Ok, this might be huge and I might leave some steps out, so if I do just ask and I will fix it.
First a disclaimer, I am not saying this is the correct or professional way to shorten a rear diff. and if you have any concerns you should probably have a professional do it, I am not (you can probably tell from my horribly messy shed) I feel pretty confident that my tube will not crack and is fairly straight (at least as straight as it was to start) and I may need to have it professionally straightened after I weld on my brackets will wait and see.
The basic premise of doing the Ford Explorer 8.8 narrowing is too use two passenger side axles and shorten the housing on the drivers side to match the passenger side, it centers the pumpkin (closer) and results in a rear diff that is of an acceptable length to fit in an early Comet (up to 1965) and you don't need to have custom axles made. In doing this modification I have discovered one other benefit that I have never heard addressed, when I put this in my Comet I will have no more fears of rollovers because it weighs more than my car so it should be like a Weeble (<--that is a joke, BTW) I measured my long axle against my short one and found out it was 2 7/8" longer so that is how much I cut out the tube. Make sure you measure is pretty close and don't cut too short.
So without further delay, here is how I did it;
First I obtained a totally rusty 8.8 out of a '98 Mercury Mountaineer for $75 that turned into $125 by the time it was out and in the back of my truck
You have seen pictures of it already but just to remind you (a very rusty diff is not required for this, nor recommended)
I did a lot of cleanup prior to actually shortening it but I am not going to post that here because all of it is elsewhere on the Forum.
The first thing I did is build a welding jig, I did this different than I have seen it done but I like to do stuff my way I guess
I took some angle iron (the smaller being off an old bed frame never, ever use that if you want to drill holes in it)
I notched the smaller angles
I don't have pictures, but I clamped the smaller angles to the axle flanges and drilled holes through to match and inserted carriage bolts and bolted the small angles too the flanges, then I used some large hose clamps and attached the large angles to the axle tubes butting up against the small angles and I welded them together. They look like this;
I also took a cutoff wheel in the angle grinder and scribed along the edge of the angles for clocking marks. I then removed the fixtures (make sure you mark which is front and back, I painted mine two different colors and marked them on the tubes as well)
I set up my chop saw on a table and clamped everything down and squared it up.
I did a couple of things to make sure the diff stayed in the same position (square and clocked the same) to help eliminate any possible errors in alignment when I welded it, clocking it the same would allow for any variation in squareness to match on both cuts (in theory). One was I put a couple of screws either side of the far tube to keep it square when I slid it forward for the second cut, I would recommend lag bolts and not screws like I used, the rear is heavy and likes to be a bully.
I also used the board to make sure the edge of the diff sat down on it to keep it clocked properly.
I made sure the ratchet straps were good and tight and my mark aligned with a new cutoff disk and slowly cut the end off, checking often to see I was still in line (or close)
I cut it off and slid the rear over and cut the second part off.
Then I bolted my welding jig on and measured the tube and found out I was a bit long, I ran a hose clamp around each cut and discovered the first cut I made was a bit off, no biggie, I just used the grinder to take the tube back to the clamp. (I also cleaned the tubes at this time, posted earlier)
I also chamfered around the tubes and in hindsight I wish I would have chamfered more, because even though I am not showing it here, I ground the welds back out wider and deeper and welded it again (a piece at a time)
I put the welding fixture back on and checked the length and axle fit, both were good.
And checked that the axle went in far enough for the "C" clip to be installed.
with all this checked I moved the axle upright on an old tire and wheel so I could weld it and spin it. (not at the same time)
After I had welded short lengths (about an inch at a time) and cooled them with compressed air as I went and waited until I could touch it with my bare hand and not burn me, I welded more and then removed one welding jig and welded around that side
Weld Penetration.
And finally removed the other jig and welded the final side, I had really beautiful welds but forgot to take any pictures
before I ground them smooth (not really recommended to grind your weld when making a butt weld unless you have a large chamfer)
At this time I put the axles back in and degreased the inside of the rear diff, I used hot water and Purple Power De-Greaser, I also scrubbed what I could with a nylon brush
I rinsed it and dried it with the heat gun, a word of warning, don't leave it this way too long because it is really clean an prone too rust.
Now I replaced my wheel bearings by first removing the old seals, I used a blue "pinch" bar, but be careful and don't insert it too far and damage the tube inner face.
I rented/borrowed a wheel bearing puller from the local parts store, the puller end looks like this and is inserted into the center of the bearing and the large washer and nut are tightened down.
It is attached to a 5lb slide hammer.
A few slides of the hammer and the bearing pops right out (at least mine did)
While the bearings are out it is a good time to scrub the insides of the tubes, I tilted the housing so it would all run back out the end and added an extension to my round toilet brush (just an old blind opening wand, taped to the handle of the brush).
My new bearings are Timken Axle savers, they move the bearing location slightly on the axle and include a seal built in, which is in a new location as well.
There is also an additional seal on the inside, not sure if this will starve the bearings or not of grease.
I added a little sealer around the bearing just to be sure and inserted it back in the tube.
With these bearings they protrude 1/4" out past the end of the tube, I failed to take a picture of this so photo edited a different one, so if this looks a little odd that is why,
I used my rubber dead blow hammer to install these and a large brass rod to tap on at the very end to make sure they were fully seated.
Next the E brakes and backing plates etc were installed.
Reinstall the axles and clip them in. A word of warning when you pull the axles the first time, put the cross pin and the cross pin bolt back in or you will be removing the "S" spring to get the spider gears lined back up and the "S" spring is a bite to get back in (ask me how I know
) You can see in this picture I just pulled the cross pin out part of the way to get the "C" clips reinstalled.
And these are infamous "C" clips that fit in the slots in the end of the axle and then the cross pin keeps the axles out so they can't move to the middle and loose the "C" clips and them the axles go flying off (really the disc brake caliper should hold the axle in)
After the "C" clips are in slide the axles back toward the outside and push the cross pin back in (don't let it fall all the way through) then install the cross pin bolt, some replace this with a new one but you can reuse it if it isn't worn bad, just put some thread locker on it (sorry about the fuzzy picture)
Now is the time to fill it up, I used Royal Purple (75-140 synthetic with friction modifier, it was on sale, can't say it is good because I don't know).
I bought a Mustang 8.8 Aluminum rear cover, no reason except I thought it looked cool, it will not fit without modification, one rib inside contacts the anti-lock ring, I highlighted it in red below.
So I trimmed it down, it barely touches it so you would not have to cut off as much as I did, but I wanted good clearance.
And smoothed down a little
I used The Right Stuff to make a gasket with and I have a seeping spot so I am going to have to take it off sometime and reseal it, I can see where I messed up in the picture above where I put grease in.
I also moved the vent to the top on the rear cover and plugged the axle vent with a set screw with the same thread, I used red thread locker on it.
The only thing left is too install the brakes, which I painted the calipers with POR15 Red Caliper Paint. I will need to pull the rotors back off sometime and adjust the E brake shoes but I will get to that sometime later.
It looks pretty good for being that old rusty hunk at the beginning, I think the truck it came out of had 125,000 miles on it, which I guess these days is not that many.
Again any questions or comments just post them.
See Ya,
Mike
Woulda taken 5-min to shave 40lbs. off! Sometimes...sigh...
I had these old tires and wheels off a Jeep that I took to town today and had them patched so they would hold air, so I bolted them on and lowered one end at a time, it is still a bite to move around.
pop