Looking for some insight into the front diff on a 99 F150.

I pulled it out of my truck 2 weeks ago and took it to a rearend guy who basically did absolutely nothing for two weeks. I finally took it back today when I went to see him and it was clear he was jerking me around.

The problem I took it to him for was the driver side axle was sloppy. (This is right next to the differential (Front axle 4x4)) You could really rock the flange on the axle that is used to bolt the inner CV to. The axle shaft is 6" long with splines that go into the differential side gear.

At first I thought the bearing was bad, there is only one, but after looking at it some more I found that the differential (Spider) gears are sloppy as well. If I hold them tight the axle play seems ok. The differential gears, I'm estimating have about .030 clearance. Each side gear has a shim, but not nearly enough to make the gears somewhat tight. The manual I have says nothing about adjusting these. Does anyone have any experience with this? Also due to the slop, the Axle has been rubbing against the pin used to hold the other gears in the diff. From what I can tell from the design there is no positive stop along the axle axis in that direction to prevent this. Seems like a bad design.

Any help would be really appreciated.

Thanks

CR

 

Sounds like you need to adjust your backlash, etc. in the differential. You might as well change the bearings while you are there. Do a search on rear differentials on the web. I have seen several sites with really good writeups on rebuilding rears. (unfortunatly they are in my favorite folder on my work computer and not my laptop, so I can't post them at the moment)

You will need a shim kit which can be purchased from summit and a dial indicator gauge. Also a blue greese pen and a few hand tools. THey aren't too hard to rebuild but it is timeconsuming. It is a little bit of trial and error until you get the right shim setup and crush.


kev

 

Kev,

Thanks for the feedback. It's not a backlash problem. The ring and pinion are fine.

After studying this thing, I've come to the following conclusion:

The short axle (Driver side) is mushroomed over from contacting the cross shaft in the center on the diff. This will happen by design, but the wear is severe and the cross shaft has two deep grooves in it from the end of the axle as well. With this wear the snap ring on the axle, which serves two purposes, is failing to keep the end diff gear tight in the diff cage. It makes sense, since when I hold the gear tight against the diff cage the axle flange feels OK. So basically the axle goes in further than designed to and the distance between the snap ring and the gear increases. This lets the gear back away from the cage and rock.

The truck has 90K miles and I don't the front end oil was ever changed. Maybe that lead to the excessive wear. Who knows, but I'm pretty sure I understand why the flange was rocking as much as it did. I'll post when I get it back together..

Nevertheless, thanks for the input.

CR