ZFQ trans, is it too harsh for a Triple pate Race clutch?

I'm running my GT40, a race 302 engine in supersprints and track days. The ZFQ has been munched again but have recently been told that Quafie has upgraded and redesigned the internals, they said it should now be ok. Before I put the car back together should I keep the Tilton triple plate race clutch or put in a twin plate to be less hard on the transaxle?
 
How much power/torque are you putting through it to require a triple plate?
It also depends on how strong the pressure plate is that you have and what type of clutch disks etc. Obviously aggressive and fast shifting and clutch dumping is going to shock load the gearbox a lot with a harsh clutch.

Quaife modified the internals because of a shifting/gear selecting issue, not sure exactly what they did.

I’m going to be running a ‘stage 1’ Kennedy organic twin on my build, 402ci 600-650hp 550ish torque. Street car however so different usage.
 

Julian

Lifetime Supporter
The clutch only serves to engage or disengage the drive and transmit power, it in itself has little bearing on the transaxle except for the manner in which the clutch is used. If your practice is to drop the clutch, fast shift or shift without full clutch disengagement then that will stress the transaxle, but a different style clutch is unlikely to compensate for those practices, unless you believe you are not getting full disengagement because of the design of the existing clutch.
 

Ian Anderson

Lifetime Supporter
Supporter
Do you use rotoflex couplers on the driveshafts or CV’s at both ends. The Rotoflex will help take up shock loading over kerbs etc.
 
How much power/torque are you putting through it to require a triple plate?
It also depends on how strong the pressure plate is that you have and what type of clutch disks etc. Obviously aggressive and fast shifting and clutch dumping is going to shock load the gearbox a lot with a harsh clutch.

Quaife modified the internals because of a shifting/gear selecting issue, not sure exactly what they did.

I’m going to be running a ‘stage 1’ Kennedy organic twin on my build, 402ci 600-650hp 550ish torque. Street car however so different usage.
495 BHP 430 ft lb, rpm 7000. Shifts are quick and smooth, Squeeze not dump to take it easy on the box.
 
The clutch only serves to engage or disengage the drive and transmit power, it in itself has little bearing on the transaxle except for the manner in which the clutch is used. If your practice is to drop the clutch, fast shift or shift without full clutch disengagement then that will stress the transaxle, but a different style clutch is unlikely to compensate for those practices, unless you believe you are not getting full disengagement because of the design of the existing clutch.
Thanks for the advice, Quaife have or will redesign the fork and better quality gears.
 

Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
This may just be my opinion and experience, but - The multidisk clutches I have worked with in the past we’re cantankerous when engaging and disengaged slowly. There was residual drag in the clutches, so it was not a “light switch” disengagement. I would suspect that the more discs, the greater the exaggeration/effect... on the flip side, the ones I worked on did not like to be slipped when engaging. Slipping them would warp the floater plate and thereby causing an even greater disengagement lag. It may have been this lag that caused excessive loads in your gear box.
 
Tyres I use are Hoosier TDR, Avon CR6 ZZ, Good Year Blue Streak. Waiting to see where the metal bits are coming from.
My RBT stripped 4th gear on two different track days. Got about 10 track days in each time before breakage. 505hp, 520 lb. ft., Nitto NT-01 semi slicks. Don't know how similar ZFQ and RBT are, but 4th gear is on the longest unsupported part of input shaft. There is a reason Ford went with the t44 trans for the high torque engines. Don't know that a different clutch will cure your problem.
 

Julian

Lifetime Supporter
My RBT stripped 4th gear on two different track days. Got about 10 track days in each time before breakage. 505hp, 520 lb. ft., Nitto NT-01 semi slicks. Don't know how similar ZFQ and RBT are, but 4th gear is on the longest unsupported part of input shaft.
I recall reading Ron McCall installing a straight cut 4th gear on a recent ZF rebuild.
 

Ian Clark

Supporter
So how did these gearboxes last 6 12 & 24hrs races in the sixties?

We installed RBT ZF 5DS-25s in five CAV GT40s - hooked up to Ford Motorsport built 347s plus one more to a Windsor 392 all through McLeod twin disc clutch assemblies, internal hydraulic throw out bearings and matching aluminum flywheel with no transaxle or clutch troubles

I agree with the comments regarding driving technique. If you watch the old racing footage you'll see the shifts are quick but not slammed across the gate. These boxes are also built to tolerances that need warming up before really getting on them, Lloyd warned me about that.

It's also almost a lost art now to be able to match revs when shifting up or down the box. That is a discipline learned requiring a well engineered pedal box working along with a properly adjusted gear selector mechanism and consistent throttle linkage. It can take enormous time to dial everything in.

Going up and down the box and getting it all right and it's very satisfying (insert most fun with clothes on here). Getting it wrong causes larger torque reversals or that horrible grinding noise we dread or repair bill nobody wants.
 
So how did these gearboxes last 6 12 & 24hrs races in the sixties?

We installed RBT ZF 5DS-25s in five CAV GT40s - hooked up to Ford Motorsport built 347s plus one more to a Windsor 392 all through McLeod twin disc clutch assemblies, internal hydraulic throw out bearings and matching aluminum flywheel with no transaxle or clutch troubles

I agree with the comments regarding driving technique. If you watch the old racing footage you'll see the shifts are quick but not slammed across the gate. These boxes are also built to tolerances that need warming up before really getting on them, Lloyd warned me about that.

It's also almost a lost art now to be able to match revs when shifting up or down the box. That is a discipline learned requiring a well engineered pedal box working along with a properly adjusted gear selector mechanism and consistent throttle linkage. It can take enormous time to dial everything in.

Going up and down the box and getting it all right and it's very satisfying (insert most fun with clothes on here). Getting it wrong causes larger torque reversals or that horrible grinding noise we dread or repair bill nobody wants.
Thanks, I match revs and never miss a cog, heel and toe etc and all changes are smooth and use brakes before down shift, some people use the box to help slow the car. See how I go, it might be the new design change in Quaife's selector fork and quality of gears will help.
 

Ian Clark

Supporter
Hi Warren,

Good to know you're taking care with the box. Kind of leaves the problem with the early Quaife version. Is this the same issue you had before? Perhaps the first fix didn't get to the route of the problem...

IMHO with 75hp more than JWA had when the GT40s won LeMans twice, you can afford the few extra pounds added by the flywheel and double plate clutch setup. Will be much kinder on the drivetrain no doubt.

Cheers
Ian
 
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