I have a D7 17a with a No. 46 front mounted hydraulic unit to operate the dozer.

I am seeing the following symptoms.
1. The hydraulics have a lot more downforce than lifting force.
2. If the blade is raised it will noticeably drop over time most of the time..
3. There are times when the blade is raised especially when it is raised quite high that it will hold its position for a considerable amount of time.
4. One of the lines to the hydraulic cylinders on the dozer seems to get much hotter than the other one. I have not determined if it's for the lift side or the downside yet.

Obviously it's desirable to have the dozer stay put where it is placed and to have sufficient up Force to move the blade up and down the way I wanted to move..

Any thoughts as to what may be the cause of these problems or what I need to look for to find the answer?

Thanks Neil. I ran it today and while backdragging up hill (don't ask why) I went over a jarring rock and all of a sudden no control of the blade. Turned out that the ball on the control lever had popped out of the socket on the relay rod to the control block at the front of the tractor. Everything in that linkage seemed quite sloppy. Anyway an easy fix and I got the machine back up the hill for service. But that got me to thinking about slop in the linkage.

I put the blade all the way down which raised the nose of the tractor. It held in that position for quite some time with no movement that I could see.
Then I raise the blade 6 inches at a time and found that there was a little difference between gently touching the controls moving rearward and a gentle touch forward. I could feel a little click or snap. This was really gentle, just a couple fingers pressure. Anyway, gently pulling back against the stop had the effect of making the blade stay more or less where I put it while gently pushing forward caused the "slippage" and the blade lowered on it own fairly rapidly. When running vibration would naturally move the lever to the slightly forward position.

yep sounds like you need to rekit those rams. one being hotter than the other is a sign of wear. your getting bypass in the ram this creates heat. cat still has the seals available. or did a few years back when we redid our rams. its cheaper to make new ram shafts then to re-chrome them if pitted, worn or scored. it involves cutting the rod eye off in the lathe and welding it to a new bit of shafting.any decent machine shop can do this. (if you want to see it done have a look at cutting edge engineering on youtube he does this work all the time.)

you will get some bleed down that is normal.
you can also have wear in the valve and pump body itself. they are a sperry-vickers design which is now part of eaton hydrualics if you can find a vickers part number you might be able to rekit it.

Inspite of all the sage advice you are getting, real troubleshooting would say repair the linkage first.
Bob

trainzkid88 wrote:

yep sounds like you need to rekit those rams. one being hotter than the other is a sign of wear. your getting bypass in the ram this creates heat. cat still has the seals available. or did a few years back when we redid our rams. its cheaper to make new ram shafts then to re-chrome them if pitted, worn or scored. it involves cutting the rod eye off in the lathe and welding it to a new bit of shafting.any decent machine shop can do this. (if you want to see it done have a look at cutting edge engineering on youtube he does this work all the time.)

you will get some bleed down that is normal.
you can also have wear in the valve and pump body itself. they are a sperry-vickers design which is now part of eaton hydrualics if you can find a vickers part number you might be able to rekit it.
 

I thought about this. Given the age we have a pump not up to snuff, valve block not up to snuff and then worn cylinders making all this not up to snuff stuff work harder. Yes the rods don't look great. Some scoring and a dull finish, not the usual shiny finish. Slight weeping during operation, but not too bad. I wonder about the cost.

bluox wrote:

Inspite of all the sage advice you are getting, real troubleshooting would say repair the linkage first.
Bob
 

Already initiated this action starting with getting the service manual.

neil wrote:

...There is a design aspect to differences in down vs. up force (or more specifically extension vs. retraction) due to the extension having more surface area to act on vs. retraction - the rod reduces the effective surface area on retraction) but you wouldn't normally notice it unless you're using retraction to lift more than just the blade.
 

This is a good observation. Blade lift should a) have less force and b) be faster because the pump has a constant flow and the volume to fill on the upstroke is less. In fact the opposite is true. So like others also mentioned a cylinder rebuild may be necessary in the near future.

Hello Top,
The manuals that you need the most(in order of most informative) are the OMI, service manual and parts book. All of these manuals are in the ACMOC library and more. The is even a 24 page sales brochure for the D7C(non-turbo17A). I also have all the manuals for your D7C for sale. If you are interested send me a PM. 
Craig