Is this a hydratrak diff?

[Ffirg 005]

Cheers

[v8sag]

Jeez,you really are attacking it!!
If you don't get an answer i'll take the cover of a normal lsd and let you know.
Are you going to get it freshened,you know its just Holden guts,so your local diff man will tell you.
Also TVR messed with them,(something to do with the plates, I cant remember what the diff specialist said now),but if you get it freshened or rebuilt($300 to $400)they'll make it work like a proper lsd.
Had the hydratrack on the first Griff and found it very unpredictable compared to the Holden freshenened lsd on the other Trevors.

[Ffirg 005]

Not attacking Paul... just taking the opportunity while it's off to check the internals are OK (they are). I thought it should be a hydratrak as my car is (was) a 4.2 and I thought they all had it. Don't see anything in there that looks like a hydraulic system though so maybe it wasn't, or somehow an LSD found it's way into it. Surely someone must know the difference from this view??? Anyone?

[gazzab]

4.2s didnt generally come with Hydratrack. 4.5s as standard. 4.2s as an 'upgrade' I think.

[Tyre Smoke]

gazzab said:

4.2s didnt generally come with Hydratrack. 4.5s as standard. 4.2s as an 'upgrade' I think.

I was under the impression the Hydratrak was bolted to the front (engine side) of the diff and not actually incorporated into it?

[oli_quick]

doesn't 'hydra' imply there is some liquid - to provide the variable resitance within the mechanism??

[350matt]

Can you see any friction plates through the holes?

If so then its not a Hydratrak and you should be grateful

as already mentioned 4.2's did not come with hydratrak as std

Matt

[Ffirg 005]

Thanks guys - I'll have another look and see if there's a friction plate visible. There are some small moving bits inside the hole that can be moved from left to right (as you look at this picture) if that helps...

[HarryW]

Thought the standard LSD's on the 4.2's was something like a BTR/GKN diff like the Griff's. Much more predictable that the hydratrak by all accounts.

[Ffirg 005]

So I understand.... I'm hoping it's not a Hydratrak

I don't suppose anyone knows of any external indication on the case - like a serial number or suffix....? Nah, that would be too easy wouldn't it!

[jensena]

As far as I know the Hydratrak is a sealed for life unit, it's a limited-slip differential system that uses vane-pump principles, rather than cogs n gears, so looking at that picture I would guess that it isnt.

But dont worry, whenever I come out with some theory, Joo always follows up to tell everyone that I am totally wrong, so just wait a bit.

[GreenV8S]

jensena said:

As far as I know the Hydratrak is a sealed for life unit, it's a limited-slip differential system that uses vane-pump principles, rather than cogs n gears, so looking at that picture I would guess that it isnt.

But dont worry, whenever I come out with some theory, Joo always follows up to tell everyone that I am totally wrong, so just wait a bit.

I thought the Hydratrak bit was just a different clutch pack with the rest of the diff fairly conventional. (Totally unlike Torsen diffs which have completely different whirly bits inside.)

I would have thought the easiest way to find out what style of diff you have is to turn the output flanges in opposite directions and see what happens. If they move freely, it's a sh*gged LSD or an open diff. If they have significant stiffness that doesn't change with speed then it's probably a friction diff. If the stiffness increases noticeably with speed then it's probably a viscous diff.

Turnin the diff with your hands you're only feeling the preload and nothing like the forces it'll produce when you're driving, but hopefully still enough to recognise what sort it is, if it's working properly.

[Ffirg 005]

As the car came to me in an undriveable condition there's not been any opportunity to roadtest it but I did notice when applying significant (!) force to undo the allen bolts on one drive shaft (with the opposite driveshaft locked in position) there was very slow movement which I assume was the LSD activating. The sound seemed more what I would expect to hear from a hydraulic system than a friction system but couldn't be sure. Would be really nice to know conclusively somehow.... is it really this hard to spot the difference between the two, or are we just missing input from the relevant experts?

[Tokyokev]

[pic] www.3rotor.com/images/clubsport/new_diff.jpg [/pic]

don't know if this pic will work, but to my knowledge, this is a hyrdratrak diff off a HSV holden.

Think a hydratrak has a few more things poking in and out? but I'm stupid so don't know. BUt mine has one and would take a pic for you if it wasn't in pieces in the garage.

K

[GreenV8S]

Ffirg 005 said:

there's not been any opportunity to roadtest it

I was suggesting turning the diff with your hands, rather than road testing it.

[JedSteel]

I specified my 4.2 with a hydratrak diff. I've had it apart once and the internals look very similar to the picture you've put up here. If yours isn't a hydratrak, then the visible difference must be subtle.

[ridds]

The internal differences are within the cast section next to the crown wheel. So it's pretty unlikely you'll be able to tell from the outside.

[Ffirg 005]

So if the mechanism is hidden, then unless there's something in the serial numbers there's no way to be certain either way. Peter - I did try moving it manually but could only get micro movement with significant effort which isn't enough to test your theory. As one of the early 4.2s it most probably is the LSD - I guess I'll know for sure when it's all back together on the road one day.

[ridds]

If it's never been tampered with it should still have it's LSD metal tag on the rear right of the casing.

[GreenV8S]

Ffirg 005 said:

Peter - I did try moving it manually but could only get micro movement with significant effort which isn't enough to test your theory.

That indicates that it's an LSD of some sort. Can you get a longer bar and get a better feel for how it behaves? It shouldn't be *that* stiff, you can normally turn them without any great effort with a couple of feet of leverage.