Wavetrac Differential Technical Info for GT

[EXP Jawa]

The diff will fit the 3.31:1 to 4.09:1 ratios. If you get one to install in your car, you'll have to change to another ratio just to be able to do the install. I've posted this elsewhere, but the 3.15:1 gear set has a different ring gear flange position on the diff case and is not compatible.

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[beefcake]

The diff will fit the 3.31:1 to 4.09:1 ratios. If you get one to install in your car, you'll have to change to another ratio just to be able to do the install. I've posted this elsewhere, but the 3.15:1 gear set has a different ring gear flange position on the diff case and is not compatible.

yep, 3.15 just won't get it done

leave it to ford to make something different.....

 

[Evilwill]

The diff will fit the 3.31:1 to 4.09:1 ratios. If you get one to install in your car, you'll have to change to another ratio just to be able to do the install. I've posted this elsewhere, but the 3.15:1 gear set has a different ring gear flange position on the diff case and is not compatible.

So basically wait til the 4.09 are out to use this diff?

 

[beefcake]

So basically wait til the 4.09 are out to use this diff?

if you have 3.15s now and are not wanting to wait, yes

 

[EXP Jawa]

That's what I'd if you're planning on going that direction anyway - do the install once. No point in buying two sets of gears, right? I have to believe that the gears will be out before too long...

 

[L8APEX]

@beefcake still in stock?

 

[WD Pro]

Only in general terms, as I have never had a Wavetrac in my hands to study it closely. On a very basic, fundamental level, they are both the same class of product - a parallel-axis, helical-gear differential. Beyond that, there are a lot noticeable and more subtle differences.

The biggest is that Wavetrac adds the mechanism to the center that is intended to provide some lockup when one tire is completely unloaded. I can't attest to its effectiveness, though I have no doubt that Wavetrac will tell you it works well. It at least looks clever. I'm not sure how it comes into play when both outputs are loaded, especially when transitioning between operating modes, or what it does when supporting side gear thrust-in loads. If it does what it is supposed to do, then it is a neat trick indeed.

Once past that, the most significant difference is the layout of the actual gear package. Wavetrac's design appears to mesh the element gear pairs together in the center, and each meshes with a side gear on the outboard ends. This is similar to Quaife, GKN, etc. A Torsen T-2 rearranges that somewhat, giving the element gears two or three mesh transfers, with the side gear mesh in the middle. This is done to balance the tipping load on the gear, which in turn reduces the PV loading on the gear bore in the differential housing. It reduces that load enough that housing no longer needs to be made of steel to withstand the load. Instead, ductile iron is perfectly reasonable. The tradeoff is somewhat less overall friction, and lower locking effect. Torsen can make up the friction elsewhere, however, and is very tunable for locking effect. The other drawback to the Torsen arrangement is that it requires more axial space to package. Fortunately, the Super 8.8 has axial length in spades.

If we look at the gearing itself, it is a matter of gear geometry, material, face width and number of element gears in the system that determine locking performance and strength. I know that the Torsen is tuned to exactly what performance characteristics that Ford vehicle dynamics wanted (the PP diff is tuned for autocross and open track use, whereas the GT350 Torsen is strictly tuned for track use). I also know that the differential far exceeds the strength requirements as set down by Ford. Impact testing has typically required multiple axle shafts to finish because the spline shaft snaps off the CV tulip. OTOH, I can't comment at all about Wavetrac's design targets for either criteria; they may well be stronger, but I have no idea what their design bogies were. They do use a more premium alloy for gear steel (9310). Although this adds cost, it does improve overall toughness and is less prone to crack. 9310 is often used in gearing when the torque requirement has outstripped your ability to add mesh length, or the geometry is fixed, but you need more out of it.

Locking performance is more subjective to use and need. If I were guessing, I think that their torque bias ratio (TBR is the metric in which locking effect is quantified) is probably fairly similar in drive mode to the Torsen, but higher in the coast mode (coast mode TBR was kept low on the S550 Torsen to improve turn-in). That is, however, a guess based on general experience with that gear configuration - I will reiterate that I've never had their part in front of me to compare. Perhaps Wavetrac will tell you what their product's TBR values are.

This is real interesting info and has raised a few questions that I hope you can answer

A) You mention that the PP and GT350 Torsens are set up differently, what handling traits vary based on which setup is selected ?

B) If you bought a Torsen from Ford Performance (only one part number), do you get the PP or GT350 setup ?

Any info would be really appreciated

Cheers,

WD

 

[TeeLew]

I think for road course work, you'd still be hard-pressed to beat the OS Giken, but this might be a good alternative for a "set it & forget it" scenario. It looks as if it might have some handed characteristics.

 

[Scootsmcgreggor]

I think for road course work, you'd still be hard-pressed to beat the OS Giken, but this might be a good alternative for a "set it & forget it" scenario. It looks as if it might have some handed characteristics.

Why do you say a clutch plate diff would be preferable to a Torsen for road course lapping?

 

[Scootsmcgreggor]

Right. Though once its locked it can't bias. Is torque biasing less valuable than people give it credit for?

 

[TeeLew]

Right. Though once its locked it can't bias. Is torque biasing less valuable than people give it credit for?

I think that might be one of the issues which creates too much heat in the Mustang rear end. In my experience, it seems like torsen diffs just never really stop internal slip/differentiation. Because of that, they produced more heat than other options.

If your were to have a plate differential with a very loose setting, it would provide a lot of slip for a short period of time, then the wear would create too much lash in the plates & it would turn into an open.

The Giken has a ramp & plate design which gives it a lot more clamping force than one that just uses the side gears, like a Traction-Lok. When set correctly, it will differentiate when off throttle/braking, but once over about 10-15% throttle it will be locked as solid as a spool.

There are issues with having it locked solid. The way in which it transitions from slipping to locked is important. It will tend to induce understeer on throttle, but that's a positive when you're driving it correctly. It might slow full-throttle direction change, but, again, that's usually a positive. Having the ability to run different locking characteristics on coast/drive, having the ability to vary lock up amount/timing and having the ability to vary preload (probably the biggest tuning tool in a differential) makes the Giken a powerful tool, but also one which can cause a fair bit of confusion. I can completely appreciate why someone would choose a less complex, but still very capable option like the Wavetrac.

There's nothing magical about fully locking the diff. If there were, we'd all be driving Detroit Lockers. Having said that, there is are tangible gains if you can do it in a beneficial manner.

Having said all this, I'd still like to put a spool on for track-only duty. I bet it would be reasonably good (possibly very good) and it would reduce rear end temps, no question. Driving it on the street would be enough of a chore, though, that I doubt I'd do it in my car.

 

[RoadCone]

Wondering if this has been updated or old information. States can only be used with 3.31, 3.55 and 3.73 gears (Ford ratios). Now the gear selection has expanded in recent years and was curious if it works with the Richmond/Strange 3.91 gearsets?

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