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Dozer getting pretty – an old friend from USA came to visit so I put him to work!
Dozer YCT306S shuttle shift - root rake, tree-pusher, backhoe
Excavator Hyundai 17 tonQLD, Australia
With the engine removed it is a simple matter to install a grease point for the rear rocker bearing. A bolt tapped through from the underside prevents the bush working loose and falling out.
Dozer YCT306S shuttle shift - root rake, tree-pusher, backhoe
Excavator Hyundai 17 tonQLD, Australia
My steering clutch compartments were full of rust from water ingress. Where the yoke shaft protrudes through the top of the housing there is only a felt ring to seal it. I machined out each housing and fitted an oil seal packed with grease which should help a bit. I can’t see any practical way to seal the brake band shaft but being on the vertical plane at least it won’t collect water.
Dozer YCT306S shuttle shift - root rake, tree-pusher, backhoe
Excavator Hyundai 17 tonQLD, Australia
Helpful tip; for assembly of the steering clutch put it in a lathe and use the tail-stock to compress the springs. Makes light work of a difficult job. Note the pinch bar mounted in the tool post to maintain alignment of the clutch plate teeth while tightening nuts.
Dozer YCT306S shuttle shift - root rake, tree-pusher, backhoe
Excavator Hyundai 17 tonQLD, Australia
Hal, the dozer is getting a complete rebuild. I’m working on it when I can but it will take a few more months to complete. The shuttle clutch, gearbox and finals are all back together now so it’s starting to take shape again. Everything is getting a kerosene clean and new paint before it goes on. I’m taking the time now to do all the little mods that have been bugging me for years. The engine is my next priority. Will keep you posted how it turns out.
Thanks Bob, yes the axle has a double-lip oil seal protected by the felt seal on the outer. At first I thought to double up on oil seals like was done behind the steering clutch but soon realized I wouldn’t be able to inject grease into an oil seal to expel dirt unless I put it in backwards which defeats the purpose of a second seal so I stuck with one oil seal and the felt.
I chamfered the grease exit hole using a carbide burr but not for the purpose you describe, rather because I didn’t want sharp edges anywhere near my seal. Appreciate as always your technical input, surface stress is a new one for me. So far the axle breaks detailed on this forum have all occurred at the root of the bull gear spline.
Dozer YCT306S shuttle shift - root rake, tree-pusher, backhoe
Excavator Hyundai 17 tonQLD, Australia
Back to front on the spring function Bob. It’s probably a different set-up to what you’re used to. As opposed to a manual clutch on a car, the dozer shuttle springs act to maintain separation of the clutch plates, not hold them together. In neutral there is about 3mm clearance between both pistons and their clutch plates. When F or R is selected oil flow is diverted through one of two galleries that run lengthways through the shuttle shaft exiting a port behind a piston. Hydraulic pressure then overcomes the force of the spring and the piston clamps the clutch plates together directing drive (in the selected direction) to the transmission.
Today I had the “pleasure” of reassembling my shuttle with new seals. For the benefit of anyone else having to do this job I will explain how it was done. Understand that it is necessary to compress and hold a strong spring while fitting a split collar retainer on one end and a circlip retainer on the other. It had me scratching my head for a while until I noticed that the shaft would slip through the 40mm bore on my lathe. To fit the split collar I held the shaft tight in the 3 jaw chuck and compressed the spring using the tool post on one side and a g-clamp on the other. This allowed enough wriggle room to fit the split collar into it’s grove on the shaft. The circlip was easier. I first set it in position against the spring then slipped the long shaft through the bore (leaving the chuck loose). The tailstock was used to push the shaft deeper into the bore until the circlip snapped into place.
After assembly I tested the shuttle function with compressed air.
Dozer YCT306S shuttle shift - root rake, tree-pusher, backhoe
Excavator Hyundai 17 tonQLD, Australia
Shifting the a-frame mounts rearwards 100 -150mm would give you more digging depth from the same length cylinder, however doing so might cause it to interfere with the floor frame in which case you would need to shift the top mount forward also. Altering the angle of the cylinder to a more vertical position will increase length of blade travel. I can’t confirm the idea with measurements because my dozer is still in bits but it’s food for thought anyway. Keep us posted if you decide to do the mod, would be interested in doing the same to mine.
Dozer YCT306S shuttle shift - root rake, tree-pusher, backhoe
Excavator Hyundai 17 tonQLD, Australia
If you have no luck with Eastwind let me know. There is an excavator dealer in Brissy who has sourced some heavy parts for me direct from the factory in China. Only parts he couldn’t get were the seals for the shuttle clutch. I’ve ordered those from Circle G Tractors in USA. Check out their website. You will find the special seals for the cylinder on page 8; https://www.circlegtractorparts.com/yuchai-bulldozer-parts?p=8
Word of warning, when you strip the shuttle clutch there is a spring-loaded seated collar retainer which requires clamps and jigs or a shop press to remove.
Dozer YCT306S shuttle shift - root rake, tree-pusher, backhoe
Excavator Hyundai 17 tonQLD, Australia
Mark, a consistant knocking sound is not good. Means something has come loose and is bashing against something else. Could even be your flywheel getting ready to fall off. Attached are some photos to help you see what might be going on inside since you don’t have a manual. Close to the oil dipstick is a small coverplate which holds the tachometer sensor. You might be able to remove it and insert a screwdriver to check for wobble in the flywheel. Check that it’s not the tacho sensor coming loose and rubbing on the ring gear.
As you can see there is not a lot between the flywheel and the transmission compartment that could account for the consistant sound you describe. Could be a bearing collapsed on one of the idler gears. Only other thing comes to mind is a problem in the engine bottom end and the knock sound simply amplifying through the bell housing thus disguising the location of your real problem.
I have the same machine and can help you out with parts manual. Hopefully we can get some better minds on this before you resort to pulling out the engine. Wait till the Americans wake up – it’s only 4am over there right now.
Dozer YCT306S shuttle shift - root rake, tree-pusher, backhoe
Excavator Hyundai 17 tonQLD, Australia
Hi Mark. I have my dozer stripped down and the shuttle clutch in pieces at the moment. The dozer was very slow to engage reverse and once engaged emitted a hydraulic squeal. I found the problem to be a damaged o-ring on the piston.
Need more information. Is the knocking sound the only issue or does your dozer have difficulty engaging forward and/or reverse? If it engages ok then I wouldn’t expect hydraulic pressure to be the problem.
Does it knock just once upon engagement or is it a continuous knocking? Did the knocking start after or before you changed the oil in the shuttle compartment? What oil did you fill it with?
Dozer YCT306S shuttle shift - root rake, tree-pusher, backhoe
Excavator Hyundai 17 tonQLD, Australia
