Pinion height dimension.

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Alec
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Pinion height dimension.

#1 Post by Alec » Mon Oct 01, 2018 8:41 am

Hello all,

does anyone have the dimension or know where I might get the figure for the pinion height on a 3.45:1 saloon differential.

The figure is not in the workshop manual and just refers to using the special setting tool.

Alec
0465

MK1.5 2.5 P.I.
Jaguar MK 2 (Long term restoration.)
Hymer 564 Motorhome.
Jaguar X Type Estate 2.5

Clifford Pope
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Re: Pinion height dimension.

#2 Post by Clifford Pope » Wed Oct 03, 2018 7:46 am

What do you mean by pinion height?
It's a hypoid axle - ie the axis of the pinion shaft passes below that of the crown wheel, but I didn't know the actual height was adjustable. That sounds rather complicated to achieve?
The degree of engagement of the pinion is presumably set by shims, but I thought had to be carefully set in concert with the crown wheel adjustment to vary the degree of backlash but retain the same point of alignment at the rim of the crown wheel.

I did once have a Triumph Roadster which had an exterior device for moving the pinion shaft axially to minimise whine, but it didn't alter the height.

But it's fifty years since I had an axle in pieces :)

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Re: Pinion height dimension.

#3 Post by Alec » Wed Oct 03, 2018 8:37 am

Hello Cliff,

the height I am refering to is between the axle centre line and the pinion top face, this determines how much in mesh the pinion is with the crown wheel. It is set by shims but the workshop manual (I have four) just refers to using a specific setting gauge without giving a dimension. Jaguar, on the other hand give a specific figure.

Alec
0465

MK1.5 2.5 P.I.
Jaguar MK 2 (Long term restoration.)
Hymer 564 Motorhome.
Jaguar X Type Estate 2.5

Clifford Pope
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Re: Pinion height dimension.

#4 Post by Clifford Pope » Thu Oct 04, 2018 9:10 am

You mean the distance out from the axle line - ie as if sliding the pinion shaft in and out?

The plan section in the book shows the two bevelled chamfers on the crown wheel and pinion being exactly in line, and I've always understood that is correct for any axle.
The degree of mesh is determined by the interrelationship of the crown wheel sideways location and the front/back location of the pinion shaft.
Setting that up from scratch is normally specified by the backlash between teeth, or more finely, by using engineer's blue on a crown wheel tooth and observing the contact area with the pinion tooth. Evening and centring the contact area needed finer adjustments to both crown wheel and pinion in concert, so as to maintain the straight line across the chamfers.
I remember a rule of thumb for adjusting a noisy axle depending on whether the whine was on over-run or drive. One was too close meshing, one too little, but I've forgotten which was which.

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Re: Pinion height dimension.

#5 Post by Alec » Thu Oct 11, 2018 3:05 pm

Hello Cliff,

I've been away so only now have I got back to this.

The height determines how far in and out of mesh the pinion will be to the crown wheel as the teeth are tapered from toe to heel. If the pinion is too high in the casing the mesh will be too high on the teeth flank and conversely if too low it will be too low on the teeth flank. This is with the correct backlash. It helps to be able to set the pinion to it's correct height initially as it then means less dismantling and reassembly (i.e. trial and error) if setting it by checking the mesh with blue.

Alec
0465

MK1.5 2.5 P.I.
Jaguar MK 2 (Long term restoration.)
Hymer 564 Motorhome.
Jaguar X Type Estate 2.5

Clifford Pope
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Re: Pinion height dimension.

#6 Post by Clifford Pope » Fri Oct 12, 2018 7:49 am

Got it. You're using "height" as if the diff were standing on the bench on its back with the pinion shaft pointing up in the air. I'm describing it in its normal driving orientation, and thinking of the adjustment as "in" and "out".
But I still don't know what distance it should be. :)

My thought is that distance would just be a consequence of setting the other parameters - backlash and alignment across the teeth bevel - rather than a measurement to be set by itself.

https://www.youtube.com/watch?v=nVb5WRUfM7Y

http://what-when-how.com/automobile/rea ... utomobile/

"Backlash is adjusted at this stage by moving the crown wheel towards or away from the pinion. Prior to the final measurement of backlash with a clock gauge, it is necessary to ensure that the crown wheel run-out is within the recommended limits.
Meshing of the gear is checked by applying a smear of marking compound to the driving side of a few crown wheel teeth and then turning the pinion in the direction of rotation while applying a resistance to the crown wheel. The marking thus obtained indicates the mesh of the gears with respect to pinion position and backlash. Figure 26.41 illustrates the change, in relation to the correct marking, when the pinion position is changed. A ‘correct’ marking
indicates only a limited contact between the teeth under light-load test conditions. But if full load is applied to the gear, the contact area covers the complete tooth."


That I think is what I am saying - ie you set the backlash initially with the crown wheel, then move the pinion in or out to even tooth engagement as shown by the blue test.
It doesn't actually say that moving the pinion will change the backlash as well, but presumably if it does take it out of range then you have to make a minute adjustment to the crown wheel and then reset the pinion again.
(It's an interesting statement in the last two sentences, that tooth contact changes under load, ie the whole set-up flexes slightly)

50 years ago I did the whole thing mismatching good gears from two axles on a Triumph Roadster, finally running it in on the bench with jeweller's rouge, before cleaning it thoroughly and refitting. It was surprisingly effective and quiet, considering I was a complete amateur improvising with the aid of an ancient manual from a different car.

:)

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Re: Pinion height dimension.

#7 Post by Alec » Fri Oct 12, 2018 9:56 am

Hello Cliff,

yes, it's the position that the case is when doing this check. Essentially it means the pinion and crown wheel are properly meshed and the only other adjustment required is to set the back lash. I can make an informed guess using the old and new components but at the end of the day I may have to dismantle the pinion again if blueing the teeth gives that the pinion is at the wrong height, i.e. it is likely to be more work.


Alec
0465

MK1.5 2.5 P.I.
Jaguar MK 2 (Long term restoration.)
Hymer 564 Motorhome.
Jaguar X Type Estate 2.5

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