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Diff rebuild update


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Diff almost back together after fitting new bearings.Pinion preload set at 15lb/inch, carrier bearings preload 3 thou and pinion/crownwheel backlash 3.5/4.5 thou, a tad tight but I`m not whipping them bearings off again for all the tea in china.Pinion depth shim replaced with same thickness one.

Not sure about the pinion to crownwheel contact pattern though,doesnt seem anything like what I`ve seen on websites.

The pattern on both the drive and coast side is identical.It looks as though its perfect and spot on but it could also be rubbish and miles away.

Any comments /suggestions gratefully received.IMG_0686.thumb.JPG.9246ab58163cd760a5a48a68b94eeb2f.JPGIMG_0687.thumb.JPG.45fbd613b046b8efc02be46ab4cbfc2e.JPG

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Hi Dave,

               the workshop manual shows the contact pattern (I think).

When you attacked your diff did you have any manuals/paperwork advising you along the way.

I intend doing mine in December so need all the help I can get.

 

Roger

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As you are smearing the crown wheel teeth rather than the pinion I suggest you apply 'engineers blue' to  as many crown wheel teeth as there are pinion teeth. (is that 11 on a 3.45?) The method of bluing the crown wheel teeth is to transfer that blue to the pinion teeth which will then transfer the blue marking back to the crown wheel teeth, that you have not blued,.  This will all happen as you turn the pinion in one direction only to fully rotate the crown wheel.  ie 3.45 turns of the pinion will rotate the crown wheel once in a standard TR6 PI diff.

Do one full crown wheel turn in one direction using the pinion to drive it and inspect.  That should shew the patterns on one side of the crown wheel teeth you have seen in books.

Then do the same again in reverse direction of pinion rotation.  Again the patterns should have appeared. 

Cheers

Peter W

 

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Hi Roger,  

I have the brown bible and a Haynes manual ,and there is plenty of information on the web and youtube, also Bullfires website gives a good account.

Its quite tedious setting the pre loads and backlash though, especially the carrier bearings,must have had the bearings on and off half a dozen times.

I cant read what the mesh pattern is telling me now though it doesn't look like anything like the images in the manuals and on the web.I can`t believe that its right first time without having to change the pinion depth at least, I`m not that lucky.

I`m hoping that an expert on diffs is going to  enlighten me, as at the moment things have come to a standstill

Peter I`ll try your suggestion and see if that makes things any clearer.

Dave

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46 minutes ago, cubehopper said:

Hi Roger,  

I have the brown bible and a Haynes manual ,and there is plenty of information on the web and youtube, also Bullfires website gives a good account.

Its quite tedious setting the pre loads and backlash though, especially the carrier bearings,must have had the bearings on and off half a dozen times.

I cant read what the mesh pattern is telling me now though it doesn't look like anything like the images in the manuals and on the web.I can`t believe that its right first time without having to change the pinion depth at least, I`m not that lucky.

I`m hoping that an expert on diffs is going to  enlighten me, as at the moment things have come to a standstill

Peter I`ll try your suggestion and see if that makes things any clearer.

Dave

Using engineers blue is a tried and tested method for fitting metallic components probably for over a 100 years! It's use was taught to  me over 50 years ago when I was an apprentice. I have not ever come across anything else that can replace it except magic marker pen ink but it is not as good.

Bruce.

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Hi Bruce ,

    The yellow stuff I used is proper gear marking paste, I thought that it would be easier to see the contact marks than the blue.

Are you saying that engineers blue may show  the contact pattern differently .

Can`t really see that it would.

Dave

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22 minutes ago, cubehopper said:

Hi Bruce ,

    The yellow stuff I used is proper gear marking paste, I thought that it would be easier to see the contact marks than the blue.

Are you saying that engineers blue may show  the contact pattern differently .

Can`t really see that it would.

Dave

It looks to me that the paste that you have used is more like grease because of its thickness and would not show the witness marks as well as engineers blue? the idea of engineers blue is to be rubbed away to show where the teeth are meshing.

Bruce.

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It did seem a tad greasy when I brushed it on the teeth but it was advertised as gear marking paste, I`ll certainly do as you suggest Bruce and try the blue.

Dave

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2 hours ago, cubehopper said:

It did seem a tad greasy when I brushed it on the teeth but it was advertised as gear marking paste, I`ll certainly do as you suggest Bruce and try the blue.

Dave

Clean it all off and try a much lighter coating.

On the images you posted it looks like the entire contact area of the CW tooth is being wiped by the pinion tooth - in both directions.  That is very odd.

Peter W

 

PS Is it this compound?  https://www.ebay.co.uk/itm/Crown-Wheel-Pinion-Gear-Marking-Compound-Paste-Axle-Diff-English-Atlas-CWP-Etc-/141911711498

Edited by BlueTR3A-5EKT
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Hi Peter , yes that's the stuff,from the same supplier also.

Yes you`re right about the contact area being the same both sides of the teeth, something doesn't seem right does it , just looks as though the pinion has completely wiped the crownwheel teeth clean.

I`ve looked at lots of websites showing diff meshing images and cannot find any showing the same thing.

If I knew what the problem was then I would be able to tackle it but at the moment don't know where to start.

The annoying part is that the diff feels very nice and smooth with no grinding or incorrect meshing.

Dave

 

 

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Think the amount of paste is acting as “grease”, avoiding intimate contact. I would wipe it clean and just use just a little, or get some engineers blue.

good luck,

Waldi

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Hi Waldi, 

      That's a reasonable assumption, I think checking the meshing pattern again using engineers blue is  maybe my next step.

Though I`ve  just found this set of mesh images on a Singer Le Mans site and the images on the middle row right hand side, seem identical to mine.

It says that the bearing is too high, doesn't explain which bearing though or how it is too high,but I imagine that it can only mean the large inner bearing

under the pinion head.I did measure the pinion depth before I removed it and when I refitted it with a new identical thickness shim, I noted that it was 15thou lower, but I thought not a problem

when I come .to check the mesh pattern I`ll get a reference point and change the measurements accordingly too correct it,  but now I`m thinking is the pinion too far from the crownwheel to get a reference pattern.

I may loosen the pinion nut a thread and tap the pinion back towards the crownwheel slightly and check the meshing again, If I then get a  recognisable pattern then I can maybe increase the shim under the pinion head bearing to correct this,does this sound reasonable.

Dave

diff meshing.jpg

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Hi Dave, before you go undoing all your good work I suggest you have another go with the indicator paste you are using.  Even the areas you say have been wiped clean still appear to be quite thickly coated.  You are only looking for a few thou misalignment so the paste needs to be no more than that.  I suggest you wipe everything clean and smear a very very thin (a thou or few) on one surface and then look at the rub marks after 1 turn.  I’ve only used blue before but don’t see why a yellow indicator should be any different.

Dave

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Have you changed the crown wheel & pinion assembly?

If so, did you transfer the shim that is fitted between the pinion head and the big pinion bearing? 

Too often rebuilders without a technique to remove the big pinion bearing just press a new bearing on the new pinion as the shim is not visible in parts lists or repair manuals, and is therefore unknown.

It is NOT listed as a spare part and is critical to set the pinion height.  It is about 1/16" thick.  I do not have a sample to check.

 

Peter W

Edited by BlueTR3A-5EKT
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Hi Peter, 

Yes I replaced the bearing so changed the shim at the same time, both old and new shims measured 40thou.Got it from Rimmers.

Crown wheel and pinion are the original ones.

Dave

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Thought I would again try to get a readable contact pattern on my diff, but not able to get any engineers blue until Monday.

Tried  a black permanent marker pen and although the film is a bit thin the finish is streak free and consistent , and after applying a load on the crownwheel and turning the pinion 4 times I achieved something more like a recognisable contact pattern.

Obviously when I get the blue on Monday the results should be clearer still.

All I`ve got to do now is interpret the results and make the appropriate adjustments, easy eh :D

Dave

CIMG6701.JPG

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Hi Dave

I've only ever rebuilt a mini diff so I'm certainly no expert, however my take on the 2 drawings is the  singer drawing stating bearing too high is indicating all the contact is on the upper part of the tooth. The 2nd drawing shows contact more in the middle of the tooth. Your photo using the marker pen seems to show the contact towards the inner of the tooth? Engineers blue will give a better contact pattern & give you an indication of where to go.

alan

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Ye need t,blue up all the teeth,

and also ned t,check all teeth for fit, as alot of the times, it dont run true, or is worn into a pattern,

which shows up better wid all teeth blued up., some are a lot longer than others, some are fatter.

as it is with little load, it looks ok,ish, if too low.

high loadings will shift pattern upt tooth, alot

so too will slack pre loadings on pin bearings

 

need a chisel wedged into casing an C/W t,really hold it whilst turning

 

one last thing at moment, if it runs quiet in a drill,  ne load,  then its generally ok

butt, pattern can be perfect, but diff meks yan hell of a racket, esp at low speed 

yee,l soon hear it  noise, as cant describe it moer than a rumble / clonk, come rattle !!!

 

and get some 85/140 penrite pro gear oil,

muchess better than owt else ive used

a drain plug, wid magnet, a sump plug will suffice

also bung  one it int fill plug, as fill plug will catch moer sheite than sump plug

 

M

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Hoping to get some engineers 

1 hour ago, GT6M said:

Ye need t,blue up all the teeth,

and also ned t,check all teeth for fit, as alot of the times, it dont run true, or is worn into a pattern,

which shows up better wid all teeth blued up., some are a lot longer than others, some are fatter.

as it is with little load, it looks ok,ish, if too low.

high loadings will shift pattern upt tooth, alot

so too will slack pre loadings on pin bearings

 

need a chisel wedged into casing an C/W t,really hold it whilst turning

 

one last thing at moment, if it runs quiet in a drill,  ne load,  then its generally ok

butt, pattern can be perfect, but diff meks yan hell of a racket, esp at low speed 

yee,l soon hear it  noise, as cant describe it moer than a rumble / clonk, come rattle !!!

 

and get some 85/140 penrite pro gear oil,

muchess better than owt else ive used

a drain plug, wid magnet, a sump plug will suffice

also bung  one it int fill plug, as fill plug will catch moer sheite than sump plug

 

M

 

Thanks for your advice

Hoping to get some engineers blue in the morning so I`ll have another go, hopefully the markings should be a lot clearer. 

Once I`m happy with the set up how do I test run it before fitting, you mention with a drill, would that be with a socket on the pinion nut.

Dave

 

 

 

 

 

 

 

 

 

 

 

 

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Hoping to get some engineers blue in the morning so I`ll have another go, hopefully the markings should be a lot clearer. 

......... bung quite a fair bit on, as it,ll go onto pin teeth as weel

note yer original set of teeth, they all diff size contact patches, look closely, concurr.

 

Once I`m happy with the set up how do I test run it before fitting, you mention with a drill, would that be with a socket on the pinion nut.

...........yes, wid an adaptor frae 1/4 drive to 1/2 drive sqaure end, got in a set

https://www.ebay.co.uk/itm/SDS-power-drill-3pc-SOCKET-ADAPTORS-1-4-3-8-1-2-DRIVE-SDS-shank-CrV/282735176988?epid=2256606954&hash=item41d4546d1c:g:ks4AAOSwWHBaDGyn:rk:8:pf:0

 

Note, ye cant bung a high loading on wid just a drill, it,ll burn it oot, been there ,fun oot,!!

 

butt, its great for running it up, t,get  a pattern up,

it,ll show all teeth markings in a wee while,

thee,s markings will be low on CW drive side, high on back { coast side }

whenst happy they all ok, then apply load, a chisel or a BiGG pry bar lever thingy, an acomplice is handy, {Herr Nibbships, will suffice }

and turn wid a long bar,or ratchet, DONT snatch it, but smooth actions

yee,l be suprised hoo much pattern alters

 

Oil t,use

Dave Parker at classic group

http://www.classicgroup.net.nz/product_pcid_344.html

 

gudluk

M

Edited by GT6M
f,got summat
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