Another which differential thread with new questions

[Chris B.]

Sometime in the next month, I'm getting rid of the 4.10 gears and going back to the stock 3.55 gears. I loved the 3.55 gears in my `08 GT for most of the tracks I've been to and the 4.10's are starting to get really annoying for both track days and daily driving.

While I have the diff apart, I was going to either get the stock traction lock rebuilt with the gt500 carbon parts or replace the LSD completely. My questions are:

1. Will a torsen type LSD noticeably affect the handling of the car compared to the T-lock with carbon clutches?

2. Will a torsen type LSD actually help acceleration out of the corners compared to the T-lock with carbon clutches?

3. Will the car be more predictable with a torsen type LSD compared to the T-lock with carbon clutches?

4. Are the Wavetrac and Quaife the only truly reliable and useful torsen type LSD's we have left as options for our cars?

Yes I know the Quaife for the Ford with 31 spline 8.8" diff is out of production and requires an order of 15 or more to restart production and it would take at least 6 months to get the diff after its ordered. I've seen several T2's and T2R's break in cars without drag racing use and heard of many others wearing out prematurely since they changed materials in 2003. I've also seen photos and heard of people here having the Detroit Trutrac LSD's that wore out prematurely and it seems their bias ratio isn't all that great for AutoX and track use. That's why I ask about the Wavetrac and Quaife.

 

[kevinatfms]

Auburn Pro 8.8 31 Spline. I had worries also and so far it has worked wonders. They also have a program that they will replace the unit in case of a failure for 1 year, and for 3 years after they have an exchange program where you just pay for labor.

only gripe is once in a while it can get noisy (clutch slip while trying to lock) during very tight parking lot maneuvers on sticky tires.

 

[Whiskey11]

Sometime in the next month, I'm getting rid of the 4.10 gears and going back to the stock 3.55 gears. I loved the 3.55 gears in my `08 GT for most of the tracks I've been to and the 4.10's are starting to get really annoying for both track days and daily driving.

While I have the diff apart, I was going to either get the stock traction lock rebuilt with the gt500 carbon parts or replace the LSD completely. My questions are:

1. Will a torsen type LSD noticeably affect the handling of the car compared to the T-lock with carbon clutches?

2. Will a torsen type LSD actually help acceleration out of the corners compared to the T-lock with carbon clutches?

3. Will the car be more predictable with a torsen type LSD compared to the T-lock with carbon clutches?

4. Are the Wavetrac and Quaife the only truly reliable and useful torsen type LSD's we have left as options for our cars?

Yes I know the Quaife for the Ford with 31 spline 8.8" diff is out of production and requires an order of 15 or more to restart production and it would take at least 6 months to get the diff after its ordered. I've seen several T2's and T2R's break in cars without drag racing use and heard of many others wearing out prematurely since they changed materials in 2003. I've also seen photos and heard of people here having the Detroit Trutrac LSD's that wore out prematurely and it seems their bias ratio isn't all that great for AutoX and track use. That's why I ask about the Wavetrac and Quaife.

1.) Yes it will have some impact on handling bias because clutch type differentials will induce some understeer as the clutch packs try to lock the wheels together and it will do so on acceleration and deceleration. Torsen type differentials don't ever lock. They torque bias which sends the power to the wheel with the most traction at a ratio of whatever the torque bias ratio is. For a T2R that ratio is 4 times the power delivered to the wheel with the least traction. I have heard it feels like the car wants to oversteer but doesn't actually break loose.

2.) I would think this depends on the car setup some as a car that gets the inside rear light enough will be faster with a clutch based differential than a torque biasing differential since the wheels are constantly trying to lock with the clutch packs. Grassroots Motorsports said in their OS Geiken test vs the stock miata Torsen that the OS felt like it put down the power better but the Torsen slalomed better and at the end their miata was .30 seconds quicker with the Torsen for autocross.

3.) I would think so. For sure the gear differentials are more consistent over the long term as their wear rate odds significantly slower than any clutch differential is.

4.) There is also DPI that Griggs racing uses.

Disclaimer: I only have experience with the stock differential so I am speculating based on information I have read from various websites and magazine articles.

 

[jymontoya]

I've driven on track...

A stock T-lock.

An extremely tight rebuilt T-lock with carbon clutches (GT500 style).

A Torsen T2R.

And now a Wavetrac.


What I learned...

A stock T-lock is fine for street tires, but as soon as you put sticky track tires on there, it will just burn up in less than a day on track.

A rebuilt, tight, carbon clutched T-lock isn't much better, as it only lasted 2 weekends on track with R-comps.

A Torsen T2R is an incredible upgrade for tracking. The ability to put the throttle down so much earlier without the backend drifting is nothing short of amazing. I really didn't know a rear wheel drive car could put the power down so early... And that was on the old 4 link + PHB setup my '97 Cobra had. I don't know about long term reliability since I sold the car shortly after. I do know that Ford Racing offering the Torsen T2 as well as the T2R has to say something. I would like to think that they worked out the metallurgy issues years ago since you really don't hear about them failing. Maybe go over the the Boss forums and talk to those guys?

The Wavetrac... A very similar experience to the T2R, but with a few nuances. I'm still getting used to the grip available on early throttle corner exit. It's truly like driving a different car. On slower, tight corners where the inside rear usually gets more or less unloaded and a typical diff applies no power, I can 'feel' the Wavetrac work here, almost a slight pulse or something as the outside gains more power and helps to rotate the car, but not only that, I can also tell the inside wheel is no longer rapidly free spinning. The T2R did this as well to an extent, but whenever I fully unloaded a wheel with the T2R, you had to wait for it to become loaded again before power was really being put down again. I went with the Wavetrac over the T2R this time for the warranty, and well, as an early adopter, have already paid the price.

You see, Wavetrac provided 2 different sized C-clips for the install, one .5mm ID narrower than the other. You are supposed to use the tightest fit. My installer (at a big time Mustang shop), unaware to anyone else, ran in to trouble with the C-clips, and damaged the tighter ones trying to install them. He took it upon himself to try and 'narrow' the others and install them anyway. Well, with less than 100 street miles, my first track day out quickly ran into problems. After warming up and starting to get a feel for the new setup, I started to get more aggressive and took the race line, hitting the T3 curbing at Road Atlanta. My ABS and Traction control lights turned on. I took it easy for the rest of the lap and pitted. A quick search showed the likely fault was an ABS sensor, so I cleaned everything and double check the connectors. Reset the ECU, and went for a test drive, everything seemed OK, the lights were off, and I decided to go out for the next session. After a couple warm up laps, everything still seemed OK, and I started to push it again, I'm not sure this time where the LIGHTS CAME BACK ON, as I was in some 'fun' traffic (See GT3's), but I noticed once I had some space on the back straight, at about 120 mph. Knowing I needed to pit, I lifted and gave a couple point bys... then braked coming down the hill for T10a...

Almost Disaster! The rear pinched and locked up, sending me spinning straight off the corner. When the dust settled, I was pointed exactly 90* toward T10b, only a few feet off track, no contact with any walls, and I even lucked out of hitting the gravel trap! Checked with the corner worker behind me and gave a thumbs up and after cleared, headed to Pit... SQUEEK! SQUEEK! Rear, Brakes? were screaming. I pulled it apart to see what was going on. I could tell the rotors CONTACTED the caliper cradle. When I pulled the rotors, the axle moved A LOT. When I pushed and then pulled on the hub/axle, the whole axle CAME OUT. Checked the other side... Same thing. I think to myself, "You mean the caliper bolts were the only thing holding the wheels on the car?!" I counted myself lucky the 'incident' wasn't worse and went to see the Installer. Apparently the guy that did the install no longer worked there... unlrelated... but after the owner tracked him down, he admitted to the botched install, and the the shop went about taking it apart to see what's what. The c-clips were in the bottom of the housing floating in oil... yay. A quick call to Wavetrac with the part # for the tighter clips in hand, and they tell us that they no longer make those! WHAT?! Apparently they had a lot of issues with them and redesigned them into a new C-clip design, with a wider thickness and much tighter fit. Great, we'll send those on there way... A couple days later, the car was back together and better than ever. The shop made it right, and now has some more experienced staff with Mustang road race setup knowledge. I can't get back the missed track time, and I ended up bending and cracking the two front wheels in the 'Off', but I'm thankful it wasn't worse!

It's unfortunate that Wavetrac and Moser did not contact early purchasers to the design change of the C-clips, had they done so, this probably wouldn't have happened. The same can be said for the Mustang shop, had the installer made aware any issues, we could have called Wavetrac then and found out then and gotten the new C-Clips.

That's my story. For better or worse, it looks like I'll be with the Wavetrac for the long term. It's performance is great, and it's makes no added noise (no rear interior + heim joints everywhere isn't quiet anyway). If I run into more issues, atleast I know it's covered.

 

[martin_nj]

the wavetrac is really appealing - what did you pay for it JY?

 

[Vorshlag-Fair]

Wow, scary story about the WaveTrac install. Yikes. I talked with the WaveTrac guys at PRI and SEMA and really liked the idea of their 8.8" diff, but I didn't want to be an early adopter - because so often something unforeseen like that happens.

I too have driven on a few different differentials in an S197 (stock T-loc, T-loc with Carbon Clutch Pack Upgrade, Torsen) and have been on the fence all year about which diff to buy. I killed the stock T-loc within a year of autocrossing it on street tires. The clutch material was literally falling off the discs.

The new part kit from Ford was very affordable. I wanna say it was around $100 for the M-4700-C kit. We did the swap here at Vorshlag and have since done a few more for other S197 folks. This is a TSB / SCCA legal upgrade for thew 2006-2007 Mustang Shelbys for F Stock but isn't allowed in F Stock class for other year S197s, btw. Of course it is legal in STX or ESP, so we did it when the R compounds destroyed the stock T-loc.

As you can see the clutch material looks very different than stock, and it is set-up with more preload. Big improvement on track and in autocross, but you can feel it and hear it groan in tight parking lots, and it will add a tick more understeer on corner entry and oversteer on corner exit. After a few months of use I have started to notice it slipping more and more, so it's days are numbered.

I want to try something new, as I am tired of getting into situations like this above. So I'm going to use the Torsen T2-R on our 2013 GT (autocross use) and I might try the WaveTrac on the 2011 GT (track use). But jymontoya's experiences with the $1000 WaveTrac have me worried. The T2-R is about $700 or so from online sources, and I know a LOT of racers who swear by these.

Decisions, decisions...

 

[jymontoya]

Terry-

With your high profile build and vendor connections, I'd just call Autotech and talk to them about the Wavetrac for the 8.8. Install issues aside, after driving the Wavetrac aggressively in the wet, I'm sold.