Diff rebuild by "pro" not going well

alcyon

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Jun 15, 2017
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Kuala Lumpur
So the rebuild by the so called pro did not go well, idiot re used crush sleeve and it made a terrible hum on accel and decel. He took diff apart again and cut down on one of the side shims, and while this has dramatically reduced the hum on accel, the decel hum is still noticable. He will have another go at it, but if it isn't solving the issue, I am gonna take it on myself.
So I have few questions:
1. How much does the crush sleeve actually crush? I ask this as I plan to make my own hard sleeve to replace the crush sleeve, but need to know a ball park value of how much longer should I make this hard sleeve over the length of the existing crush sleeve, my guess is 1 to 2mm ?
2. Does the crush/hard sleeve preload effect the pinion depth ? If i get a good preload but my pinion depth is off what are my options ?
3. I am guessing I would need some thin shims for pinion and carrier bearings, any aftermarket shops I can buy some thin shims ?
4. How do I load the ring gear when I want to check the contact pattern ?
5. All 4 bearings are new but they have some use since i drove the car around (My guess 500 to 1000km), when re setting preload should I use values for used bearings or new bearings ? I am also guessing I shouldn't need to remove the bearings or the outer races.
Diff is an open diff so my guess is I shouldn't need to mess with whats inside the carrier.

Thanks in advance.
 

Asterix

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Weir Performance sells a solid pinion spacer kit for our differential. No need to make your own. It includes shims so you can get both bearing preload and position correct.

McMaster is a good source for shim sets. The big side spacers are Toyota only.

Time to find another rebuilder. Crush sleeves are 100% not reusable. Just loosen the pinion nut and it's done.

@Piratetip rebuilds diffs, if you want to go that route. He surely can answer your questions better than I can.
 
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alcyon

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Does anyone have a cross section diagram of the mk3 diff ? I dont want the exploded diagram, but the cross section, it would help me understand better the relation between pinion depth and preload if i knew how the pinion bearing outer race is captured.
 

Asterix

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This one is for a 1967-1969 Camaro, but it's the same mechanically. There's a shim (item 23) between the bearing and pinion gear to set location. The crush sleeve or spacer (item 5) sets preload.
 
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alcyon

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This one is for a 1967-1969 Camaro, but it's the same mechanically. There's a shim (item 23) between the bearing and pinion gear to set location. The crush sleeve or spacer (item 5) sets preload.
Thanks I looked at the diagram, and if i am correct , if the crush sleeve/pinion bering spacer is too short, the bearings will be heavily loaded, and if the spacer is too long, you cant preload the bearings, is this the correct conclusion ?
Also since i suspect that the crush sleeve is now too short, what effect will this cause to the diff? Will it cause the humming on decel ?
 
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Asterix

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I don't know what noise occurs when the spacer is too small. I will guess that if there's too much preload, the pinion bearing will wear out faster, and the pinion will be too far forward (away from the ring gear). There will then be too much backlash and the mesh pattern will be biased to the outside. Differentials are quite picky, requiring very tight tolerances, like 0.002" or less.

I've only rebuilt one, and have little experience troubleshooting noises.
 

alcyon

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Jun 15, 2017
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Kuala Lumpur
Anyone can recommend a suitable low upper limit beam torque wrench (max 25in.lb) that costs about $50? I am having hard time locating one, most of the ones on the market have a much higher limit so I can read the values on the lower end of the scale.
 

supraguy@aol

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Dec 30, 2005
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Anyone can recommend a suitable low upper limit beam torque wrench (max 25in.lb) that costs about $50? I am having hard time locating one, most of the ones on the market have a much higher limit so I can read the values on the lower end of the scale.
I just got one off Ebay. It a 1/4" drive, but I simply addded an adapter.
 
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Piratetip

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Just seeing this now but:

Who was this "pro" that "rebuilt" it?

1. Not much - its not really a crush but a deformation of the material to set spacing between bearings properly and provide a bit of pressure against the inner races of the bearings. (This provides preload)
I could take some measurements of old vs. new later.

2. No the crush sleeve does not set pinion depth at all, if it is affecting this or moving pinion depth AT ALL you have problems with the overall setup.
If the pinion depth is off you completely disassemble the diff, pull the inner bearing, and swap to a different thickness pinion head shim.
Put everything back together and check again.
repeat, repeat, repeat

It can take me 10-15 full teardowns before I get all shims and tolerances in spec on a diff rebuild.
Some shim stack changes will be as little as 0.0005" to get things exactly where I want them.

3. You either use a new crush sleeve ( 1 shot use, never re-use them) or you move to the solid pinion spacer.
If you need to change the carrier side plates ( 1-for setting backlash, 2-for setting bearing preload) You buy the thicknesses you need from Toyota.
They are all listed in the TSRM.

4. You hold the pinion flange with a rag very tightly in the hand, put a spanner on the ring gear bolts and go around 5-6 times full rotations in both directions to get coast and drive patterns. Use yellow marking compound.

5. Use new bearing values, they are basically still brand new.
Or you could drop the new in/lb numbers by 1 or 2, and still be in a good range. Either way would work.


One extremely bad mistake amateur diff "builders make, is re-using the crush sleeve.
As @Asterix already mentioned, you can only tighten and set preload once with the crush sleeve.
Attempt to loosen the nut and re-do something will result in big problems later.

Essentially what this causes is ->
Next time the pinion nut is tightened, rather than the crush sleeve pushing back against the inner races and providing proper preload, the pinion nut has to be tightened only a fraction of the torque previously used to set preload.
Since the pinion nut is now setting preload there is serious problems to come.
(Think of it like crappy trailer bearings and the method used to set preload on those, that is what is being done without a functional crush sleeve in the center)

This causes a cascade of problems down the road:
-The pinion nut isn't torqued properly and will want to back off.
Does not matter if it is staked and / or red threadlocker is used.
-The bearing preload is lost
-Pinion becomes sloppy & noisy
-Backlash is not held securely and additional noise because of that
-Contact pattern is not constant & will result in strange wear patterns on the ring & pinion gear faces
-On and on with problems

Good luck on the rebuild, take your time and don't skip any steps.
If something is out of spec, get the right shims / tools / method down & rebuild it correctly before attempting to use the diff.
Anything not done correctly will come back and bite you later.
 

alcyon

Member
Jun 15, 2017
84
18
8
Kuala Lumpur
Just seeing this now but:

Who was this "pro" that "rebuilt" it?

1. Not much - its not really a crush but a deformation of the material to set spacing between bearings properly and provide a bit of pressure against the inner races of the bearings. (This provides preload)
I could take some measurements of old vs. new later.

2. No the crush sleeve does not set pinion depth at all, if it is affecting this or moving pinion depth AT ALL you have problems with the overall setup.
If the pinion depth is off you completely disassemble the diff, pull the inner bearing, and swap to a different thickness pinion head shim.
Put everything back together and check again.
repeat, repeat, repeat

It can take me 10-15 full teardowns before I get all shims and tolerances in spec on a diff rebuild.
Some shim stack changes will be as little as 0.0005" to get things exactly where I want them.

3. You either use a new crush sleeve ( 1 shot use, never re-use them) or you move to the solid pinion spacer.
If you need to change the carrier side plates ( 1-for setting backlash, 2-for setting bearing preload) You buy the thicknesses you need from Toyota.
They are all listed in the TSRM.

4. You hold the pinion flange with a rag very tightly in the hand, put a spanner on the ring gear bolts and go around 5-6 times full rotations in both directions to get coast and drive patterns. Use yellow marking compound.

5. Use new bearing values, they are basically still brand new.
Or you could drop the new in/lb numbers by 1 or 2, and still be in a good range. Either way would work.


One extremely bad mistake amateur diff "builders make, is re-using the crush sleeve.
As @Asterix already mentioned, you can only tighten and set preload once with the crush sleeve.
Attempt to loosen the nut and re-do something will result in big problems later.

Essentially what this causes is ->
Next time the pinion nut is tightened, rather than the crush sleeve pushing back against the inner races and providing proper preload, the pinion nut has to be tightened only a fraction of the torque previously used to set preload.
Since the pinion nut is now setting preload there is serious problems to come.
(Think of it like crappy trailer bearings and the method used to set preload on those, that is what is being done without a functional crush sleeve in the center)

This causes a cascade of problems down the road:
-The pinion nut isn't torqued properly and will want to back off.
Does not matter if it is staked and / or red threadlocker is used.
-The bearing preload is lost
-Pinion becomes sloppy & noisy
-Backlash is not held securely and additional noise because of that
-Contact pattern is not constant & will result in strange wear patterns on the ring & pinion gear faces
-On and on with problems

Good luck on the rebuild, take your time and don't skip any steps.
If something is out of spec, get the right shims / tools / method down & rebuild it correctly before attempting to use the diff.
Anything not done correctly will come back and bite you later.
Amen, this answers all my questions thus far. have mentioned in another thread before that I am not from the US, but a tropical country called Malaysia, pretty sure its now well known cause of MH370 and all. The shop is this one.


I thought he would be good since he builds race skylines and all, but local mechanics suck. They just wont take the time to do it right.
A friend of mine swears by him, maybe he is good with ECU and wiring and tuning, but he sure sucks with diffs.
Below is a screenshot from a video i took in his shop , my car is the white on inside, flanked by a R34 skyline and a R33 above and behind.

1660179587744.png
I bought the 0-3Nm torque beam wrench, slide hammer, the Weir spacer, and permatex prussian blue. I would prefer AC delco yellow, but its very expensive to import so I went with P.B.
Hopefully I do not have to remove the 3 bearings, that would simplify a lot of the work. yes, I am gonna go slow, and tear into the diff and then check what carrier shims do i need if any. If it takes me 6 weeks to get it done, so be it. The diff ain't going back in till I am satisfied.
Gonna bring the diff to my workplace since it has a table with a large vise and good dial indicator.
 

Piratetip

Far From Maddening Crowds
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Dec 30, 2005
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You are correct, I remember your location now.

Going to need a large press as well.
I use it to press the pinion in and out, as well as remove the pinion bearing to change the shim.
 

alcyon

Member
Jun 15, 2017
84
18
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Kuala Lumpur
You are correct, I remember your location now.

Going to need a large press as well.
I use it to press the pinion in and out, as well as remove the pinion bearing to change the shim.
I was hoping that a 3 jaw puller would suffice, or perhaps I wouldnt need to remove the inner pinion bearing, hopefully the inner shim is correct, if not I would just get some one to press it out for me.

Update, just went behind, found this rack pinion type press.
1660187108690.png
 
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Asterix

Lurker of Power
Mar 31, 2005
437
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Vienna, VA
That press probably will do the side bearings and pinion bearing races. But, getting the rear pinion bearing off the pinion takes lots of force. I doubt that press will work.
 
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alcyon

Member
Jun 15, 2017
84
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Kuala Lumpur
Guys, it doesnt look good so far. I drained the oil and the drain plug was dark with some metal shavings, the oil was also dark yellow.
and the diff only has 10 to 12 hours of use.
The drain plug residue
1660614190912.png

1660614265593.png
The diff also has noticable backlash, my guess is 1mm. I will be inspecting the gears this weekend, and just in case I need to buy new gears, where can i get them. I tried asking Weir but he isnt replying, and Nitro Gears have a set but the spline count is different (29 vs original 27)
I may need a 41/9 set, which is a 4.556 ratio.
1660614488231.png
 

Piratetip

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Definately not a 4.5 ratio.
Is the diff original to the vehicle?
Chassis plate on the firewall has a Gxxx code, that will tell you ratio. (Once decoded)
Year / engine will tell you.
Or can look up via VIN which cross references to the chassis code.

I doubt Weir has much gear ratios on hand, better to call him. He does not respond to emails quickly.

I have a number of ratios on hand, and can locate anything needed used or new.
Currently aquiring a gearset for someone in Greece right now.

29 spline will work you just need the corresponding pinion flange and larger seal for it.
 

alcyon

Member
Jun 15, 2017
84
18
8
Kuala Lumpur
Definately not a 4.5 ratio.
Is the diff original to the vehicle?
Chassis plate on the firewall has a Gxxx code, that will tell you ratio. (Once decoded)
Year / engine will tell you.
Or can look up via VIN which cross references to the chassis code.

I doubt Weir has much gear ratios on hand, better to call him. He does not respond to emails quickly.

I have a number of ratios on hand, and can locate anything needed used or new.
Currently aquiring a gearset for someone in Greece right now.

29 spline will work you just need the corresponding pinion flange and larger seal for it.
Yes Piratetip, it is a 4.556. I know it is awfully high for you 7M guys, but 1G engine is mated to a 4.3 for MT and 4.556 to AT. At 62mph in OD, The 1G engine RPM is 2800. At 112mph its 4800rpm. The 7M spins at 4000rpm at 112mph.
here is a resource for GA70/GZ20


 

alcyon

Member
Jun 15, 2017
84
18
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Kuala Lumpur
Ah 1G engine. That's why.
Gotcha

You can get one here
Will this flange be the same length size as the original ?

The original spline count is 27 spline correct ?
 
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Piratetip

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It's the same, other than the mounting flange diameter slightly larger and triple drilled.
Does not affect the diff setup.
Original is 27 spline yes.
That flange kit is what you would want with the 29 spline R&P.
 
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