8.8 differential revelations

Been chasing a rumbling bearing type noise in my '97 explorer (SOHC 4WD with 93k miles) for the last few years. Recently it's been getting pretty obnoxious. I'll spare everyone the various steps I took to resolve things and fast forward to today. Opened up the rear diff to change the axle/wheel bearings, and while I had the cover off I measured the ring gear backlash at 0.040". Also noticed about 0.01" R/L play in the carrier. Time for more investigation.

Unbolted the carrier and it basically fell off in my hands due to the lack of preload. Bearings and races were totally shot! That explains my roadnoise and the "gold" metallic particles I found in the first ever oil change a few weeks ago. Some pics below. I am SO GLAD to have finally found the root cause.

I'm thinking I will just swap in new carrier bearings and shim it to a suitable preload. I want to leave the pinion alone - this is my first differential work and I'm already a bit nervous about it. The pinon seems to spin smoothly and has no discernable play. Sound like an OK plan to get back on the road?

Also, I noticed the left axle tube has a lower relief for oil return, but the right axle tube does not - only an upper one. Is this normal??

BK

BK_89iX said:

I'm thinking I will just swap in new carrier bearings and shim it to a suitable preload. I want to leave the pinion alone - this is my first differential work and I'm already a bit nervous about it. The pinon seems to spin smoothly and has no discernable play. Sound like an OK plan to get back on the road?

Also, I noticed the left axle tube has a lower relief for oil return, but the right axle tube does not - only an upper one. Is this normal??

Click to expand...

It looks like so many others that have been posted on here. I have already read your other thread (maybe just the last of a series??) about the diff fluid and was thinkin that seeing brass filings means your bearings are dying.

Sounds like a good plan, or at least the plan that I would follow. I have had 2 of these Limited Slips rears apart and didn't notice the lower relief. I would imagine its normal.
By the way, and not trying to sound condescending in any way, but that little bolt that holds the cross pin in place is notorious for snapping. If you have not purchased a replacement, I strongly suggest you do so. They are not fun to remove after they have broken, possible yes, just not all that fun.

10-4 on the little bolt. I had my 14yr old helping me out today, and when it came time to remvoe "the bolt" I had him rub some good luck powers on the wrench to make sure the bolt came out intact. Virgin bolt is definitley going back in....

BK

Decided to swab out the axle tubes. The lube that gets held up was clean and clear, but there was a thick black paste coating the interior walls - very nasty stuff. LOTS of those "gold" particles were trapped in there, so I'm glad that I went to the trouble. Simply wadded up bundles of rags and pushed them through with a metal rod until the walls were clean looking through the tubes. Just like cleaning a gun. Squeaky clean now. Rubbed a neo magnet over some of the rags and it picked up plenty of metal....

BK

I did the same when I swapped out the whole rear end, but I saturated the rags with brake cleaner. TONS of gray garbage came out.

AS long as your pinion doesnt have any play the bearing should be good. When the bearing go bad though it is bad news. You hear griding noises and the pinion will deflect off of the ring gear and break teeth. Had it happen before.

Finally got tool to get the carrier bearings off. I cut off the cage to have a look underneath - not too pretty. In addition to being severly pitted, the one on the left is very wavy on its surface - hard to tell from the pic. The right one is bronze colored. That'll be the "gold" I found in my oil. I suppose it's heat damage. Fun stuff. Glad I caught this before everything blew up.



BK

New Koyo carrier bearings are on! Heated them to 285F for 30min, then tapped them into place with the help of the old bearing, a 46mm impact socket and a brass mini-sledge. Supported the works with a flat stainless piece. Took a few minutes of tapping to get it down all the way. Verified after cooling that it did not creep up. Now on to shimming for backlash and preload....



BK

PS: Thanks to EF vendor ericautopart for a great price on the master install kit (and axles).

Another long day today.

Rigged up a first-class billet setup to measure backlash:



The "supershim" sandwich-type shims in the master install kit were awesome to work with. After I got things where I wanted them, I added 0.0055" shims on both sides and crammed in the second shim pack with a shim driver tool and deadblow hammer. Torqued the caps and measured 0.011"-0.012" backlash at 7 different locations around the ring gear:



Pattern check, coast side:



Pattern check, drive side:



Anyone have any comments on the pattern?? This is a 100k mile gearset that ran excessive backlash (0.04") and sloppy carrier preload for at least several thousand miles! The pinion bearing felt fine in terms of smoothness, preload and lack of free play, so I left it alone.

New Yukon axles, new clutch pack, new spider gears and new pinion shaft. The pinion shaft barely fit, so I'm glad I didn't go any taller on the shim stack:



Sealed things up with black RTV, and the cover got a thick coat of black rustoleom paint last week. Will cure the RTV for a few days before I get a chance to fill it up with gear oil. Almost there!



No test ride yet, but that crunchy, notchy feeling from manually turning the tires is gone, so the prospects are good.....

BK

I'm officially declaring victory on this one. Filled it up with fresh gear oil and friction modifier last night. Took it for a test drive just now and all is good! Bad noises are gone and there are no whines, vibrations or gremlins.

This was the final laundry list:

- Master 8.8 install kit with Koyo bearings (left the pinion alone)
- Ford Traction-Lock limited slip clutch pack
- New Ford spider gears
- Fresh Mobil-1 75W140 synthetic + Ford friction modifer
- New Yukon axle shafts, Timken axle bearings and axle seals
- New Wagner brake shoes
- New Spicer solid u-joints (two 5-790x for the rear and one 5-785x up front)
- Cleaned and lubed rear driveshaft slip joint

I want to thank the good info and advice I got here at EF, as well as the EF vendors. Hopefully my photodocumentation will encourage other first-timers to tackle their rear diff. I'm already finding myself looking for an excuse to tear into the front D35 differential....

BK

rookieshooter said:

Click to expand...

This is how a tech write up should be done. Including taking the time to take good quality pics with proper lighting. Excellent close up of what a bearing should not look like.
Looks like your on your way to tackle any repair that could come your way.
This reminds me, that I have a whine coming from my 8.8 and needs to be addressed like you did.

Love your recipe for cooking bearings. Did about the same thing on my D44 rebuild, but also took carrier out and layed on ice while in a plastic bag.
Just how did you decide on 285F for 30 min.?

rookieshooter said:

This is how a tech write up should be done. Including taking the time to take good quality pics with proper lighting. Excellent close up of what a bearing should not look like.
Looks like your on your way to tackle any repair that could come your way.
This reminds me, that I have a whine coming from my 8.8 and needs to be addressed like you did.

Love your recipe for cooking bearings. Did about the same thing on my D44 rebuild, but also took carrier out and layed on ice while in a plastic bag.
Just how did you decide on 285F for 30 min.?

Click to expand...

Thanks!

I scoured the globe for info on getting the carrier bearings on. At one place I read that one manufacturer (timken?) set an upper limit of 300F, but I could not verify that info. One person reported he needed to heat up to 450F to get the bearing to go on easily. Another site suggested a hot plate and "too hot to touch". I wanted to first use the minimum temp necessary. I thought about placing the carrier in the freezer for a few hours ahead of time, but the wife already had it packed with icecream. We have an ample supply of dry ice at my research lab (-108F) and I thought about placing just the end of the carrier in a bucket of that, but I thought that might be going too far. 285F worked OK, but next time I would also cool the carrier to make it even easier (or just finally buy a 12ton press).

BK

Some related threads on my recent project, just to consolidate everthing:

First fluid change - metal particles
http://www.explorerforum.com/forums/showthread.php?t=270146

Clutch plates - worn out
http://www.explorerforum.com/forums/showthread.php?t=272697

Spider gears - old vs. new style
http://www.explorerforum.com/forums/showthread.php?t=273208

BK

good on ya....!