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“do you have in mind what caused this?wrong or lack of lube ,poor assembly?”
Well first and foremost the oil had got a bit low (main seal to bell housing is perished, but I am not too offended as it is Chinese and nearly twenty years old. Also I had not realized that the clutch housing has a separate dip stick to the gear box, so hadn't been checking it.). Second I got stuck and gave it some welly getting out (nose up hill in a drain buried in mud), which would have worked her harder than I normally would.
But there are a couple of issues with design. Firstly as Bob points out the thrust bearing is rather little and is really a clutch release bearing, not a clutch engaging bearing! So the life expectancy is a bit limited straight off. Secondly the yoke pushing on the selector slip ring would only need to be a tiny bit off true to put all the load on one side of that bearing.
If she goes again, I would be inclined to try and find some sort of self aligning roller thrust bearing…
But I have my hopes that as long as I keep the oil to the right level that she will serve surprisingly well.
Oh and the dead bearing looked like this after I pulled it off.
Gosh I just had to use that smiley!!! 
Update, got the shuttle out and dismantled. The forward thrust bearing was cooked and seized. Clutches them selves seem in good order. I have been able to source the bearings locally (should turn up Monday), but the return springs (cooked and lost temper. Needs to be a matching pair) are proving more difficult. The selector ring and pressure plate I have tided up on the lathe and I think will be fine.
Been working on my shuttle issue today
I removed the selector shaft and yoke or fork… and low and behold it looked just like your one, Greg. Badly burnt, worn, and misshaped.
So certainly the yoke needs either replacing or possibly making an improved version (which at present I am thinking is the wise way to go as it appears there is a weakness here)… but the question remains as to what other damage there is.
I think I may do a temporary repair of the yoke, and just try it to see is it will free up the pressure plate… else it is out with the engine and make my dozer look like your one!
Where did you manage to get parts? The Chinese dozer chap in NZ said he couldn't help, and put me on to East Wind in Aussie, but they have their doubts too on parts for a 252L. 🙁
Cheers
Just to update, I had a bit of a go at working through the possible issues.
The actuating cylinder has 40 mm of travel, 20 mm each way, and with it disconnected from the crank it appears to move smoothly both ways and returns to center as it should. So that suggests that the hydraulics and ram all works fine.
With the cylinder attached it appear to move about 10 mm for reverse and about 6 mm for forward… Look at the yoke inside the housing the movement seemed a bit odd. In reverse the yoke moved maybe 5 mm but forward it seemed to barely move, though I could see the shaft turn slightly.
Cylinder detached again I tried moving the selector yoke with a lever to get a feel of it. Reverse one could feel it pushing on the return spring and then contact the plates and go firm. Forward there was slack and then contact and no movement. No sign of the return spring of the sliding of the pressure plate.
Next drained the oil. There was a fair bit of bronze flecks and a few small chunks, sort of what you would expect after maybe 1000 hours, but rather a lot for just 170 hours on the clock. Then I removed the selector shaft and yoke… and low and behold it looked just like Greg's one in 'Total tear down of dozer'. Badly burnt, worn, and misshaped.
So certainly the yoke needs either replacing or possibly making an improved version (which at present I am thinking is the wise way to go as it appears there is a weakness here)… but the question remains as to what other damage there is.
I think I may do a temporary repair of the yoke, and just try it to see is it will free up the pressure plate… else it is out with the engine and pull it all apart.
Hey Bob thanks for your help.
In the manual it does talk of adjusting the clutch… but I can't say it is over clear what it expects one to do!
It does imply that there should be 2.5mm-9.2mm gap with the pressure plate released on each clutch pack, with should equate to a max travel of the pressure plate from reverse to forward of 18.4mm (should be only 5mm with the clutches in new condition) so I think that is the first thing I will check. It tells one that if it is greater than this to adjust it, but as far as I can tell, not how to adjust it!
It would appear that it runs of the same hydraulic system, but at a different pressure (500 psi as opposed to 2000 psi), so there must be a pressure regulator somewhere.
Jolly good. I still think there is a possibility that it is something to do with the clutches fight against each other… Humm, is Greg the only guy on here that has the older 2cyl 252 Dozer or is there a few of us?
Seems I need to learn a bit more about different oils…
Well I better clear out a shed and get her in and see if I can figure out what the story is… got rather a lot of work lined up for her, and the weather is drying out, so the sooner I get her back into action the better.
Greg, I'm not sure if you have them, but I have the operation manual and the parts list for the 252L if you need copies.
Cheers
Hi Bob, that's a lot of questions! 🙂 “If I understand correctly, you're saying that with everything in neutral it shifts fine into reverse, but lugs the engine when you shift into forward.” Yep that's right.
“What that tells me is that your reverse servo is not releasing fully and creating a drag.” Ok, sounds an interesting and logical idea…
Ok, so the 'servo' is the small hydraulic ram on the left side of the housing that activates the shuttle yoke?
I have not noticed an accumulator anywhere… I can see one would soften the shuttle engaging though, so it would be a good idea.
I haven't done a service yet, so no idea of it's service record… I did check what I thought was all the oils when I got it (but I hadn't realized that the shuttle clutch housing was separate from the gearbox). The hydraulics was low on oil, and as it turned out was the shuttle housing.
The manual suggests “#20 gear oil or diesel engine oil grade T14” for the clutch housing… I have used 15W-40, is that ok?
I going to attach a pic of the exploded diagram of the shuttle assembly, in case my old machine if different to the more modern ones.
For the hydraulics I used the hydraulic oil as I use in our excavator.
Cheers
