[Matt79w150]

Hello all,

I have a heavily modified 1979 W150, 97 360 magnum engine up to a NP435 (using a 78 bell housing). I relocated the z bar mount from the body pan to the frame to fix a binding issue, when I take off in 2nd or decelerate in any gear the truck shakes like something fierce, people watching it say it’s axle wrap / hop, it could be but I don’t think it’s what’s causing the shudder. The truck is sitting on an 8 inch skyjacker lift and I’m running 35s.
Before buying ladder / traction bars I thought I’d post here to see if anyone else had any ideas.

thanks!

 

[Canadian country boy]

Sounds like clutch chatter to me caused by a weak pressure plate. How old is the clutch or whats the quality of the clutch? It also could be from the clutch being partially engaged. When you changed your pivot point did it engage the clutch a little?

 

[Matt79w150]

Brand new clutch, pressure plate, flywheel. I guess I could check to see how far it engages, if it wasn’t engaging full then I’d have issue going into gears right? It goes into gears great. Could a z bar from the wrong year cause it to not enter the pressure plate fully?

 

[Canadian country boy]

Correct, if the clutch was not fully engaging it would not go into gear very well but if the clutch has a slight preload on it then it would not be gripping the clutch disc fully and therefore allowing for slippage. Ive had some cars that just shook to pieces because the power just overcomes the cluch. Ive had to use serious pressure clutches to stop the chatter but they are no fun in town going light to light because they are so stiff. Hearing about the lift height and tire size on your truck could easily cause a weak or weaker clutch to chatter.

 

[Matt79w150]

Someone had told me that I may not be getting a good interface with my input shaft and pilot bearing, could that cause it as well? Tomorrow I’ll take a look at my z bars and experiment with the 3 I have

 

[Canadian country boy]

That could cause a chatter issue also. Did you have this issue before you changed the Z bar mount?

 

[DODGEBOYS]

to me it sounds like driveshaft spline bind or shaft out of phase

 

[Matt79w150]

That could cause a chatter issue also. Did you have this issue before you changed the Z bar mount?

Honestly I can’t remember if It did or not, I still go into gears without grinding still think it could not be engaging fully?

to me it sounds like driveshaft spline bind or shaft out of phase

it’s a new driveshaft, did it with the original as well

 

[DODGEBOYS]

block lift or spring lift on the rear

 

[Canadian country boy]

Does it happen right when the clutch starts to grab where the pedal typically starts to grab it just above the floor? Or does it happen after the clutch has engaged and when you stop on the throttle?

 

[chuck408mpfi]

Is there any chance there’s a greasy fingerprint or two on the clutch disc or flywheel somewhere?
I definitely had a bad chatter before with a rear lift block and less than tight u bolts, the u joint was rather unhappy and it let me know about it. Easy to see if the u joint has been hitting its limit of angularity by checking the yoke ears for rubbing.

 

[neil4224]

What gears are you running in the rear end? My np435 in 2nd wheel hops like a mother just on take off with any type of load against it. I have 4.10's in mine.

Let me just say with the trailer loaded behind it, the truck will literally bounce the crap out of you from the springs repeatedly unloading from the climb of the ring gear. Now in first (granny low) it does not do this (not trying to spin it too fast for the springs to wind up) and when you shift to second I have to be easy on the throttle, powershifting under load will cause the same effect, but much more muted its a big drop from 1st to 2nd gear. 3rd and 4th there is no sign of any wheel hop as I am already moving pretty quickly by this point.

When I had the 3.23's under it it would never do this at all no matter the situation.

I also don't get any hopping or shaking when downshifting either. Just my .02 but I bet you are wheel hopping on launch and agree with Dodgeboys you may have a binding issue on the downshift side of things.

I have added 1 or 2 leaves for load weight and have standard rear blocks under the spring on mine with 32-33 inch tall tires just for your reference.

Neil