9" Ford Rear Diff








F150 9” Axle

The Ford 9” is reguarded as a fairly tough axle, but anything can fail. This one had an especially good reason. Pulling a 4 axle trailer weighing at minimum 30,000 lbs? I don’t think Ford would recommend even half that, but it did it. In low range and low gear in the C6 the 429 pulled at 5000 plus RPM at full throttle with the Holley street Avenger 770 for over 3 hours (with a few breaks). Over Pine Lake from Issaquah Wa, there are some nasty uphills, we were only clocking around 10 to 20 mph on these. There are a few downhills too, and that helped to cool off this beast. Even with 2000 to 2500 lbs tongue weight it wanted to spin in 4 Low to get rolling.

All that seems to have taken a toll on the 9” Ford. The spyders look like “new” but the ring and especially the pinion look like 3.5 miles of bad road. 3.50 gears, too bad we didn’t have 4.10, or 4.56. The edges of the pinion were razor sharp with burrs and it was blue from the heat. The wear surface was gaulled and gravelly looking on accell and decell sides, there looked to be a couple wear patterns where it had been messed with before and not adjusted properly. This is beyond repair even for a hash backyard job. I was going to try to grind off the high spots and re set the back lash, but I just couldn’t bring myself to do it, that would take forever, and be a crappy short lived fix. So we called junk yards, we found a limited slip for $450, ouch. and a open for $350, both guaranteed for 90 days. Then we found a “maybe, 3.50, we’ll have to pull it to see” for $125, (not a limited slip)....Now we’re talking my speed. It should be a 28 spline, and we need 31, but I can take the ring and pinion and transplant them into this housing with a little work.









[F150 4x4] [429-Pre-Holley] [77 F-150] [77 Dodge 203] [New Process 203] [9" Ford Rear Diff] [Bits and Pieces] [Pinion] [Housing] [Good Used]

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