1 (edited by Jimmy 2024-10-22 11:52 AM)

Topic: Eaton TrueTrac Question

Does anybody have any experience with Eaton TrueTrac differentials? These are limited slip set ups that uses helical-cut gears. No clutches. Its not a Locker .

I put one in one of our Dobas so it would go up the hill at NH and we were really disappointed in how it worked.  Saturday It felt better that the open diff on the other car. It wasn't going up the hill sideways but wheel spin was better than the open diff.  But on Sunday it seemed about the same as the open diff. Tire smoke galore .  Not sure why but maybe because our tires by Sunday were garbage.

Am I missing something ?

Cordoba

Re: Eaton TrueTrac Question

Torsen style lsd doesn't work as predictably as a disc type.

That guy

3 (edited by X-args 2024-10-22 12:06 PM)

Re: Eaton TrueTrac Question

I've got one in the Ranger axle in the 544 and they are sensitive to weight transfer. There needs to be SOME resistance otherwise it just acts like an open diff. Play with your corner weighting to get a few more percent on that tire. I ended up p building a three-link that solved it but that's pretty extreme: smile

2x Volvo PV544 (RIP '63) B20 power!
2007/2012/2013 Driver's Championship (what was I thinking!?) 150 races and counting.
10/1/24

Re: Eaton TrueTrac Question

X-args wrote:

I've got one in the Ranger axle in the 544 and they are sensitive to weight transfer. There needs to be SOME resistance otherwise it just acts like an open diff. Play with your corner weighting to get a few more percent on that tire. I ended up p building a three-link that solved it but that's pretty extreme: smile

That makes sense ... These girls lean like drunken giraffes.

Our tires were so hard on Sunday they were almost undrivable. ( That's saying a lot for Cordoba's). Would that lack of traction or resistance exacerbate the issue?  Sound like it might

Also - what has your reliability been with you truetrac? How often do you drain the fluid. Any other nuggets of knowledge ?

Really Appreciate the info

Cordoba

Re: Eaton TrueTrac Question

A TruTrac is a torque sensing/biasing mechanism.
The problem is that if one wheel has no traction the diff
cannot sense any torque going to that wheel, and cannot
bias torque to the wheel with traction.

"The car will not move with one of the wheels in the air. If one wheel is in the air or has no traction at all, it will only take very little torque to turn that wheel. It is necessary to apply torque to the gears to generate the required thrust force to maintain the bias ratio. Without torque, the gears will not be pressed together and no friction will be generated, so the gears can rotate freely. The unloaded wheel will have high speed, but can only transfer very little or no torque. The helical LSD will send torque to the wheel with traction according to the bias ratio, BUT four times zero still equals zero. This means the wheel with grip will not receive any torque and the LSD acts as an open differential."
From https://kmpdrivetrain.com/differentials … ferential/

You might be better of with a welded diff.

Capt. Delinquent Racing
RUST-TITE XR4Ti - '21 ARSE-FREEZE-APALOOZA  I Got Screwed
The One & Only Taurus V8 SHO #31(now moved on to another OG Delinquent)
'17 Vodden the Hell - (No) Hope for the Future Award, '08 AMP Survivor, '08 ARSE-FREEZE-APALOOZA Mega-Cheater

Re: Eaton TrueTrac Question

Thanks Delinquent.... I guess the combination of hard tires, significant weight transfer and maybe the track was getting a little slick after two days of Lemons hoopties dripping all over added up to very limited traction that wouldn't let the " system" work as wanted.

I did a good bit of homework before choosing this option. I originally liked the concept because my impression was that the Truetrac limited slip was supposed to be more gradual and only engaged when needed . My thought was this would be better for my horrible drives. My guys are hardly drifters.  Ahh well..more lessons the hard way

Thanks Again

Cordoba

Re: Eaton TrueTrac Question

Jimmy wrote:

My thought was this would be better for my horrible drives. My guys are hardly drifters.

I've driven two different cars with welded diffs at Lemons races in the rain.
Both powered out of corners with aplomb. The first time I drove one
of these cars in the rain I expected crazed, sideways exits to corners.
Nothing but great traction and drive as I applied power.
They are challenging in the pits, however.
YMMV, tho.

Capt. Delinquent Racing
RUST-TITE XR4Ti - '21 ARSE-FREEZE-APALOOZA  I Got Screwed
The One & Only Taurus V8 SHO #31(now moved on to another OG Delinquent)
'17 Vodden the Hell - (No) Hope for the Future Award, '08 AMP Survivor, '08 ARSE-FREEZE-APALOOZA Mega-Cheater

Re: Eaton TrueTrac Question

Hey Jim, Ken from the 295 "Supra". Our car has a factory Torsen LSD in the transmission we swapped in. I can confirm that all day friday, saturday, and sunday we were one wheel peel all the way up the hill, every lap, on a fresh set of 615k"s. With us being FWD we just had to modulate the throttle up hill in 2nd gear to make the most of it.
With the Doba's being what they are you're going to need to move some weight over the rear end, and keep in mind that as your fuel load gets lighter it's going to dynamically shift where the grip is. Like X-args said you may want to corner balance it and to get that weight on top of the drive wheels. Throttle modulation has a big part to play though. If I had just planted my foot down up the hill I'd have destroyed our right front in a few hours.

FWIW at Thompson coming out of the hairpin our car will also do a one wheel burnout all the way under the bridge if you don't feather the throttle.

#295 1997 Chevy "Supra-Carlo" 2.0 LSJ F35 5spd

- 1x I.O.E.
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Re: Eaton TrueTrac Question

I had a ranger with the torsen, and if you lifted a wheel, it was like an open, so when 4 wheelin, if a wheel came off the ground, you would apply the ebrake and it would pull out.

88 Festiva  -  Damn Tree!!!
"We Are Not Really From Iran" Festiva  -  Motor and Trans to be anounced

Re: Eaton TrueTrac Question

I have been told you need a clutch style LSD like a Gripper.

Team whatever_racecar #745 Volvo wagon

Re: Eaton TrueTrac Question

Don't weld a diff in Road racing. I can't understand how many people think this is alright! A wheel has to spin at a different rate from the other one on the same axle. Recipe for disaster. Last year a Mustang with a welded rear rolled over at Thompson almost killed the driver. It couldn't even turn into Headquarters.  If it were up to me they would be outlawed. BUY A FUCKIN POSI!!!!!
Manny.

Re: Eaton TrueTrac Question

Mkotzias wrote:

Don't weld a diff in Road racing. I can't understand how many people think this is alright! A wheel has to spin at a different rate from the other one on the same axle. Recipe for disaster. Last year a Mustang with a welded rear rolled over at Thompson almost killed the driver. It couldn't even turn into Headquarters.  If it were up to me they would be outlawed. BUY A FUCKIN POSI!!!!!
Manny.

Well, when one of my drivers rolls the car due to a welded diff I'll agree with you.

In the meantime, please provide some empirical evidence that the Mustang rolled due to the welded diff.
I don't really want to unecessarily endanger my drivers.

And, if A FUCKIN POSI was readily available for my diff I would have put one in.

Capt. Delinquent Racing
RUST-TITE XR4Ti - '21 ARSE-FREEZE-APALOOZA  I Got Screwed
The One & Only Taurus V8 SHO #31(now moved on to another OG Delinquent)
'17 Vodden the Hell - (No) Hope for the Future Award, '08 AMP Survivor, '08 ARSE-FREEZE-APALOOZA Mega-Cheater

Re: Eaton TrueTrac Question

fitsbain wrote:

I had a ranger with the torsen, and if you lifted a wheel, it was like an open, so when 4 wheelin, if a wheel came off the ground, you would apply the ebrake and it would pull out.

Perhaps a little left foot braking going up the hill would make the loaded side tire bite better.
(I know... hooptie brakes don't need any help wearing out.)

Re: Eaton TrueTrac Question

guardrail028 wrote:

  and keep in mind that as your fuel load gets lighter it's going to dynamically shift where the grip is.



Man I didn't think about that either . That's a significant contributor.

How are you people so smart?

Cordoba

Re: Eaton TrueTrac Question

A rear anti-roll bar might help, too.
It would help keep the weight from
transferring in corners due to body roll.

Capt. Delinquent Racing
RUST-TITE XR4Ti - '21 ARSE-FREEZE-APALOOZA  I Got Screwed
The One & Only Taurus V8 SHO #31(now moved on to another OG Delinquent)
'17 Vodden the Hell - (No) Hope for the Future Award, '08 AMP Survivor, '08 ARSE-FREEZE-APALOOZA Mega-Cheater

Re: Eaton TrueTrac Question

DelinquentRacer wrote:

A rear anti-roll bar might help, too.
It would help keep the weight from
transferring in corners due to body roll.

Adding a rear anti-roll bar and stiffening up the front of our Volvo with a solid rear axle helped a little bit.  If there is not an available stiffer bar for the front, you can double up the sway bar.  More bar in front may cause it to push a bit more.

Team whatever_racecar #745 Volvo wagon

Re: Eaton TrueTrac Question

How are you people so smart?

They're not driving a Cordoba.... :lol

I followed your Cordoba's up the hill a few times last weekend. No wonder there were no mosquitos around that area...lol

It looks to me like you have stock suspension? Stiffening the front would help the car from leaning a bit, and help keep weight on the right rear wheel. Not a cure-all by any means, but a step in the right direction.

1991 VW Jetta #38 - cuz Whoopie Pie!

Re: Eaton TrueTrac Question

I change the TruTrac fluid every other weekend with a mix of 1qt Heavy Shockproof and 1qt of GL4 90w.
The LSD has held up fine for 6 years and maybe 35 races in two cars behind ~65 - 240hp.

Once I got enough  weight on the spinny side (a combo of the three-link and more front bar) it gets off corners nicely.

2x Volvo PV544 (RIP '63) B20 power!
2007/2012/2013 Driver's Championship (what was I thinking!?) 150 races and counting.
10/1/24

19 (edited by Jimmy 2024-10-30 11:55 AM)

Re: Eaton TrueTrac Question

X-args wrote:

Once I got enough  weight on the spinny side (a combo of the three-link and more front bar) it gets off corners nicely.


I am giving up on conquering my hill nemesis at New Hampshire. It won.

I just signed up for the new West Virginia race in 2025. Its only 3.5 hours away which will be so much nicer. That NH ride was 8 hours for us. I think the TrueTrac will be fine on most other  tracks. I am going to leave it in. The dobas do have front and rear sway bars and I put a larger one in the front than std. I am not sure I want to mess around with getting an even bigger one at this moment. I got at least one tranny that needs changing . I am hoping the motor on the blue one is still good. Little or  no oil pressure at idle but obviously enough to make it thru two days of racing.  Always something

Cordoba

Re: Eaton TrueTrac Question

Tires tire tires... also good shocks and the correct rear sway bar help. I'd think a "true locker" would likely lead to a lot of tire smoke. We found that Bilstein's (the cheap non-adjustable) worked best with a small rear sway bar. The extra large WS6 bar wouldn't allow enough travel and it would burn up one side or the other, depending on the turn. I'd think a "sure-grip" would work best. I can't remember are yo all running and 8.25 or a 9.25?

"get up and get your grandma outta here"

Re: Eaton TrueTrac Question

Jimmy wrote:

Does anybody have any experience with Eaton TrueTrac differentials? These are limited slip set ups that uses helical-cut gears. No clutches. Its not a Locker .

I put one in one of our Dobas so it would go up the hill at NH and we were really disappointed in how it worked.  Saturday It felt better that the open diff on the other car. It wasn't going up the hill sideways but wheel spin was better than the open diff.  But on Sunday it seemed about the same as the open diff. Tire smoke galore .  Not sure why but maybe because our tires by Sunday were garbage.

Am I missing something ?

TrueTrac aka Torsen are based on multiplication. They all have set multiplier that cant be changed, just messed with. So if inside tire can do 15ftlbs of torque, and multiplier is 2, than outside tire can receive 30ftlbs.
Based on that typically need to move the roll point forward, aka disconnect the rear sway bar, softer springs, and front needs more spring more sway bar. So all weight transfer is handled by front not back or less.
Alternatively, the clutch type dont care. And they work much better overall. They based on torque input, more torque more lock up. So dont care about lifting the tires of the ground.

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