Measure from the edge of the seal (Not the output shaft) to the centerline of the rear u-joint.
**Please do this at ride height**
The car can be lifted under the differential but make sure it has the weight on the rear springs**
To properly measure the rear end yoke, first determine if the yoke has (2) tabs that the rear joint will sit-in between or if there is not tabs (tabs are in the picture above) or if it has a flat plate.
Be very careful with this measurement. The size changes in increments of 1/16(1-1/16|1-1/8|1-3/26)
Please Provide the Following Information:
1. Transmission Year/Make/Model (please advise spline count if possible)
2. Differential Info: What did it come from (did it have u-bolts or straps and (4) bolts or it was a flat plate)
3. What HP and torque does the engine currrently produce?
4. If the car is being built for competition, please give us a full run down of the car, weight , tire size and rear ratio all of this will help get you the correct shaft.