More steering issues. D65P-8

[Twisted]

I'm a bit stumped and looking for advice. I have a D65P-8 Komatsu dozer. A little history first... Auction sale machine that looked very nice. I bought it cheap then the issues started popping up. The machine had been abused and maintenance was dismal. It began with steering issues. I did all of the easy fixes first. Filters, strainers and pumps. No go so I pulled it apart so the only thing left in the case was the pinion. All cleaned, new seals, clutches, plates, bearings etc.

At that time I pulled the steering control valve apart as it was in rough shape. It was full of crud and scored badly. I honed all of the mating surfaced for all of the plungers and such. I also cleaned up the relief and set the pressure to the high end of the suggested window. So now everything is cleaned and in probable working order. I assembled the dozer and took it for a test drive. It wasn't perfect but it felt very close.

The issue now is once the oil warms up. The clutches begin fading and after a few hours of operation I shut it down rather than burning up the clutches and brakes. The pressures at the ports falls a bit but still in the low end of the window. I tore it down again expecting to find a blown seal or maybe something I missed. Nothing....

The only thing I can see that would cause the clutches to not release completely are the splines on the pressure plate and brake drum. Could it be that the plates and clutches won't slide properly on worn splines? How bad can they be before they cause issues? Any other suggestions that I may have missed?

I'll try to attach pics of the splines.

Thanks in advance, Twisted.

Pressure plate.





Brake drum

 

[02Dmax]

I think you answered your own question. I'm by no means an expert but those splines in the drum could definitely make things sticky.

 

[John C.]

What do you mean by "the clutches start fading"?

Maybe they don't release properly or maybe they start to slip in a hard push?

 

[Twisted]

The clutches never slip. They release ok at first then not as good as the case heats up. The machine will pull the engine down in heavy clay and never slip a side. It gets worse as things heat up so I assumed oil or seals. Pressures are still ok so maybe it's just the expansion of the bits causing issues???? I'm really at a loss.

I'm not a wet clutch guy but I asked two different shade tree wrenches this weekend and got two different answers. I'll bring it to a good friend of mine who has a great shop but works on ag equipment. Clutches are clutches and he's seen 100's of them so I'll see what he says. I don't know where else to go. They will be expensive to replace but I will if need be.

Pushing makes more money than not pushing. This rig makes me pull my hair out....

Thanks for the advice so far.

 

[Scrub Puller]

Yair . . . .

Twisted I have seen a lot of well worn drums and plate splines and can't ever remember it causing issues.

As John C. asks, just exactly what is it doing, are the clutches slipping under load when hot? . . . I take it they are not releasing and are driving through the brakes.

Both tracks should stop instantly and completely if you pull the levers on a push.

Cheers.

 

[Twisted]

"Clutches start fading" I mean they stop releasing. They will never release completely. I should be able to pull the levers back and stop the dozer without brakes but I still need a little help. As things heat up, I need more brake pressure to turn. It keeps getting worse as things heat up but the oil pressure is still fairly good. That's what has me stumped.

 

[Shimmy1]

We had the same problem on our 68 several times. Each time we changed out the steering pump. On the 68 it's a little gear pump on the front left side of the flywheel housing. After the third pump ($2200 each time) we changed from the SAE 30 non-detergent to a SAE 10 non-detergent motor oil. It's been running 5 seasons now and seems fine yet. Don't know if that's your problem, but what you're describing was identical symptoms on ours. Pressure was way low, almost spec, but not quite.

 

[tctractors]

At 1 time I used to look after about 20 D65 6-7-8 series komatsu tractors, the 1 thing that "Never" needed any work was the steering clutch packs, the valve control used to wear out but the clutch stack hight etc always managed to come within spec' to go on, the swapping sides of the clutch packs would get you sorted on any wear in the hub or drums, the drum spline wear is usually the result of top pinion issues or flange disc's loose on the pinion this being not un-common, your problem is involving oil control to the release side with pressure or flow, I used to look into the bevel case via the rear blanking plate to study oil waste from the steering control valve, the steering pump in the U.K. knocks out around the £500-600 spot so you would be getting tucked up at this price, the steering oil screens and filters would need investigating also the suction hose, always drain down the High pressure filter from the bottom before pulling out the filter, the easy and best place to pressure test is from the purge plug on the filter, changing oil grade is something I have never had to do.
tctractors

 

[Twisted]

It looks like I pulled the clutches for nothing. I'll swap then during install to insure that isn't causing an issue.
Steering pump is making good pressure and flow. When looking in the back, all the oils look good. Oil cooler is flowing freely. New strainers and filters 4hrs ago. It looks like I'll be sourcing a steering control valve next.

 

[Cmark]

It's been maybe 25 years since I was in the rsend of a dash 8, but I seem to remember the clutch release oil flowing through a housing, into the clutch hub and sealed by two piston rings. If the bevel gear bearings collapsed the hub would wear into the housing and steering oil pressure would be lost.

Am I thinking of the right thing tctractors, or am I on the wrong track?

 

[Twisted]

You are correct Cmark. Those seal are new and all of the surfaces are in great shape. There is a certain amount of oil that bypasses from those seals when oil pressure is applied. I know some oil is expected but not sure how much.

I can pretty much eliminate anything common to both sides because the right side is considerably worse than the left.

 

[Twisted]

I'm thinking that I found the issue. On each side of the bevel gear there is a housing that the clutch release oil is sent through. A flange slips inside of that housing and there are two ring seals to hold the oil. There seems to be considerable wear in the area of the ring seals. The flange is worn, not the housing. A little more measuring this morning will tell the tale.

Thanks for all of the advice guys.

 

[Twisted]

I got this miserable chunk of iron back together and still no-go.
Everything inside the case is perfect. All of the measurements are good, seals are perfect and I swapped everything left to right to see if the issues changed sides. Right side is still bad and the left side fades as the oil warms up.

I checked pressures and it has me a bit stumped. Pump pressure is good at about 285psi. Left side clutch makes correct pressure as long as I'm above low idle. Right side is only about 175psi. Both sides drop as tem rises. Pump pressure is still good.

When I'm checking clutch pressure and pull the lever all of the way out so the brake booster is engaged, the pressure rises to spec but only with the booster engaged. I don't believe the clutch is actually getting enough pressure to release.

TCT had mentioned something about the steering control valves wearing out. Does this seem like the culprit??? I'm thinking there is nothing else to replace.

 

[02Dmax]

In your original post you said the steering valve was scored badly and full of crud.

In my experience, once those are fouled up, no amount of honing or polishing will fix it. It's basically like a control valve. Once it's junk, it's junk for good unless it could be bored and sleeved or something.

I have very little experience with those on a Komatsu but I've done a ton of work on Fiats and been through the same problems. I'd definitely lean toward the valve being your problem.

I'm sure TC will chime in. Hopefully. Lol

 

[mikebramel]

You have pressure between the pump and valve but not between the valve and actuator. You know what the problem is

 

[Twisted]

Replaced the valve and it steers like a champ. Back to work.

Thanks.

 

[02Dmax]

Good deal.

 

[tctractors]

I did say to look in through the back case blanking plate at the oil dumping from the valve, with the clutch lever pulled enough to activate the clutch, then the brake at half engine speed also with the clutch levers not activated the oil dump should change considerably, well at least your clutch packs are good for 20 years ahead of hard work, I have fitted 3 sets of brake bands to some D65's and still found the clutch packs to be well within spec' they never give trouble.
glad things are good. tctractors

 

[Twisted]

Thanks for all of your help on my dozer issues TCT. Your knowledge is second to none. Now I'm hoping to bill out a couple thousand hours without any more major issues. I'll gladly send it to the scrap yard then. The engine is fresh, finals are rebuilt and the hind-end is basically new.

I have a few nagging problems left but nothing big. Hydraulics are a bit weak even with a new pump and there are some charging issues. That will give me something to do between ice fishing trips when it gets cold this winter.

Thanks to all!