Front Differential Rebuild - Tooth Contact Pattern (2 Viewers)

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G'Day,

I'm currently rebuilding my front differential with new bearings and have now put everything back together for the first time.
Quit the effort. I now get why shops usually put this off or charge four digit prices just for the labour...

Either way: Backlash and preload are perfectly within spec and the tooth contact pattern is as follows.

20200927_094443.jpg


20200927_094430.jpg


To me and to what I've found on the internet the drive side looks spot on for the used gear set and reused pinion bearing shim.
However, the coast side looks rather off and towards the toe. Is there anything I can do? Do I need to do anything?

I'd probably put it back together, but since this is my first diff: What do you guys think? :)

Cheers for the input,
Mark
 

chap79

Wheel. Break. Fix. Repeat.
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@dbmaxpayne i looked back through my old build thread for my numbers, not that they’ll be equal to yours. But to give a better idea.

My original OEM pinion spacer was .0780”, I ended up at .0755” when I was done to get a better drive and coast pattern. I know it doesn’t seem like a lot but it makes a difference. :meh:

Builds - chap79's Build Thread
 
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Thanks, chap79 for the attached guide. A really helpful piece of information and the best I've seen so far!
However, from the section about used gear sets: Why should one disregard the drive side when setting up the contact pattern? Isn't that the more important side that bears the load 95% of the time when going forward?

Also to answer your question:
My current shim thickness is 1,91mm (greetings from Germany :) ), so basically your final .0755”
Unfortunately I don't have any other shims. Sourcing them in Germany is nearly impossible without falling into bankruptcy - lol
I'd order some from Amayama, but that takes weeks and without knowing the correct thickness it's even more annoying.
But if the general census is that I'll have to go thinner, I might just order a few.
 

chap79

Wheel. Break. Fix. Repeat.
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Thanks, chap79 for the attached guide. A really helpful piece of information and the best I've seen so far!
However, from the section about used gear sets: Why should one disregard the drive side when setting up the contact pattern? Isn't that the more important side that bears the load 95% of the time when going forward?

Also to answer your question:
My current shim thickness is 1,91mm (greetings from Germany :) ), so basically your final .0755”
Unfortunately I don't have any other shims. Sourcing them in Germany is nearly impossible without falling into bankruptcy - lol
I'd order some from Amayama, but that takes weeks and without knowing the correct thickness it's even more annoying.
But if the general census is that I'll have to go thinner, I might just order a few.
Is there any cruiser clubs in your area? When regearing most master setup kits include a variety of shims. Someone might have some stuffed in a drawer you can have. I’m sure some vendors here would ship to you but your correct in the cost and time. How about Partsouq.com?

As for the metric system, my wife is Russian. I’m well versed. Didn’t even bat at eye at the use of the comma.
 

inkpot

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Check out getting parts from Partsouq.com in the Middle East. Much closer, similar prices, and 1 to 2 week delivery to me in Arizona, USA.
 
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Check out getting parts from Partsouq.com in the Middle East. Much closer, similar prices, and 1 to 2 week delivery to me in Arizona, USA.
Thanks, I did exactly so. DHL Express managed to get the parcel to me within two days. Crazy^^

However, I only now got around to putting everything back together with a thinner shim.
This is the pattern with a 1.85mm / .0728"

Coast Area 1.jpg
Coast Area 2.jpg

Drive Area 1.jpg
Drive Area 2.jpg


To me it looks like I shouldn't have used a thinner, but a thicker shim?
At least when I look at @chap79 's gear installation manual.
It meantions only to look at the coast side for used gear sets.
Accordinly I should move the pinion closer to the ring gear (thicker shim), right?

Cheers,
Mark
 
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You should absolutely not disregard the drive side contact pattern when shimming the gearset. This is where the major load is and it has to be right. From your first photos, the contact patter is a little closer to the root than I'd like to see; it usually wears in not out. You were correct in your earlier post, you needed a thicker shim, not a thinner one.

Ideally you want the drive side pattern centered between the heel and toe and between centered and two thirds up the face, away from the root. This is a general guideline and there are recommendations which vary, for specific gearsets, but I do not believe Toyota would have mass produced any of those for the Land Cruisers.

The coast side, ideally should be in the same place, but it's more forgiving than the drive side and when the axles are built on the assembly line, if the drive pattern is correct and the coast is close, it ships.

You can get an unlimited number of opinions on how to setup a spiral bevel set, but very few of them will be worth listening to. The gear designers don't even know how to do it. This is one of the very few things that you have to learn by doing it. It took me weeks to learn how to do it, and I was doing it daily and building about 300 axles a day. Once you get the idea, you can get it almost immediately, but if this is your first time, it may take a hour. Or two. The only real advice I can give is if you see the pattern drifting off from where you think it should be, and adding the thickness you calculate doesn't work, pull all the shims out and start over. This is the way I taught my assemblers and it will save you time and grief.
 
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Check out this web site, he goes through every differential rebuild with a ton of information and photos:
Thanks, Kernal. Great website. I have indeed read a few of his articles. Very interesting stuff :)

Das sieht viel besser. Schon fertig!
:)
You reckon? To me it also doesn't look too bad on the drive side.
What about the coast side, though? That's way down at the toe.

You should absolutely not disregard the drive side contact pattern when shimming the gearset. This is where the major load is and it has to be right.
[...]
The coast side, ideally should be in the same place, but it's more forgiving than the drive side [...]
Thanks. That's what I thought. However, some writeups mention to only focus on the coast side when setting up used gears, which still leaves me confused about my coast side's contact pattern. To my understanding I would completely mess up the drive side's contact pattern to get the coast sides's right, wouldn't I?

From your first photos, the contact patter is a little closer to the root than I'd like to see; it usually wears in not out.
On the weekend I will try the original shim again. Sorry about the bad "marking compound" which was just paint from a spray can as nothing else was available :(


Either way, I have messed around a bit more and can present the following contact patterns:

3rd Try (T=1.79mm / .0705")

Coast Area 1.jpg
Coast Area 2.jpg


Drive Area 1.jpg
Drive Area 2.jpg
 
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4th Try (T=2.00mm / .0787")

View attachment 2497053
Coast Area 2.jpg


Drive Area 1.jpg
Drive Area 2.jpg


It looks as if the 1.85mm shim is not too bad to get the drive side right.
However, that would'n match Malleus' opinion that I would've needed a thicker shim.
Either way, 2.00mm / .0787" is the thickest I have right now. To me a thicker one won't do any more good, though, would it? The drive side's contact pattern has already started to shift towards the toe.

Cheers,
Mark
 
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Thanks, Kernal. Great website. I have indeed read a few of his articles. Very interesting stuff :)


:)
You reckon? To me it also doesn't look too bad on the drive side.
What about the coast side, though? That's way down at the toe.


Thanks. That's what I thought. However, some writeups mention to only focus on the coast side when setting up used gears, which still leaves me confused about my coast side's contact pattern. To my understanding I would completely mess up the drive side's contact pattern to get the coast sides's right, wouldn't I?


On the weekend I will try the original shim again. Sorry about the bad "marking compound" which was just paint from a spray can as nothing else was available :(


Either way, I have messed around a bit more and can present the following contact patterns:

3rd Try (T=1.79mm / .0705")

View attachment 2497048 View attachment 2497049

View attachment 2497050 View attachment 2497052
You are correct. And, BTW, there's no magic in the marking compound; I've used a Sharpie before. The gooey stuff just works better. And gets everywhere.

I agree with @pinhead; using worn gears is a crap shoot of sorts. I'd focus on getting the drive side right, and let the coast side be. As long as it's not all the way to one end or the other, it'll work. It has been for years, right?

Your problem is that the tooth faces were cut in the same setup and it's the drive side that's seen most of the wear. I expect this is the basis for the anecdotal advice to focus on the coast side, knowing the drive side would be hard to match. Assuming the gear was good to begin with, and assuming it was set up properly to begin with and that the drive side has worn significantly more than the coast side, maybe it makes sense to setup the coast side and "hope" the drive side will match the pinion in that position. That brings up a question, though, what does(do) your pinion tooth face(es) look like? Unprinted, I mean.

I honestly have very little experience setting up gears which have been in use for decades. All of the returns I saw from my assembly line were months old, at most. So take my comments in the context of my experience, building new axles and assessing problems with relatively new ones.
 
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The other thing that may be instructive is to play with the backlash. As gears wear, the backlash grows, so the pattern may look better with more backlash, which is the way they have worn in. The two sets of used gears that I set up never did give an ideal pattern, but as long as I centered the pattern from root to flank, it worked out.
 
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1,79 mm looks good too. You can keep paying with it but you may never get an ideal pattern with used gears. You would want to try a thinner shim than 1,79.
I will do that, thanks. Will have to wait for Toyota to get it, though. Although 1.70mm marks the lower end of the shims anyway.

I agree with @pinhead; using worn gears is a crap shoot of sorts. I'd focus on getting the drive side right, and let the coast side be. As long as it's not all the way to one end or the other, it'll work. It has been for years, right?
It indeed has for 360.000kms. I only rebuilt the thing because it was severely rusted. Either way I discovered a spun bearing too, so it probably wasn't too bad to open it up.

Your problem is that the tooth faces were cut in the same setup and it's the drive side that's seen most of the wear. I expect this is the basis for the anecdotal advice to focus on the coast side, knowing the drive side would be hard to match. Assuming the gear was good to begin with, and assuming it was set up properly to begin with and that the drive side has worn significantly more than the coast side, maybe it makes sense to setup the coast side and "hope" the drive side will match the pinion in that position.
Wow, so many ifs :D
Thanks for the explanation. Makes sense to me.

That brings up a question, though, what does(do) your pinion tooth face(es) look like? Unprinted, I mean.
20200926_145002.jpg

That's the only picture I could find. Is this what you meant?

The other thing that may be instructive is to play with the backlash. As gears wear, the backlash grows, so the pattern may look better with more backlash, which is the way they have worn in. The two sets of used gears that I set up never did give an ideal pattern, but as long as I centered the pattern from root to flank, it worked out.
Thanks fot that. It actually brings up a question I had the other day, but forgot to ask:
You are supposed to measure backlash in various spots around the ring gear, which I did.
However, it ranges from like 0.10-0.15mm now. The spec says it should be between 0.13-0.18mm, so basically I'm under the spec in some spots.
If I take the ring gear one adjuster notch away from the pinion, the backlash also goes out of spec to a maximum of like 0.25mm in a few areas.
My question here would be: As I can only alter the backlash by loosening one adjuster and tightening the other by one notch also, I'm kinda restricted in how much I can do about it.
Would it be better to have too little or rather too much backlash?
To reduce driveline clunk, I wanted to keep it between 0.10-0.15mm rather than increasing it by almost 0.10mm.

Cheers,
Mark
 
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The ring and pinion backlash is such a minor component of overall driveline play of an AWD vehicle that you can disregard it as a concern.
 
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I will do that, thanks. Will have to wait for Toyota to get it, though. Although 1.70mm marks the lower end of the shims anyway.


It indeed has for 360.000kms. I only rebuilt the thing because it was severely rusted. Either way I discovered a spun bearing too, so it probably wasn't too bad to open it up.


Wow, so many ifs :D
Thanks for the explanation. Makes sense to me.


View attachment 2498208
That's the only picture I could find. Is this what you meant?


Thanks fot that. It actually brings up a question I had the other day, but forgot to ask:
You are supposed to measure backlash in various spots around the ring gear, which I did.
However, it ranges from like 0.10-0.15mm now. The spec says it should be between 0.13-0.18mm, so basically I'm under the spec in some spots.
If I take the ring gear one adjuster notch away from the pinion, the backlash also goes out of spec to a maximum of like 0.25mm in a few areas.
My question here would be: As I can only alter the backlash by loosening one adjuster and tightening the other by one notch also, I'm kinda restricted in how much I can do about it.
Would it be better to have too little or rather too much backlash?
To reduce driveline clunk, I wanted to keep it between 0.10-0.15mm rather than increasing it by almost 0.10mm.

Cheers,
Mark
Yeah, I was wondering is there was more wear on the pinion than the ring. That'll tell you something about the bearings.

What's done on the assembly lines, for a random quality check, is three points 120° apart. Any other three points could be off even if those three were dead on, so you are basically guessing there; the assumption is that the ring bore is round and the tooth contact circle is too, and is concentric with the bore.

If you can only fit the set together too tight or too loose, and both are within 0.002" of spec, go with too tight. Too tight will loosen, too loose only gets worse. The downside to too tight is your gears are worn already. There's no telling from your photos exactly much hardened case is left. You'd have to assess that yourself. Visually, if the wear looks even (it' sploshed all over throughout the wear pattern) you're probably OK. If there are gaps in the wear pattern...
 

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