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Speedo gear not engaging....it seems...

bandit67

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Ok Guys, some major milestones reached this week. Got my 73 project fired up and moving...finally after 15 years. I purchase a used A833 and got it installed where a po had put in an automatic. Had the dash out and tested the gauges and speedo needle bumped up as should be when hand tweaked. New cable but had no speedometer movement. Pulled speedo gear and found a 36 tooth [red] and the chart said a 33 tooth was needed for my 3.23 rear. I found a 34 tooth in a spare tranny and installed that one. Still no speedo movement. When I push the tip of the gear in with my finger and spin the driveshaft I can feel it is not engaging or trying to turn at all. The trans has a Dec. 1969 build date and I believe I have the right size gearing, the big one, not the smaller pre 65 ones.....what am I missing.
 
on the speedometer gear holder theres three
marks that identifies the gear tooth range that’s installed. you have to line up the mark
that relates to the tooth count with the mark that’s on the tail shaft housing at the speedometer gear opening. If this isn’t done the gear will not engage the output shaft correctly if you look closely at the gear holder you can see that the gear shaft is offset from center.
 
Ha ha, I bet thats it. I did notice those marks but was not aware that needed to be installed that way. Thanks Bee....I will work with that.....
 
on the speedometer gear holder theres three
marks that identifies the gear tooth range that’s installed. you have to line up the mark
that relates to the tooth count with the mark that’s on the tail shaft housing at the speedometer gear opening. If this isn’t done the gear will not engage the output shaft correctly if you look closely at the gear holder you can see that the gear shaft is offset from center.
Searched on speedometer gear and ran into your post, thank you for this! While my '66 Charger was in the shop last week, I asked them to replace the original speedo gear with a green, 39 When I picked the car up today, it seemed to work for a few miles, then I got the bouncing needle and occasional chopping sound like helicopter blades. That continued the rest of the way home and speedometer was all over the place. I'm hoping the shop didn't know what you shared regarding the three settings on the case and left the tail setting where it was for the original 3:55 (or whatever they were) instead of moving for the 4:10's. THANK YOU for the tip, I'll have him try it.
 
Yes, somewhat. After rotating the driven gear holder to the correct orientation for the gear teeth used, we got rotation. The speedometer works, but is screaming pretty loud. Unpluged cable at the gauge and all went quite. Seems when I had the dash out cleaning up everything I should have taken gauge apart enough to lubricate. Car was a basket case when I bought it and just assumed it would still work. Ive had GM stuff not working for 40 or more years and had them just go back to working fine. Live and learn....
 
@bandit67 did you get your speedometer issue corrected?
The saga continues. Today, the shop will pull out the speedometer unit and send to a speedo shop for refurbishment. So far, we have replaced the speedo gear and seals, double-triple checked the clocking, replaced the cable and lubricated it, and triple checked there are no kinks in the new cable. According to the shop, at low speeds, the speedometer is reading 150 mph. This makes no sense. What frustrates me, is that the speedo was working perfectly fine, though reading about 20mph higher than actual, for many years, until I tried to have them replace the speedo gear with the correct one for the 4:10 gear and mag wheel height. That's when all the trouble started. I should have left it alone I guess.
 
The saga continues. Today, the shop will pull out the speedometer unit and send to a speedo shop for refurbishment. So far, we have replaced the speedo gear and seals, double-triple checked the clocking, replaced the cable and lubricated it, and triple checked there are no kinks in the new cable. According to the shop, at low speeds, the speedometer is reading 150 mph. This makes no sense. What frustrates me, is that the speedo was working perfectly fine, though reading about 20mph higher than actual, for many years, until I tried to have them replace the speedo gear with the correct one for the 4:10 gear and mag wheel height. That's when all the trouble started. I should have left it alone I guess.
There’s a slip joint in the shaft in the speedometer head it’s probably gummed up and needs some servicing
 
You have to clock it right. Check the number of teeth on the gear.

Speedo_adapter-01.jpg
 
There’s a slip joint in the shaft in the speedometer head it’s probably gummed up and needs some servicing
Thank you - I feel better about giving them the go-ahead to pull it and send to a speedometer shop fairly local for refurb. My fear now, is that in removing the speedo, they will do something to goof up the electroluminescent lighting, which I paid a small fortune to get working correctly (except the radio, which I didn't know was also supposed to light up). Please tell me the speedometer should be able to be removed, refurbed and re-installed without it being very likely to screw up the lighting?
 
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