Hi guys,
As a certified (certifiable?) Pantera Dork, I have been kicking around with ZF gearboxes for almost 20 years. One of the best online resources for Pantera guys is a website run by a fellow named Mike Dailey in Atlanta, www.panteraplace.com
In the technical information section, he has a couple of pages that are dedicated to the ZF. This one is very interesting, for it shows in-depth photos of the gearbox during each stage of assembly:
http://www.PanteraPlace.com/page151.htm
On this page, he has a downloadable Excel spreadsheet which is really quite brilliant.
http://www.PanteraPlace.com/page32.htm
Don't waste your time reading the poorly reproduced magazine articles; instead just click on the link for the downloadable Excel file.
It assumes 'standard' ZF gear ratios, with a 4.22 ring and pinion, and a 26.5 inch tall tire (BFG says their 295/50-15 is 26.7 inches tall, so that's a good starting point). The spreadsheet allows you to change any number of variables, including tire diameter, each gear ratio, and the ring and pinion ratio. It is actually set up to display data for a ZF six-speed; the first five gear ratios displayed are the standard ratios for the standard five-speed.
The only flaw in this spreadsheet is in its presentation; the column headings don't line up properly with the data, so the data for 1st gear, for example, is displaced to the right, almost under the heading for 2nd gear. To correct this, I downloaded the read-only file, then did a save-as with a new filename. This new file I could then manipulate, and I highlighted the 'results' cells and changed them to 'centered'.
Once properly formatted for human viewing, the results are quite illustrative. Lloyd Butfoy told me that unless otherwise ordered, the new gearboxes that he is quasi-mass-producing are fitted with 3.77 ring and pinions, which is different from the 'standard' 4.22 ratio fitted to Panteras and (most) Mangustas. Although that is great for top-speed bragging purposes (assuming a 26.5 inch tire, 6500 rpm equates to 193 mph), it has been my experience driving 3.77-equipped Panteras that the taller rear end ratio really blunts acceleration.
While admittedly the GT40 received 3.77 gears when running at the high-speed tracks like Le Mans, a host of different ratios were available, and on the short tracks gearboxes with as low as 5.25 were sometimes fitted.
Even with the 4.22 gearing, most race tracks in the USA are so tight that you will rarely (if ever) get into 5th gear; a 3.77 virtually guarantees that you will spend almost all your time in 2nd and 3rd gear, getting pulled coming out of the corners by cars that arguably should be slower than yours.
The one advantage of the 3.77 for street use is that it provides more relaxed freeway cruising. But consider that 4th and 5th gear are unusually close together; at most speeds there is only about a 500 rpm drop shifting from 4th to 5th.
It seems to me that if low rpm freeway cruising combined with electrifying back roads and racetrack performance is the goal, the ideal combination would therefore be a 4.22 ring and pinion coupled with a taller 5th gear. Lloyd sells both .655 and .642 5th gears to replace the stock .705 ratio; the .642 ratio gives about a 1000 rpm drop when shifting from 4th to fifth at freeway speeds.
The spreadsheet shows a gearbox so-equipped would deliver 144 mph in 4th gear at 6500 rpm, which is about all you could expect on an American track, yet 5th gear would allow a top speed of 189 mph at the same rpm. More importantly, it would allow you to cruise at a mere 2500 mph at 70-ish (actually 73) mph.
This presumes that relaxed cruising is your ambition, which is far from universally true. Personally I would just stick with the standard gearing.
In any case, before plunking down your hard-earned cash on a gearbox that is available with a variety of different options, you owe it to yourself to spend a few minutes honestly assessing how you intend to drive the car, and then fooling around with this spreadsheet to ensure that the gearbox delivers what you want it to.
And remember this--there will be virtually no opportunity to actually drive the car at 200 mph anywhere in the USA. But you can cheerfully lie about it at the car show and tell people that it’s a 200 mph car, then blow their doors off with the acceleration that your lower gearing affords you.
As a certified (certifiable?) Pantera Dork, I have been kicking around with ZF gearboxes for almost 20 years. One of the best online resources for Pantera guys is a website run by a fellow named Mike Dailey in Atlanta, www.panteraplace.com
In the technical information section, he has a couple of pages that are dedicated to the ZF. This one is very interesting, for it shows in-depth photos of the gearbox during each stage of assembly:
http://www.PanteraPlace.com/page151.htm
On this page, he has a downloadable Excel spreadsheet which is really quite brilliant.
http://www.PanteraPlace.com/page32.htm
Don't waste your time reading the poorly reproduced magazine articles; instead just click on the link for the downloadable Excel file.
It assumes 'standard' ZF gear ratios, with a 4.22 ring and pinion, and a 26.5 inch tall tire (BFG says their 295/50-15 is 26.7 inches tall, so that's a good starting point). The spreadsheet allows you to change any number of variables, including tire diameter, each gear ratio, and the ring and pinion ratio. It is actually set up to display data for a ZF six-speed; the first five gear ratios displayed are the standard ratios for the standard five-speed.
The only flaw in this spreadsheet is in its presentation; the column headings don't line up properly with the data, so the data for 1st gear, for example, is displaced to the right, almost under the heading for 2nd gear. To correct this, I downloaded the read-only file, then did a save-as with a new filename. This new file I could then manipulate, and I highlighted the 'results' cells and changed them to 'centered'.
Once properly formatted for human viewing, the results are quite illustrative. Lloyd Butfoy told me that unless otherwise ordered, the new gearboxes that he is quasi-mass-producing are fitted with 3.77 ring and pinions, which is different from the 'standard' 4.22 ratio fitted to Panteras and (most) Mangustas. Although that is great for top-speed bragging purposes (assuming a 26.5 inch tire, 6500 rpm equates to 193 mph), it has been my experience driving 3.77-equipped Panteras that the taller rear end ratio really blunts acceleration.
While admittedly the GT40 received 3.77 gears when running at the high-speed tracks like Le Mans, a host of different ratios were available, and on the short tracks gearboxes with as low as 5.25 were sometimes fitted.
Even with the 4.22 gearing, most race tracks in the USA are so tight that you will rarely (if ever) get into 5th gear; a 3.77 virtually guarantees that you will spend almost all your time in 2nd and 3rd gear, getting pulled coming out of the corners by cars that arguably should be slower than yours.
The one advantage of the 3.77 for street use is that it provides more relaxed freeway cruising. But consider that 4th and 5th gear are unusually close together; at most speeds there is only about a 500 rpm drop shifting from 4th to 5th.
It seems to me that if low rpm freeway cruising combined with electrifying back roads and racetrack performance is the goal, the ideal combination would therefore be a 4.22 ring and pinion coupled with a taller 5th gear. Lloyd sells both .655 and .642 5th gears to replace the stock .705 ratio; the .642 ratio gives about a 1000 rpm drop when shifting from 4th to fifth at freeway speeds.
The spreadsheet shows a gearbox so-equipped would deliver 144 mph in 4th gear at 6500 rpm, which is about all you could expect on an American track, yet 5th gear would allow a top speed of 189 mph at the same rpm. More importantly, it would allow you to cruise at a mere 2500 mph at 70-ish (actually 73) mph.
This presumes that relaxed cruising is your ambition, which is far from universally true. Personally I would just stick with the standard gearing.
In any case, before plunking down your hard-earned cash on a gearbox that is available with a variety of different options, you owe it to yourself to spend a few minutes honestly assessing how you intend to drive the car, and then fooling around with this spreadsheet to ensure that the gearbox delivers what you want it to.
And remember this--there will be virtually no opportunity to actually drive the car at 200 mph anywhere in the USA. But you can cheerfully lie about it at the car show and tell people that it’s a 200 mph car, then blow their doors off with the acceleration that your lower gearing affords you.
