As you might know, I have begun undertaking the project of replacing the bellows seals in my D6 9U. This is my first dozer, and my first major repair project with it. The machine # is 9U5896. Old magnet, as well as some others have already helped me, so I wanted to start a new thread to show some pictures of my progress, and, or course, ask some more questions.

I got the tracks split last Thursday with some help from Old Magnet on making a track pin punch holder. Mine is very crude, but it did the job!

After I got the tracks split, I had to pull the front idler. That was relatively easy. One problem that I did notice was that one of the four pin bolts that runs vertically through the bearing block is broken off. I'm not sure how big a deal that is, but it hasn't been a problem yet.

Now, yesterday, I had the pleasure of working on my extremely-difficult-to-move manual track adjuster. By the way, I'm only working on the one side of the dozer for now. After a days worth of heating, hammering, turning, and swearing, I got the large bolt and nut off. I think I will take the bolt and nut to a machine shop and try to get the threads chased.

Here are the pictures of the adjuster.

So today I got to remove the track frame. Another all-day job. It was no problem getting the front of the track frame off the equalizer spring, but I broke off three of the four large bolts that hold the back in. I will have to figure those out later. I built a little 4x4 dolly with some heavy metal casters I had to move the track frame. That worked good.

After getting the track frame out of the way, I pulled the bearings, and got to the rear sprocket. I am concerned because I did not need a puller to remove the sprocket. It pryed off with a bar quite easily. The teeth don't appear to be worn out? What do you think? Also the outer bellows seal was not the greatest but the inner one turned out to be nothingbut a tangled mess! Guess that's why it was leaking!

Here are a few pictures of my sprocket hub.

So, can anyone tell me what number seals I need to order? What else should I replace while I'm in here? Any other thoughts- especially regarding the sprocket and the way it fit/came off. Thanks a million.

Hi Joel59,
Good to see you are making some progress:D
The broken bolt you are showing (1 of 4) is actually just the spring tension loading bolt for the guide plate.
There is one taper pin/nut in each arm, the one towards the middle that ties the arm to the shaft. Be sure to tighten this one a little before you go to loosening the nut. This makes sure you seat the taper so it won't spin when you remove the nut. Can really be fun to remove once they start spinning on you. Once the nut is removed along with the spring plate a good whack with a hammer will send them flying.

That's one of the worst destroyed bellows seals I have seen. Having the sprocket loose like that is not a good thing and although the splines are in fair shape I doubt if they would make spec for required fit. Dimension "A" needs to be 0.006 to 0.190 in. with a 35-40 ton press fit to meet spec. It is not a case of just running up the taper until tight.

Attached is the parts breakdown for your tractor (I think) as it was still in my files. You will need new bellows seals, either the original style or the upgraded rubber style replacement or go to the duo-cone replacements. Check with Cat or your local source for what is available. You will also need new seal washers for the seal wear plates (quan-4). The wear plates themselves can be flipped over if they are worn/grooved. Also get the special gasket cement for attaching the seal washers.

The adjuster bolt threads look pretty bad to me, at least in the picture. I wouldn't invest much in thread chasing as these bolt are available aftermarket and are not all that expensive. Make sure the threads are good in the adjuster nut.

Hi Joel59,
Good to see you are making some progress:D
The broken bolt you are showing (1 of 4) is actually just the spring tension loading bolt for the guide plate.
There is one taper pin/nut in each arm, the one towards the middle that ties the arm to the shaft. Be sure to tighten this one a little before you go to loosening the nut. This makes sure you seat the taper so it won't spin when you remove the nut. Can really be fun to remove once they start spinning on you. Once the nut is removed along with the spring plate a good whack with a hammer will send them flying.

That's one of the worst destroyed bellows seals I have seen. Having the sprocket loose like that is not a good thing and although the splines are in fair shape I doubt if they would make spec for required fit. Dimension "A" needs to be 0.060 to 0.190 in. with a 35-40 ton press fit to meet spec. It is not a case of just running up the taper until tight.

Attached is the parts breakdown for your tractor (I think) as it was still in my files. You will need new bellows seals, either the original style or the upgraded rubber style replacement or go to the duo-cone replacements. Check with Cat or your local source for what is available. You will also need new seal washers for the seal wear plates (quan-4). The wear plates themselves can be flipped over if they are worn/grooved. Also get the special gasket cement for attaching the seal washers.

The adjuster bolt threads look pretty bad to me, at least in the picture. I wouldn't invest much in thread chasing as these bolt are available aftermarket and are not all that expensive. Make sure the threads are good in the adjuster nut.