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Speedo bounce

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sp53

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How steady should Speedometer needles be on a tr3? They must have been dead flat new, but the ones that I have tried have always had this bounce. I cannot seem to get rid of this small bounce( 3 or 4 miles). I have tried different heads and bought a new cable from Moss and was surprised how inexpensive it was. I paid, I think 15.00. Anyways, are the ones from TRF of a higher quality? I was thinking that I might take the one I have to a local shop and have them use that for a pattern. The guy said he wanted like 30.00 bucks to make one. I just do not know if that will make a difference. They do not seem to be a very complex unit, but perhaps the nylon deals act as carrier bears or whatever and have to have some kind of clearance or something. I do believe that the problem is in cable because if I hold the new cable over to one side a little when driving the needle steadies up, but I cannot tell if I am putting unwanted drag on the whole system.
 
If everything is working as it should you should not have any bounce. The usual suspect is the cable. If it has any tight bends in it the cable will jump a bit. If you don't have overdrive fitted you should have a right angled adapter at the gear box end. This will eliminate any tight bends. I suppose another problem could be a tight odometer which may cause the bounce you are experiencing.
 
Given that description, I would be tempted to pull out the driven gear from the side of the gearbox/OD. Almost sounds like a broken tooth.
 
I hear you Randal and I have another brass sleeve with the gear setting on my work bench, but this problem dates back awhile. I rebuilt that gear box 20 years ago out of three I had kicking around; however, perhaps I used the same speedo gear. I just do not remember/know. I guess a guy could just pull that long locator bolt and swap in a different gear without a lot of trouble if everything goes right. I have not done that with the tranny in place. What do you think?
I might have over simplified the commonality of the bounce because each unit has its own unique problem. I am going to call Mo Ma later today and ask them some questions about drag and needle bounce. I am starting to think the units might be moving to freely do to their age. When I took the dial face off, I notice a small screw on the bridge where the needle fixes and this screw places some drag on the needle, and I was able to get my bounciest speedometer to calm down some. So my latest perfectionist nothing to do theory in metaphor form would be the same as a fishing reel with the drag to lose.
 
Mine was bouncing 10 - 15 MPH at 60 - 70 MPH so I bought a new cable. The old sheath was cut through by the sharp edges of the floor pan where the cable is driven at the output of my "A" type overdrive. I slid a hose onto the new cable so the outer sheath for the speedometer cable won't get cut where it come out the overdrive.

It has been rock solid on the dash since then. So much so, that I had forgotten all about it bouncing before.
 
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