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Wilkinson has an effort underway to reproduce transaxles for Panteras, GT40’s, and similar cars. The new transaxle is called GTT (Gran Turismo Transmissions). One of the components in the new transmission is the differential and he already has some of them in hand. He opted for a differential with a higher level of performance. They are 70% locking versus 40% that came in our cars. The GTT differential uses special clutches and beveled washers under high pressure to get the extra locking.

He needed to test his new differential and asked if I would be willing to put one into my 74 Euro Pantera.  I agreed and we planned out the swap.  I pulled the transaxle from my car and took it to his shop and prepared it on a special stand for the new GTT differential .  The next day they had the differential installed in my ZF case within a couple of hours.  I took my ZF back home, put it back in the car, and have been driving it since then.

Thus far, the new GTT differential has two notable characteristics compared to my 50 year old unit.  The first thing I noticed is that a bunch of slop was gone.  Previously when driving at slow and steady speeds the car tended to lunge.  Wilkinson examined my old differential and noted that the clutches were worn (.050” on one and .060” on the other), and there could be wear on the spider gears as well.  The other thing I have noticed is the increased locking that is now 70%.  The car feels more sporty with the improved traction.  

Here are photos of the new differential.  The last photo shows it installed in my ZF.



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I wish him luck. This isn’t a trivial undertaking. I wonder which manufacturer he’s working with? I know Holinger has been working on a ZF direct replacement for a few years now. Quaife has been trying to perfect their ZF replacement box for over a decade. I know of one in a Pantera race car but they’ve had lots of problems with it, mostly related to heat and the “flipped” orientation of the gearbox in a Pantera. Hopefully Quaife will get their reliability issues resolved and the ZFQ becomes a viable option.

I have been driving with the new differential for about a month now and it is proving to be a good improvement to the car.  Cornering is better than before. Burn outs (I don't do a lot them) launch straight ahead and leave parallel lines of rubber.  And, as I wrote earlier, slop in the transmission is reduced and lunging at slow, steady speeds has essentially gone away.  The car has an aluminum flywheel by Centerforce and I learned yesterday from Tommy Hodges that it can contribute to the low steady speed lunging problem.

I learned yesterday from Tommy Hodges that it can contribute to the low steady speed lunging problem.

Steve, I’ve heard that before but not sure it’s the case. Not only do I have an aluminum flywheel but I have a 152 tooth flywheel and lightweight aluminum pressure plate. I also have a lightweight crank damper and a lightened steel crankshaft; all in an effort to let the engine rev as quickly as possible. I have zero lunging issues and can drive my Pantera onto a trailer perfectly smoothly. I believe the lunging issues some people experience are actually a tuning issue, nothing more.

@davidnunn posted:

I have zero lunging issues and can drive my Pantera onto a trailer perfectly smoothly.

David, my driveway is steep and it is pretty much like driving the car up into a trailer but I have never had a problem with that. The car has always driven smoothly up into the garage.

The problem that was fixed by the new differential occurred when driving  through my neighborhood in second gear at a steady 20 MPH and the car would consistently start to “bunny hop” as Tommy Hodges described it. I have had five Panteras and this is the only one that has ever done such. Tommy was thinking that the aluminum fly wheel initiated the hopping and at this point I am thinking the worn out differential amplified it.  He said that two Panteras with aluminum fly wheels that he has worked on were bunny hoppers.

The hopping problem with my car as described above is now fixed.

Is your ZF newer or perhaps thoroughly rebuilt, including the differential?

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