beamjp

Need to adjust the speedo on my 1961 Dynamic 88. Running smaller wheels and different rear end. Speedo is off 85mph is really 70mph. Can you change the speedo gear or by a gear reduction unit for this transmission (stock) thanks

svnt442

On some of those older full size cars the speedometer cable goes to the left front wheel instead of the transmission. I am unsure about your car so you may want to confirm where it goes.
I don't know about the gear reduction units.

Ozzie

The Olds service manual says that it is driven from the transmission. Do you have Hydra-matic or Synchro-mesh? Do you know the axle ratio? The code is stamped on the flange below the U-joint. It will be a single digit. You'll probably also need the tire size or equivalence to the original sizes. Unless it's outside the range of the original specs you can do it with a driven gear change. Otherwise you may need the adapter. Do you know how many teeth are on the current driven gear?

beamjp

Thanks I will get under the car this weekend. I was thinking that since the speedo is off 15%. I could just increase the teeth on the driven gear by 15% for example if the current gear is 20 teeth if I could locate a 23 tooth gear my problem would be fixed. I can't seem to locate any driven gears for my Hydro-matic or "slim jim"?

Ozzie

The tooth counts for the driven gears for the Hydra-Matic for 1961 were:

26, 27, 28, 29, 30, 31

You may be able to tell the number of teeth on the driven gear by looking at the flange of the driven gear assembly. It is supposedly stamped there.

beamjp

Great, thanks got busy with a honey due list, I will get under the car this week and take a look.