I have a wrecked 2000 F150 that has a 9.75" rearend that was rebuilt about 20-30,000 miles ago.

My dad has a 1999 F150 with a leaking, worn out, howling 8.8". I want to put the 9.75" in there.

BOTH TRUCKS ARE 2WD

I know there is an issue of gear ratios, since my dad's is 3.55 and I had just changed mine to 4.10. I'm not concerned with that issue, I'll take care of it on my own. What I AM concerned with is my dad's axle sounding worse every day, an him being left stranded somewhere (We live on a farm.) and having to pull him back with a tractor. I've done it before. A night. In the winter time. It's not fun.

SO will his driveshaft work or not?
Thanks guys

 

If both trucks have the same tranny and are the same bed length and cab style then use the drive shaft out of the truck with the 9.75. If not try a bone yard or get the existing one adjusted. The 9.75 diff is bigger so it sits closer to the tranny on the frame than the smaller 8.8. If memory serves it is about 1½ inches closer. That means that the 8.8 drive shaft is longer and will need to be shortened. Remove the drive shaft on the 8.8 truck and with the truck on the ground measure from the companion flange on the diff to the end of the output shaft on the tranny. Keep the measurement. When the 9.75 is installed measure again. The difference between the two measurements is what the 8.8 drive shaft needs to be shortened.

JMC