66 SB, tap, tap, tap,... there goes my tach

[Bill Richards]

While listening to my motor run I could hear a rapping, tapping sound coming from the distributer, you could feel the noise with your hand. As I watched the tach the noise stopped, so did the tach. The cable seems to be unbroken however the distributer end is a little chewed. Is the problem in the distributer? Bill

[Ed Jennings]

Re: 66 SB, tap, tap, tap,... there goes my tach

Sounds as though the gears in the distributor have headed south. More than likely, you will need to replace the shaft, but once in a while I have gotten by with replacing the small gear only.

[Joe C.]

Quoth the Raven...........Nevermore

If you heard a rap, tap, tapping at your distributor's door, then you'd be smart to inspect the tach cable, and clean/lubricate it with fresh lubriplate (or white lithium grease). Remove and inspect the tach cable driven gear. If this needs replacement, then the distributor mainshaft must be inspected, too. Now is a good time to retrofit your distributor with a brass thrust button.

Joe

[Joe L.]

Re: 66 SB, tap, tap, tap,... there goes my tach

Bill-----

I can virtually guarantee you that you'll find both the cross gear and mainshaft gear damaged. That means a new mainshaft and cross gear. If you install a brass thrust button in the distributor housing end (as per instruction you will find in many discussions in the archives), you will prevent this from happening again. GM added a nylon button to distributors manufactured after about 1970, including SERVICE distributors for earlier applications. This simple addition made a HUGE difference in the longevity of tach gears.

[Bill Richards]

Re: 66 SB, tap, tap, tap,... there goes my tach

Thanks for the help. After taking things apart I discovered the tach drive gear was toast, the shaft gear however is in good shape yet. Thanks....Bill

[Joe L.]

Re: 66 SB, tap, tap, tap,... there goes my tach

Bill-----

I would be sure to clean and inspect the main shaft gear very carefully before putting it back together. So, far, I've not seen one of these fail without, at least, some damage to both gears.

[Bill Richards]

Re: 66 SB, tap, tap, tap,... there goes my tach

Will do, thanks Joe.... Bill