Diesel 5-Speed Speedo Drive Gear Options

[Jetmugg]

I'm in the middle of creating a bit of a Frankenstein 190. I've got a 2.5 Turbodiesel engine, a 5-speed tranny from a 2.2 Diesel car, and I'm putting the drivetrain into a '93 190E 2.6 chassis.

The 2.2 5-speed car would have had a very "deep" rearend (maybe 3.42). The rearend in the 190E 2.6 chassis is a 2.88. I have an instrument cluster from the 2.6, and an instrument cluster from the 2.5 Turbo car, which had a 2.65 rearend. I think you can see that I'm going to have a mismatch problem between the speedometer drive gears in the tranny and the instrument cluster. I believe that my speedo will be WAY off.

What is the correct way to eliminate this discrepancy? Are there different sets of drive gears to put in the tranny for each possible rearend ratio? Will I need to come up with a different speedometer, or is it possible to recalibrate the speedometer to work with the tranny and rearend in the car?

I've actually done a similar swap before, but in that case I just replaced the auto tranny from a 2.5T car with a 5-speed from a 2.3 8V car. The discrepancy wasn't too much in that case, but I'm afraid that I'm going to be way off now.

Any help would be appreciated.

SteveM.