Hi guys- recently bought a 2001 4x4 with the 4.6. During the test drive I didn't get the truck up over 65km/h and of course, right at 70 the rear end starts howling like crazy. Pulled the cover and the spider gears are chowdered. Looking for a junkyard axle to throw in and was wondering if one from a 2wd bolts directly on. It's an 8.8 posi with 3.55 ratio, H9 sticker code. Also I am under the impression that they switched to rear discs in 99? My first Ford so I don't really know a whole lot about them. Thanks in advance.

 

Direct swap as long as it's a 8.8 out of a 97-03 with the same type brakes.

To the best of my knowledge, rear discs were not standard till 2001 - but I think they were either optional or only on high end models before then.

 

My 2000 F150 Scab XLT 5.4 4x4 has disc brakes on the rear 9.75".

 

Spider gears do nothing when you are driving down the road. FYI. .. as the entire carrier is rotating and BOTH wheels are rotating at the same speed. The spider gears ONLY rotate when there is a difference in wheel speed.
Next. The 8.8 is the same from 4x2 to 4x4 per chassis. They all interchange with eachother EXCEPT the SCREW short bed. (it's special) MAYBE...the shocks are arranged different on the short bed SCREW. They might have the same bracket on the housing just mounting the shock to it different.
Disc brakes: considering this is your FIRST ford...swapping from drum to disc is quite an undertaking DEPENDING on YOUR resources.Reprogramming the ECM, ABS, and swapping several other components is a PITA. YES you can do it...NO it is not really cost efficient to PAY somebody else to do it.

 

When you say spider gears, do you mean the actual spider gears, or are you talking about the ring and pinion? The spider gears are the four small gears inside the carrier. Those are inexpensive and easy to replace. An axle swap is not necessary.

If you mean the ring and pinion gears, then yep, you need an axle swap unless you have the skills and tools to set up a new ring and pinion. The best thing to do is to get the 5 digit code from the metal tag on the differential and have the parts yard look up compatible axles. The tag looks like this:



Re your question about years for disc vs drum, I have a 99 2WD work truck and mine has drum brakes. Many different 8.8 axles from from different years and models are compatible with your truck though, so you will almost certainly be able to find plenty of matches. The Hollander code lookup that the parts yard guys use will have all the interchanges. For example, I had an S852A (3.08) and replaced it with an S862B (3.55) without issue.

Piece of advice: plan on replacing the axle shaft bearings, and probably the axle shafts while you are at it. All 3 of the 8.8 axles that I have broken down had a groove worn in the shaft where it rides on the bearings, especially on the passenger side. One of the trucks only had 120K miles and was well maintained, so I think it's just a design flaw. A new OEM shaft with bearing and seal is only $115, so it makes sense to get that done while you have it apart. Oh yeah, and if you are swapping in an LS Diff then service the clutch packs too.