RBT ZF 5 speed gear ratios....

Gary Gibbs · 06-13-03, 09:30 AM

FYI. I have ordered a new ZF 5 speed from RBT with a different combination of gear ratios which I feel give you a nice combination of first gear and top gear. The spread on the stock (traditional) ZF is relatively tightly spaced and forces one to choose a good launch gear and suffer on top speed (and highway cruise), or have a nice top speed and highway cruise and suffer off the line performance. Anyway this is just my opinion and as they say everybody has one [img]/ubbthreads/images/graemlins/smile.gif[/img]

You can see a list of my selected gear ratios on my site:
http://2gmotorsports.com/news.htm

This setup has the same first gear overall ratio and top gear ratio as the Saleen S7 (featured in C&D magazine with a 3.3 second 0-60 mph time), but only has 5 gears instead of 6 (i.e. more spread between each gear).

The main reason for this post is if someone is wanting a new ZF and has a concern like I have expressed above there is an available compromise.

Glenn · 06-17-03, 04:05 AM

Just curious Gary, is it a -1 or -2 box?

Gary Gibbs · 06-19-03, 09:27 AM

It is a new box that I believe is based on the -2.

Knighton · 06-20-03, 07:18 PM

Hi Gary,

These ratios and speeds look better to me than the stock ratios, especially for a 2300 lb car with 600hp and 600 lbs ft (yours). Second gear should be a riot and will see you pull away from almost everything on the street, sportbikes included - like Suzuki's Hayabusa 1300.

Will you be running traction control?

How in the world will you be able to keep er' under 100 mph?

Would love to see some 1/4 mile and roll on times when you get er' up and running. Know when this will be?

Gary Gibbs · 06-21-03, 08:16 AM

[ QUOTE ]
Hi Gary,
Will you be running traction control?
How in the world will you be able to keep er' under 100 mph?
Would love to see some 1/4 mile and roll on times when you get er' up and running. Know when this will be?

[/ QUOTE ]

I will begin using the car with a Race Demon Carb, and later develop a stack EFI system with probably Autronic Controls including traction control. Looking at my calculations the car will only take about half throttle in first and should hold up well in second. Third on up will definitely not be traction limited and should pull like a freight train. I just received the Tilton clutch system and will be posting picks soon. It should be running soon after I receive the transmission in early July. I have had to upgrade the stock fuel pumps which are good for something like 500 HP. I am using a dual Aeromotive Pump setup. At this point I have to:
Work out clutch release.
Install upgraded fuel components.
Finish A/C bracket (I am developing a new trick accessory bracket system).
Install motor and transmission.

Ross Nicol · 06-28-03, 09:37 AM

Gary
I have ZF 5 speed with 3.2:1 final ratio and 1st gear
is 2.23, 2nd 1.61,3rd 1.31,4th 1.09, 5th .74.After my track test yesterday I can tell you that 2nd to 3rd to 4th ratios are fantastic and the tight track didn't require 5th gear but I have quite a drop from 1.09 to.74. Your first gear you may find too high as although I haven't done a race start yet my 2.23 compounded with 3.2 final drive takes some revs to get going
regards Ross

Gary Gibbs · 06-29-03, 03:38 PM

Ross,
I was wondering how tall first could be without it being too tall. Your overall in first is 7.18 mine will be 8.31. How is your first gear?

Ross Nicol · 06-30-03, 09:09 AM

Gary
I think your 1st gear ratio is too tall.I have never liked having to rev a motor and slip the clutch but my compounded ratio is on the border I reckon.My gearcalc program tells me that if I rev to 4000 for a standing start,I should be doing 70 km/h.whether I can clutch slip to get away on a racing start will depend on the cars weight and most likely wheel spin.As you know too much of that and you go nowhere.I will be able to confirm for you one way or the other on the 19th and 20th of july as I have 3 races with standing starts.At US$500 per set from Lloyd at RBT, changing that ist gear ratio will be costly.
regards Ross

Gary Gibbs · 06-30-03, 05:33 PM

I have uploaded a very nice compilation of data and calculations concerning transaxle gear ratios to my website. Please see:
Transaxle gear ratios

In this I have included my transaxle, yours and a bunch of well known high performance autos. I have been looking at the cars in the upper section which had high torque v-8's, etc. I have highlighted those in yellow and green. It would appear that my ratio for first gear (8.31) is about the same as a Viper, and the S7. A little shorter then the McLaren F1, but a little taller then the SVT Cobra, and Z06. We will see as the GT40 is a much lighter car then any of the other cars, and has (in my case) has lots of torque.

Ross Nicol · 07-01-03, 06:17 AM

Gary
That is a very impressive list of vehicles and ratios. I have printed it out for further study.You must have spent some time compiling it.I really enjoy comparison charts like this,although I've been so busy finishing the car I haven't done much research lately.I hope that 1st gear ratio does work out ok. I can recall hearing about race cars with such high ratios they have trouble getting out of the pits.Thanks again Gary.
Regards Ross