Differentials--for corner carving

[AutoXRacer]

ASA has a ProAutoSports PS0 class where the Trak Paks race... I am not too familiar with it. Just know thats where most of the limited production Trak Paks are being raced.

 

[Sam Strano]

Well, there's a new one on me...

There are a lot of hole in the wall "race series" around. Hell I have one customer that runs one in Louisiana and kicks the crap out of most everything with his Firebird... doesn't mean much if the competition isn't top of the heap.

I found the website. Even found a "Trak Pak" for sale. Noticed in the list of mods some odd things. Gears, but not mention of which differential. Also that the seats in the car aren't race seats, but street seats (which would never pass tech for say an SCCA road-race).

Look you have a Roush car, I don't expect anything I say to matter much to you. If it help, my car was originally sold to Roush Industried then kicked back to a dealer where I bought it brand new.

 

[Shaffe]

well ima jump into this just cause im bored at school right now and its a good thread lol.

From what i understand, the true trac acts like a normal LSD during normal driving, but almost like a locker under stress correct? the main thing that many people seem to like is its gear driven, no clutch paks which means it only goes if its trashed. I think that may be one of the main reasons autox went with it. after reading his posts, it seems like his biggest concern was having something that lasted.

Now im not a corner carver, i like straight lines. I dont see how the true trac would be beneficial for corner carving. sure its durable and no clutch packs to replace, but if it acts like a locker under a load wouldnt that be bad for corner carving,

 

[AutoXRacer]

From what i understand, the true trac acts like a normal LSD during normal driving, but almost like a locker under stress correct? the main thing that many people seem to like is its gear driven, no clutch paks which means it only goes if its trashed. I think that may be one of the main reasons autox went with it. after reading his posts, it seems like his biggest concern was having something that lasted.

Correct; considering my car only has 25K mile and my T-Lok is toast, I really don't want to deal with taking my rear end apart frequently!! Reading what owners of the Truetrac have posted, it seems like this LSD is bulletproof!! Regarding the locking feature, according to the engineers at Eaton, it actually transfers the torque of the spinning wheel to the other wheel with more traction. But yes you are right (according to Eaton) if you smash the throttle, it will act somewhat like a locker. So there is a learning curve with throttle input.

Now im not a corner carver, i like straight lines. I dont see how the true trac would be beneficial for corner carving. sure its durable and no clutch packs to replace, but if it acts like a locker under a load wouldnt that be bad for corner carving,

Great point!! Again, from what I've read from owners and what Eaton tells me, the LSD does have a torque bias (depending on the fluid you use, you can increase or decrease the bias) meaning that upon entering a corner its acting like an open differential. At part throttle its slipping...meaning there is a torque differential between sides/wheels. The Truetrac is categorized as a limited slip, not a locker... According to friends and forum members that own a Truetrac, they say I will be ecstatic with its performance. Its 1000X times better than the factory T-Lok. I've only heard positive reviews about it...except for one...

Again, I'm just passing along the information that was given to me from various sources. Once I install it in December and start racing in Jan, I will post up my impressions of the Truetrac.

 

[Shaffe]

see the only thing that puzzles me still, is that must people i know that have and use a true trac, as well as members here use it as drag racing diff.

 

[AutoXRacer]

Actually if you search on the net, there are tons and tons of people that use it for off-roading and road racing. Plus a little bit of everything else...

I would venture to say the Truetrac is not recommended for extreme drag racing. The POSI would be better suited for that or a locker.

I've been researching that in certain applications when running slicks, the actual Truetrac housing may flex under stress and overtime loosen its retaining bolts that keep it together. Of course though, that was in a carrier that also flexed under loads/stress. But the slicks were the common attribute.

 

[Sam Strano]

A TrueTrac gets nothing like a locker, ever. In fact what helical diffs do is act not like limited slips, but OPEN diffs--then torque bias some power around as you get inside rear wheelspin. The amount of torque bias is how much power is moves. A TrueTrac has a prett low bias number, something like 2.5 which is pretty much what a Torsen T2. A T2R was 4.25 on the torque bias--at least while they lasted.

So anything thinking that this diff is in anyway like a locker is completely wrong. Helicals need resistance to work, and if you pick up or carry an inside tire--they go completely open. But how much limiting they do depends on their bias ratio, and the TrueTrac doesn't have much of a ratio at all.

They actually work the best going straight.

 

[AutoXRacer]

Truetrac bias ratio: 3.5:1 Can fluctuate (+/-) with type of oil used...
OEM T-Lok: 2:1 at best.

 

[Shaffe]

so basically sam just reinforced my point they are pretty much best for drag racing

 

[Gray Ghost GT]

Which 8.8" 31 Spline LSD is STRONGER - the Eaton #19588-010 or the Eaton Detroit True-Trac #913A561? This will go in a daily driver that will see a lot of road course time too. I plan to have an upgraded LSD installed this January that can take a lot of abuse without making too much noise. Thanks!

Sam - can you answer this question? Thanks, Mike

 

[Sam Strano]

Truetrac bias ratio: 3.5:1 Can fluctuate (+/-) with type of oil used...
OEM T-Lok: 2:1 at best.

That's very optomistic.... In fact I just don't buy it for a number of reasons. Having run T2R's for years before they started eating themselves up, I know what a 4.25 ratio feels like. Having run Camaro's for years, with T2R's, stock Torsen and T2's, and TrueTracs I have a direct comparison on those. And a TrueTrac works like a T2, no better, no worse.

And pray tell, how do you think the bias ratio actually changes with oil? Don't get me wrong, I play with oils because they are friction devices, and a thicker oil can help a little. I found that helicals worked better with cold oil (like first runs when the car was trailered in), so I tended to run a heavier oil.... but nothing that could be considered a changing in actual mechanical ratio--because that's dictated by the angles cut on the gears.

 

[AutoXRacer]

And pray tell, how do you think the bias ratio actually changes with oil? Don't get me wrong, I play with oils because they are friction devices, and a thicker oil can help a little. I found that helicals worked better with cold oil (like first runs when the car was trailered in), so I tended to run a heavier oil.... but nothing that could be considered a changing in actual mechanical ratio--because that's dictated by the angles cut on the gears.

Can't tell you first hand. But thats what the Eaton engineers told me. They specifically stated not to run synthetic fluid with the Truetrac. Along with some owners that claim their Truetrac acted like an open diff with synthetic fluid. The Eaton engineers told me that synthetics are not recommended, but that they will yield the least amount of bias, a conventional fluid will yeild nomial torque bias, and conventional fluid without friction modifier will yield even higher bias. Even playing with a thicker multi-grade oil will generate slightly higher bias ratios.

Like I've said before, I'm just passing along the info given to me so that others can make the best decision...

I plan to test that theory with my unit once its installed... I'll report my finds and review then...

 

[fiverivers]

I talked to the Eaton technical and they mention to use 80w-90 oil. Also friction modifier is for clutch packs only, since the true track doesn't have one, it doesn't need any.

 

[sqidds]

I’m running a Torsen T2R (same one that comes in the FR500). It has so much feel that you can tell when it is transferring power to the tire with the most grip while exiting corners. It tells you everything you have going on with your rear contact patches and makes charging off of corners very uneventful. I have run the Truetrac, Auburn, Auburn Pro and the OEM trac Lock with the carbon plate pack in the past and the Torsen is lightyears better IMHO.

 

[Sam Strano]

I’m running a Torsen T2R (same one that comes in the FR500). It has so much feel that you can tell when it is transferring power to the tire with the most grip while exiting corners. It tells you everything you have going on with your rear contact patches and makes charging off of corners very uneventful. I have run the Truetrac, Auburn, Auburn Pro and the OEM trac Lock with the carbon plate pack in the past and the Torsen is lightyears better IMHO.

And for years I ran those... until they started eating themselves up. Many have had the issue, I burnt two up in a year at one point.

Torsen works great, and years ago was super durable. But for whatever reason (my guess is cheap metal) they don't last.... and frankly they made a mistake when they refused to acknowledge there was an issue to me--when I sold more than 150 of them over the years. Anyway, I won't sell them anymore because they just don't hold up now (used to, still running one from 1999 in a Camaro, and it works fine). But I know many with both GM and Ford units that have had the same issues.

 

[Cookiemonster]

Im beggining to get wheel spin on the inside tire when im exiting corners, however I can still do 11s. Is my stock LSD on its way out? or am I gettin on the gas more durring the turn? Im totally lost when it comes to diffs and how they work (or dont).

 

[Sam Strano]

That's the differential wearing. And there is the rub..... Those that don't drive very hard, or have very much grip don't really see that happen. The faster you go (say you are learning on an autox or track), the more it will happen anyway--and the more it happens the more the stock diff wears. Kind of a snowballing effect.

In the end there are lots of folks with weak or fried LSD's who have no clue. But it's very, very obvious the minute they get a good one. Car is more stable, predictable, and faster because it actually puts power down.

 

[Gray Ghost GT]

Sam, thanks for your recommendations and lessons learned - I plan to purchase the Eaton LSD #19588-010 in two weeks. I'll provide my initial impression on how well it performs when I take my car to the Virginia International Raceway (VIR) for a weekend of road course activities this May. It's also my daily driver, so I'll provide feedback on how it feels on the street too.

 

[AutoXRacer]

Finally got my TruTrac installed and broken in...

All I have to say is WOW!!!! Instant lock when pressing the throttle.
The car is so much more predictable, repeatable, and so much more quicker out of a corner!!!

I can't get over how different the car is. You literally can't have the steering wheel turned and be aggressive with the throttle or else the car will go sideways every single time. Regardless of the sideways motion, the car is pulling forward like never before!!

I really love this differential... My only slight complaint is that its noisy. It brought out all the drivetrain noises. You can hear the damn thing lock, unlock, lock, unlock...though its not obvious to those that don't listen for it.

If I were to do it all over again, I would have chosen the POSI Trac. It seems to be virtually silent. One Ford shop I went to said they never install TruTracs on street driven vehicles because of the noise they make...its not really that the unit is noisy, its that its all solid metal and there are no clutches/composite material to absorb sound/vibrations.

Performance-wise, this thing is freakin awesome!!! I just can't get over how well it performs. Noise-wise, I wish it were a little tiny-bit quieter...

Overall, I'm really happy with it.

 

[fiverivers]

what type of oil did you use when the TruTrac was installed.