Ford 9 inch rebuild questions

Hey guys, want your opinion on some upcoming plans to rebuild the rearend of my truck.

The truck has 33s, C6, 4x4, and a mild 351w. I enjoy light off-roading. No rock crawling or mudding. A lot of highway miles and backroads. I don’t drive it like I stole it but I do get up to speed. No burnouts or the like but I’m not afraid to put my foot into it. I also tow frequently but it’s relatively light and the most I ever see myself towing is another half ton pickup.

I say all that because I’m looking at a couple options for the rebuild of my 9 inch.

The two options I’m considering

1) rebuild kit- including bearings, ring and pinion, complete limited slip differential, all the various little bits I’m forgetting. Less expensive.

2) complete third member- nodular iron third member, fully built and patterned, ready to install, limited slip, yada yada. More expensive.

The big question. Can a simple rebuild of the stock unit stand the torque and tires that I’m running? Or should I just spend the money and upgrade? I know anything will survive with a light enough foot and light use but I don’t want to drive around scared I’m gonna break something either.

Would love to hear some experiences you guys have and advice, thanks!

I have had Ford 9" rear ends in several cars and trucks with no real problems with the stock housing and insides. They ranged from a 1966 Shelby GT350 with 3.89 gear and Detroit Locker which got some really hard use to a 1977 F150 converted from a 300 C4 to a 390 C6. This one had a 3.25 gear and the 31 spline axles with roller wheel bearings. It hauled an 11.5' Wolverine slide in camper and towed an Omni, later a Horizon behind it. Tamest one was the 1958 F100, originally a 223 with 3 speed, later a 1957 T-Bird special 312 with Borg Warner T85 and OD, that one had a 3.55 gear.

The only one I rebuilt was the Shelby as it had been used as a drag car and had 4.11 gear when I got it. I ordered the gear set, bearings and shim kit from the local dealer and found the locker through a friend (way pre-internet, 1970). As to rebuilding, it is probably one of the easiest to do, pinion bearing preload is the only real hard part as it uses a crush sleeve. A pin spanner is needed for the side bearing adjustments and that is the only special tool. I would suggest, drilling and tapping a hole in the bottom rear of the center of the axle for a 3/8-NPT plug and use a hex socket one that will go in near flush so the gear oil can be drained in the future.

Thanks Bill. That makes me feel better about just rebuilding it. Every forum and automotive article I read they instantly jump to beefy aftermarket parts because “that’s what makes it tough”. They act like a normal vehicle is gonna spit the pinion out the front like the drag cars do. That made me get cold feet on just the basic rebuild. Later on down the road I plan to have more power that may warrant beefy parts. But like I said, I’m not hard on the truck so it probably wouldn’t matter anyways.

As far as the crush sleeve goes I’ve seen people use solid spacers instead. Is that a good option?

You can use a solid spacer, but you will put it together and take it apart several times to get the pinion preload right. The Ford 9" is one of the strongest stock rear ends ever built, all the NASCAR teams run them. Once you have the pinion bearing preload correct, you take the yoke off, install the seal, reassemble with the seal and nut to the proper torque and that's finished. Pinion depth is set with shims on the bearing housing. Backlash, the instructions I used said to take up all slack on the ring gear side against the pinion, then there was a number of holes you turned the other side adjuster in to preload the differential bearings then measure the backlash and run a pattern. From there you determine whether the pinion or ring gear need moving. One more tip, don't put the O-ring on the pinion bear housing until you have finished the adjustments, then lube it with gear oil before trying to push it in.

Thanks Bill! That’s answers my questions. I hope to get on it sooner than later, once work slows down for winter I should have some time.

If you’ve not seen it, we have Ford’s instructions from the factory shop manual on the page at Documentation/Driveline/Axles & Differentials. Then the Real Axles tab, then the Instructions tab, then the 9” tab.