Differential overhaul

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Declan_Burns
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Re: Differential overhaul

Post by Declan_Burns »

Phil,
Yes you are right. Billavista says only paint on 3 or 4 teeth of the ring gear in at least two different places. I took that diff apart so many times and I was too lazy to clean it all off again but will do when I get back to it.
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Declan.


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Declan
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ndevans
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Re: Differential overhaul

Post by ndevans »

Thanks once again gents, you've come up with the goods!
So, to clarify for a bear of little brain, are the contact patterns that I should see on the Minor the same as those in the articles? Roughly central along the length and the depth of the crown wheel teeth?

And Happy New Year, by the way!

Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
Declan_Burns
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Re: Differential overhaul

Post by Declan_Burns »

Neil,
Yes happy New Year to you too.
Yes, you should be looking for the same contact pattern. Read through the "Bellavista" on contact patterns once again before you go at it.
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Declan


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Declan
philthehill
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Re: Differential overhaul

Post by philthehill »

The crown wheel and pinion gear marking compound purchased from English Diff came with comprehensive instructions on how to achieve the correct meshing of the gears and also included were illustrations of the correct and incorrect meshing positions of the gears.
As per Declan:-
The tooth contact/drive pattern should be centred (vertical and horizontal) on the tooth. There should be some clearance between the pattern and the top of the tooth.

The coast (overrun) contact/drive pattern should be centred (vertical and horizontal) on the tooth but may be slightly towards the toe of the tooth. There should be some clearance between the pattern and the top of the tooth.

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ndevans
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Re: Differential overhaul

Post by ndevans »

Any chance you could scan and send them to me please Phil?
I did try English Diff company, but got no joy from them.

Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
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ndevans
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Re: Differential overhaul

Post by ndevans »

Any chance you could scan and send them to me please Phil?
I did try English Diff company, but got no joy from them.

Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
philthehill
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Re: Differential overhaul

Post by philthehill »

You have a PM.

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ndevans
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Re: Differential overhaul

Post by ndevans »

Thanks Phil.

I have got the crown wheel and cage, minutes the sun and planet wheels, back into the carrier now, and the bearing caps loosely bolted down. My plan is to see what the contact pattern looks like as it is, then dissemble, add a shim &/or replace the crush washer on the pinion, then reassemble and check the contact pattern again. Unless the backlash is well out, I don't want to touch the cage bearings.

Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
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ndevans
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Re: Differential overhaul

Post by ndevans »

Ok, I have this evening rigged the diff up in the vice, gripped as firmly as possible, and measured the backlash using a dial indicator. I haven't used one of these since college, and it's not a top of the range model.

I've measured in two places, approx. 90° apart, on the less inclined side of the crown wheel teeth. The backlash seems to be between 0.2 & 0.3 mm, say on average about 0.25mm. The BMC manual states 0.178mm maximum.
I haven't yet used the marking fluid to check the contact pattern.

To recap, I have had the cage out of the carrier, but not had the bearings off the cage. I have also replaced the pinion oil seal, but not removed the pinion from the carrier (yet). When I replaced the pinion nut, I was unable to obtain the correct pre-load-even though I got the nut torqued up to 140ft-lb, I couldn't get more than about 4"-lb pre-load. When I replaced the cage, to measure the backlash, I tightened the bearing cap nuts down to the manual figure of 60ft-lb.
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cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
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ndevans
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Re: Differential overhaul

Post by ndevans »

Had a first trial with the gear marking compound today. If I'm interpreting the contact pattern correctly, the pinion height is about right, but the backlash needs decreasing. Pics below, drive side first:-
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And the coast side:-
IMG_20200112_205114~2.jpg
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IMG_20200112_205229~2.jpg
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So, does it look like I have interpreted it correctly?
Is it now time to order a couple of new cage bearings, some shims, and remove the existing cage bearings?
Do I replace the pinion bearings as well, while I'm at it?

Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
philthehill
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Re: Differential overhaul

Post by philthehill »

The pinion markings look to be near spot on.

As regards the backlash - The factory specified backlash measurement is etched on the rear face of the crown wheel. How does your measured backlash compare with the etched measurement?

Whilst you state that the backlash is slightly more than stated in the manual I personally would leave well alone.

Unless the bearing feel rough I would not replace them.

Declan_Burns
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Re: Differential overhaul

Post by Declan_Burns »

philthehill wrote: Mon Jan 13, 2020 8:28 am The pinion markings look to be near spot on.

As regards the backlash - The factory specified backlash measurement is etched on the rear face of the crown wheel. How does your measured backlash compare with the etched measurement?

Whilst you state that the backlash is slightly more than stated in the manual I personally would leave well alone.

Unless the bearing feel rough I would not replace them.
I would do the same-leave it as it is. The pattern looks very good-well done!
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Declan


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ndevans
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Re: Differential overhaul

Post by ndevans »

Thanks gents! That is good to know.
The only thing left then is to add a shim or two, in order to get the pinion pre-load correct. I don't know whether the spacer innate is solid, or a crush spacer, but I have a new crush spacer ready. I believe I need to remove the pinion to do this-as I'm not replacing the bearing, or the pinion head shim, that shouldn't change the pinion height, as I understand it. I will check the contact pattern again when I've done it.

Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
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ndevans
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Re: Differential overhaul

Post by ndevans »

As far as I can tell, the markings on the back of the crown wheel are 1055, and 008, both without a + or - sign in front of them. Photo below:-
IMG_20200113_192808~3.jpg
IMG_20200113_192808~3.jpg (469.58 KiB) Viewed 2013 times
Does this mean 0.008" of backlash? If so, that's 0.208mm, and my measured value of between 0.2 & 0.3 mm isn't far out at all.

Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
philthehill
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Re: Differential overhaul

Post by philthehill »

I would read as you have, torque everything up and leave as is and use.

Phil

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ndevans
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Re: Differential overhaul

Post by ndevans »

I have now got the pinion reassembled, with a 0.003" shim between the crush washer and the outer bearing. That has now enabled me to get the pinion pre-load up to around 13in-lb, but that is with dry bearings, and without the cage and crown wheel fitted. The pinion nut torque was slightly under 130lbft at this point, about 128lbft.
Before I go ahead and put the cage in and check the contact pattern again, does this sound ok?

Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
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ndevans
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Re: Differential overhaul

Post by ndevans »

Unable to edit the above post, so adding here that the oil seal is also fitted. I checked the pre-load again tonight, it is almost exactly 12in-lb.
Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
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ndevans
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Re: Differential overhaul

Post by ndevans »

Diff back in one piece now, planet wheel shaft locating pin (new, as is the shaft) in place and entry hole peened over. Diff ready to be fitted to the axle. Apart from renewing a couple of brake hoses, and rerouting the brake pipe from the master cylinder, and bleeding the brakes, it's ready for a test run.
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
don58van
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Re: Differential overhaul

Post by don58van »

I will be keeping my fingers crossed for you that it will be perfect. You certainly have been getting the best advice and you have shown that you can carry out the required steps.

I was intending to have a go at a diff overhaul, but I think it might be too tricky for me.

Don
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ndevans
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Re: Differential overhaul

Post by ndevans »

Well, it's taken a while to get it back on the road, but nearly 1000 miles in, there's no sign of trouble from the overhauled diff. It's a bit quieter, but not massively quieter.



The gearbox, which I stripped and rebuilt last year, also seems fine, although slightly whinier. I guess that is because teeth are meshing in slightly different places, as it beds in it is getting quieter (I had to move all the bits into a different bellhousing, and took the opportunity to replace some bearings etc).

I've done a 1000 mile engine oil change-what is a sensible mileage to replace the gearbox and diff oil after a rebuild?

Cheers N
cheers N

Image
33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
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