ostie13

I have a question that I hope someone will help me with. My speedometer is of about 5 to 7 MPH off. I have the original tires and rims on my 71 Toronado but I have changed out the differential from a 3.08 to a 3.21. I see in my service manual that on the transmission that there is a speedometer assy, what part do I change out to correct the speedometer? Ther looks to be several different gears in there and also where do you get replacements.

ostie13

Can anyone help.

joe_padavano

The speedo cable is driven by a set of gears in the trans. The gears MUST match the final drive ratio and the tire diameter. I don't know if TH425 speedo gears are the same as those for a TH400. On the TH425, the speedo drive gear is part of the governor assembly, and the speedo driven gear uses a holder similar to those on the RWD transmissions. If you can't get a correct speedo gear, you can get a speedo ratio adapter that will accommodate the different ratio. There are numerous vendors who will custom make these. Try Google.

ostie13

I will look for a vendor now. Thanks Roy

MDchanic

Call these guys - it can be more complicated than you initially think:

http://www.transmissioncenter.net/sp..._____va.htm#gm

- Eric

ostie13

I will do that. Thank you