Rebuild Trac-lok vs Torsen upgrade

[ShifterX]

The limited slip in my 2011 GT is gone. Any lateral loading creates a one wheel peel. On the lift, spinning one wheel creates no movement in the other. Other trac-lok cars, both wheels spin the same direction. This car behaves like its full open.

Option one, replace with a Torsen or tru-trac. Obviously next level performance. Next level expense as well. Cost for parts not really a concern, more labor. I am capable, but don’t really want to take on setting up the gear depth and backspacing. Don’t have the tools either. Really not sure on labor, guessing at least $500. Plus all the parts

Option two, rebuild the trac-lock without pulling the diff apart. I feel I can do this comfortably. Small upgrade with the carbon plates. Parts about $100. No where near the performance of the Torsen but much better than what I have.

My car is HPDE, my skill level is intermediate. I know the Torsen is way better. I have read the Billy Johnson articles. My question for those that have used both a fresh trac loc and a Torsen. Is the Torsen worth 10x or more in price.

Or maybe a better way to put it. If the Torsen is a 10 and an open diff is a 0, what is a fresh trac-lok?

 

[Dave_W]

You need to factor in repeated rebuilding of the Trac-Lok, as it will always wear out the friction rings - the carbon fiber rings just last longer. A top-level autocrosser would rebuild his every year before Nationals.

 

[ShifterX]

Makes sense. I am not racing just HPDE, so I don't need absolute peak performance. Also, no auto-X, just open track. What I am trying to get a sense of is the functional performance of a 100% (new) trac-lok vs a torsen. Also, how long a rebuilt TL can deliver near max performance. Will it be wasted after 1 track day? If yes, that is a certainly not good ROI.

Thanks,

 

[SMGDHG]

Having gone through your exact dilemma, my recommendation would be go eaton. What tire (compound and width) are you running? This has a large impact on track lok vs eaton vs torsen. For me a freshly rebuilt traction lok did not have enough bias ratio to lock up both wheels when I went to 315 200tw tires. Therefore, it was a total waste of money getting it rebuilt. I did the whole "upgraded" clutches thing and the shop said they would pack it in such a way that it would lock harder. Didn't work. With the stock wheels and tires the trak lok performs pretty well but does need to be rebuilt. Once you put proper rubber on the car the traction lok becomes a paperweight IMO.

I have an eaton in the car now and it's been great.

 

[stevbd]

@ShifterX I went from a functioning OEM trac loc to an Eaton in my 2011 GT. Similar to you, I usually run in advance level HPDE and my car is daily street driven.

In that context, I found the Eaton to be a noticeable but not transformational improvement. My lap times before and after were similar and within the noise of me and my car. I'm sure the torsen is measurably faster for an experienced racer. Subjectively, the rear end feels more planted and predictable with the torsen, it stays behind you better through all three phases of the corner. Wanting to avoid too much confirmation bias, I guess I would say that was a noticeable improvement but not wildly so. I probably felt as much or more improvement in terms of rear stability by removing the rear sway bar as I did by installing the Eaton.

Billy J talks about the disadvantages of an upgraded clutch kit in his article, as you probably saw.

So to answer your original question, I guess I would put a functioning OEM trac loc somewhere around a 7 to 8 on your scale. If you are working on a budget (aren't we all), I would consider just installing a new OEM trac loc clutch kit given how you describe your use case.

 

[stevbd]

For me a freshly rebuilt traction lok did not have enough bias ratio to lock up both wheels when I went to 315 200tw tires. Therefore, it was a total waste of money getting it rebuilt.

I'm not understanding this comment. An Eaton or Torsen won't lock up both wheels either, quite the opposite, no? I think that is their biggest advantage.

 

[EF1]

I rebuilt the trac loc in my 2011 with carbon clutches once. It needed it again after a couple of years. Replaced it with a true trac and couldn’t be happier. Better acceleration out of the corners and lower rear diff temps. Also doesn’t need friction modifier. Thst stuff is vile.

 

[Mad Hatter]

Never had anything but a Torsen on my car. When a new mustang would arrive at the track the first thing I would as is if they upgraded the diff. If not, then you know his lap times would not be competitive. Its part of the secret sauce of these cars.

 

[blacksheep-1]

IMO the T2 represents a significant boost in performance. I would def do that, as I'm not a fan of the Tru Trac, but some guys swear by them.

 

[RodS197]

I used a Trac-Lok until my HPDE 4 days (2006 Mustang GT) when I replaced it with a Torsen T2R. At that point in my driving I noticed a huge difference, some under braking and most from apex to exit. The Torsen (I don't have experience with the Tru Trac, but the function is the same) will literally drive you around the corner as it puts power to the outside wheel (the one with more traction). My Trac-Lok would push me through the corner as it drove both wheels, I would have to lift sometimes to make the track out. Under braking the Torsen acts like an open diff, so it doesn't fight the rear axle at turn in or under trail braking.

If you aren't worried about the money, spend a little more now and get the Torsen/Tru-Trac. I had about 4 years on mine T2R before I sold the car, and I have 3 years on my current car (2014 Mustang GT) with the same diff. It will be great in the long run and the car will handle better as you progress.

 

[ShifterX]

Having gone through your exact dilemma, my recommendation would be go eaton. What tire (compound and width) are you running? This has a large impact on track lok vs eaton vs torsen. For me a freshly rebuilt traction lok did not have enough bias ratio to lock up both wheels when I went to 315 200tw tires. Therefore, it was a total waste of money getting it rebuilt. I did the whole "upgraded" clutches thing and the shop said they would pack it in such a way that it would lock harder. Didn't work. With the stock wheels and tires the trak lok performs pretty well but does need to be rebuilt. Once you put proper rubber on the car the traction lok becomes a paperweight IMO.

I have an eaton in the car now and it's been great.

285 200TW is the plan. I am looking for more of a long wear kind of 200TW like maybe the GY SC3. I am not looking for a RE-71 type tire if that makes a difference.

Paperweight is not very encouraging.

 

[ShifterX]

@ShifterX I went from a functioning OEM trac loc to an Eaton in my 2011 GT. Similar to you, I usually run in advance level HPDE and my car is daily street driven.

In that context, I found the Eaton to be a noticeable but not transformational improvement. My lap times before and after were similar and within the noise of me and my car. I'm sure the torsen is measurably faster for an experienced racer. Subjectively, the rear end feels more planted and predictable with the torsen, it stays behind you better through all three phases of the corner. Wanting to avoid too much confirmation bias, I guess I would say that was a noticeable improvement but not wildly so. I probably felt as much or more improvement in terms of rear stability by removing the rear sway bar as I did by installing the Eaton.

Billy J talks about the disadvantages of an upgraded clutch kit in his article, as you probably saw.

So to answer your original question, I guess I would put a functioning OEM trac loc somewhere around a 7 to 8 on your scale. If you are working on a budget (aren't we all), I would consider just installing a new OEM trac loc clutch kit given how you describe your use case.

Appreciate this. Obviously not saying much but my car is the best handling solid rear axle car I have driven. What I mean by that, is the rear axle does a surprisingly good job of hooking up even with a near open diff. I am currently running no rear bar and still have plenty of setup work to do but the foundation is there. Drive out of the corner is not great but better than expected.

In my mind I was thinking I would rebuild the TL if it was a 3-5 on my 0-10 scale. 7-8 would be a pretty good ROI. Of course I may spend all summer on the track and come away craving the extra 10ths an Eaton/Torsen would give me. But a refreshed trac-lok gets me out there quick and cheap.

 

[stevbd]

Obviously not saying much but my car is the best handling solid rear axle car I have driven. What I mean by that, is the rear axle does a surprisingly good job of hooking up even with a near open diff.

Set up right, putting power down off the apex is the S197's secret weapon. Google the Phoenix cars if you haven't already. Awesome stuff.

I agree with others here that a torsen/eaton is definitely better than a trac lock. @RodS197's description is how I feel about mine and I agree that if you can find the budget it is a good upgrade that you can grow into. But where you have a failed diff and no LSD at all, are running intermediate HPDE, learning the car, and are on a budget, I think pretty clearly your maximum ROI will be to repair the stock setup. That will get you from zero to a B+. Good luck

 

[DaveW]

When my car was in street class autox trim, I actually had to rebuild the trac loc 2-3x per year even with carbon clutches.

Regardless, what I always disliked about the stock diff, whether it was fresh or not, and whether autocross or track days (I used to do) was the inconsistency from cold to hot and then from fresh to worn. It drove me nuts. Torsen fixed all that.

My main point in posting, however, is about the diff install. I won't say it is easy, but I install a decent amount of ring and pinions and more importantly, differentials at my shop. Not 10 a week, but probably 10-20 per year. I cannot remember the last time any diff only install, on any kind of axle, needed any shim changes. Get new bearings, find someone to press them on the new diff, remove old diff keeping track of which shim comes off which side, put new in with new races and slap it back together.

DaveW

 

[ShifterX]

When my car was in street class autox trim, I actually had to rebuild the trac loc 2-3x per year even with carbon clutches.

Regardless, what I always disliked about the stock diff, whether it was fresh or not, and whether autocross or track days (I used to do) was the inconsistency from cold to hot and then from fresh to worn. It drove me nuts. Torsen fixed all that.

My main point in posting, however, is about the diff install. I won't say it is easy, but I install a decent amount of ring and pinions and more importantly, differentials at my shop. Not 10 a week, but probably 10-20 per year. I cannot remember the last time any diff only install, on any kind of axle, needed any shim changes. Get new bearings, find someone to press them on the new diff, remove old diff keeping track of which shim comes off which side, put new in with new races and slap it back together.

DaveW

Hold on a second here. Are you saying it’s possible to just swap out the oem diff without resetting the pinion depth and backlash? Just by using all the same parts, minus the diff? Are you saying to transfer the carrier bearings to the new diff?

If true, I would definitely try this. Other than the LS, my axle is fine. I could find someone to press on the new bearings and I can reassemble everything myself.

 

[DaveW]

Hold on a second here. Are you saying it’s possible to just swap out the oem diff without resetting the pinion depth and backlash? Just by using all the same parts, minus the diff? Are you saying to transfer the carrier bearings to the new diff?

If true, I would definitely try this. Other than the LS, my axle is fine. I could find someone to press on the new bearings and I can reassemble everything myself.

100% on pinion depth. You aren't removing the pinion when you change the diff so the pinion depth won't change and that is what sets most of the pattern.

The backlash is set by the shims between the case and the diff carrier bearings. I don't think I have ever had a 8.8 need different shims from just a diff change. Assuming it is on the OEM ring and pinion, it will probably be thick one piece shims, but regardless make sure that the cap and shim from the left stays on the left and the cap and shim from the right stays on the right. And the shims will be tight to put back in, you might have to use a hammer to get it all back together...this is the preload on the carrier bearings.

However, you will want new diff/carrier/side bearings. You will never get the old ones off without damage and new are cheap.

Diff work is not super hard, just take your time and don't overcomplicate it. I'd put it at a 5-6 on a difficukty scale of 1-10

DaveW

 

[JDee]

Torsen is good, but it's not bullet proof. If you're hard core you need a cooler on it. Especially true with tracks that have high speeds. I used to get axle overheats with my '16 regularly on hot days. And this is in the great white north, I can't imagine how these things live in the south. Eventually the heat killed the diff. Not the biggest thing in world, but up here a new Torsen was going to cost $3K plus install. In retrospect, a cooler would have been a sharp investment the moment I started taking the car to the track. Thankfully, the Mach 1 comes with factory coolers on everything.

 

[EF1]

Torsen is good, but it's not bullet proof. If you're hard core you need a cooler on it. Especially true with tracks that have high speeds. I used to get axle overheats with my '16 regularly on hot days. And this is in the great white north, I can't imagine how these things live in the south. Eventually the heat killed the diff. Not the biggest thing in world, but up here a new Torsen was going to cost $3K plus install. In retrospect, a cooler would have been a sharp investment the moment I started taking the car to the track. Thankfully, the Mach 1 comes with factory coolers on everything.

The OP has a S197 not S550. The solid axle in the S197 is not as prone to overheating. The housing holds more fluid and the axle tubes dissipate heat better.

 

[TA28]

The torsen 2r I've used in 3 different rears. I like them and yes t2r are expensive. New rear I am going Detroit locker. May reason is see if there difference from t2r.
Also the Detroit locker are rebuildable and parts are available the torsen's either t2 or t2r are NOT rebuildable nor do they sell parts for them. Just a thought.

 

[JDee]

The torsen 2r I've used in 3 different rears. I like them and yes t2r are expensive. New rear I am going Detroit locker. May reason is see if there difference from t2r.
Also the Detroit locker are rebuildable and parts are available the torsen's either t2 or t2r are NOT rebuildable nor do they sell parts for them. Just a thought.di

When the Torsen went on my '16 I was able to order, and I received, a complete Torsen diff for it from the local Ford dealer. It cost ~$2K in Canuck mini bucks. Then I decided to trade that car on the Mach 1 and I left the replacement Torsen (uninstalled) with the Ford dealer as part of the deal. I saw the replacement diff for it, so they are available. As I recall, it was in a red canister type of thing and did not look anything like any diff I have ever seen before. Looked like this picture, only the body of it was red.