73 Tach not working
Thread Starter
Cruising
Joined: Dec 2005
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73 Tach not working
My 73 has a tach that does not work, the previous owner said it would occasionally show very brief signs of life if you got the cable at the distributor seated just right. 
The connection to the distributor seems tight, the cable end looks ok (to me) so I do not think the cable needs replacing so I am suspecting it is the gear in the distributor. Is this a difficult replacement job? Anyone have any ideas of the problem and hopefully a fairly simple fix?
The connection to the distributor seems tight, the cable end looks ok (to me) so I do not think the cable needs replacing so I am suspecting it is the gear in the distributor. Is this a difficult replacement job? Anyone have any ideas of the problem and hopefully a fairly simple fix?
Banned Scam/Spammer
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I would first check for a dist. drive problem by pulling the cable off the distrubutor side, spin the cable by hand and watch the tach. If the tack moves its a problem on the drive side. It the tach does not move, remove the cable. You can do this by lowering the steering column, lossen the upper dash and drivers side dash. Reach in behind the tach through the space between the uppper dash pad and drivers side dash. You can pull the cable out on the engine side of the firewall. Inspect the cable. If the cable is fine, then it is probable a tach problem.
Tech Contributor
Joined: Aug 1999
Posts: 14,382
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From: At my Bar drinking and wrenching in Lafayette Colorado
Most common problem is that the distributor cross gear wears itself into the side of the distributor housing, locks up, and strips the gears off the mainshaft and the cross gear. Pull the cross gear out of the distributor and take a look at it. If there is any damage, you need a distributor rebuild and repair. If you need assistance with the repair, drop me a note for info:
V8FastCars@msn.com
V8FastCars@msn.com
Melting Slicks
Joined: Sep 2000
Posts: 2,408
Likes: 418
From: Chester Virginia
The distributor shaft gears were damaged when my cross gear gave-up three years ago. No point in putting a new cross gear in if the drive gear has damaged teeth. I bought both pieces from The Last Detail in Georgia. Verify that the bushings that the distributor main shaft runs on are in good condition: round not 'egged out'. I also bought the replacement seals for the top of the didtributor just below the points breaker plate.
Roger
Roger
Roger
Roger
Safety Car
Joined: Jun 2004
Posts: 4,652
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From: Lakeland Florida
You should also look for the bend in the cable connection to the distributor. One reason for the cross gear failure is that the cable connection to the distributor input starts to bind due to the unusual angle, between 45 to 90 degrees that it has to go through in order to be connected. As the distributor gets turned to set the timing, it may create a tighter bend than normal, which can lead to binding and impinging on the rotation of the inside cable.
To compensate for this there is a method to reduce the binding on the distributor cable. To make the cable to the distributor connection a better fit the spark plug wires can be moved over 1 postion with a corresponding movement of the distributor in the same direction so the relative position of the firing between rotor to spark plug lead is not changed.
Your first step though is to look at the cross gear and look for any wear. This can be removed from the back of your distributor with a small flat head screwdriver. Their is a large screw that holds the gear in place. Once this is out, then you can remove the gear without pulling the distributor.
kdf
To compensate for this there is a method to reduce the binding on the distributor cable. To make the cable to the distributor connection a better fit the spark plug wires can be moved over 1 postion with a corresponding movement of the distributor in the same direction so the relative position of the firing between rotor to spark plug lead is not changed.
Your first step though is to look at the cross gear and look for any wear. This can be removed from the back of your distributor with a small flat head screwdriver. Their is a large screw that holds the gear in place. Once this is out, then you can remove the gear without pulling the distributor.
kdf
Thread Starter
Cruising
Joined: Dec 2005
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update, 73 Tach not working
Thanks to all of the insight here on the forum, really appreciate the accurate and helpful info. Based on the input, first i pulled the cable and spun it, the tach moved so the problem is not in the cable or tach unit. Then I pulled the gear housing off the back of the distributor (simple thanks to input), the gear was well lubricated but looked pretty worn. So i had a good excuse to place an order from Ecklers for a new gear (told the wife the other $200 worth of parts that got on the order were by accident 
) Once I replace the gear we will see if that helps or if I am looking at more significant internal distributor work.........hope not........thanks again.
) Once I replace the gear we will see if that helps or if I am looking at more significant internal distributor work.........hope not........thanks again.
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Thread Starter
Cruising
Joined: Dec 2005
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Per my previous post, I did the diagnostic assessment as recommended by the forum. I changed out the drive gear and fired her up and we had a tach 
Bounces around a little but that is for another day......
Bounces around a little but that is for another day......
Safety Car
Joined: Jun 2002
Posts: 4,135
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there is a 4 dollar thrust washer that has to be instaled in that side gear lars is talking about, if you installed a new tach drive($125) and that gear without the 4 dollar thrust washer,,it will go anywhere from 5 miles to 105 miles before it wipes out the cross gear and or the tach drive again. im glad you got it going,,,but take this advice,,just because it works now in your garage,,its not gonna within any amt of time without that thrust washer.i wiped out 3 of them! look at a man ual or diagram of a distrib, and you'll see that puppie ,,, i had to learn that one the hard way..after i did learn it. (the 300 dollar lesson). i took the oudated piece of crap distributer off my car,, put it in a box on the shelf and got a msd billeted distrib,,6al box and call it quits...by the way ,,thats probably why its bouncin...4 dollars !!!!
Last edited by carl a; Feb 22, 2006 at 04:01 AM.
