Thread: Ford 8.8 Differential Woes

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Through a random series of events I pulled my rear wheels on the old 1990 F150 work truck, expecting to find a blown wheel cylinder. Instead I found a badly leaking rear axle seal, then discovered the problem with the brake in a rusted through & blown hard line tucked into a hidden spot on the frame. So, a trip to NAPA for a couple of sections of brake line and a new seal, and after replacing the line I jumped into the seal replacement, which I expected to take about an hour, maybe two at at the outside since the rear end is an Ford 8.8 which has c-clip axles. It turned into a mess, and I've learned that it's not an uncommon mess but not many people seem to be aware of it, so I'll post the story.
To change the axle seal you just pull an axle, but on a c-clip that means pulling the rear cover to drain the gear lube, then partially removing the pinion shaft between the spider gears, which then allows the axle(s) to be pushed in far enough for the c-clip retainer to be removed. The pinion shaft is held in place by a lock bolt/pin that's torqued into the carrier.
I removed the lock bolt,

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but only the nominal 1/2" long threaded portion came out. Here's that piece, shown beside a new bolt for comparison.
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The pin portion remained in place, locking the pinion shaft in place which creates a real Catch 22. You simply cannot do ANYTHING to the axles/carrier/spiders/ring & pinion until that pin is out. Some research told me that while many people think that the locking bolt breaks during removal, and there are recommendations to slightly tighten the bolt before trying to remove it, supposedly to prevent breaking. The truth is that they break because of the cyclic movement of the pinion shaft during operation, continually stressing the pin against the fixed threads above, causing a stress failure at the last thread. One site stated that in their experience over 50% of the locking bolts removed are broken this way.

As seen in the pictures, this bolt is not in the best position for "traditional" methods of getting to the broken part - like using an angle attachment on a drill, removing the passenger side carrier bearing cap, and trying to drill into the pin portion without taking out the threads, ruining the whole carrier. After fighting this thing for several hours trying magnets (hoping the pin broke just below the last thread), a scribe (trying to rotate it out), and several whacks with a BFH I started looking for help. The best solution I found was an "Extraction Kit" put together by Nick Fabbri in Riverbank, CA, which had many positive comments.

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The key parts are a pair of 5/16" hex socket bolts which have been precision drilled through the center, forming guides for the drill. Next is a 5/32" bit 12" long, plus a square extractor and a traditional spiral extractor EZ Out. The instructions tell you to use the shortest bolt that bottoms out against the broken piece, to help hold it from rotating, finger tight. Then it's a matter of slowly drilling, without excessive pressure, and with frequent removal to flush chips. Note that the long bit makes it easy to access the bolt.

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With the Extraction Kit removal of the offending piece was literally a five minute job from threading in the guide bolt to having the pin portion, with about 3/4 of one thread at the top, in my hand. As suggested by the instructions, I tapped the square extractor into place, and then tried to rotate it out by hand. I resorted to a pair of pliers to provide a bit better grip, and felt it start moving. Then it was simply a matter of backing out the piece.

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For anyone with a good lathe, making the drill guide bolts would be a piece of cake, but without a lathe all but impossible. With a drill guide bolt one could source a long bit from a local tool supply and accomplish the job. For me, the broken bolt was discovered late on Thursday afternoon, and I was leaving for the Old Marais River Run in Ottawa Friday. I finally broke down and ordered the Extraction Kit around noon, it arrived by USPS Priority Mail Monday afternoon, and the problem was gone this morning. Cost me $44 for the kit, a new locking bolt, and the shipping. I'd do it again in a heartbeat!

Originally Posted by DennyW

Did you double check any play between the pin, housing, spider gears, and bolt. That usually is the problem. Have replaced a few over time. Nice kit.

Yes, there was no play in the carrier. From the Extraction Kit site (Link - KIT INFORMATION ) :

Mechanics estimate 80% of differential pinion shaft lock bolts (sometimes referred to as a cross pin, locking pin, or retaining pin) are found in a broken state when servicing this type of rear end.

I'm convinced that this is a combination of a marginal design by the OEM, plus 131,000 miles of trouble free operation. The lion's share of these c-clip rear ends (other than those in Jeeps seeing off-road duty) never have the rear cover removed, and the locking bolt breaking is of zero consequence to continued safe operation. The threaded portion of the bolt remains torqued in place, trapping the fractured pin, and the pinion shaft remains securely locked in position. The only issue is an internal failure or leaky seal that necessitates pulling it apart, when the broken pin is discovered and Catch 22 is applied.

This is all good stuff to know, Roger. Thanks for posting! I picked up an 8.8 rear end to swap into my '66 F100 at half-price day at Pickyourpart a while back. It's from a '93 Gran Marquis with 3.55 gears, limited slip and disc brakes. It will be replacing the old Dana 44 limited slip with 3.54 gears whenever I get around to it. My 8.8 appears to be in good shape from a car that doesn't appear to have been abused but you never know. It's good to have foreknowledge of potential problems to contemplate when you're sitting along side the road waiting for the tow truck! Ha! Great pics!

FWIW, the drill bit you used looks a lot like the bits used at McDonnell Douglas. When I first hired on and going through orientation the fellow in charge grabbed a handful of drill bits and put them in a piece of plastic conduit. He proceeded to bend the conduit breaking the drill bits and I never forgot the results. A lot of drill bits will just break in half under stress, these didn't. He dumped them out on the table and there were shards all over the place. The object was to convince us to always wear safety glasses and/or goggles and for me it struck home. Just a word to the wise. BTW, I have a container of those in varying sizes, all about a foot long.

Originally Posted by NTFDAY

FWIW, the drill bit you used looks a lot like the bits used at McDonnell Douglas. When I first hired on and going through orientation the fellow in charge grabbed a handful of drill bits and put them in a piece of plastic conduit. He proceeded to bend the conduit breaking the drill bits and I never forgot the results. A lot of drill bits will just break in half under stress, these didn't. He dumped them out on the table and there were shards all over the place. The object was to convince us to always wear safety glasses and/or goggles and for me it struck home. Just a word to the wise. BTW, I have a container of those in varying sizes, all about a foot long.

Fabbri's instructions are quite clear on the importance of drilling slowly, pulling the drill back often to expel chips, and most important wearing safety glasses/goggles while drilling. It's prudent to pass on the good advice, Ken, and the story of the trainer breaking the bits reinforces the need for safety first.

Thanks Roger, for a easy quick solution to an exasperating problem. I have put it in my bag of tricks and sure its principles will lend itself to other similar repairs.

Ahh, it is a floating pin design held ridged at one end, it is doomed to breakage. Luckily, the bolt end traps it and prevents it from backing out. I would bet there is a service bulletin on this from Ford somewhere.

Originally Posted by 36 sedan

Ahh, it is a floating pin design held ridged at one end, it is doomed to breakage. Luckily, the bolt end traps it and prevents it from backing out. I would bet there is a service bulletin on this from Ford somewhere.

This differential design is common to Ford, GM and Chrysler, including JEEP's. It's one of those things that is cussed and discussed, but has never been changed. Seems that drilling the pinion shaft a bit larger, and then drilling and tapping the carrier through to the opposite side would increase the strength a bunch (longer threaded bolt, all the way through the pin into the opposite side, but not to daylight), but it's only an issue when the differential requires service, which on most vehicles seeing normal highway service is never. Other than Jeeper's who are in & out of high water, how many people even drain & replace the gear lube, much less change an axle seal? The payback on a design change is just too small and it causes no safety concerns - it's just a maintenance headache. Pity the poor guy who breaks an axle 20 miles back in the hills, crawling in the rocks, and then finds the locking bolt sheared, preventing him from getting the splined stub of axle out.... Makes a guy think about the need for a battery operated drill and an extraction kit in the spares box....

I have been lucky that all I needed was a magnet to get the rest out.

Originally Posted by junkyardjeff

I have been lucky that all I needed was a magnet to get the rest out.

Looking at the threaded part on mine, I really thought that it had broken just below the threads, Jeff, but it had just enough thread to have to be spun out. I tried several different magnets before ordering the extraction kit.

I also was able to work them out with a small screw driver on the 8.8 thats in my bronco,its howling now so its going to get a 9 inch when I find some 3.50 or 3.55 gears.