Switching from a 9 1/4 to an 8 3/4. Am I looking at a driveshaft change or modification?

Your current drive shaft is at the edge of being too short or too long. The difference is only about 3/4'" if I remember correctly. I can't remember which one was longer though...There should be enough clearance in the drive shaft length to accommodate the difference between the two rear ends.

Of course I was assuming you have the same size rear joints. If you don't, most auto parts stores have conversion u joints to handle the u joint issue. Gene

hi dart, the 9 1/4 has a centerline of axle shaft to center of rear universal of 11.69" . and the 8 3/4 has a centerline measurement of 12.35" . .66 difference. what is your driveshaft to trans boot seal distance ? check and measure it BEFORE you take things apart. ronnie

Most vehicles have plenty of spline length and engagement depth to accommodate that difference going the other way. You may need to have your shaft shortened though I was able to move my trans rearward 1.25" when I did the lock up conversion on my 92 without issue, just had to get the aftermarket output shaft seal without the dust boot.