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Diff backlash
http://auszookers.com/forum/viewtopic.php?f=5&t=30287		 Page 1 of 1
Author:  Jackson [ Wed Feb 08, 2012 11:46 am ]
Post subject:  Diff backlash
Hey fellas.

A little bit confused at the moment about backlash. Pretty much my question is can you see the movement of the crown gear if it has the right backlash setting?

I have two diff centres the one coming out of the car has a buggered pinion seal but I can't really see any backlash, I'm a bit skeptical of this centre though as one of the smaller cross pings is missing 8O and the side cup thingos that adjust the backlash look nothing short of frucked so I hardly trust taking anything from this centre... and the other center I'm thinking of using seem to have heaps of backlash I can see it, hear it clunk etc however I took this centre to a diff place in Newcastle and he reckons its good to go :?
Author:  stocker [ Wed Feb 08, 2012 1:43 pm ]
Post subject:  Re: Diff backlash
Sounds like you got a she'll be right, why don't you take it to a diff shop and get it checked out??? Or measure the backlash
Author:  christover1 [ Wed Feb 08, 2012 2:18 pm ]
Post subject:  Re: Diff backlash
Don't know any technical diff stuff.
But too tight is bad, need room for heat expansion.
Bit of slasck when cold is essential.
Too much slack and things get hammered and shocked too much.

I set my diff backlash with a strip of tuff cardboard in between pinion gear and crown gear.
Is easy to get out after its all tightened up.

This is not right, but works for me.
Author:  Jazzor [ Wed Feb 08, 2012 2:59 pm ]
Post subject:  Re: Diff backlash
I found this thread with a link to the manual:
http://auszookers.com/forum/viewtopic.php?f=5&t=29755

And the backlash should be between 0.10 > 0.15mm which is tiny.

I have done it myself and the backlash was probably like 1cm which is a pretty huge and they worked fine for years :S, I was amazing at how tiny the backlash was when i got them setup correctly when changing dif gears recently, just a nice small bit of movement, no movement at all doesn't sound right...
Author:  mrw82 [ Wed Feb 08, 2012 3:06 pm ]
Post subject:  Re: Diff backlash
4 - 6 thou measured with dial gauge. You can develop a 'feel' for it with experience, but I wouldn't recommend going by feel for someone who's never done it before.

If checking the backlash then bearing preload should be checked too.
Author:  christover1 [ Wed Feb 08, 2012 3:08 pm ]
Post subject:  Re: Diff backlash
PS. Most types of auto locker add a lot of drive line slack.
So may not be wrong, if theres an auto in there.
Author:  Jackson [ Wed Feb 08, 2012 6:05 pm ]
Post subject:  Re: Diff backlash
mrw82 wrote:
4 - 6 thou measured with dial gauge. You can develop a 'feel' for it with experience, but I wouldn't recommend going by feel for someone who's never done it before.

If checking the backlash then bearing preload should be checked too.


Looking at this I don't quite understand what sets the bearing preload? http://www.4x4.in.th/manual_sj413/chapter16.pdf

The backlash stuff is on page 10. It tells you to do the side cap bolts up a bit then adjust the backlash then it gives you some way of calculating the side bearling preload required (but doesn't say what that means) then tells you to give it to the side cap bolts.... :?
Author:  larry [ Wed Feb 08, 2012 6:44 pm ]
Post subject:  Re: Diff backlash
if you move the gear with your hand you should feel a tiny bit of movement.
i just measured the backlash with a dial gauge before disassembly, and set it back to the same on assembly.
Author:  Hybrid [ Thu Feb 09, 2012 7:00 am ]
Post subject:  Re: Diff backlash
Jackson wrote:
mrw82 wrote:
4 - 6 thou measured with dial gauge. You can develop a 'feel' for it with experience, but I wouldn't recommend going by feel for someone who's never done it before.

If checking the backlash then bearing preload should be checked too.


Looking at this I don't quite understand what sets the bearing preload? http://www.4x4.in.th/manual_sj413/chapter16.pdf

The backlash stuff is on page 10. It tells you to do the side cap bolts up a bit then adjust the backlash then it gives you some way of calculating the side bearling preload required (but doesn't say what that means) then tells you to give it to the side cap bolts.... :?


Been a while since I did this and can't quite remember that bit but by looking at the manual section you refer to pinion preload alone is set by the crush tube. The second preload it speaks of is pinion plus ring gear preload. So basically the amount of force on the pinion before the ring gear moves once the backlash is set correctly. My assumption would be increasing the torque on the bearing caps (the threaded caps either side) would increase preload while backing it off would reduce it. Remember you need to torques both caps the same amount each time or you could put backlash back out. The manual does seem really vague there. I guess that's why they tell guys like you and me not to fiddle with our diffs. :lol:

Please someone correct me if I'm wrong.
Author:  Jackson [ Thu Feb 09, 2012 7:36 am ]
Post subject:  Re: Diff backlash
Ok so this is what I have done to minimize the backlash to what I can still feel and see but isn't so severe.

First I undid those four bolts a little (marked red) and took those retaining clips off (green) then I tightened the cap closest to the ring gear one notch (blue)

Image

Then I loosened the cap furthest from the ring gear one notch (yellow)

Image

I did this twice and the backlash seems a bit better. I then tried to tighten the yellow cap but was firm so I just left it.

Then I filled a glass with water, weighed it at 1.8 kg, and wrapped a piece of rope around the flange then tied it to the glass and lifted the centre. It didn't turn so I filled the glass and it weighed 2.4 kg repeated and it was able to turn it. Does that mean it is right?

Image

Cheers.
Author:  wolf_rt [ Thu Feb 09, 2012 9:28 am ]
Post subject:  Re: Diff backlash
Hmm, by looking at the manual the 'special tool' (rope and water) is for checking the pinion preload, not the ring gear preload... since you didn't have the pinion out, probably not relevant...

There doesn't seem to be much on adjusting the ring gear bearings, just "Screw in each adjuster till it contacts bearing outer race so that outer race is prevented from inclining."
Author:  Hybrid [ Thu Feb 09, 2012 9:36 am ]
Post subject:  Re: Diff backlash
Love your "jar guage". You McGyvered the shit out of it hehe. I just use a digital luggage scale. Regardless that is the way to measure both preloads mentioned in the manual. Pinion is just pinion alone, no ring gear contact. Pinion plus ring is with it all installed and backlash set.
Author:  Lockie666 [ Thu Feb 09, 2012 12:05 pm ]
Post subject:  Re: Diff backlash
Jazzor wrote:
And the backlash should be between 0.10 > 0.15mm which is tiny.


^^ This, use a dial gauge on the tooth of the crown wheel and rock it back and forth, you can feel where the teeth and the crown wheel are meshing.

Also if you haven't already get new carrier bearings too :wink:
Author:  Lockie666 [ Thu Feb 09, 2012 12:09 pm ]
Post subject:  Re: Diff backlash
I don't know what you are attempting with the water and the flange, but just because you can get the diff to spin with 2.4 kilo of pressure doesn't mean that the backlash is right. The only way to know is to use a micrometer, if in doubt take it to a diff-shop and ask them to measure the backlash for you. I doubt it'd cost much.
Author:  atari4x4 [ Thu Feb 09, 2012 12:22 pm ]
Post subject:  Re: Diff backlash
Lockie666 wrote:
I don't know what you are attempting with the water and the flange, but just because you can get the diff to spin with 2.4 kilo of pressure doesn't mean that the backlash is right. The only way to know is to use a micrometer, if in doubt take it to a diff-shop and ask them to measure the backlash for you. I doubt it'd cost much.


x 666.666
Author:  just_cruizin [ Thu Feb 09, 2012 12:45 pm ]
Post subject:  Re: Diff backlash
Backlash = Micrometer

Total Preload = Flange torque

wolf_rt, it checks all the bearing preloads, unit as a whole, that's how it's described in the manual.

Luggage or fish scales are the best as the force can be applied at the correct radius and must be perpendicular to the radius, thus providing a torque.
(side note: does the manual provide different forces for preload NT v's WT to allow for flange hole PCD differences? WT should be less)

It's not hard just fiddly, set the total preload first then adjust the side bearings ensuring you screw the retainers across the same amount to keep preload untill the backlash is correct.
Author:  Jackson [ Thu Feb 09, 2012 12:53 pm ]
Post subject:  Re: Diff backlash
Lockie666 wrote:
if in doubt take it to a diff-shop and ask them to measure the backlash for you. I doubt it'd cost much.


Learning and tinkerin is much more interesting...

Plus
jackson wrote:
I took this centre to a diff place in Newcastle and he reckons its good to go


Hybrid wrote:
Love your "jar guage". You McGyvered the shit out of it hehe. I just use a digital luggage scale. Regardless that is the way to measure both preloads mentioned in the manual. Pinion is just pinion alone, no ring gear contact. Pinion plus ring is with it all installed and backlash set.


So does this mean if I was to rebuild the whole diff you would do up the pinion nut until it got within the 1.8-3.4kg and note what the starting torque is then you would install the ring gear then set your backlash then check the starting torque is within range shown on that graph? I'm guessing the side bearing preload is set by those caps that adjust the backlash pushing the bearings into the middle?
Author:  wolf_rt [ Thu Feb 09, 2012 1:07 pm ]
Post subject:  Re: Diff backlash
I believe that is the strength of it.

note that the 'special tool' they used for checking the preload has a radius larger than the pcd of the flange, it didn't appear to state the radius.
Author:  Hybrid [ Thu Feb 09, 2012 2:10 pm ]
Post subject:  Re: Diff backlash
Jackson wrote:
So does this mean if I was to rebuild the whole diff you would do up the pinion nut until it got within the 1.8-3.4kg and note what the starting torque is then you would install the ring gear then set your backlash then check the starting torque is within range shown on that graph? I'm guessing the side bearing preload is set by those caps that adjust the backlash pushing the bearings into the middle?


I wouldn't touch the pinion nut unless the starting torque is well outside of range. The preload for it is set by torqueing down on a crush tube. The idea is its a one shot thing. To do it properly you would need a new crush tube.

For the remainder of your post, yes, that's the gist of it. As JC said it might be easier to set the backlash after getting the total preload/starting torque right depending how good you are at tightening each cap the same amount. You can do it either way.

just_cruizin wrote:
Does the manual provide different forces for preload NT v's WT to allow for flange hole PCD differences? WT should be less)


the tool seems to run a standard radius. It shouldn't matter what the PCD is as it doesn't pull from the bolt radius, rather the outside radius of the tool itself. Provided the tool has both bolt PCD's drilled in it it would work for both with the same settings you would think. Can't say I've ever seen one though. Would there really be a massive different whether you tested in 50mm from centre or 60mm from centre for example?
Author:  just_cruizin [ Thu Feb 09, 2012 4:02 pm ]
Post subject:  Re: Diff backlash
20% difference so yes

What radius is the tool, that's critical if using a force. If the state a torque that would be the best as then you just divide the N.m figure by whatever radius, in metres, you are going to apply the force
Author:  wolf_rt [ Thu Feb 09, 2012 7:50 pm ]
Post subject:  Re: Diff backlash
There's a picture of the tool in the manual, i reckon you could get it close enough by eye.
Author:  jdk81 [ Sat Mar 10, 2012 10:19 am ]
Post subject:  Re: Diff backlash
As per setting backlash, go to a tool shop and buy a dial indicator, and clampable arms with magnetic base plate etc.
Not overly expensive and always handy. Do it right.

http://www.transquip.com.au/products.ph ... DICATOR-MM
http://www.transquip.com.au/products.ph ... NETIC-BASE

Only diff tool I need are the fishscales
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