View Full Version : D7E 48A track adjuster seal replacement. Little help....Bob?

08-19-2016, 04:18 PM
I found the threads on this subject but I must be dense because I still don't quite understand how this assembly works. I pulled the 7 out of the field where it has been sitting for quite some time. one track lost tension and grease is pilled up around the chrome rod area of the tensioner. Bob seemed to have this all figured out where you can do this pretty easy without track or idler removal. I need to try that before I go deep. I just don't have time. If I could get a few hrs per pump up, I could make do but sounds like once they puke, it is over? I am in a bad way needing the machine and I don't have the tools and man power onsite for this repair right now.

I think I plan to wrap a chain between the blade and idler and pull everything forward hard to get maximum space. And then somehow I guess I weasel the cylinder or rod loose? I am a little foggy here if someone can clarify?

SN is 48A60XX

08-21-2016, 09:08 PM
Well, I tore into it a little trying to grasp the concept. I get it on the design. The cylinder is parked inside the spring, the rod pushes out against the rod that pushes the idler yoke forward.

However, I simply cannot get past how the rod would simply come out if I break the 4 bolts for the union between the yoke rod and adjuster chrome rod? I mean, if it will come out enough to swap seals, that is the same distance as I would need to tighten the track. Unless we are talking insane track tension?

Or maybe we are talking about breaking the 4 bolts, sliding the yoke and rod forward, then getting the yoke rod to come loose to remove it? With that out of the way, I could do it.

I did test the relieve valve for the cylinder. No pressure there at all. I assume safe to say I could not pump this up to run for a bit? Piz right out? I did notice some rust spots on the chrome rod. I am hoping the spot I need to run at will work. Not looking forward to a major repair here.

08-21-2016, 10:33 PM
Been a while since I've had one of those apart.
The chrome surface you see is not the sealing surface.
That barrel is hollow with a piston inside it.
When you pump grease in the piston stays stationary and the sleeve moves.
A lot of grease must be pumped in before you see any on the outside.
Hope this helps.
Andrew. K.

08-23-2016, 06:35 PM
You separate the shaft at the track cylinder and move the idler yoke with shaft attached forward enough to reach in the cylinder and pry out the slug to replace the seal. There are also 2 fiber split bearings that can replaced. Not sure you can do it without breaking the track, I have always split the track but had alligator links so no big deal. If the idler is all the way back you can weld 2 gussets one on the swing frame the other on the idler side plate and use a hydraulic jack on its side to jack the idler forward. You might if lucky get enough room, if not you have to break the track. Good luck

08-23-2016, 06:45 PM
Fastline--if you were referring to Bob/Ontario he passed on a while back--he will be well missed!!

Old Magnet
08-23-2016, 08:34 PM
That doesn't sound like the info that Bob/Ont would put out. There was another Bob with "Blueox" handle that I believe stated he was able to do the job without splitting the tracks but I don't recall if enough space was obtained to get the piston out.

08-23-2016, 10:04 PM
Here is where I am at. I think there is enough room to get the piston out but not sure how long it is. I have 4" or so.

Problem is I cannot get the chrome cylinder to back any further. It moved nice and easy back to this point and stopped. I ran out of light and had to stop.

can I pull the piston out with pliers?

I know the user name of the guy was "bob". I chatted with him before. Super sharp and is the one that indicated it could be done. Looks like it will work. I am SO close! at this point I can get the retainer off and could almost grab the seal with pliers but rather just get the piston out and inspect things.

I had to move the machine a bit to get the slack where I needed it and it puked even more grease doing that. No doubt something is toast. Hope it is the seal.

08-23-2016, 10:06 PM
I did both sides on my 47A.

First one I broke track, pulled piston and cylinder, honed cylinder with bottle brush hone, and replaced front seal and both split piston rings.

Second one I did not split track, but was able to slide idler forward enough to get piston far enough out to replace front seal and one of the two split piston rings.

This is a 20% worn U/C.

There is a goofy extrusion ring/oring setup to pay attention to where the flanges mate also.

Both sides seem to hold equally well 2 years later.

Looking back I believe the front seal was sole culprit. It had the consistency of a children's crayon.

Edit after seeing what you just posted:

That is not far enough to remove piston. I used channelocks carefully on the nose to work a stubborn one forward. Also, try putting a 4x4 short block in between the flanges and then pry rear flange back with a 5' bar, taking care not to harm flange face. Used that trick on my 36A and it shot the piston forward a good bit. You may find the front seal in pieces thus making piston tight.

08-23-2016, 11:00 PM
Yeah i was trying not to get too rough w it. I will ramp thing up a touch.

Curious how your phenolic wear rings looked? I got new ones but wont chase em if they are not a concern. Usually phenolic lasts a long time.

I am a bit curious about my UC condition tho. Still wanting to figure that out but seems really nice. Sprockets idler chains grousers all look solid.

Old Magnet
08-23-2016, 11:25 PM
For what it's worth the service manual clearly states splitting the track to remove the piston and cylinder.
You need to acquire the service manual.

08-24-2016, 05:14 AM
I was able to change mine out on my 48A without breaking the track. It seems like it was Bob/Ont that explained it could be done.

08-24-2016, 05:57 AM
I reckon you can change the front seal if you can get the piston forward enough, but to remove the piston and change the wear rings, the track must be split or the complete recoil spring removed, which is another heavy operation.

08-24-2016, 05:14 PM
Well the job is done and holding! :clap2: Got the piston all the way out. Had to just pull it from the bore. Super easy. I fought for an hour to push cylinder back further and gave up.

The seal had seen better days. came out in chunks. It was toast.

However, when tightening the tracks, I was pumping up with grease and my gun got to a point of super hard to operate, yet there was no pressure in the cylinder because I had the relief open to try to purge air. I finally decided to remove the grease inlet valve with the zerk on it. Sure enough, something was blocked in it. Took it all apart and found the check ball wedged in the center of its spring. I got that out and reinstalled everything and tested the valve again while removed. Worked for a few pumps, then plugged again, same issue.

I would LOVE to know how this little valve is ported and what was going on with it. I was trying to beat rain so I removed the spring and threw the ball back in. Figured it would either function as a check ball still or grease would just bypass it. Seemed to work fine. When I install the grease gun, there is no pressure at the zerk meaning the check ball must have plugged the hole. Still puzzled.

In any case, I ran the machine and problem solved. Chrome outside of cylinder is all screwed up but inside seemed to still look great.

Old Magnet
08-24-2016, 05:28 PM
Good to know you can get the piston out without splitting the track.
Was the idler rod pushed out all the way to the stop?
Here is what the fill/bleeder valve looks like. They are available aftermarket.

08-24-2016, 05:45 PM
Thanks for the pics! I was looking around here for some as I thought I had seen something.

I can tell you with certainty that I could not pass a piece of wire from one end to the other even with the ball system and zerk removed. It was like it was diverting the path elsewhere at the middle of the body. I did not have the tools or cleaners to get it clean enough to see what was really going on. If there was supposed to be a straight hole through it, there was something steel in the way.

And to see the check ball rammed into the inside of the spring was strange. I guess if they are available aftermarket, there might be a reason.

Magnet, hey, you may know right off but what is the exhaust size on these 7E's? Mine is about 2ft long and just right to feed it all to me. I need to take that up higher. Actually, my exhaust elbow is completely gondy but I will have to make do for now.

It seemed like an odd size. Would not surprise me with CAT.

Old Magnet
08-24-2016, 07:57 PM
Can't seem to find my list of muffler and pipe sizes. Some one is bound to know.
When you had the piston out of the adjuster did you have the idler push rod out all the way to the stop?

08-24-2016, 08:27 PM
Can't seem to find my list of muffler and pipe sizes. Some one is bound to know.
When you had the piston out of the adjuster did you have the idler push rod out all the way to the stop?

No, it had about 3/4" to go. Right now, with things tensioned properly, it has around 3/4". What is new? I am pretty curious about the UC condition on this machine. It all looks and runs really nice but always like to know.

08-24-2016, 09:02 PM
I believe stack is 4.5". I have a spare stack, clamp, and exhaust elbow that is correct length when you are ready.

My guess is you have some pin and bushing wear, or else devised a better way to pull idler than I did.

There is a 5 pin stretched spec that you can calculate % from. Rail height spec too. OM helped me on that.

See here:


Post #17 by OM

Old Magnet
08-24-2016, 09:05 PM
The stop is the limit of extension travel and an indicator of overall track wear. The stop should represent 4" of travel from the flange front. They don't give a adjuster measurement for new. Undercarriage wear is determined by a series of measurements not just the adjuster position.

Found the exhaust pipe info. Original pipe is a 1M5270, 4.5" diameter, 30" long for s/n up to 78A6882.

08-24-2016, 11:06 PM
Thanks guys. 4.5" is about what I measured and was hoping it was more of a standard size. At some point I would like to paint the old girl and give her a shiny stack for the heck of it.

CAB, please PM or email on some numbers for the parts. My exhaust elbow is certainly gone. It will probably do for right now but by winter I would like to have a fix for it.

08-25-2016, 08:39 AM
I'm amazed that you managed to get the piston out without splitting the track, it would be interesting to know how much stretch there is in the chains but as OM said, all wear in undercarriage components is part compensated for in track adjustment.

Old Magnet
08-25-2016, 08:44 AM
Any chance you measured the length of the piston or the gap so we know what is required to get it out?
Cat is not wrong with their instructions to split the track. Seems it depends on how worn the chains are as to whether you can extract the piston without the split and you would definitely need to split the tracks to get the cylinder out.

08-25-2016, 11:59 AM
I was in a rush to beat the rain so I did not get details but I can tell you the piston was about 3.0-3.5" long and I had probably another 1/4" or more of room to get it out. Because the seal was toast, it did not put up a fight in coming out. TO reinstall, I just used a pry bar to pop it back in.

I will look at the previous link provided to see if I can determine some wear points on the machine. At least at this point, I don't see anything in the track system that stands out as a problem. All links, sprockets, idlers, rollers, look decent.

I do have some grousers that are loose and I attempted to tighten them only to realize that seems like a cut and replace sort of deal. They won't budge.