Can't keep a clutch in my 75 3/4 ton gmc

[spencer_cam@hotmail.com]

Hey guys,

My 1975 3/4 ton gmc has been in the family for 2 generations.

I have a 6 inch lift with 35's and as a daily driver I lose the clutch once a year, I buy the clutch from car quest.

It is installed correctly and there is no worn out linkages seeing as I replaced them.

Is it possible my tranny has bad in put and output shaft bearings ? When I hit slopes in the road my clutch peddle will rattle... And rattles sometimes at idle.

Any help is greatly appreciated !

[VileZambonie]

Is the linkage properly adjusted? How much pedal freeplay do you have? How is the flywheel? How is the disc wearing? What is your final drive ratio?

[Fairlane514]

Is it the original pilot bushing?  Original bell housing? If the bell housing is aftermarket they can sometimes be off center and need offset dowel pins to correct it. If your motor has been line bored it can also change the crankshaft location and cause problems. 

[spencer_cam@hotmail.com]

Lots of peddle free play, it's not the disc that wares, it's always the throw bearing coming apart, pilot bearing is new with every kit as well.

Fly wheel is original and never cut, bell housing ball joint is new, I think I will try a new fly wheel. Apparently that is where peddle rattle ones from but still it don't always rattle !

[Fairlane514]

Could be your front bearing retainer on your transmission. The throwout bearing rides on the shaft and if its worn enough the throwout will wobble.............does it shudder when you let the clutch out in first gear?

[VileZambonie]

You don't want all that free play.

1. Disconnect return spring at clutch fork.
2. Position clutch lever firmly against rubber bumper on brake pedal bracket.
3. Push outer end of fork rearward until release bearing lightly contacts pressure plate.
4. Loosen locknut and adjust rod length so that swivel slips freely into gauge hole. Increase length until all lash is removed from linkage.
5. Reinstall rod into lower hole on lever. Install two washers and cotter pin. Tighten locknut without changing rod length.
6. Reinstall return spring and check pedal travel. Pedal travel should be 1 3/8 to 1 5/8 inch.

[pholliday1]

While you may have multiple problems your contending with follow the above advice it is very good, however pay strict attention to your pilot bushing and front output bearing.

[spencer_cam@hotmail.com]

Thanks guys, I believe it is the front shaft bearing, when I'm driving down the road and I hit a quick slope in the road ( something enough to make the truck want to bounce ) the clutch peddle rattles with the movement of the truck, ( and sometimes at idle ) so basically when the rear suspension compresses, it pushes the shaft towards the tranny, causing the front shaft to move as well seeing that the bearing of the input shaft is bad ?

Do this make sense ?

I have the clutch adjust properly I even had it checked at the garage, about an inch of free play. I adjust the rod Hand tight untill it's snug In the cup.

[Fairlane514]

There should be about 3/4 inch from bottom on the driveshaft front yoke and the output shaft of the transmission. In other words the drive shaft should be able to move in towards the front another 3/4 inch from where it sits now.

[Sartobuilt]

With the bigger tires you might want to upgrade on the clutch. Also if you have a gear smaller than a 4.10 that will add more stress to the clutch. Not resurfaceing the flywheel can also contribute to early clutch failure.  There is supposed to be 3 springs on the clutch pedal and linkage, one that ties the fork to the Z bar, one that goes from the fork to the frame and one under the dash on the pedal itself. And also a quality clutch should say LUK or Valeo on the pressure plate.

[zieg85]

Check your cab mounts and trans mount.  Something doesn't sound right.  Does your slip yoke on the drive shaft actually move in and out?  I have had them frozen in the past...

[pholliday1]

LOL Zieg, we had one truck when you pushed the clutch in the cab moved!

[VileZambonie]

Thanks guys, I believe it is the front shaft bearing, when I'm driving down the road and I hit a quick slope in the road ( something enough to make the truck want to bounce ) the clutch peddle rattles with the movement of the truck, ( and sometimes at idle ) so basically when the rear suspension compresses, it pushes the shaft towards the tranny, causing the front shaft to move as well seeing that the bearing of the input shaft is bad ?

Do this make sense ?

Not from my house