A lot of people have asked me about my “full float” 8.8. I have never seen or heard of another person on this site that had one of these. I had to do some service on it and I thought I would do a write up (with pics) for those interested. First I will show you whats involved and give some pros and cons at the end.
This is a Mitchell Differential kit I bought in about 98’ I had it installed in my 88’ Bronco for about 4 years and then I moved it to my new (to me) 90’ Bronco. since it has been installed for many years, this will not be a install write up, but it’s pretty easy to see how it goes together.
This is how it looks on the truck. Kind of like a one ton without the eight lugs.
Next, with out the wheel it, it looks much the same. Note the stock drums have to be machined out in the center just a bit. Mine were shot on the 88’, so I bought new ones from Mitchell. But they are not part of the kit. Also you can install discs with this kit.
Now you can see the hub. It is very similar to a front Dana 44 hub.
With the axle bolts removed the axle just pulls out. (no c-clips) In fact, you don't have to jack up or remove the wheel to remove the axle. The hub will still support the truck.
You can see the hub is held by the familiar spindle nuts like in front. These are the old style, one nut with a pin, a keyed washer that locates the pin and a lock nut.
With the hub removed, you can see the spindle. It is held on with the 4 bolts that hold the brake plate on. I’m not going to tear this down any further right now. But I will tell you that the spindle has a spigot that fits very tight in the original axle bearing race. So the 4 bolts don't really hold the weight of the truck. Once you pound it in, it’s pretty strong. If I was sure I was going to keep this housing, I would machine off the flange and weld the spindle on. But it was good I didn't do that on my 88’, since I ended up moving it to this truck.
If you take note, I made these steel “doughnut” spacers to fit perfect in between the spindle flange and axle flange. They didn't come with the kit. I didn't feel comfortable with the bolts trying to bend the axle flange. (the spindle flange is strong).
First, let me say that the reason I got this kit was I kept warring out wheel bearings on the stock setup with 35” tires. Because of the pour design of the 8.8, the wheel bearings tear up the axle too. Many people on this site and others say that the TTB cant take 35” tires. Well I had many more issues with the 8.8 than out front. Since I installed this kit, I have yet to ware out a wheel bearing. (And I’ve been running 38” tire with 14” wide wheels for most of the time.)
But I have had some problems. The first problem was after about eight years. (4 years on the 88’) The axle flange cracked and the spindle worked out a little and tilted enough to allow the axle to scrap the spindle. I had to drive home from a nearby town (about 50 miles) and it cut a groove in the axle all the way around. I welded the flange and all was well for about 6 months. Then going around a corner with my foot on the gas, Kaboom!! The axle snapped right at the groove. Since the hub kept the wheel on, I was able to drive home (400 miles) with the locker driving the other wheel. I got another axle from Mitchell.
The next problem was about two years ago when The flange on the hub cracked all the way around. This effectively made my wheel/drum wobble on the hub. The way it cracked, it couldn't get off and I was able to get home. It was only about 5 miles, but it was scary.
I called Mitchell and they said they never heard of this happening. But they did say that now the hubs are machined out of one solid piece. (my flanges are welded on to the hub) I enquired about a new hub, but they changed the design so it could except 35 spline axles and bigger bearings. They no longer make the hub I have. The new hubs must be installed on new style spindles. Of course if I wanted the benefit of the 35 splines, I would have to buy new axles and locker. So basically, I would have to buy a whole new kit. I just welded the flange back on.
About six months ago, the flange cracked again. (my weld was probably not very good) Again I was lucky in that I was only about 5 miles from home. This time I really ground it out and welded it good. It would probably work fine, But I never trusted it. So I machined up a new hub (out of billet) for a spare. I changed it slightly by making the flange thicker. I just installed this hub and will keep the welded one for a spare.
Besides these problems, I’ve had leaks occasionally.
The big question is would I recommend this kit? Well, that depends. It has been good to me for a lot of years. I use to do some serious wheeling. (not to much any more) It is expensive (about $1100) I have some rare wheels on my truck (Alcoa forged 15 x 14) and I wanted to keep them. So if you want a lot of strength with 5 lug wheels, this is the way to go. Also its nice that it installs quick and doesn't affect your VSS. And of course, it gets rid of the dreaded c-clips.
On the other hand, if I was building a new truck (I am), I would just get a pair of one ton axles off a Superduty for about the same money. It is certainly more work, but still is mostly “bolt on”. And the one ton Sterling solves some other problems that the 8.8 has. You can check my “Molasses project” in the SAS section if you want to see how easy it is.