Speedometer problems

[Carolina Carl]

Hello to everyone and maybe somebody can help me. I have been having a terrible problem with the speedometer gear in the dash on my '68 RR. I had the trans rebuilt and the transmission speedometer gear was installed wrong and so it ruined the gear in the dash. I found another one and installed it and used the gear that currently is in the trans. It seems to work ok until it gets up to about 35 mph and then starts humming and bouncing around. I don't want to have to replace it again. I have a 34 tooth green gear in the trans and have a 3:23 rear end with P225 R70 14 tires. I have the gear in the trans set at 31. Is the problem with something not being adjusted right, the cable, or in the trans gear. It seems like if the problem is with the gear in the dash it wouldn't work at all not just when it gets to 35 mph. Any help will be great as I am about to pull my hair out with this.

 

[Coronet 14]

You changed the speedo gear on the trans. How is the speedo cable is it worn through or kinked? I've had that problem on a vehicle before it was a bad cable

 

[Budnicks]

I'm not sure if this will help at all, but here's a couple charts someone else posted a while back that might help, check the cable & housing too, I'm not sure what to do about the gears in the actual dash cluster, have you taken it out ??, maybe you can try to lube up the speedo gears in the dash, with some type of brake clean or electronics spray cleaner, then blow it out, maybe use some type of WD40 or other water repellent type penetrating lube that wont ruin the electronics & circuit board on the cluster & maybe then use a variable speed drill to try turn it possibly from the cable end ?????, see if you can isolate where the problem is maybe... Also maybe see if the speedo gear is installed properly, seated all the way in, in the trans ?? sorry I can't help much, good luck

 

[Bruzilla]

Sounds like the problem is in the speedo. I had the exact same problem with mine, and replaced the speedo cable, which did nothing. I was told the unit needed to be taken apart and lubricated. I shot some WD40 into the back of it, and at first it did nothing, then several weeks later POOF! it started working just fine.