Pinion pre-load during differential setup (1 Viewer)

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I'm just setting up my first differential and am following the FSM religiously. But it seems a little unclear regarding preload.

First the pinion gear goes into the housing, and without adding the crush tube, oil slinger or oil seal, the pre-load is set on the bearings. For new bearings this is 1.9 - 2.6 Nm (16.5 - 22.6 inlbs). I have mine sitting at about 2.0 Nm (17.7 inlbs) right now.

Then the ring gear will go in, and the carrier bearing pre-load is set by the adjuster nuts (while maintaining backlash). The FSM says this should add a further 0.4 - 0.6 Nm (3.5 - 5.2 inlbs) of pre-load at the pinion flange.

Then comes the pattern checking and eventually the crush tube etc. go in for the final torquing of the pinion nut, but here the FSM becomes confusing, as it mentions a final pre-load of 1.9 - 2.5 Nm (16.5 - 22.6 inlbs). I accept the difference between 2.5 and 2.6 Nm as a strange rounding error (I have seen it before in other sections), but where has the carrier bearing pre-load gone?

Should I in fact be working towards a final pinion flange move-off torque of 2.3 - 3.1 Nm (20.4 - 27.4 inlbs)? (that's the addition of the pinon and carrier bearing pre-load), or the stated 1.9 - 2.5 Nm? If the latter, why is the intial pre-load of the pinion bearings only, the same as the final pre-load of the whole diff?

Would appreciate any guidance.
 
I agree with your logic. Makes sense. It's what I do on the mini truck 8" diffs. Maybe take a look at Zuk's site. I think it's toyotagearinstalls.com

If you have a solid pinion spacer available, I recommend using one. It makes any future pinion seal replacements super easy.

Good luck with whatever you decide. And good for you for going for it with your first diff build.
 
This is why I use solid spacers ALWAYS. Set the pinion depth first, then set the pinion preload with shims, then install oil slinger, seal, flange, stake nut, then set backlash/carrier preload. The order of operations in the FSM for this is bizarre
 
^^

Solid Spacer makes is much easier. Why the Hell Toyota used those 'crush' washers, is open to a lot of guessing. Following the FSM always leads to too much preload.


Solid.jpg
 
The crush sleeve makes sense in OEM factory installation where they have a huge pre-set torque gun that gets it right first try.

To be perfectly honest I am physically not strong enough to get them to crush myself.
 
TOTAL (New Bearing) preload is the Pinion Preload of 1.9Nm to 2.5Nm PLUS the Carrier Preload of .4Nm to .6Nm.
 
I pre-crushed my crush bearing in my press but not more than it would be inside the diff. Once I got the metal crushed by a few mm torquing it was super easy. If you crush it too much in the press your screwed and need a new sleeve.
 
This is why I use solid spacers ALWAYS. Set the pinion depth first, then set the pinion preload with shims, then install oil slinger, seal, flange, stake nut, then set backlash/carrier preload. The order of operations in the FSM for this is bizarre
That would be nice to have, I like that each step is independent, but I'm working with what I have here. The FSM here is pretty crap, I have various versions and the older one from 1980 which describes a solid spacer setup actually has a better explanation of each of the steps.
 
^^

Solid Spacer makes is much easier. Why the Hell Toyota used those 'crush' washers, is open to a lot of guessing. Following the FSM always leads to too much preload.


View attachment 3213649
I guess just cost saving, once your production/assembly line is sufficiently precise that you can just use the same pinion shim and crush tube torque to set every diff up.

Could you explain what you mean about too much preload? Do you mean that the FSM quoted pre-load is too much, or that the process of crushing the crush sleeve always leads to too much pre-load (beyond FSM specs)?

I have a specially made cage for my diff and plan on using a long pole on an 18" breaker bar to start the crush.
 
I pre-crushed my crush bearing in my press but not more than it would be inside the diff. Once I got the metal crushed by a few mm torquing it was super easy. If you crush it too much in the press your screwed and need a new sleeve.
Sounds like a good idea, my worry would be making sure it is crushed absolutely squarely in the press. As I don't have anything resembling a decent press (I use a 6 ton jack under my house to press on bearings using various plates/spacers made from junk gears and bearing races against the floor beams) it's not really an option for me.
 
This is my existing front differential. High mileage car but with little/no off road use. The diff had some rust inside on the bearings and carrier (thankfully nothing on the ring gear/pinion) and the pinion bearings were slightly notched from lack of use, but overall it's a like new-diff. I used the same 1.30 mm pinion shim that came with it. Here is my contact patter with 0.17 mm ring gear backlash.

Drive side (convex) (actually the coast side on a front low-pinion diff):

20230108_134213.jpg

Looks perfect to me.

Coast side (concave):

20230108_132024.jpg


A little close to the toe, but centered root to top.

Does this look good to go?

EO
 
Goes in the rear?
When I checked mine, the additional preload from the carrier didn’t do much difference (as for total preload) cause of the 4:1 ratio?
The total preload should be measured before installing the seal (the drag from the seal may add a false preload)
 
This is my existing front differential. High mileage car but with little/no off road use. The diff had some rust inside on the bearings and carrier (thankfully nothing on the ring gear/pinion) and the pinion bearings were slightly notched from lack of use, but overall it's a like new-diff. I used the same 1.30 mm pinion shim that came with it. Here is my contact patter with 0.17 mm ring gear backlash.

Drive side (convex) (actually the coast side on a front low-pinion diff):

View attachment 3213991
Looks perfect to me.

Coast side (concave):

View attachment 3213995

A little close to the toe, but centered root to top.

Does this look good to go?

EO

Looks perfect. Run it
 
Goes in the rear?
When I checked mine, the additional preload from the carrier didn’t do much difference (as for total preload) cause of the 4:1 ratio?
The total preload should be measured before installing the seal (the drag from the seal may add a false preload)
This will stay in the front, open diff.

I found it hard to pin down carrier pre-load, it seems to be about 0.4 to 0.6 Nm now that the pinion nut is backed off, and that is about the incremental that I saw on top of the pinion pre-load when it was all together. But I'm not sure how accurate my little deflection bar torque wrench is at such low toque readings.

It's not possible to set the 'final' preload at the flange without the oil seal, as you'd then be left with a finished diff with no oil seal!
 
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Well you are right, when tightening the nut with a crush sleeve, you can’t back off the nut. Sorry

As for the total preload, my understanding is that you add .4 to .6N-m to the pinion (1.3 to 2.0 N-m new bearing)
So the total should be 1.7 to 2.6 N-m
These number are from 1990 Toyota LC repair manual
 
Well you are right, when tightening the nut with a crush sleeve, you can’t back off the nut. Sorry

As for the total preload, my understanding is that you add .4 to .6N-m to the pinion (1.3 to 2.0 N-m new bearing)
So the total should be 1.7 to 2.6 N-m
These number are from 1990 Toyota LC repair manual
Thanks for that, the manual (1987?) I was using mentioned 1.9 - 2.6 Nm for the pinion bearing alone, but it seems this is in fact what the final pre-load should be. I'll aim for a bit over 2.0, but no idea how hard it is to fine-tune it with the crush sleeve.
 

Otramm is using an impact gun to crush the sleeve. I could see it to start the crush process but I would tight the nut very slowly with a bar (like 2 degree) I personally went too fast and pass the target ;(

I've watched that, must be quite a powerful impact gun (which I don't have)! I'm generally against using an impact to build/tighten anything but it seems like a good way in this case. One thing I notice is that with the crush sleeve tight between the bearings, there is a good bit of movement in the pinion shaft, so it won't be a case of the initial crush taking it past the correct pre-load.
 
Revisiting the FSM make me confuse too ahah
Seem like everywhere else the preload is measure while slowly turning the bearing.
But in the FSM it says (at starting)
Does it really mean the torque it take to start the movement? Which is likely more than measuring while turning.
 
Revisiting the FSM make me confuse too ahah
Seem like everywhere else the preload is measure while slowly turning the bearing.
But in the FSM it says (at starting)
Does it really mean the torque it take to start the movement? Which is likely more than measuring while turning.
I've always taken it to mean the breakaway torque (hence why you can't use a click-type torque wrench).
 

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