2020 RBT ZF transaxle power/torque ability?

Most of the discussion about GT40 RBT ZF transaxles are more than a decade old. I've been told that the lastest RBT ZF has been "beefed up" and is now capable of handling 600+ HP/Torque in a GT40 under track conditions. However, I see a lot of older posts that say the transaxle longevity is compromised under these conditions. Obviously, you can't take any transaxle with hot, sticky tires and try to spin them up leaving of the pit. Something will break. But, a driver doesn't want to worry about hitting a bump on the straight and having the the transaxle destroy itself.

So, I'm asking the experts. Currently, there is a 12 month lead time at RBT, so an informed purchase is important.

Also, there have been some newly developed transaxles (Supercar System, etc.), that seemed to have fizzled. Anything in the works that will soon come to market? It seems like the market exists if RBT has such a lead time.
 

DaveM

Supporter
My experience with over 500 ft. lbs. torque is an RBT will not stand up to multiple track days with slicks. The weakness is 4th gear.
 

Julian

Lifetime Supporter
My experience with over 500 ft. lbs. torque is an RBT will not stand up to multiple track days with slicks. The weakness is 4th gear.
It would be worth qualifying whether your experience is with running u-joint half shafts or CV axles?
 

DaveM

Supporter
I have an SPF with CV's. I'm not hard on transmissions. The RBT is the only trans I've broken (twice) in 30 years of racing. This includes a SwiftDB4, Brabham BT38, and IMSA GTU Datsun 280Z. Admittedly not as much torque as a Roush 427SR. The RBT sheared 4th gear teeth off after 10 track days each time.
 

Ron McCall

Supporter
I have an SPF with CV's. I'm not hard on transmissions. The RBT is the only trans I've broken (twice) in 30 years of racing. This includes a SwiftDB4, Brabham BT38, and IMSA GTU Datsun 280Z. Admittedly not as much torque as a Roush 427SR. The RBT sheared 4th gear teeth off after 10 track days each time.
What were you using for a clutch??

Ron
 
These are typical of other past reports. Does anyone know if they have improved the transaxle in the last few years? DaveM, what transaxle are you now using, or are you committed to the ZF due to the car construction?
 

DaveM

Supporter
What were you using for a clutch??

Ron
Single plate McLeod #272180R disc which is ceramic puck/fiber combination. Not sure on McLeod pressure plate, but not an excessively heavy one. I'm still using the RBT, but no more track days and no problems in street use. In talking to Lloyd he admitted there is a limit with slicks and over 500 ft. lbs. He cited his Indy car days and the need to inspect and replace trans parts. Easy to do on a Hewland race box, but a lot more work on ZF/RBT. Seeing that the same failure occurred at 15-20 hrs. of track use kind of reminds me why Ford went with the T44 for 24 hour races.
You've seen a lot of ZF/RBT's Ron- what's your experience with track use/high torque?
 
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Eric B

Eric
Like Bigfoot, there are only rumors of the elusive 2020 RBT ZF transaxle. No one has ever seen one. :p

E
 
Spoke to the mecanics of David Hart last year and they also confirmed the RBT will break.
They use the RBT for qualifying and swap box for racing.
 

Bill Kearley

Supporter
600 HP with RBT from Griffin 5sp transaxle, Porsch 930 CV shafts and a Spec clutch, I hope this stuff lives! If I did it over, I like the McLeod twin disc.
 
Hi. Iv'e been watching classic GT racing from Goodwood in England. These GT40's of old are really getting a good work out. So what transmission are they using? what is the best trans strictly for track use?
 

DaveM

Supporter
Hi. Iv'e been watching classic GT racing from Goodwood in England. These GT40's of old are really getting a good work out. So what transmission are they using? what is the best trans strictly for track use?
The vast majority of GT40's running at Goodwood are Mk1 with 289c.i. Ford and ZF trans. I do recall a couple of Mk11's in 2013, but they have T44 trans. Even replicas of T44's are almost unobtainable. ZF (and the RBT replica) can handle the torque of a racing 289, but they're marginal for the 427. If you want to do track days with over 500 lb. ft. of torque I would look at a Hewland or Ricardo trans. The Hewland is a true racing box with dog gears and quick accessibility.
 
Thanks for your reply Dave. Is the Hewland still available and from where? Are you thinking of a particular model? The Ricardo you refer to is that the same as the 2005 /2006 modle GT?
 
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