Diff Rebuild Walk-through - '81 with 4.11s and New Rear ARB Locker (2 Viewers)

[theamigo]

As part of my restoration I'm rebuilding the diffs. This includes installing an ARB locker in the rear. If you'd like to see the overall build check out the build thread linked in my sig. I'll have to post this in pieces.

I am not a professional mechanic. Please offer feedback and suggestions if you see something I could do better. Regardless, I try to be well prepared for tasks like this. I read a lot and ask a bunch of questions before starting.

First, I ordered everything from Cruiser Outfitters. This includes front and rear rebuild kits, plus the locker and compressor. I also bought knuckle kits and a whole bunch of other stuff, but this is about the diffs. The kits included preload and depth shims, bearings, gear marking paint, paint brush, pinion nut with integrated washer....everything really.

I've had a bunch of questions for @cruiseroutfit and they've always been quick with an answer. One issue that popped up I actually discovered while I was browsing their flange tech info page here: Cruiser Outfitters. I noticed I had course spline flanges(on an '81...) and that led me to finding out that a PO had rebuilt the diffs prior. But, I had all the right new parts regardless. I decided to keep the existing ratio.

For the job I recommend these tools:

• The factory service manuals. I couldn't imagine doing this without them.
• Mitutoyo .0001" dial indicator. I've read lots of people throw out numbers at .001" precision, but the factory service manual goes to .0001" on many recommended tolerances so I went with that.
• NOGA magnetic dial indicator base.
• Brass Drift
• Shop Press
• OTC 4520 Differential Side Bearing Puller Kit
• OTC 1123 Bearing Splitter (1/2" to 4-5/8").
• Micrometer
• Homemade jig for holding the diff in two positions. Flange up for checking pinion preload, and flange down for everything else.
• It was also very helpful to use the old bearings for pressing and hammering on the new ones.
• Beam-type inch-pound torque meter/wrench and adapters to size up to the pinion socket.
• Iphone... For pics - and slow-motion video of preload tests so you can snag the exact reading

 

[theamigo]

Everything was disassembled months ago. As I disassembled everything it was tagged, bagged, and photographed. It really helps if you keep everything well organized, especially if you're coming back to it later.

I then sent the frame and axle pieces off for powder coating.

You can see the pinion as it came off. Left to right - original nut, washer, preload shim, preload shim, adjusting washer, and bearing. The pinion depth shim is in the diff housing, under the race for that inner bearing. The kits I bought came with a new nut that replaces both the nut, and that thick washer with a single nut. Plus, it has shims, and of course a new bearing.

I used a bearing splitter and my press to separate the bearing from the shaft.

 

[theamigo]

Powder coated, lots of parts, and a jig to hold it during assembly.

 

[theamigo]

I also had all my hardware plated.

 

[theamigo]

First, I cleaned all parts thoroughly and laid it out in an organized fashion. I like a clean work area, at least to start with.

I pressed off the larger pinion bearing using my bearing splitter and press. I originally used a crappy harbor freight splitter that was too thick to fit under the inner bearing cone assembly so I cut off the bearing cage, to remove the rollers, and got a good hold on it that way. I then used the OTC puller kit for the carrier bearings. Worked perfectly! I then pressed on the new bearing using the old bearing cone and my press plates with the small hole to press against. Went on easy. Same goes for the carrier bearings - I used the old ones as protection to "tap" on the new ones.

I then installed the inner and outer races in the diff housing, being careful to replace the old pinion depth shim under the larger inside race with a new one of the original thickness. I used the old races to tap in the new so as not to damage the new ones. I also used a bearing race driver set for that.

 

[theamigo]

I then measured the existing pinion preload shims(there were two), and found a combination of new shim(s) that approached that same thickness. I then assembled the pinion shaft. First the adjusting washer goes on with the beveled side facing the inner pinnion gear, then the shims. I then inserted it up through the diff, with the smaller outer bearing in place on its race. Then covered it with the slinger, installed the flange, and the new pinion nut, and torqued it down. I did >not< install the oil seal. I'll do that once everything is known and set, so that I don't damage it.

The manual states that tightening torque for the pinion nut is 145 -173 ft-lbs.
The manual states that for new bearings the preload is 16.5 - 22.6 inch-lbs.
Reused bearings are 7.8 - 11.3 inch-lbs. I wanted to get it to the higher end of that range so that as it's used and loosens up it remains as tight as possible.

My first try was a bit low, only hitting about 15 inch-lbs. I needed to move the smaller outside bearing closer in, so I went with a single, thinner preload shim. That, and, with the pinion nut torqued at 154 ft-lbs. This gave me right at 20/21 inch-lbs.

It's pretty hard to accurately gauge the inch-lbs reading as you're spinning the thing in circles. I used an iPhone recording in slow-mo as I spun the torque wrench. Also, as you're spinning it and moving things around you're varying the torque quite a bit, so it helps to practice and develop a rhythm so that you're trying to capture the best reading while you're using the most steady pressure on the torque wrench/meter.

 

[theamigo]

Once the pinion preload was set I moved on! Again, I cleaned all the parts and oiled up the bearings. I placed the carrier into the diff housing carefully. Installed the bearing caps with adjusting nuts, and made sure everything was lined up properly and hand tightened the cap bolts down so that things were mostly snug. Then you snug down the bolts until the spring / lock washers are slightly compressed.

Now, to set the initial ring gear backlash. The manual states you want an initial backlash of .008". Once that's achieved it tells you to tighten down the drive pinion side's adjusting nut so that things are really snug. The goal here is to make sure that there's no play in the bearings. It has you check to see if snugging it down has increased your backlash at all(pushed the ring away from the pinion). If it does, tighten up the ring side adjusting nut to get back down to .008" of backlash. This is only the initial starting backlash, not final. But, I kept playing with this until tightening the pinion side failed to increase backlash.

Right at .008" of initial backlash.

The adjusting "nuts" are the big circular things with holes around the outside edge. It's threaded around the edge, and combined with the bearing caps they're made to adjust ring-gear-to-pinion distance in order to increase/decrease backlash.

After that, time to set carrier bearing preload to zero. Loosen the pinion side adjusting nut(the one you see in the photo above) to back that bearing off. Then, place the dial indicator against the ring gear-side bearing adjusting nut. Now, tighten the pinion side until the dial indicator moves. Now, for me, .0001 is really finite, so I made sure it moved... Then, from there, it says to tighten 1 - 1.5 "clicks". I take this to mean "holes in the adjusting nut." So, I did 2 since everyone says it's good to ensure those are tight.

Dial indicator, waiting for movement:

Now, time to check carrier bearing/overall preload. The manual states carrier preload is 3.5 to 5.2 in-lbs for both new and reused bearings. And, remember, we've already got about 20/21 inch-lbs of preload on the pinion, so our total number should be that plus the 3.5 to 5.2. I ended up with approximately 25 total so that gives me about 4 inch-lbs on the carrier bearings, and 21 on the pinion. I'm happy with that.

Then time for the final backlash check. The manual states the ring gear backlash should be .0059" to .0079". I checked in several places around the ring gear and, after adjusting, settled for approximately .007", right in the middle of the range. To adjust you use the adjusting nuts to move things in or out. Tighten one, loosen the other, etc. Turn both sides equally so as to retain the previous preload setup.

I then tightened the bearing cap bolts down to 70 ft-lbs, as the manual stated. I then moved on to checking the contact pattern.

Here's my specially made tool for the adjusting nuts..

 

[theamigo]

My current contact pattern. I think the drive side is good, but I would like to know what you think about the coast side. So, this is where it stands now. If the contact pattern is good then I'll add the oil seal and begin buttoning it back up.

UPDATE... Actually, the more I look at it the more it looks a little too close to the heel?

 

[theamigo]

I then moved on to checking the differential gear backlash. Carefully place the dial indicator, then holding the pinion gear steady, move the side gear slightly. The manual states acceptable tolerance is .0008" to .0079". Mine was right about .006".

In most of the other threads I don't see this step. Any reason why?

 

[theamigo]

With all that said, there's my contact pattern. What's the consensus?

Next up, the rear diff.

 

[B y r o n]

You might want to check out this site for pattern help. Contact Zuk and he will make sure you're OK or not.

 

[theamigo]

You might want to check out this site for pattern help. Contact Zuk and he will make sure you're OK or not.

I've read both of the FJ40 stories on that site and several off the other Landcruiser jobs he did. it has a lot of great info and pictures. I would like to know why he uses a starting torque of 10 inch-lbs for preload. Start torque should be way higher than the specified pinion preload I mentioned above?

 

[Infinity00]

Nice work! I can’t comment on any of it, since it seemed way too complicated for me to do it myself. Kudos for doing it and posting up the steps. I contracted mine out to Robbie here in Boulder and watched him do it. How much time did it take you to get this far?

 

[theamigo]

Nice work! I can’t comment on any of it, since it seemed way too complicated for me to do it myself. Kudos for doing it and posting up the steps. I contracted mine out to Robbie here in Boulder and watched him do it. How much time did it take you to get this far?

Thanks. Just for the diffs, probably ~5 hours of browsing forums to read about it to become familiar with the general process. The actual effort expended on the job is probably, now, around 6-8 hours. Includes cleaning, setup, building that setup jig, and several start-overs to reshim. I'm taking my time.

I'm going to re-shim the pinion depth now to see how that affects the coast. The Sierra Gear & Axle instructions(from the kit) say that when setting up used ring and pinions pay more attention to the pattern on the coast side of the ring gear teeth.

 

[Cruiserdrew]

Nice going for a first try! Your pattern looks just slightly deep. I'd change your pinion shim for a slightly thinner one. You're close though so again, very nice work.

 

[Infinity00]

I got my kit from Kurt also - I really like working with those guys. Hmmm, I might try to find pics if I took any. I kinda remember it’s a trade off, but most importantly, it sounds like you’re having fun while checking what differences you can produce. The time you have into it doesn’t sound bad at all!

 

[B y r o n]

I've read both of the FJ40 stories on that site and several off the other Landcruiser jobs he did. it has a lot of great info and pictures. I would like to know why he uses a starting torque of 10 inch-lbs for preload. Start torque should be way higher than the specified pinion preload I mentioned above?

I know for a fact he has done way more than two FJ 40 builds. He was the go to guy when I rebuild my front and rear ends. When I had questions as to my patterns I e-mailed him and he provided valuable advise as to the direction I needed to go with spacer size to get the best pattern. Don't be afraid to contact him for advise.

 

[theamigo]

I know for a fact he has done way more than two FJ 40 builds. He was the go to guy when I rebuild my front and rear ends. When I had questions as to my patterns I e-mailed him and he provided valuable advise as to the direction I needed to go with spacer size to get the best pattern. Don't be afraid to contact him for advise.

Oh I can tell he has done a lot! I'm just saying as far as I can tell there were only two FJ40 posts/stories on his site for me to look at. I know other Landcruisers share the same parts.

 

[theamigo]

Nice going for a first try! Your pattern looks just slightly deep. I'd change your pinion shim for a slightly thinner one. You're close though so again, very nice work.

Thanks. And yeah, doing that now. I'll post more pics.

 

[theamigo]

Nice going for a first try! Your pattern looks just slightly deep. I'd change your pinion shim for a slightly thinner one. You're close though so again, very nice work.

So, when you say "deep" which direction do you mean? Is the pinion gear protruding too far into the diff? Or not far enough?

And the thinner shim... being the pinion depth shim on the inside race of the inner(large) pinion bearing? You're saying I want the pinion to move away from the ring gear, ie not protrude so far into the diff?

It's funny, people seem to use so many different words for these things. I just want to ensure I know what exactly you're saying. Thanks.