I have manuals, the quality of the images is lacking so I am also using the online manuals, which have colour photos:

http://www.kubotabooks.com/AutoInde...s/&AutoIndex=1786e1006a6663a0fc94d072a5a914ff

I had the tractor up in the air and spun the wheels, and the left side was defintely harder to turn. Checked the linkages and all seem working properly. Undid linkage on left and cam moves back and forth freely. At this point i suspect the the discs and springs.

Trying to do tear down without taking off open canopy ROPS. Like others, need less work, not more.

Don't know when I'll get a chance to update as summer here in the Yukon is very short, and snow is 2 months away. And i don't have a shop to work in- hoping one day to get around to it.

Its been raining past couple of days so I have a moment to jot down some progress, and thoughts.

PB Blaster and Nut Cracker are my friends for rusted bolts. I have had to start disassembly of ROPs which is something i dreaded since previous owner did such a nice job of wiring up 6 flood lights, front and back, unfortunately thru the metal tubing of the frame, which means cutting wires, and removing lights.

I have the bottom frame rail free and can't help wonder why "they" didn't make it easier for removal. The metal cross brace that attaches to the frame rail and vertical support for ROPS - could have been bolted, instead of welded, making for a less invasive procedure. Considered cutting it and then reattching but decided against this, as any fabrication would be complicated by the fender. I have worked on a few assembly lines, most notable AMC and McDonnel Douglas, so i look at things from a manufacturing perspective at times.

All in all, it's not that difficult, with impact wrench, breaker bar, basic tools and should have it off by the end of the day.

One last thought, the left brake cam lever moved back and forth very freely (ie., 3-4"). Need to compare with the right side, once linkage detached. Something tells me that if the spring inside were intact, this would not be happening. Wonder if my assumption is correct? Anyone with experience in this area, please confirm. Thank you.

Got the left brake off yesterday afternoon, after a couple of rain showers came through. Very straight fwd, no complicated procedures.

The description of how the brakes work is very bare bones in the manual, and leaves a lot to the imagination. There is no internal spring. For those who want or need a better understanding, here is a humble attempt at a slightly more detailed description (refer to manual when trying to visualize):

The Cam lever actuates the cam plate and causes it to rotate a few degrees. Toward the transmission side are 6 steel balls that are in fixed cups. These balls mate with conical depressions on the facing side of the cam plate. The opposite side of the cam plate is smooth and flat and faces the discs.

The cam plate moves back and forth because there is enough area with the cones to allow some movement but the as more pressure is applied the angled surface of the cone(s) starts to ride up against the fixed steel ball(s) in turn causing pressure on the the cam plate and making it press against the disc(s).

Said differently, when rotated, the cam plate acts like a wedge, pushing off the stationary steel balls and transmission, on one side, and applying force against the discs on the other side- in fact, very simple in design but ingenious in it's application and effectiveness.

What I found:

- bluing from heat build up on conical seats in cam plate
- bluing from heat on smooth surface of cam plate from heat build up
- minor scarring on one very small area of brake disc hole
- The brake discs and central plate "seemed" stuck together

The last item is interesting because it took quite a bit of effort to separate the discs and middle plate- like they were held together from either 1) a vacuum created as a result of the surfaces being machined so smooth and flat and/or, 2) having all the oils squeezed out between them, and the rough side of the discs becoming embedded in the central plate? I wonder out loud if this is a normal state of brake disc functioning but can't understand why or how that would be? Doesn't seem likely to me, but again, this is my first adventure with wet brakes.

Other than that, everything appeared normal and there were no metal shavings or bits in the drained oil or within the brake case. Bearings and gears all intact, in fact in excellent shape.

Obviously leaving the parking brake on caused excessive heat build up. Anyone ever experience brake discs "stuck" together? Not sure if this explains the drag, unless the cam plate got stuck in the "wedged" position after release of parking brake?

Also, the is a long straight metal wire (spring)behind the steel balls inside the transmission. Cant see what or how it's attached inside. But part of it is dangling down inside the transmission case next to planetary gears. If my phone wasn't already full of pics I could attach one. Can't find it in the diagrams. Hope this is normal. Can anyone confirm?

Wolfman, any thought about the stuck discs?

greenacresnorth said:

the friction and steels will try and stick with a oil film, with oily fingers they can be a bugger to get apart. if you have signs of heat trauma and the hard steels are torn up then the are probably warped causing them to compress together when assembled.

Click to expand...

Thanks for your thoughts greenacres. Heat trauma is there but "appears" minimal. Just inside the cones of the cam plate, but then again, makes me wonder about warping-The fact that heat damage transferred from one side of cam plate to the direct opposite side makes the cam plate a suspect, will definitely check. Other than that, no metal debris, nothing torn up.

The excess pressure (not releasing parking brake) and heat may have caused cam plate to get stuck and discs to stick together but I don't have a lot of experience with this and would like to confirm this. I'm thinking releasing parking brake should have brought cam plate back to neutral and trying to understand what would make breaks stick and cause drag. The motion of the tractor moving should have caused the discs to release- become unstuck (?),

Warped cam plate makes most sense.

North Idaho Wolfman said:

The return springs are right at the pedals.

If it created that much heat to blue parts, it really messes with the disks, I have even seen them become "sticky" from the heat.

I would bite the bullet and buy all the moving parts including the balls (heat would have transferred to them and I'm betting they even might be warped or squashed.

Click to expand...

Thanks wolfman. Again, there is heat damage but "seems" relatively contained to cam plate. I will check for flatness of all parts today. Probably best surface I have for that is table saw or joiner or similar.

Inspected the cam plate, discs and middle stationary plate, steel balls on 3 different machined surfaces, since surfaces have their own peculiarities:

-Steel balls have no scratches, score marks or heat damage

-middle plate is marred on the tangs that butt up against casing, making it difficult to check until/if I grind off deformity

-one of the discs showed signs of warp along one side. Aprox 0.002"

-cam plate showed signs of warp in a similarly small area (2-3" stretch) of approx. 0.002"

need to check manual for specifications...:confused doesn't "seem" like a heck of a lot.

going to dealer to see if I can get parts...

Quick update: Took parts to dealership. Mechanic and parts person looked at discs and cam plate and detente balls and noted that all looked in exceptional condition considering hrs. They felt that the amount of blueing was indeed minimal as well as the amount of measured warp. The fact that there was wheel drag was considered as a problem else where, perhaps linkage. They encouraged me to save money and not buy new parts. This was different, but then there are new staff, and i know one of the fellas father.

Spent last couple days cleaning and prepping for reassembly. Roughed all surfaces with emery cloth. The discs seemed slightly smooth, not quite glazed, but sanding definitely helped.

Spent 12 hrs yesterday putting it all back together, except for fender and cable shifter assembly.

1. The brake cam lever operates good but tightening the nut causes lever to stick to the point where if i tighten too much, cannot operate lever (???)- makes me wonder. No torques in manual.

2. The cable on the bottom of the speed shift selector assembly is in trouble. The hollow metal bolt that the cable passes thru as it passes into the selector is broken. Similar to what one sees on bicycle brake cables in the brake grip. Going to try and RR. saw in another thread where it cost from $450 to over $600 for cables. No detailed discussion of how this comes apart?

3. Having trouble attaching brake linkage. Seems to want to attach in activated position. Wondering how linkage moved? since when I took it off, brake was "off" - disengaged.