450c Engine Lugging When Releasing Clutch Pedal

[Airman89]

I think it’s best to start a fresh thread designated to this one issue.

History:
I had a brake adjusted too tight that made it so steering lever was very tight and would not disengage the clutches, it would only steer with the brake. I backed it off and my steering was fixed. I measured clutch travel and have just shy of 4”, manual states it needs adjusted if less than 3.25”, ideally 3.75” is good. All adjustments seem good..

Issue:
Engine lugs no matter if I am in R N H Or L, the very second that I start releasing the clutch pedal. All the way to the floor disengages everything including PTO(2nd stage of clutch), when I let up a little PTO will engage but the drive is still disengaged(1st stage of clutch), all the way up and drive and PTO will be engaged. So initially I thought something with the PTO or hydraulics was the culprit BUT.. then I noticed both tracks tighten up like it wants to drive and engine bogs down like it’s under load (keep in mind this happens when clutch is in 1st stage and drive should still be disengaged, AND EVEN in neutral).

Engine is strong running, 47 psi oil pressure at full throttle, hydraulics all work great, no leaks of any fluids at all, really lugs but will push dirt and keep spinning tracks good power, steers nice and easy, brakes work good. I haven’t changed the transmission fluid or filter but after running it I checked it and it looks like new. No sign of water. I do wonder about the filter condition (the mesh one), but I really didn’t want to replace the trans fluid when it looks new.

Question:

-What would cause the engine to lug/drive to be somewhat engaged, with clutch depressed and in neutral, and yet not drive?
-Do I have a slipping clutch causing pedal to not disengage drive? I don’t think this would explain it even happening in neutral though.
-Do I have a HL or R clutches staying engaged?
- Does transmission pressure release or engage the HLR clutches? Maybe the control valve is stuck giving some pressure to one of the clutches?

Thanks for any help you all can give. This forum is invaluable in helping with these old machines. I appreciate it greatly,

Adam

[Airman89]

Here is a video trying to show what I’m talking about. https://youtu.be/qH0vBoiOLgM?si=kYZuvj6XUzIi-ql_

[Jim B]

The clutch is only a single stage clutch, the two stages you feel are two different things working together. The engine clutch, you called the second stage is mechanical and the first stage, as you called it, is the pedal operating a hydraulic valve of the H-L-R. Partially depressing the pedal moves the clutch valve to stop travel movement by removing engagement pressure to the H-L-R clutches. The mechanical engine clutch itself is still engaged until the pedal is pushed fully down to allow the power shaft to drive a winch or PTO while travel is stopped. Yes, this arrangement provides action similar to a dual (two) stage clutch on a wheel tractor however to be clear it is only a single stage clutch. I post this clarification as sometime in the future someone will say they don't have a dual (two) stage clutch and ask if they should put one in their crawler.

A slipping engine clutch is generally seen as slipping while engaged and driving. Symptoms are that the engine speed doesn't drop off/lug down as it should under load however travel slows or stops, even at full throttle. If a clutch disc comes apart, and piles up between the flywheel and pressure plate, or a finger breaks the result is generally the opposite of a slipping clutch-- pushing the pedal won't disengage the clutch.

Did you do all the adjustments and pressure checks yet? Start with the engine clutch and work through the transmission tests, then the steering.

Some possible things it might be are it is possible pressure is getting to a H-L-R clutch pack when it shouldn't be due to a valve issue, possibly warped discs or something wrong in a H-L-R clutch pack, or a bearing that is turning all the time in the powertrain could be failing.

[Airman89]

The clutch is only a single stage clutch, the two stages you feel are two different things working together. The engine clutch, you called the second stage is mechanical and the first stage, as you called it, is the pedal operating a hydraulic valve of the H-L-R. Partially depressing the pedal moves the clutch valve to stop travel movement by removing engagement pressure to the H-L-R clutches. The mechanical engine clutch itself is still engaged until the pedal is pushed fully down to allow the power shaft to drive a winch or PTO while travel is stopped. Yes, this arrangement provides action similar to a dual (two) stage clutch on a wheel tractor however to be clear it is only a single stage clutch. I post this clarification as sometime in the future someone will say they don't have a dual (two) stage clutch and ask if they should put one in their crawler.

A slipping engine clutch is generally seen as slipping while engaged and driving. Symptoms are that the engine speed doesn't drop off/lug down as it should under load however travel slows or stops, even at full throttle. If a clutch disc comes apart, and piles up between the flywheel and pressure plate, or a finger breaks the result is generally the opposite of a slipping clutch-- pushing the pedal won't disengage the clutch.

Did you do all the adjustments and pressure checks yet? Start with the engine clutch and work through the transmission tests, then the steering.

Some possible things it might be are it is possible pressure is getting to a H-L-R clutch pack when it shouldn't be due to a valve issue, possibly warped discs or something wrong in a H-L-R clutch pack, or a bearing that is turning all the time in the powertrain could be failing.

Sorry for the delayed reply. Yes I have finally adjusted a few things and tested pressure. I adjusted the clutch pedal free travel to 3-3/4” and I adjusted the clutch valve per the instructions.

The pressures in gear at 1800 rpm’s is 165psi on the dot for H and L but for R it’s only 160psi. The range spec is 165-185psi. With the pressure lower in reverse but no slipping, does this indicate some pressure leaking to either H or L clutch packs maybe? I can’t figure out how to raise the pressure. The manual says to add shims in a certain port but when I look in there i only see a 1/2” or 5/8” pipe plug. It doesn’t go into further detail of where these shims should be.

At one point while idling, after warm, there was almost no lug down while in reverse. I’ve noticed something now, when it’s warm the lug on the engine while in reverse is less.

[Airman89]

I forgot to mention. Shift speeds are very fast except reverse. This video is showing H to L shift first, then L to H, then lastly H to R.

https://youtube.com/shorts/-OsNParrmmY ... -B7vC4Zu-B