Procedure needed to replace rear axle assembly

[shealykt]

There is a whine coming from the rear end of my 1999 Explorer. The pitch of the whine is proportional to the speed of the vehicle but it’s only there under load. I've been told by a reputable shop that I should replace the whole axle assembly otherwise more problems will come up if I replace one thing at a time. Not to mention the labor cost to go into it each time. I'm not capable of “going into” it but I do think I could replace the whole thing. Does anybody have a procedure written up for this? The Haynes manual doesn’t show how to change out the entire axle assembly.

 

[obie]

Well, first off you need to know your gearing. Also if you have a limited slip differential or not. The tag on your door gives you your axle code. Then find one that matches it at a junkyard or something.

To be honest, replacing the entire axle seems overkill. Unless you have a ridiculous number of miles or have abused the everloving crap out of it, its probably mostly in good shape. New axle shaft bearings and seals are cheap, and diff rebuild kits aren't that bad. The 8.8 axle is tough, very tough. It'd be very difficult for you to have actually broken or fully worn a gear or tooth. Most likely cause of that noise is a worn bearing.

I'd say bring it to another shop and ask them to quote you on an axle rebuild vs. Axle replacement with labor and parts.

 

[blue89bird]

You should bring it to a real shop that's capable of diagnosing/fixing the problem. Almost any offroad shop or even performance shop will be able to work on a 8.8 rear. You likely need bearings, and like was said, replacing it is just way overkill. Sort of like asking for a heart transplant when you have indigestion.

 

[shealykt]

I'm going to assume this forum is about overcoming ignorance so I'm going to show mine!

First, I'm going to assume that my differential is ok. It does have 204K miles on it but that's not a "ridiculous" amount is it? It's pulled a boat or trailer occasionally but mostly my wife is back and forth to work and taxiing the kids around.

I see rear wheel bearings at AdvanceAutoParts.com for $15 each. I just did the front wheel bearings successfully so I feel confident that I can do the rear.

Here's where I show my ignorance. When you say axle shaft bearings, do mean the bearings in the rear wheel hub or is there another bearing closer to the differential? I read that if you're going to change the axle shaft seal you should also change the bearings. But if you're just going to change the bearings (seems you can do this without messing with the differential), should you also change the seal?

Perhaps I should change the wheel bearings first and see if the noise goes away. If it doesn't, then I could look into a differential rebuild kit. Between doing the bearing replacement and the differential rebuild, maybe I'll just change the oil in the differential housing.

What do you think?

Thanks for your help!!

 

[obie]

The axle shaft bearings and seals I was talking about are on the wheel ends of the rear axle. Those are best replaced as an assembly. Rock Auto sells Timken sets for pretty cheap. As for replacing just those...
Well, you have to open your diff cover and unclip your C Clips to remove the axle shafts, which isn't too bad. If you're already in there though, you might as well inspect the diff. You'll want to remove your rear driveshaft though and spin the pinion yoke. The most likely cause of that noise you have is a pinion bearing. They take the majority of the load and typically go out first. If those need replaced, you'll pretty much need a full diff rebuild, minus gears if those aren't damaged.

If you are a pateient and thorough person, rebulding a diff isn't too hard. If not, you may want to bring it to a shop that specializes in driveline work.

 

[RomeovilleIL]

If you decide to swap the rear end, the basic procedure isn't terribly complex just a bit time consuming. Consider it a weekend project for your first go at this job. You will need some wrenches, a set of sockets, a long breaker bar, big hammer, large c-clamp and plenty of pb blaster. Air tools are very helpful here. There are detailed write-ups with pictures for most of these steps either in the sticky section or can be found with the search.

Basically the steps needed are:

raise back end of vehicle and place jack stands under frame on both side, forward of tires
place a floor jack under the differential to support it and allow to be smoothly dropped and rolled out from under vehicle
remove wheels
disconnect drive shaft from rear
unplug/remove abs sensor from top of differential
disconnect flexible brake line from steel lines and plug so your fluid does not drain
remove breather hose (often missing)
remove brakes and disconnect calipers from the hard lines on the axle (the hard brake lines are not designed to be removed from the axle)
remove rotors, disconnect parking brake cables (parking brake shoes should probably be replaced as these are not done often and usually find them in poor shape)
remove the lower shock bolts (all 3 on rear)
remove rear anti-sway bar
remove u-bolts
unbolt rear spring shackles
lower differential and roll out to rear

Installation of the new axle is basically the reverse. It is recommended to use new u-bolts, especially if you live in the snow belt. (You will understand when you look at them.) While the axle is off the truck you should open the differential cover to inspect everything. With the cover off pulling the c-clips to let the axles slide out will make replacing the parking brakes much easier. Replace the gear oil & limited slip additive (if required) then put cover back on with either a new gasket (yes Feldco makes an 8.8 gasket) or rtv. Run new steel brake lines in basically the same position on the axle as the old lines. Green easy bend line is the best option (sorry don't recall the name, but it is $6 a side and doesnt require special tools to bend, plus ends are already flared).

Roll the assembly under the truck and lift, then put it all back together in reverse order with the added step of bleeding the brakes.

 

[imp]

........Perhaps I should change the wheel bearings first and see if the noise goes away. If it doesn't, then I could look into a differential rebuild kit. Between doing the bearing replacement and the differential rebuild, maybe I'll just change the oil in the differential housing.

What do you think?

Thanks for your help!!

This is a 2nd. Generation, right? Solid axles, rear, with outboard bearings totally different from the front, especially if 4WD. Whine present only when power is being delivered to the rear wheels, not during coasting at no throttle? Rule out pinion gear bearings, rear wheel bearings, but not differential side bearings, although they generally do not fail in such a way as to cause gear whine. IMO, the 2 BEST things to do are:
1. Run the vehicle while up on jack stands, have someone apply brakes while speedo indicates about 20-30, to simulate road loading, while you listen with a stethoscope to the CENTER SECTION of the axle assembly and the outboard ends of the axle tubes, where the wheel bearings are located. Careful listening can locate the place originating the whine. If noise is in the CENTER,
2. Remove the center cover plate, wipe off carefully several successive sets of ring gear teeth, looking for ANY surface condition other than bright, shiny, mirror-like on the tooth surfaces. The narrower, smaller surfaces are the DRIVE SIDE. They would be responsible for the whine, if surface finish damaged. If bright & shiny, they might STILL be responsible, if MISALIGNMENT has occurred due to differential side bearing failure. This would indicate time to check tooth contact pattern. This can be done easily from under the vehicle, by hand, with driveshaft removed, wheels off the ground, cover plate removed, spray degreaser on gear teeth until rotation back & forth of the ring gear's several adjacent teeth to engage pinion gear teeth, remain clean & oil-free. Then apply Prussian Blue cream lightly to several successive drive and coast ring gear teeth, rotate back and forth into mesh with pinion, then look at where the pinion teeth have "wiped" away the blue stuff off the ring gear teeth. Good patterns are centered, or only slightly offset towards outside. If pattern, especially on DRIVE SIDE, is way off of acceptable, but tooth finish is shiny and nice, likely diff bearings are at fault.

If this procedure seems difficult to understand, don't hesitate to ask further questions. I have been diagnosing & repairing hypoid gears for 50 years. imp