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Posted 22 October 2014 - 05:26 PM
^ and great pick up from line with wheel spin to spare...seems really odd that one axle needed trimming...pull it down and have look.
Not sure about disc brake set up's on those but you would think the axles would be same length ?
"If" it was just slapped together they could have used any thing...it don't sound good.
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Posted 22 October 2014 - 05:43 PM
This is a long shot...but it may have been put together with a banjo case,they are about 11mm shorter than the small sals. which would mean about 5mm
packing on drivers side to get it nearly right...never measured up properly but just a thought.
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Posted 22 October 2014 - 09:55 PM
Different body mounts too. You can get these - http://www.ebay.com....=item2342de0c33 but I've never used them so I dont know if they're any good.
Thanks, but those are for a salisbury diff. I need something that mounts a banjo diff to a salisbury body.
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Posted 22 October 2014 - 10:05 PM
^ and great pick up from line with wheel spin to spare...seems really odd that one axle needed trimming...pull it down and have look.
Not sure about disc brake set up's on those but you would think the axles would be same length ?
"If" it was just slapped together they could have used any thing...it don't sound good.
No, it doesn't sound good at all. I suspect this may have been thrown together from other parts - judging from the whine it certainly hasn't been set up properly. And the reason only one axle needed trimming is because the pinion shaft is offset- the other axle had plenty of space.
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Posted 23 October 2014 - 05:04 PM
Interisting stuff,just put a sals. case inside the diff. housing and measured from flange to pinion shaft and was same from both sides,roughly 660mm
Believe it or not the pinion shaft is in the center of the case/and diff housing as you would expect considering both axles are same length.
Weird fault,can only think that if it was banged together that whoever did it put both the side bearing preload washers on one side, but that
would mean some terrible CW-Pinion backlash...but they are around 5mm thick...strange one for sure?
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Posted 23 October 2014 - 07:42 PM
Interisting stuff,just put a sals. case inside the diff. housing and measured from flange to pinion shaft and was same from both sides,roughly 660mm
Believe it or not the pinion shaft is in the center of the case/and diff housing as you would expect considering both axles are same length.
Weird fault,can only think that if it was banged together that whoever did it put both the side bearing preload washers on one side, but that
would mean some terrible CW-Pinion backlash...but they are around 5mm thick...strange one for sure?
That's an interesting theory - will have to check that out. It would explain the horrible whining noise when it decelerates. I'm also suspecting that the drive pinion and diff center are mismatched - it may not be a 3.9 but some bastard creation of thrown-together parts!
I'll try and get round to taking the cover off tomorrow - won't take long to check your theory about the preload washers - it would certainly explain things. Will keep you posted. Thanks for the suggestion.
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Posted 24 October 2014 - 05:06 PM
Well congrats: you were right. Both spacers were on the right hand side. And while the crownwheel has 39 teeth the drive pinion has 13 - making it a 3:1 not a 3.9:1. Since this combination isn't listed in the manual it seems it is indeed a thrown-together job.
Not amused.
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Posted 24 October 2014 - 05:48 PM
39 on crownwheel is from 355,13 pinion is from 308 if i counted right ?
And just looking,it looks like the pinion size increases and crownwheel thickness decreases sort of without measureing (maybe not) as ratios get taller,my mistake.
i would be frokin spewin and spittin chips
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Posted 24 October 2014 - 06:07 PM
The 13 pinion is from the 3.08, the 39 crownwheel was used on the 3.9 and the 2.78, with the 10 and 14 pinions respectively (according to my manual anyway). I don't see any listing here for a 3.55 but that may not have been used on the UC.
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Posted 24 October 2014 - 06:17 PM
I remember looking at a list of tooth counts and remember there was a 'double up" on a count,cant' remember or find it ( as usual).
According to HK shop manual 355 & 278 use the 39 count on CW,37 on 336...will have to search 
not sure on 390.
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Posted 24 October 2014 - 06:30 PM
Yep,your right,390 has 39 CW teeth,,triple up?...but after the woodstock era who knows what was going on
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Posted 24 October 2014 - 06:43 PM
Judging by the state of this diff, whoever put it together spent WAAAAYYYY too much time at Woodstock...
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Posted 26 October 2014 - 08:54 AM
Okay, played around with it this morning, here's the situation:
The reason whover put both spacers on one side is because it won't fit any other way. The 3.9 crownwheel is thicker because it is supposed to engage with a smaller drive pinion. Attempting to mount it in the middle with spacers on either side causes it to jam on the drive pinion. So the only way to get this mismatched setup to work is if I had the right combination of spacers to muont it slightly off-center and yet maintain the correct backlash etc. So it's effectively useless.
Edited by Steve TPF, 26 October 2014 - 08:55 AM.
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Posted 26 October 2014 - 03:25 PM
I know not many people use these things anymore but here is the tooth count for banjo/small sals.
Wouldn't be surprised if the two 11 pinion gear counts are different diameter as well ?
Best to go on the number stamped/etched on CW/pinion to make sure they are the same.
seems to be too many "rip off merchants" in this world at present...making life hard for genuine people!!
[attachment=48399:BTC.JPG]
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Posted 26 October 2014 - 04:45 PM
Forgot to mention the backlash,the backlash is important but when set up on set of gears that has seen a few miles the contact patch is more important.
The way to get correct backlash/contact patch on one of these things involves removing the pinion bearings and adding/subtracting shims from
between inner bearing race on pinion gear,frok of a job to say the least,best off put up with good CW/Pinion contact and live with "excess" backlash.
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Posted 26 October 2014 - 08:29 PM
Yeah, I'm just going to put it together with new bearings and see what the contact area is like. Take it from there. It's just annoying that the diff I got isn't even driveable while I fiddle with mine.
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Posted 31 October 2014 - 07:31 PM
I'll bump this rather than start a new thread: I have a question. What exactly does the collapsible spacer in the diff do? The pinion pre-load is the amount of torque required to turn the pinion when the yoke nut is correctly tightened, so it's the pressure of the bearings against their cups that determines the pre-load, The spacer sits between the bearings, I don't see how it affects the preload at all.
Can someone please explain to me what it actually does?
Posted 31 October 2014 - 08:59 PM
It has little affect on static pre-load, but during operation the spacer limits bearing movement so that the load does not change significantly from the pre-load amount. It stops them from being able to move closer together, while the nut stops them from being able to move further apart.
edit: compared to say a wheel bearing pair, the diff pinion can experience quite a bit of end loading due to climbing the crownwheel, in addition to side loading which would allow undesirable bearing movement without the central spacer to help hold things square (bad description but)
Edited by 76lxhatch, 31 October 2014 - 09:03 PM.
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Posted 31 October 2014 - 11:49 PM
Thanks. I had an inkling that it did something along those lines but it's good to hear someone confirm.
I wasn't going to put the diff together without it - just wanted to have some understanding of its function.
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Posted 01 November 2014 - 04:01 PM
Dumbest idea ever a crush tube,why did't they put a solid spacer that could be shimmed..a bit more rootin around but at least when right you could pull the nut up tight..the book reckons that if you go too far with the preload that you will need to pull it apart and pack (shim) the tube to get a bit more length on it and go again?
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Posted 01 November 2014 - 10:07 PM
According to the diff bloke I spoke to that's an option (solid spacer). But you would need to know exactly how far to shim it, which is probably the hard part. How do you measure the gap between the bearings when it's done up tight?
Posted 01 November 2014 - 10:10 PM
The collapsible spacer is more convenient for one-step installation, and adequate for purpose. Yes if you go too far then you may as well not have the spacer because it would be loose if you backed the nut off (you'd be better off having a touch more preload than backing it off if its within range or very close)
According to the diff bloke I spoke to that's an option (solid spacer). But you would need to know exactly how far to shim it, which is probably the hard part. How do you measure the gap between the bearings when it's done up tight?
Most people start with a collapsible spacer then pull it out and measure it. You'd probably still have to either sneak up on it which means installing multiple times and machining small amounts off, or by adding shims.
The preload measurement itself is still approximated with the torque required to turn the pinion.
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Posted 02 November 2014 - 02:53 PM
Here is an idea worth stealing if it has not already been done !!
Make or get made a solid tube and some shims,make tube a tad smaller than needed length wise.
Hone the inner race of the outer pinion bearing so that it can be got on/off more easy..just enough to slide on/off
firmly by hand...
This will make life much nicer when pre-loading bearings...it won't spin on the pinion shaft once that big nut
is pulled up to a couple hundred ft/lb. against the tube and shims.
Have often wondered what the pre-load would be in thousandths of an inch...must some sort of
rule for it as specified by the mob who make bearings.
Posted 03 November 2014 - 06:54 AM
You'd have to hone it very accurately so you don't introduce side movement, there's a reason they are a press fit. Most people set up a spare outer race so that it will slip in and out, and use it for setting the shims that sit behind it for setting pinion height, then install the new race once done. Could also use this when setting up a fixed spacer, the bearings tend to be quite accurately machined.
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Posted 03 November 2014 - 10:31 PM
You'd have to hone it very accurately so you don't introduce side movement, there's a reason they are a press fit. Most people set up a spare outer race so that it will slip in and out, and use it for setting the shims that sit behind it for setting pinion height, then install the new race once done. Could also use this when setting up a fixed spacer, the bearings tend to be quite accurately machined.
Thanks! That should save me some grief!
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