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My '47 Custom Clipper's clutch chattered when trying to move slowly in 1st gear and more so in reverse. I removed the anti-chatter rod and found the rubber bushings to be in bad shape. I replaced the anti-chatter rod bushings with some new shock absorber bushings. The shock absorber bushings are thicker than the old ones I removed. I set the length of the rod to where there was just a small compression of the bushings. It is a relatively easy job to do once the car is jacked up and on stands.

The clutch chatter all but disappeared. More impressive, was the way the shift into high gear improved. The shift from 2nd to high most always resulted in a gear cruch. It was better with the overdrive engaged, but would still happen. Earlier, I went to a 140W mineral oil for the transmission and overdrive, but no improvement was noted. I was bracing myself for a 2nd-3rd synchro repair job. However, after fixing the anti-chatter rod, the shift into high gear is now almost without any cruching. It now only happens when the transmission oil is cold. The 140W oil is probably too stiff at this temperature. I will probably change to 85W-140 GL-5 gear oil. It is also more smooth and positive shifting in all gears.

Just thought I would share this fortunate benefit of two fixes with one repair job. How often does that happen?

(o{I}o)

John, I also replaced the worn rubber bushings with shock absorber ones that seemed to fit. It made a big difference and the chatter I was getting especially in reverse is gone. I was a bit concerned after replacing the clutch disc, pressure plate and throw out bearing and finding that the clutch was chattering. It is amazing what a difference a few stiffer rubber bushings can make on that rod. Packard engineers sure are amazing to think of this support rod as a solution.

In addition to those things mentioned, clutch chatter, especially in reverse, can often be traced to a bad or broken motor mount.

DaveK - It was your success with the new bushings that inspired me to do mine. Still puzzled about the bonus of a smoother shifting transmission.

(o{I}o)

OK folks you lost me where is the anti-chatter rod located?

I have experience the chatter in reverse.

Not sure they were on cars 51 on because of different motor mounts but if so, it is a straight rod or bar like arrangement with a turnbuckle type thing to adjust length. Located between frame and transmission end area and designed to control or limit the range the engine/trans assy can move on it's mounts fore and aft in the car. There is also a service bulletin written for earlier cars pertaining to chatter & listing some causes which may be of help figuring out yours.https://www.packardinfo.com/xoops/html/downloads/SC/SL-VOL17NO16.pdf

Isnt this also called "The Snubber"?