GT40 Transaxle.

Can anyone have, or put in a SADEV SL90-20 trans for a GT40 car just for track? I believe some GT40's have the SADEV SL90-20. The ZFQ/RBT ZF has had too many failures on my car and like many other's, who have experienced the same fate from using the ZFQ/RBT ZF. My car has a 302 Windsor, Webers, with 495bhp, 420ft/lb. I did two laps before it broke, gearbox engineers have told me a ZF will last only two laps, it's a common story. And always breaks on the upshift NOT the downshift. The car will go on the stands until I can find a decent trans.
 

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Hi Warren. Have you considered the Holinger MFT? Australian made and supported, and rated to some ridiculous torque levels for 24hr racing. Mine is behind a twin turbo V8, and they reckon it's well within capacity. Not cheap, but an SL-90 is also in the upper end of the price scale.
 
Can anyone have, or put in a SADEV SL90-20 trans for a GT40 car just for track? I believe some GT40's have the SADEV SL90-20. The ZFQ/RBT ZF has had too many failures on my car and like many other's, who have experienced the same fate from using the ZFQ/RBT ZF. My car has a 302 Windsor, Webers, with 495bhp, 420ft/lb. I did two laps before it broke, gearbox engineers have told me a ZF will last only two laps, it's a common story. And always breaks on the upshift NOT the downshift. The car will go on the stands until I can find a decent trans.
Question Warren... The first time it broke was any research done to check the housing in the areas that have now failed looking for an issue that might have been inherent in the castings & if so the problem was always there. I work on a lot of stuff here in NZ and some of it is Pfitzner, Jerico, G-Force etc. In the Pfitzner gears you could 'see' the tooth markings 'straight cut' with taper wear caused by the housing deflection, Jerico mag housings that distorted the size of the layshaft that could have there life extended by fitting O/S bushings to restore their alignment and center distances. Now most people would regard these trans to be up top strength wise, but these guys were able to break them and in-car footage shows how tough the shifts, up or down, really were. HP/Torque were about 50 down on your numbers. One car has run the same Jericco for nearly 20 years, No failures and been down for a cautionary check twice with only bearing replacement, The guy that drives it has put in many miles in dog box cars and has shifts down to an art. Have you looked at the ALBINS 6 speed transaxle?
 
Question Warren... The first time it broke was any research done to check the housing in the areas that have now failed looking for an issue that might have been inherent in the castings & if so the problem was always there. I work on a lot of stuff here in NZ and some of it is Pfitzner, Jerico, G-Force etc. In the Pfitzner gears you could 'see' the tooth markings 'straight cut' with taper wear caused by the housing deflection, Jerico mag housings that distorted the size of the layshaft that could have there life extended by fitting O/S bushings to restore their alignment and center distances. Now most people would regard these trans to be up top strength wise, but these guys were able to break them and in-car footage shows how tough the shifts, up or down, really were. HP/Torque were about 50 down on your numbers. One car has run the same Jericco for nearly 20 years, No failures and been down for a cautionary check twice with only bearing replacement, The guy that drives it has put in many miles in dog box cars and has shifts down to an art. Have you looked at the ALBINS 6 speed transaxle?
The Quaife ZFQ box has had numerous refurbs over the past 10 years, the recent refurb was done for the gears, mostly synchros and 4th gear. After having that done that at the next track day, the diff blew, when apparently a carrier bearing for the CV fell apart so the diff was completely rebuilt by a Quaife tech. So the ZFQ was pretty new on the insides, I only had a few laps at Eastern Creek to test it before I took it to Bathurst. Two laps in the case broke in half. I'm still waiting for an analysis of what happened. In the mean time I am looking for a better option.
 
Question Warren... The first time it broke was any research done to check the housing in the areas that have now failed looking for an issue that might have been inherent in the castings & if so the problem was always there. I work on a lot of stuff here in NZ and some of it is Pfitzner, Jerico, G-Force etc. In the Pfitzner gears you could 'see' the tooth markings 'straight cut' with taper wear caused by the housing deflection, Jerico mag housings that distorted the size of the layshaft that could have there life extended by fitting O/S bushings to restore their alignment and center distances. Now most people would regard these trans to be up top strength wise, but these guys were able to break them and in-car footage shows how tough the shifts, up or down, really were. HP/Torque were about 50 down on your numbers. One car has run the same Jericco for nearly 20 years, No failures and been down for a cautionary check twice with only bearing replacement, The guy that drives it has put in many miles in dog box cars and has shifts down to an art. Have you looked at the ALBINS 6 speed transaxle?
Yes I looked at Albins and discussed the ABG but it's too long.
 
The Quaife ZFQ box has had numerous refurbs over the past 10 years, the recent refurb was done for the gears, mostly synchros and 4th gear. After having that done that at the next track day, the diff blew, when apparently a carrier bearing for the CV fell apart so the diff was completely rebuilt by a Quaife tech. So the ZFQ was pretty new on the insides, I only had a few laps at Eastern Creek to test it before I took it to Bathurst. Two laps in the case broke in half. I'm still waiting for an analysis of what happened. In the mean time I am looking for a better option.
Could the case have been damaged when the diff blew previously? I feel your anguish over repeated failures. I gave up track days after twice breaking 4th gear on my RBT. I'm not familiar with SADEV, but going to a non synchro box with straight cut gears should be more reliable.
 

Rune

Supporter
Can anyone have, or put in a SADEV SL90-20 trans for a GT40 car just for track? I believe some GT40's have the SADEV SL90-20. The ZFQ/RBT ZF has had too many failures on my car and like many other's, who have experienced the same fate from using the ZFQ/RBT ZF. My car has a 302 Windsor, Webers, with 495bhp, 420ft/lb. I did two laps before it broke, gearbox engineers have told me a ZF will last only two laps, it's a common story. And always breaks on the upshift NOT the downshift. The car will go on the stands until I can find a decent trans.
Go for a Porsche G50 it is strong.
 

Howard Jones

Supporter
I am right at the point of putting together a new motor for my SLC. I am going up 100hp from 435hp/350sbc to a 535hp/406SBC. I called up California motorsports who built my G50. It is upgraded with all the good parts available for a G50 to make it stronger, side plate, steel synchro, and better gears when I changed ratios. I asked Rodger how much power I could put through my GRBX and he looked at my build sheet and told me he was comfortable with 500 ft/lbs. The car weighs 2500ish, runs Hoosiers, and has a Quaife TBD in the GRBX I will tune my motor on the engine dyno to that number. The smaller diameter 7.5-inch R&P in the g50-01-03s is the limiting factor whereas the 9-inch G50-52 is quite a bit stronger.

So that is what I can tell you about a well-built G50 run as a track car GRBX. If I was doing your car with a Porsche I think I would be looking at a G50-52 or a 930 which also uses a 9-inch R&P.

What about the offroad Porsche-derived GRBX's like the Fortin, Albins etc,



Then there are the $$$$$$ race stuff



 
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Neil

Supporter
I am right at the point of putting together a new motor for my SLC. I am going up 100hp from 435hp/350sbc to a 535hp/406SBC. I called up California motorsports who built my G50. It is upgraded with all the good parts available for a G50 to make it stronger, side plate, steel synchro, and better gears when I changed ratios. I asked Rodger how much power I could put through my GRBX and he looked at my build sheet and told me he was comfortable with 525 ft/lbs. The car weighs 2500ish, runs Hoosiers, and has a Quaife TBD in the GRBX I will tune my motor on the engine dyno to that number. The smaller diameter 7.5-inch R&P in the g50-01-03s is the limiting factor whereas the 9-inch G50-52 is quite a bit stronger.

So that is what I can tell you about a well-built G50 run as a track car GRBX. If I was doing your car with a Porsche I think I would be looking at a G50-52 or a 930 which also uses a 9-inch R&P.

What about the offroad Porsche-derived GRBX's like the Fortin, Albins etc,



Then there are the $$$$$$ race stuff



It also helps to keep the car as lightweight as possible.
 
With all this discussion, the much vaunted T44 only has a ~8'' Ring gear and the torque figures were less than those being quoted here for ~302 cu in. They were expected to go for 24 hr's and in the winners case usually driven in a manner that would make sure that happened.
 
I am right at the point of putting together a new motor for my SLC. I am going up 100hp from 435hp/350sbc to a 535hp/406SBC. I called up California motorsports who built my G50. It is upgraded with all the good parts available for a G50 to make it stronger, side plate, steel synchro, and better gears when I changed ratios. I asked Rodger how much power I could put through my GRBX and he looked at my build sheet and told me he was comfortable with 525 ft/lbs. The car weighs 2500ish, runs Hoosiers, and has a Quaife TBD in the GRBX I will tune my motor on the engine dyno to that number. The smaller diameter 7.5-inch R&P in the g50-01-03s is the limiting factor whereas the 9-inch G50-52 is quite a bit stronger.

So that is what I can tell you about a well-built G50 run as a track car GRBX. If I was doing your car with a Porsche I think I would be looking at a G50-52 or a 930 which also uses a 9-inch R&P.

What about the offroad Porsche-derived GRBX's like the Fortin, Albins etc,



Then there are the $$$$$$ race stuff



Thanks for the info, I’m leaning towards a MFT Holinger sequential, it’ll fit in my SPF. The MXT is a bit too long.
 
Probably they put in the ZF for Historics. In the US I think you can race but the ZF and ZFQ aren’t sting rough. They break all the time so fixing them is expensive, time consuming and depressing.
 
Probably they put in the ZF for Historics. In the US I think you can race but the ZF and ZFQ aren’t sting rough. They break all the time so fixing them is expensive, time consuming and depressing.
Perhaps its time to stop all the cheating and make everyone use engine parts that produce 1966 power levels along with tire sizes and compound as used in the day. No, never work would it.... cant believe I just wrote this..
 
Does the use of any transaxle other than the ZFQ or ZF/RBT disqualify the car for use in vintage car racing?
As Ive heard, David Hart uses the RBT for qualifying and the ZF for racing during historic racing.
As Ive heard. both are not up to the job as these days 289's produce way more then back in the days.


RBT Transmissions said:
Historic Restorations / Recreation
If you are constructing an FIA vintage racer and require an acceptable transmission, reproduction of a period-appropriate GT40?

RBT can provide you with approved and appropriate transmissions.
If the transaxle in your BMW M1 or DE Tomaso has worn out, replacement gearboxes are available.
Ill assume the RBT is eligible for historic racing.
 

Rick Muck- Mark IV

GT40s Sponsor
Supporter
Perhaps its time to stop all the cheating and make everyone use engine parts that produce 1966 power levels along with tire sizes and compound as used in the day. No, never work would it.... cant believe I just wrote this..
Jac,
Yes, it is "racing" but it sure ain't "Vintage"! GT350s running here with 8K RPM engines and brakes/suspension that didn't exist in the day. I rather like the Goodwood model with the Dunlop spec tires, less grip, more slip! Makes for very entertaining racing.
 
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