tach woes
Thread Starter
Instructor
Joined: Sep 2005
Posts: 166
Likes: 2
From: Marvin N.C.
tach woes
I have a '72 vert with a 350 and the tach gear won't fully engage with the distributor shaft gear. It will touch it and work sometimes but I can't get the gear to securely mate. I can feel it touch the shaft, but turning an wiggling it doesn't seem to help. Was there more than one driven gear for these ? Maybe I have the wrong gear. I just bought the car and this is really bothering me. I took the gear out and it isn't showing much sign of wear. I originally thought the gear was worn out causing the tach to jump. Any suggestions will be appreciated.
Race Director
Joined: May 2006
Posts: 18,708
Likes: 2,574
there was only one gear. Did you look in the hole in the distributor where the gear goes for any obstructions. This component may have dislodged preventing the gear from going in completely
http://www.ecklerscorvette.com/corve...1962-1974.html
http://www.ecklerscorvette.com/corve...1962-1974.html
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
There are other factors that can cause the cross gear to not mate up with the main shaft.
On distributors made from 1962-1969 the wall of the distributor housing would wear out as shown in the picture below. Staring in mid production 1969 GM added a Teflon bushing and a hole in the distributor wall to prevent this. (pictured below)
If the Teflon bushing fails or falls out the cross shaft will not align with the main shaft.
If the Teflon bushing fails or falls out the cross gear can also wear into the back housing of the distributor.
On 62-69early distributors the gear did wear in the housing as shown below.
The coupling can also be a problem area for the distributor. If you look at the picture below you’ll see where the cross shaft surface has worn in to the coupling which will allow the **** outward and not align with the main shaft.
Distributor shaft upper and lower bushing wear can be another cause...
The best advice I can share with you is to remove the distributor and start looking for issues in the above area's.
Willcox
On distributors made from 1962-1969 the wall of the distributor housing would wear out as shown in the picture below. Staring in mid production 1969 GM added a Teflon bushing and a hole in the distributor wall to prevent this. (pictured below)
If the Teflon bushing fails or falls out the cross shaft will not align with the main shaft.
If the Teflon bushing fails or falls out the cross gear can also wear into the back housing of the distributor.
On 62-69early distributors the gear did wear in the housing as shown below.
The coupling can also be a problem area for the distributor. If you look at the picture below you’ll see where the cross shaft surface has worn in to the coupling which will allow the **** outward and not align with the main shaft.
Distributor shaft upper and lower bushing wear can be another cause...
The best advice I can share with you is to remove the distributor and start looking for issues in the above area's.
Willcox
Melting Slicks
Joined: Oct 2001
Posts: 2,064
Likes: 1,382
From: Halifax, Nova Scotia, Canada
My tach stopped working last summer. The teeth on the main shaft were worn and decided to break off. The driven gear also took a hit and lost some of the teeth as well.
Any chance the main shaft has no teeth on the gear ? Or are mangled ?
Note: I have a June built 1970 that came with the old style dist., no button, no hole. It now has a brass button. (Still no visible hole, just didn't drill all the way through.
Any chance the main shaft has no teeth on the gear ? Or are mangled ?
Note: I have a June built 1970 that came with the old style dist., no button, no hole. It now has a brass button. (Still no visible hole, just didn't drill all the way through.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Barry-
I have to say yes... It is very unusual for one gear to tank and not take out the other one. If the cross gear was replaced then it tanked.. more than likely taking out the main gear of part of it.
When people call us wanting just the top gear we try to warn them of this. When you have a cross gear worn out there is a cause of this wear and putting another gear in the distributor is usually throwing good money away. If the main shaft gear is toast it will eat up the cross one.
A good way to test the gears when installed is to turn the distributor forward and then backwards. If the gears are installed properly you'll have limited run out, and no binding in both directions.
IMHO,
Willcox
I have to say yes... It is very unusual for one gear to tank and not take out the other one. If the cross gear was replaced then it tanked.. more than likely taking out the main gear of part of it.
When people call us wanting just the top gear we try to warn them of this. When you have a cross gear worn out there is a cause of this wear and putting another gear in the distributor is usually throwing good money away. If the main shaft gear is toast it will eat up the cross one.
A good way to test the gears when installed is to turn the distributor forward and then backwards. If the gears are installed properly you'll have limited run out, and no binding in both directions.
IMHO,
Willcox
Thread Starter
Instructor
Joined: Sep 2005
Posts: 166
Likes: 2
From: Marvin N.C.
Thanks for all the good suggestions. I think I have found the problem. The tip of the cable was broken off. At first glance it looked ok, but looking closer, a small section of the tip was missing, apparently just enough to make light contact, thus the "work-not work" issue.
Thanks again for the responses.
Thanks again for the responses.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Thanks for all the good suggestions. I think I have found the problem. The tip of the cable was broken off. At first glance it looked ok, but looking closer, a small section of the tip was missing, apparently just enough to make light contact, thus the "work-not work" issue.
Thanks again for the responses.
Thanks again for the responses.
Willcox
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