mikes1966

My tack bounces around in between shifts. At a steady speed its ok but if you rev it up it bounces around or even seems to float, any ideas?
Thanks Mike

MelWff

Have you removed the distributor driven gear and checked it?

GUSTO14

Mike,
The bouncing Tach needle is typically attributed to a worn TACH DRIVE CROSS GEAR ASSEMBLY. This allows the Cross Gear to move in and out of the assembly as engine RPM increases or decreases. Under steady acceleration or deceleration, the gear will stabilize as will the Tach needle. Change gears, and the needle bounce begins again until it dampens out.

Often times a new assembly along with replacing the original nylon button that slips in the back of the housing that the cross gear leans against, will correct this situation. Paragon also offers a bronze Tach Drive Distributor Gear Button to replace the original nylon buttons. The important thing is to remove all of the play between the Cross Gear Assembly and the Tach housing. Some of the new Cross Gear Assemblies even have a roller bearing that the Cross Gear spins on.

Paragon Corvette Reproductions offers a Tach Drive Distributor Kit that you might find useful to rehab your Tach drive. It includes a set screw along with the guides to drill and tap the housing, that can then be adjusted to remove any play in the Cross Gear. I first saw this used back in the 60's to tighten up the notorious bouncing Tach in the Corvette with the mechanical tach drive.

Tach Drive Distributor Kit
Paragon Number: 577K
Tach drive distributor kit. Includes tach gear, installation tool, threaded drill tool, tap insert tool and set screw. Includes cross gear, coupling, and thrust washer.
Years 1962 - 1974
Price: $59.00
https://www.paragoncorvette.com/p-35...butor-kit.aspx


Good luck... GUSTO

mikes1966

Thanks I will pull apart and check

tuxedo

I have this problem and have done everything but this. Nothing has worked so its time to pull the distributor. But I am going to hook a drill to the cable from the engine bay and see if the tach needle does not bounce that way. I think that would confirm it has to be the gears.