Center diff check

gtirx2

gtirx2

Member
Can anyone tell me if there is a way to check what condition the center diff is in when it is out of the gearbox?The reason i ask is because i am about to rebuild my gearbox and i have the choice of four different diffs and after reading that thread about center diff wear i would obviosly like to use my best diff.
Thanks for any help.
 
K

Keira

New Member
theres nothing you can see or poke about at as the actual diff is a sealed viscous unit, you will see the spider gears and could check for wear but the working ability of the diff you wont know, even by stripping the whole lot down you'd be none the wiser.

one of my boxes that has come apart recently had at some point had the viscous fluid changed as the diff was plugged.
 
gtirx2

gtirx2

Member
Ok i need to drag this up again as i doing another box and the diff i have chosen to use seems to slip a lot easyer than the other diffs i have laying about.
Basicly if i push the diff on the shaft coming out of a transfer box and connect it up i can hold the the diff and spin the flange that gos to the propshaft fairly easily by hand,so i am basicly slipping the center of the diff. ie the plates in the diff slipping through the viscous fluid fairly easily by hand.
Where as the other center diffs i have i have to put a couple of bolts in the flange to the prop and use a large bar to be able to slip the diff and its only a just aswell as its hard to hold the diff,but it will still slip its just a hell of a lot tighter.
So would you guys say that this diff is fooked or is this normal?
I know its when the diff starts to slip faster that the viscous fluid and plates starts to grab more but surely i should not be able to turn it by hand?
The problem is i have just put new bearings on this diff and they will be a right bugger to get back off without damaging them so i thought i would ask on here first just to double check but i am pretty sure it is knacked?
Also i have not put much thought into this yet but if i was to weld up this center diff would it cause any driveabilty issues?
Also how would you go about welding it up?would you just weld the planet wheels in the diff up or is there another way?
 
jjs

jjs

Member
hi my son welded his front diff up on his vauxhall astra, it is excellent for of road driving, but wouldnt recomend it for road use as it puts a lot of strain on the drive train when turning tight corners, especially on tarmac,
 
gtirx2

gtirx2

Member
Thanks for the reply bud,i am on about the center diff in the gearbox not the front diff but i have thought about welding a front diff just for the odd qtr mile but i am not sure if it would turn very well on tarmac.
I have got a lsd front diff but need to find some replacment plates for it to work which would be the sensible option really lol.
Its the center diff i have trouble with atm which locks the drive to the front and back wheels so i think it would be alright to weld it.
It is definatally a bog standard center diff, i am just unsure if it should slip so easy,i am pretty sure it is knacked which is a pain but i thought i would see what every one else thinks as i could be wrong?
 
PobodY

PobodY

Moderators
Staff member
I think the confusion here is that it's not really a diff; it's a viscous coupling (so it acts like a limited-slip diff). - It sounds like it's gone to me, but I freely admit that I don't know anything particular about them... just what teh interweb tells me.

I think you've got a response from someone who knows what they're talking about anyway. ;-)
 
gtirx2

gtirx2

Member
Thanks guys,just as i suspected really:cry:At least i can be sure now:)
Just got to try and get the bearings back off it now:doh::lol:
 
PobodY

PobodY

Moderators
Staff member
That shows you what I know then - I'm sure I called it a centre diff in the past and was told I was wrong it was a viscous coupling.

Anyway, if you can turn it by hand it's not working any more?
 
gtirx2

gtirx2

Member
I decided to cut open the diff to have a nose so i thought i would post up a few pics of what it looks like inside.

On closer inspection you could see a seal hanging out and where the fluid had been leaking.



The stack of plates from inside the diff.



I think there is around 56-57 plates in total.



There are 2 types of plates one that fits to the center part of the diff and one that fits to the outer casing of the diff.



 
jjs

jjs

Member
the plates look simmilar to the clutch plates on a motorbike, with the drive and friction plates, are you still planing on tryin to weld the center diff solid ?
 
gtirx2

gtirx2

Member
jjs said:
the plates look simmilar to the clutch plates on a motorbike, with the drive and friction plates, are you still planing on tryin to weld the center diff solid ?
Click to expand...
Nah i have managed to get the smaller bearing back of the diff now which is the important one as its a nissan bearing which you cant get in the after market,where as the larger bearing on the diff i can get a lot cheaper than nissan prices from an aftermarket bearing supplier,plus i have a few spares.
Luckily i had a spare diff with a knacked crown wheel so i swapped them over and i am good to go:).
I have keep the main part of the broken diff with the planet gears in etc so i may look into welding it up one day and using it in another box as i have a few other gearboxs that i need to rebuild in the future.
I should not of cut open the viscous unit really but i thought fook it and wanted to have a look inside:lol:
The plates do look a lot like clutch plates but its just the drag of the viscous fluid between the plates which enable it to distribute the power i think.
 
jjs

jjs

Member
hi ,would be interested in hearing how you get on with the welded center diff if you do it , i managed to pick up a modena front diff, and a cusco rear, will fit into the autocross car for next season , looking forwar to see the difference scuse the pun, also managed to pick up a close ratio box, do you have any idea about the ratio of drive on the pulsar front and rear ? IE 60% front 40% rear ? ,
 
PobodY

PobodY

Moderators
Staff member
50% front 50% rear if you weld it, but obviously with the viscous coupling it shifts the power about depending on which is spinning more; is it slightly offset to preload the coupling?
 
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