Upgrade Vf open diff centre

[losh1971]

Does a (numerically) lower diff-ratio possibly equate better highway fuel economy?

I think going from 3.45 to 3.9 made a difference to my economy, at a guess 1/2 a litre or better per 100km. Holden's have been too tall for as far back as HQ maybe longer. Probably fine on flat highways without lots of turns but average driving those tall ratios are not great IMHO.

 

[Skylarking]

The boss at work looked up the part number and said it appears to be a diff from an auto SS. previous owner must of blown the original diff and put a truetrac converted open diff from an auto into it?. Diff has (LSD : N) on it

There is no such thing as a Truetrac open differential (as far as I know).

Truetrac is a brand name for a Torsten limited slip differential (a helical spider gear arrangement that automagically stops slip when both wheels are on the ground).

Truetrac provides LSD action without requiring clutch packs and special oil. For road use it’s a superior product and an upgrade over the standard LSD

PS: if you want to change the diff gearing, that can be done independently of the Truetrac LSD centre (which is a better centre than the standard clutch pack factory LSD centre).

 

[losh1971]

Don't mess with a Trutrac. Get a Kaaz and be done with it. I could be biased though.

 

[_R_J_K_]

Does a (numerically) lower diff-ratio possibly equate better highway fuel economy?

In theory yes, but it also makes it much harder (and slower) to take off from a standstill, so unless you're only constantly doing highway K's with no stops the opposite can happen because of the amount of extra energy it requires to take off. It's a balancing act unless you're at the polar opposites trying to set a land speed record or just ripping massive skids.

 

[_R_J_K_]

I don’t understand the terminology, isn’t a TruTrac a proper LSD? I mean it’s not a bodgy clutch one like OEM, it’s considerably more sophisticated Torsen-type which is a better design … isn’t it?

What is a "proper" LSD?

Admittedly Holden's stock clutch type ones have been pretty bloody average, but like everything else there are advantages and disadvantages to each type of LSD. There are different styles of clutch based LSDs (clutch packs, cup and cone), and there are some excellent clutch pack based LSDs that can be had depending on what your application is.

 

[Forg]

What is a "proper" LSD?

That was referring to the "open" near the start of this thread, I thought TrueTracs were "real deal" Torsen types.

Having said that ... clutch type ones do irk me in a "planned obsolescence" way. Something that's designed to wear & die just bothers me, it feels like we're being conned by the diff manufacturer. Nothing to do with the fact they probably work better in some circumstances, eg. zero-grip scenarios, and/or the fact they're cheaper to make & probably won't die before the car does or anything like that ... it's more like how I'm irked when I see a totally deserted shared bike/foot path & the only other person is walking on the wrong side directly over the top of the symbols painted on the ground that are telling them they're doing it wrong.

 

[Jeda]

Sounds like the previous owner has installed a 3.27 diff from a v6 in it and changed the yoke to suit the 8. There are no true trac diffs that are non lsd.

Is there a part number on the diff?

Also, the series one vf ss auto had a 2.92 lsd diff and series 2 had 3.27 lsd.

Just out of curiosity, why do you think it's a true trac centre?

 

[[paradox]]

Sounds like the previous owner has installed a 3.27 diff from a v6 in it and changed the yoke to suit the 8. There are no true trac diffs that are non lsd.

see my thoughts would be the original owner got hold of whatever diff housing they could get, install the trutrac, and then do the swap, that way you dont have your car out of action as long if you had to pull your current diff and replace on the go.

but without looking inside, no one will have any idea whats in there.

but there are far too many questions in this story for anyone to understand

 

[losh1971]

see my thoughts would be the original owner got hold of whatever diff housing they could get, install the trutrac, and then do the swap, that way you dont have your car out of action as long if you had to pull your current diff and replace on the go.

That's pretty much what I did, just with a Kaaz.

 

[Jeda]

but without looking inside, no one will have any idea whats in there.

but there are far too many questions in this story for anyone to understand

100% agree.

Because the OP didnt bring up any issues other than the diff being a single spinner, I reckon someone has incorrectly told him that a single spinner or open diff is called a trutrac which is why he said he has one.