?'s about rebuilding LSD

[MrShorty]

I'd like to rebuild the LSD on my '92 Explorer, and I have a few questions about doing it myself. For reference, here's a brief rundown of the procedure as given in Motor.

1. Open differential
2. Remove pinion shaft
3. remove axles
4. remove S spring
5. remove pinion gears
6. remove side gears and clutch packs
7. place new clutch packs in special tool to determine thickness of new shim.
8. soak clutch packs in "suitable lubricant"
9. Install side gears and clutch packs.
10. Install pinion gears
11. install S spring
12. install axle shafts
13. install pinion shaft
14. close differential and refill.

Here are my questions.

1. step 7. How important is shim thickness? I expect I will have a hard time locating the specified tool for this part of the job, and I don't know if Ford would do this for me. What have others done at this step? Reuse the old shim? Does the rebuild kit come with shims or do I need to get those separately?

2. For removing and installing the pinion gears, the manual refers to a "pinion gear rotator tool" and a 12" socket extension. What is the nature of this tool? From the diagram it looks like a metal rod or tube.

3. Finally, what is a "suitable lubricant" to soak the clutch packs in? I've seen both gear lube or friction modifier. Which one or a mixtur of both?

Sorry to be so long, but I want to be reasonably sure that I'm going to be able to finish the job once I get started. The Ford dealership quoted me $600 to do the install. If it's going to cost that much, I'd rather leave the differential as is, or replace it with a more durable traction device. But, if I can manage to do this myself, $80 every 3-5 years is acceptable.

 

[riffman]

im not exactly sure why they have you pull the pinion, but thats dumb. the best way to do this, is thus:

obvious steps, put the truck on jackstands, pull the tires, open the diff, pull the c-clips, and then the axle shafts. once thats done, pull the centerpin, and then the side gears and spider gears. you will then see a seris of frictions (clutch material) and steels (shims) on each side. The thickness of the shims is not all that important. Its just if they get too thin, they will start to warp when they get hot, and wear down the clutch material faster. Similar to warping brake rotors. anyway....It has 3 frictions on each side, but there is room for more. basically all you are doing is replacing those, with new ones and the putting back in the side gears and spider gears. its really easy. now....there is room on both sides for additional frictions and steels. you can add at least one set to each side, increasing your holding power. so you can find your best old clutch, and add that on the outside to increase traction, or leave it the same to remain stock. i added a 2 to each side...it helped a bit offroad, but is still far from a locker.

the appropriate lube they are talking about is limited slip fluid. use Red Line 75W90. its basically 90 weight with a LS additive.

that help a little? maybe??

 

[MrShorty]

So step 7 could be considered superfluous.

Your response was really helpful, but has raised new questions...

How thin is "too thin" on those shims? Anything thicker than "paper thin" be OK? If there's a spec or rule of thumb out there, I do have a set of calipers and can measure the thickness to within 0.01 in when they come out.

What is the stock spec on the limited slip? 10%? 25% 40%? anyone know? I expect I would leave it stock unless it's really low in which case I could do as you suggested and add a clutch to each side.

What they called a pinion shaft is the same as what you called the centerpin.

 

[riffman]

im not really sure about the thinest recomended or the specs on it. my sploder was already a trail rig by the time i added the innards to it, so i wasn't really concerned about how thin they were. I would immagine if you call a ford dealer service center, they would probably be able to look up the specs for you. and i guess a pinion shaft=centerpin makes the directions make sence now...boy i feel dumb!

 

[Mbrooks420]

I think the LSD has a breaking force of 90ft.lbs

 

[MrShorty]

Thanks for everyone's help so far. Now can anyone comment on the second question in my original post? About removing and installing the pinion gears. Do they come out and go in pretty easy? What about this "pinion gear rotator"? Sorry to be stubborn on this, but I want to know if I need a special tool or not. I don't want to find out I need one in the middle of the job, because nobody in this county will even know what I'm talking about, let alone be able to get me one in a hurry.

 

[MrShorty]

Found this write-up today about rebuilding the LSD. Sounds like it's easy enough to do without the pinion gear rotator tool. http://www.scoa.org/venom/1999/venom071.pdf Look on page 3 and four.

 

[MrShorty]

Well, finally got around to doing this. Been in the process of moving so I couldn't get to it. It was pretty easy to do; The hardest part was putting the spring back in. The recommended "brute force" method for getting it in works, but not as smoothly as I would have liked (hit my finger with the hammer and split it open. hope I didn't leave too much blood behind in the differential.) The only other hiccup was measuring the clutch packs for shims. I think I put a little extra in there, because, where it's supposed to take 20 ft. lbs. to turn one wheel with the other on the ground, it takes 30 ft. lbs. Don't think it's a problem; just have a little bit more limited slip in my limited slip. It doesn't chatter in corners on the highway or anything. Still have to test it offroad, but I'm pleased so far with the results.

 

[410Fortune]

Thanks fella's! I'm re-gearing my 8.8 soon and the factoryL/S will be getting rebuilt with some extra clutch's for more grip. This post is a big help.......

 

[MrShorty]

clutch arrangement in 7.5 vs. 8.8

Got the rebuild kit for the 7.5 differential in my BII this week and found an interesting difference between the two. Where the stock clutch arrangement on the 8.8 is clutch-steel-steel-clutch-steel-steel-clutch, the arrangement on the 7.5 is clutch-steel-clutch-steel-clutch-steel-clutch. Which, incidentally, is the same as the "performance" arrangement suggested by many for the 8.8. I guess it got me to wondering what the advantage is in the arrangement of the 8.8 clutches? longer life?

 

[MrShorty]

%$#@! pinion shaft lock bolt

Got to doing the Trac-loc in my BII and found the pinion shaft lock bolt broken!!!:fire: Anyway so now I have to figure out how to get it out. Found this http://www.skywaytools.com/autopg2.html (interestingly, they claim that the lockbolt was likely broke off before I even pulled the cover) from skyway tools; sounds like the easiest way, but then I have to wait to get the tool. Gonna keep looking at this, if anyone has any input right away, it would help.

 

[MrShorty]

Looked closer at that pinion shaft removal kit, and it looks like it consists of two screw extractors, a 12" long drill bit, and bit guides (I'm guessing to help center the bit on the lock bolt). So I decided to assemble my own kit. Picked up a set of screw extractors, which called for a 5/64 or 7/64 bit in a 1/4" bolt. Couldn't find anyone locally who had such a drill bit, so I ended up taking half the day finding someone in Salt Lake who had it. Used a center punch to help get the bit started in the center and, within minutes, the rest of the lock bolt was out.