Hello again, Got another questions for those who might know... And yes, I searched the topic but only found problems with an auto.

I have a really bad virbration when accelerating mostly in 2nd gear and a little bit of 3rd. It does not happen in 1st/granny or in 4th, probably because there is not enough torque?

It only happens when I gas it in 2nd and the beginning of 3rd, almost like it only happens when there is a lot of torque/strain. I guess 4th is too low to have that much torque applied and 1st just revs too quickly with very little strain. and only does it when im hard on the gas. Immediately I thought it was the U-joints so I replaced them all except for the intermediate shaft. Its a highboy and all suspension components are stock so the driveline angle shouldnt be the problem. The only other thing I could think of is that it may be the clutch.

I slowly engaged the clutch while it was idling and the pedal seemed to vibrate as soon as it made contact with the flywheel. could cause the vibration under strain? would it be in the clutch or the flywheel? or both? supposedly the title says its a 72 but its got a 73-77 body and 73-75 front end so I dont know where to post but I think the drivetrain should be the same, right? I have a 390 with a T-18 and a NP 205.

any help would be very much appreciated.

 

What you described does sound to be clutch chatter. I've had the vibration you described only when letting out the clutch. I dropped the tranny and had the flywheel resurfaced since I saw "hot" spots. I also saw "hot" spots on the pressure plate. So, I ended up replacing the pressure plate and the clutch disc. BTW, I haven't had much luck with rebuilt pressure plates or discs. I always buy new.

 

I experience the same vibration but it really sets my teeth chattering too. It usually happens through the top end of 2nd and all the way through 3rd. Is it possible that this may be caused by a bad drive shaft bearing? I am also looking for a shop manual for this truck. Any Ideas? 1971 F100 360 4x4......

 

danh71, what's your e-mail? I have two manuals I can sell you if interested.

 

Also check your t-case mounts. It has a tendancy to swing foreward under torque. Just hang your head out the door and jump the clutch a little and you will see the t-case leap foreward. It could be moving enough under the torque of 2nd and 3rd to cause a driveline vibration. If you ever get a chance to look under an early 77 they put a brace on there to remedy the problem. I have built a couple copying this design.

 

Oh I've checked the T-case mounts. When I got the truck, it used to bob back and fourth everytime you take off because the T-case mounts were so loose that you could get under the truck and rock it back and forth with your hands. Thats fixed and really stiffened everything up but the vibration was still there. It feels as if it had a bad driveline angle, you know when the angle at the U-joints are too extreme? But its all stock. Both my Dad and brother say its the clutch and I'm gonna replace it all either way, I just wanna know if this has happened to anyone else. It only happens under load.

 

When you change the clutch, be sure to check the pilot bearing in the end of the crankshaft. It could be missing, which can cause vibrations in the transmission.