Pulsating clutch pedal

[Paul prinzo 0]

On my 86 DM, if I push the clutch all the way in, it pulsates. The truck goes into gear fine. What could be causing this? 

[Truck Shop 1,162]

                             How old is the clutch? Normally when you feel the clutch peddle pulsate the clutch fork is rubbing or hitting the pressure plate when it's depressed. 

                             Several things can cause this. Worn cross shaft bushings and cross shafts and sometimes the clutch is worn out and at the end of it's adjustment.

                            Drop the inspection cover and take a look see.

 

                            Truck Shop

[theakerstwo 752]

Also if the flywheel has been ground too deep it will do same thing.

[steeler 20]

Or a worn out clutch brake, worn front seal housing on transmission. Either will allow the throw out bearing to travel too far rearward causing the release fork to contact pressure plate.

[br549 49]

I have seen where people adjust free pedal on the clutch with the outside adjustment that is for the clutch brake adjustment and it will and after several adjustment that way the clutch fork will start hitting the pressure plate when mashing the pedal all the way down.  Look inside the bell housing hole and see if it is hitting when mashing the pedal all the way down, you should be able to see a mark where it is rubbing.  If it is you can set the clutch brake with the outside linkage and put free travel in by winding the clutch up on the inside adjustment on the pressure plate and it will move the throw out bearing back out away from the pressure plate.

[gearhead204 1,824]

all things above can cause this issue as well as a worn release yoke and a out of tolerance front bearing retainer .  fought with a mack 12 sp. for hours before discovering a excessive amount of material had been removed on  the bearing retainer by a reman outfit.  over thickness clutch brakes are available to help correct for excessive flywheel machining . in the case of the reman trans I had to put two clutch brakes in it  and grind the facing off of the mating brakes to make it work right.  ( the truck had a drop axle, and the trans and  all the extras were in place or I would have pulled the trans again to fix properly)      

[theakerstwo 752]

And also a set of thrust brgs on the crank can do this.