I just finished swapping a 1988 350 into my 1989 2.8 car. I swapped the engine trans driveshaft and rear along with the gauge cluster all from the same donor car. I took the car for a drive and I'm sure the speedometer is running high by 5-10 mph at 70 mph. Is there something else I needed to change or could something else need recalibrated after a swap?

 

If the rear is different ratio, the speedo gear has to be changed.

 

I did swap in a different rear with a different ratio but I also swapped in the tranny that matched with it. Am I wrong or is the speedo gear in the tail of the tranny and if so it should be correctly matched. If I am wrong could you tell me where the speedo gear is.

 

It is in the tail. One side of the gear is around the tail shaft and the other part of the gear is what sticks through the tail casing. I just recently switched from auto to manual and had the same problem cause I have 3.73's and the speedo gear in the trans was geared for 3.42's.

 

there is a speedo box (can't think of the name)very small chance on this being whats wrong well, long story short it is mounted to the same bracket as the ecm so if you pull it down there you go, that is the only other thing I can think of right now. since the trans and rear are from the same car. unless that doner car was off too?

 

Very well could have been changed in the donor car. I have a cable driven speedo, so I can't program mine. Have to change the speedo gears.