Okay, I perused 2000 posts and didn't find an answer, so here goes:

I have a 69 F100 with a 302. The original rearend was a 3.50, but grampa put in a 4.11. I am looking for a 3.50 or a 3.25, but I don't know the spline number. From what I've been told, it's either 29 or 31, and I'd rather not pull the axle myself to verify, if I don't have to.

The pumpkin has 7F13 stamped in it. Does this help? Is there another number I can look for?

What is the axle spline ratio?

For day-to-day driving (w/ Interstate speeds) which is better: 3.50 or 3.25?

If I have to pull the axle to check the spline #, can anyone give me directions for dummies?

Thanks,

Drew

 

Drew, First of all, to my knowledge there is no 29 spline axle. There is a 31 and a 28. Next, I don't think there is any way to know the difference for sure without pulling an axle out. It is very simple and quick to pull one out, so you don't need to worry about that. Jack up the rear of the truck. Put a jack stand between the 2 U bolts that hold the spring to the rear end on which ever side that you decide to pull out. Pull off the wheel. Adjust your break shoes in and take off the drum. There will be a hole in the end of the axle next to the wheel studs. Turn the axle around slowly and look through that hole. You will see 4 nuts. Stick a socket through that hole and take off the four nuts. Put you break drum back on the wheel studs backwards. Then screw your lug nuts back on, but do not get them tight. Screw them on until the stud gets to the out side of the nut. You should be able to move the drum back and forth about 1/2 an inch. Push the drum against the axle and give it a quick jerk out towards the lug nuts. It may take about 2 or 3 tries, but the axle will come loose. After it's loose, take the drum back off, and slide the axle on out of the housing. Be very careful because the splines are sharp. If you pull out both axles, you can change the third member realy easy without replacing the whole rear end. There is a tech article on here about rebuilding a Ford 9 inch. Look at it and it will show you how to pull the third member out, and put it back in. It also has the torque specs for putting the axels back in. As far as the gear set to go with. I had a 3:50 in mine, and it was kind of a gas drinker. I replaced it with 3:00 gears. They work much better, but I have a big block in mine. I think if I were you with that small block, I would try to get a set of 3:25 gears. I think they will be a good comprimise between fuel economy and over all driveability of your truck. Let me know if you have any questions or problems with the axle procedure.