Ok got a 88 w100 4x4 but how do I find out what kind of differentials are under my beast? Would like to rebuild to ensure my future off-road adventures!

 

Do not take this the wrong way but if you don't have the knowledge to identify what differential you have my advise is to leave it alone. Differentials require special tools to set them up correctly when reassembling them. A differential is a very precise piece of equipment that if set up wrong will lead to its early demise or it can even catastrophically destroy itself. That being said I will now answer your question.

There should be an ID tag on one of the differential housing bolts to determine the gear ratio. If not I can tell you how to figure it out.

Our half tons use 8 3/8, 8 3/4, and 9 1/4 inch ring gears. Look on the inside of the brake backing plate for a flange type axle retainer. If it is there you have an 8 3/4 inch axle. If it is not there you have an 8 3/8 or 9 1/4 inch that both use c-clips too retain the axles. The 8 3/4 inch also does not have a removable rear cover. The 8 3/8 inch has 10 bolts on its rear cover while the 9 1/4 inch has 12 bolts.

Next, raise both wheels off the ground and turn one of them. If they turn in the same direction you have a Sure-Grip differential. If they turn in opposite directions it is a conventional differential.

On the front drivers side axle tube you might have a shift motor on top of the tube. If it is there you have a Spicer 44-8FD axle. The shift motor engages the axle shaft for 4x4 driving.

I hope this helps.

 

Hey thanks for the info! I know it sounded bad but I have always had cars but I fell in love with this truck! So I have been doing my reserch into the entire 4x4 system. once again, thanks!