M816 Wrecker clutch issues

[tstone]

I've got a clutch issue with my 5 ton truck. My truck will move in 1st or 2nd gear about 15 feet then it will stop moving as the clutch petal appears to "depress" and no power is transfered to the transmission. I greased the throw out bearing, transmission shaft (to lube the throw out bearing travel), fork shaft bearing points and all linkages and still have the same problem. I inspected everything through the bell housing maintenance port and all appears to be in great operational shape. I bought the truck in January and have put about 300 miles on it; all local driving, no problems until yesterday.

When the truck is put in gear it moves about 15', the vehicle stops moving, the petal appears to slip to a slightly depressed state, manually trying to pull the clutch petal out back to "normal location" does not work. The petal remains in a slightly depressed state. During this "anomalie" I can shift the transmission (witnout depressing the clutch) into any gear without grinding the gears; very strange. After leaving the vehicle sit overnight the clutch petal returns to normal and the issue continues when put back into gear and releasing the clutch. No metal filings or any other reason to believe that there is any issue with the the throw out bearing, clutch fingers, etc.

I also believe that this is a new clutch as the engine and transfer case look like new or replacements. All components appear to be normal and in good shape.

Any ideas?

 

[fasttruck]

As you know, there is an air operated cointrol for the clutch in front of the rear winch to disengage the clutch when operating the rear winch or the crane. Air cylinder for this is on the right side of the engine bell. Is air leaking through the control valve and causing this cyl,inder to partially disengage the clutch ?

 

[fasttruck]

Attached photos show detail under truck. When problem occurs; if you shut truck off and drain air out of it and restart and problem is absent until air pressure rebuilds this could be it.

 

[fasttruck]

RFight photo above shows similar air cylinder that is sued to operate rear winch on M123.

 

[doghead]

Simply removing the slave cylinders air line, would be a great way to test this idea.

I wonder if his lever is "on" a little bit.

 

[tstone]

Guys, thanks for your advise! I'll check out the system this morning and let you know what happens. Have a great 4th!

 

[Danl]

Danl M915A1

This sounds like it could be a Hard one, if is't not air, than the pressure plate is not happy. Are you Smelling Clutch smoke at times?

 

[crasheej]

That cylinder linkage will sometimes freeze to the clutch shaft an cause you a little problem like that.

 

[jimmcld]

Clutch

Sounds like the air valve to the clutch is open. When pressure is applied to the slave cylinder, it depresses the clutch. Change the position of the valve and see if that makes a difference. You may have had someone up there playing with the valve and left it in the "on" position.

 

[timntrucks]

yes that sounds like thats the problem look 5 dogheads