Diff Education Needed.

[Red CV8 R]

Wavetrac is only any better if you have a zero load condition on one side; ie off road when you c0ck a leg. Other than that the added components add no benefit that i can think of in our applications

Interesting, you may be right, although I thought the WaveTrac was also less clunky?

[macca_779]

I doubt it. The clunkiness you sometimes hear in a truetrac is the biasing engaging. That function is identical in the wavetrac so I can't imagine it would be any different in that regard

[ChrisCV8R]

I doubt it. The clunkiness you sometimes hear in a truetrac is the biasing engaging. That function is identical in the wavetrac so I can't imagine it would be any different in that regard

Hi, I've been reading up about this trutrac clunkiness a bit.

I drive a VY Monaro with a mild cam, full 3" exhaust and 3.9 + trutrac and experience a loading/unloading of the diff at freeway speed (100km/h in 6th, just below 2K revs) when going from no accelerator to touching the accelerator and vice versa. Is this the same thing you guys are talking about?

A similar thing happens in 1st gear when coasting with no accelerator in slow traffic, but causes the whole car to become unsettled. It starts lurching back and forth (and requires clutching)

So I'm wondering if swapping out the trutrac for a wavetrac will help keep the car more settled as low speed and get rid of the loading/unloading effect at high speed.

I guess I can always keep my foot in it and avoid the problem haha

[duke5700]

Wavetrac is only any better if you have a zero load condition on one side; ie off road when you c0ck a leg. Other than that the added components add no benefit that i can think of in our applications

A few of the more serious circuit guys used to prattle on about a KAAZ being better as if you hit a decent ripple strip with the Trutrack it would open up on the unloaded side.. I never managed to do it and I cooked more apexes than I care to remember. I'm only guessing that the unsprung weight/wheel weight/brakes kept mine locked.

I guess the Wavetrack would eliminate any possibility?

[duke5700]

Sounds more like a tune problem to me. Some kind of surging.

I never noticed my centre engage or disengage.

Hi, I've been reading up about this trutrac clunkiness a bit.

I drive a VY Monaro with a mild cam, full 3" exhaust and 3.9 + trutrac and experience a loading/unloading of the diff at freeway speed (100km/h in 6th, just below 2K revs) when going from no accelerator to touching the accelerator and vice versa. Is this the same thing you guys are talking about?

A similar thing happens in 1st gear when coasting with no accelerator in slow traffic, but causes the whole car to become unsettled. It starts lurching back and forth (and requires clutching)

So I'm wondering if swapping out the trutrac for a wavetrac will help keep the car more settled as low speed and get rid of the loading/unloading effect at high speed.

I guess I can always keep my foot in it and avoid the problem haha

[ChrisCV8R]

Sounds more like a tune problem to me. Some kind of surging.

I never noticed my centre engage or disengage.

I spent some time with a tuner in the passenger seat (fixing other idle/stalling issues) driving around a carpark while this was happening, and was told the fuel/air was stable. Just seems like there is some 'slack' in the drive line. There is a clear/mechanical sound to this engaging/disengaging.

[Smashfist]

I spent some time with a tuner in the passenger seat (fixing other idle/stalling issues) driving around a carpark while this was happening, and was told the fuel/air was stable. Just seems like there is some 'slack' in the drive line. There is a clear/mechanical sound to this engaging/disengaging.

You can't fix that. You're going from tight in one direction to tight in the other. My 10,000km old cammed VF does the same thing when I drive it the wrong way. Avoiding the surging is the only way to avoid clashing in the drivetrain.

You may be able to lessen it with a shorter set of gears though. Will increase the revs at lower speeds moving it out of the surge zone.

[ChrisCV8R]

You're going from tight in one direction to tight in the other

That's why I was wondering if a wavetrac centre could help in this situation.

[Smashfist]

That's why I was wondering if a wavetrac centre could help in this situation.

It won't make any difference. The lash will be in things like unis, gearbox output/diff input yoke splines etc. Even a tiny amount of play in each component will add up to a bit down the drivetrain.

[duke5700]

Yep, I'm with Smash on this. Changing the centre won't make a difference unless it hasn't been setup correctly to begin with.

When I did my centre, I had new Harrop CV's, changed to a single piece carbon driveshaft(moved to unis, no rubber) etc there isn't much slack in the drivetrain these days. Hasn't been driven much since then either sadly.

Cammed cars can and do surge a bit despite best intentions. For an auto, you just tune the parameters of the gearbox to avoid those areas in the map. In a manual, you are the loose nut that controls gear selection. Seeing as you have 3.9s, not much more you can do really other than drive around it.

[ChrisCV8R]

Yep, I'm with Smash on this. ... not much more you can do really other than drive around it.

Thanks for the replies. I might go back to APS, see if they can find and remove some of this drive line slack. There was no slack/slop issues like this before the trutrac went in. (cam went in at the same time as the diff)

[Micks]

Once you start the upgrade process, unfortunately you'll end up with a more aggressive/noisy drive train. A compromise may be too hard to achieve.

[duke5700]

Luis has a pretty good reputation, I would think the tune would be spot on.

Thanks for the replies. I might go back to APS, see if they can find and remove some of this drive line slack. There was no slack/slop issues like this before the trutrac went in. (cam went in at the same time as the diff)

[SASLS1]

From Eaton Differential Owners Manual FAQ'S, link below...

Here...

"My Truetrac has more internal “lash” then an open
or plate style limited slip differential. Is this normal?

Eaton Detroit Truetrac differentials are a helical gear
style limited slip differential. At a high level system
view, the units are constructed similar to an open
differential – except all gears are helical and the
“pinion” gear is split into two intermeshed gears.
Because of the three gear tooth mesh interfaces, the
design must have lash. While all Truetracs (and helical
gear differentials in general) have internal lash, units
with preload are less noticeable. Typically, Truetracs
have a maximum lash of three to four degrees side to side
between gears. This is normal and required for the
superior torque transfer design of the product."


Same part number Eaton on Harrop page ($1099.01), "912A642" bit of a price difference...

https://www.summitracing.com/int/par...a642/overview/

$507.99 USD ($666.44AUD) plus $84.86USD shipping, total $777.77AUD...


The extra lash in the Truetrac compared to the std LSD, you can drive around it and avoid the clunk at low rpm from coasting to picking up the throttle in a manual, when driving like miss daisy.

Spirited driving, mine never makes any noises / clunks what so ever, can't get enough of how well it works, compared to the absolutely useless, POS OEM std lsd...

[blackvussii]

Hi, I've been reading up about this trutrac clunkiness a bit.

I drive a VY Monaro with a mild cam, full 3" exhaust and 3.9 + trutrac and experience a loading/unloading of the diff at freeway speed (100km/h in 6th, just below 2K revs) when going from no accelerator to touching the accelerator and vice versa. Is this the same thing you guys are talking about?

A similar thing happens in 1st gear when coasting with no accelerator in slow traffic, but causes the whole car to become unsettled. It starts lurching back and forth (and requires clutching)

So I'm wondering if swapping out the trutrac for a wavetrac will help keep the car more settled as low speed and get rid of the loading/unloading effect at high speed.

I guess I can always keep my foot in it and avoid the problem haha

I have similar mods in my vu, small cam, ls2 heads full exhaust 3.91s and trutrac and have the same symptoms...
I ordered the centre from summit when the dollar was good and bought a set of second hand genuine gears. I had a aftermarket warranty at the time so when the original diff started to go they paid for the install. The guy that did the work does diffs for Power Torque here in Brisbane so knew what he was doing.
He said I'd prob get a bit of a whine on decel due to using second hand gears because its impossible to set the pattern the same once they are worn a little. That didnt worry me cause new ones were $900 at the time and I could barely hear it over the exhaust.
He also changed the allen key bolts over to decent high tensile ones and locktighted them cause he said they can be a problem.

It did make a clunk when engaging 1st and on roll back on the highway and I read quiet a bit on here and US forums of the same issue.
Mine has progressively got worse and hops around at low speed in car parks at low rpm.
I have done plenty of high rpm launches at the drags on ETs which has definately caused it. There is quiet a bit of play in tail shaft when u grab it and rotate it back and forth. I going to get back under there today and put it in gear to do it to rule out the gearbox. Its not in axles/ cvs.

My theory is that the extra loading at the track has caused the pinion to move away from the ring and crush the sleeve further than its meant to be. I've never pulled a diff apart but now that we have a 3rd car and I can get away with having mine in the garage for a while I think I'm going to pull it out and have a go at rebuilding it with new seals and pinion sleeve to see if improves it. Have found some good DIY threads so keen to have a shot at it. Going to have a chat with a local diff place and see what they think but if I go down that path I'll put a thread up.

Overall its one of the best mods I've done and its never slipped with a fair bit of punishment but the clunkiness is pissing me off at the moment.