Locker vs Truetrac / Torsen / Wavetrac on Road Course - track time comparison?

[Uhcoog1]

I've got a nascar locker in my car right now, and I'm considering 'upgrading' to a worm gear differential. Thoughts on how much 'better' it would be? Say, on a 2.9 mile road course? On 'street' tires.

I'm hoping to find input from someone who has swapped from one to the other and has lap times to share on what the change netted in performance.



The biggest deficiency in my car right now is me. If my money is better spent on additional track time and tires at this point, then that's what I'll do. But at the end of the day, I want to run with well driven modern cars, and that means my car needs to be there as well.

Car:

[Cobra 498]

I have run a Detroit Locker, a Torsen and a Salisbury in a fairly light car (2340 lbs). The Detroit softloc was way too violent when it would lock and unlock and actually upset the car. I don't think that would be a problem with a heavier car say 3000 lbs though. When you throttle up the rear end locks and may cause some understeer depending on your set up. The Torsen would spin the inside tire exiting a corner if I had much rear roll stiffness, it was very smooth but I pulled it because of wheel spin. The Salisbury has a set of clutch disks with belleville washers to preload the clutches, the spiders are also set up on v ramps so it really locks up if you have traction. I like this system the best because it always smooth locking and unlocking and it does not spin the inside tire with a stiff rear bar. I think you would really have to be on top of your game to see much time difference on a road course with any of these differentials to answer your question. Seat time is always a good investment vs spending money on your car.

[71RS/SS396]

I did not have very good luck with the wavetrac in my car, didn't even last a full season. I've been running a tru trac since without issue.

[Uhcoog1]

I did not have very good luck with the wavetrac in my car, didn't even last a full season. I've been running a tru trac since without issue.

Really? What went wrong? I was under the impression that the wavetrac was 'superior', and thus was the one I was going to buy.

[Bryce]

I love my detroit locker in my falcon. Maybe 300 torque.... I have not noticed an issue with push while autocrossing.

[71RS/SS396]

It started doing the the one wheel peel, I sent it back to wavetrac and they rebuilt it free of charge, but they weren't very forthcoming with what they replaced. They were very adamant about the amount of axle protrusion which could have been a contributing factor since I'm running a floater. The tru-trac has been performing very well so I didn't bother putting the wavetrac back in.

[Uhcoog1]

I have a floater as well - what does axle protrusion have to do with a wavetrac failure? Weird...

Wade

[bret]

Tried several wavetracs...trutrac is what we've had the best luck with, and what we currently use.

[72BBSwinger]

If I ever do a Dana 60 I would probably go Tru Trac but the Spicer Power Lok in my 8.75 is so far a total non-issue. Never has it one legged but it also acts like its not there.

[GeoffP]

Interesting thread - I didn't realize the Wavtrac had reliability issues other than Karl's problems in Blu-balz. Didn't he end up with a clutch style diff? I personally prefer an Eaton/GM clutch style over all else but that's just me from familiarity and not from driving experience cause my driving stinks.

Tim McGilton - does your car have a 9" or a 12 bolt?

[TheJDMan]

I purchased a surplus NASCAR 9" center section from Roush Racing. It came equipped with a Detroit Locker. The locker was so harsh that the car was virtualy undrivable and in fact was down right dangerous as it would push in turns. Traded the locker for a Tru trac and have not had any further issues.

[shmoov69]

I got a locker, and it pushes like a dump truck under power. I'm not a good driver, and I'm sure the car is not set up great as well. But when I "factored in" the push, it was ok running around Putnam Park and on the auto-x also. Finch said it was "ok" when he plowed it around the cones, just pushed. That could have been from many items, but under power I think it's from the Locker.
Just my ¢2

[72BBSwinger]

A locker is not good for left AND right turns.

[Bryce]

A locker is not good for left AND right turns.

The locker works great for me.

[71RS/SS396]

Interesting thread - I didn't realize the Wavtrac had reliability issues other than Karl's problems in Blu-balz. Didn't he end up with a clutch style diff? I personally prefer an Eaton/GM clutch style over all else but that's just me from familiarity and not from driving experience cause my driving stinks.

Tim McGilton - does your car have a 9" or a 12 bolt?

Geoff, it's a 9".

[71RS/SS396]

I have a floater as well - what does axle protrusion have to do with a wavetrac failure? Weird...

Wade

Wade, I was told by wavetrac that it interfered with how the gears locked.

[Ron Sutton]

I purchased a surplus NASCAR 9" center section from Roush Racing. It came equipped with a Detroit Locker. The locker was so harsh that the car was virtualy undrivable and in fact was down right dangerous as it would push in turns. Traded the locker for a Tru trac and have not had any further issues.

Steve, the challenge with buying a used NASCAR locker is you don't know what springs are in it. We tune the locker with different spring rates from 25# to 125#. The softer the spring the easier it releases when turning. The stiffer the spring, the more it takes to get it to release. On big tracks like Daytona & Talladega the last thing you want is for the locker to release. So they run the 110# to 125# springs.

If you bought a used locker with that much spring rate, it would be a bear to get it to unlock. With street tires, I don't think the tires have enough grip to force those 110# to 125# springs to unlock consistently ... and would on occasion simply slide the tire instead.

For short track ovals, road racing & autoX, the hot ticket is softer springs. I typically like the 58# spring for these applications.

A locker is not good for left AND right turns.

Lockers are the most common & preferred differential in most full size car road racing applications.

They turn left & right equally ... unless ...
a. You have different rate springs on the right & left side.
b. You bought a CTR Detroit Locker, designed for oval track racing that only unlocks turning left. You can tell when you take it apart, because it only has one spring.

[no go nova]

Where do you get the lockers from that are good for street tires, auto x, and road racing?

[Ron Sutton]

Where do you get the lockers from that are good for street tires, auto x, and road racing?

The word "good" can be a little broad & has different definitions for different people. I'll do my best to add a little tech info on lockers to help you make a better informed decision for what you want.

As long as it's not a c-clip type axle, all passenger car Detroit Lockers sold new today are "Soft Lockers". You can tell because of the SL in the part number. Like a 187SL17B is a "Soft Locker" for a Ford 9" with 31 splines. Eaton no longer offers the "Standard Locker" if they offer a soft locker.

The Soft Locker design utilizes some additional parts in the center that build in preload, so the bang & clunk is less. Still there ... but less than an older design standard locker. Unfortunately for folks with C-clip rear ends, the c-clips are in the way of these additional parts, so Eaton can not make their Detroit Locker in a soft version for c-clip axles. Even if you go to C-clip eliminators, there is no option for a soft locker & a standard locker can not be converted to soft locker. A soft locker can be converted to a standard locker by removing the parts from the center that build in preload, but why would you want to? There is no performance gain.

The preload in the soft lockers does not make them disengage any easier. They still come with 78# springs, just like the standard lockers. The only difference is the degree of bang & clunk. With either standard or soft lockers, you can change the inner springs to different rates. By stepping down in rate ... like we do to the 58# spring ... the locker disengages easier when cornering.

Summary:

• If you have a non c-clip style rear end, like a Ford 9", Chrysler 8-3/4", Dana 60, etc ... and you want to run a locker ... the soft locker will bang & clunk a little less.
• If you have a C-clip style rear end like a GM 10-bolt, 12-bolt or Ford 8.8" ... and you want to run a locker ... the standard locker will bang & clunk a little more.
• Both can be made to disengage easier with lighter springs.

In my experience, nothing is better for durability, consistency & track performance than a locker, if it is set-up right. But their street manners are a little too coarse for some folks.

[Uhcoog1]

I purchased a surplus NASCAR 9" center section from Roush Racing. It came equipped with a Detroit Locker. The locker was so harsh that the car was virtualy undrivable and in fact was down right dangerous as it would push in turns. Traded the locker for a Tru trac and have not had any further issues.

I bought my center from Roush as well, detroit locker 3.60:1 gear. Sounds like I got lucky. My locker is not nearly as harsh as you describe. Actually, I just went in the garage to 'test' it. Lifting one tire and then the other, my locker will 'ratchet' at about 20 ft-lb. I also went out to do a little road testing to refresh my memory on how she feels when driving. If I'm completely off the gas pedal, the rear ratchets quite freely. I couldn't hear if it was ratcheting under moderate throttle (sustaining speed), but at some point (as I just tested on a skidpad) the inside rear starts to squeal and kicking the rear out isn't far behind.

Steve, the challenge with buying a used NASCAR locker is you don't know what springs are in it. We tune the locker with different spring rates from 25# to 125#. The softer the spring the easier it releases when turning. The stiffer the spring, the more it takes to get it to release. On big tracks like Daytona & Talladega the last thing you want is for the locker to release. So they run the 110# to 125# springs.


If you bought a used locker with that much spring rate, it would be a bear to get it to unlock. With street tires, I don't think the tires have enough grip to force those 110# to 125# springs to unlock consistently ... and would on occasion simply slide the tire instead.


For short track ovals, road racing & autoX, the hot ticket is softer springs. I typically like the 58# spring for these applications.






Lockers are the most common & preferred differential in most full size car road racing applications.


They turn left & right equally ... unless ...
a. You have different rate springs on the right & left side.
b. You bought a CTR Detroit Locker, designed for oval track racing that only unlocks turning left. You can tell when you take it apart, because it only has one spring.

That's interesting to hear that a locker is the preferred differential for full size road race applications. I've been reading about how to drive around a locker rear when road racing, but didn't get the impression that many folks preferred them. What's the reasoning on the preference?

In my experience, nothing is better for durability, consistency & track performance than a locker, if it is set-up right. But their street manners are a little too coarse for some folks.

Can you expand on what is the right set-up for a locker rear on a road course?

Additional info on my car that might be useful:
-55% front weight bias, 3620 lb - no driver (bias doesn't change with driver)
-~80% front roll couple, car is a bit on the understeer side on a skidpad with gas just enough to maintain speed (but not sliding rear at all)
-6.9* caster both sides, 2.5* camber both sides, 0" toe. 0* camber on ford 9" floater rear
-Have outer front tire wear. Tire temps on skidpad agree (say, 125 outer, 123 middle, 105 inner after 5 consecutive turns with no heat in the tire before). Rear tire temps on skidpad are good.
-I'm probably losing some camber to body roll

My thought is to add some roll stiffness to the rear to get closer to neutral.

Would really like to know what a locker wants regarding chassis set up and driving style.

Thanks,
Wade