Quick question about the speedometer in my car. I got an 86 T/A 700R4 2.73 rear and stock tires. It had the 85 mph speedo in it but I found and installed a 140 mph speedo in it. I haven't got much drive time in it but it appears my speedo is off. So my question is: do I need a different gear in the Trans or should both speedometers work the same?

 

Both should work the same.
Is the 86 a recent purchase?
Did 10 miles on the highway = 10 miles on the odometer?
Odometers can be correct even if the speedo doesn't read correctly.
Pop the speedo gear out and figure out what gears the tailhousing has in it.

 

No. I have had this car for 20 years now but I'm just getting it back on the road. I've gotta double check the rear end gearing. The rear dif was replaced after a wreck about 10 years ago by the body shop and I'm not sure the gears are correct. I have only had it out for testing and only put a few miles on it since then. I just didn't know if the 140 and 85 clusters operated the same.

Thanks for the info, I will be out there tomorrow working on it and I will check a few things. The Trans is also new to me and I just put it in so I have no idea what gears are in it now.

 

Could it be that I'm using the Speedometer buffer for the 86 T/A? The T/A had a 85 MPH speedo and the cluster is a 140. Do I need a 140 buffer?