SPF ZF Gearing

Attached is the dataplate from my ZF.

Driving the car for over an hour yesterday, the shifting is stiff/slow but very direct - the pattern is fairly narrow. Reverse is left and up, a normal H for 1st through 4th and 5th right and up.

The clutch is heavy, but take up is very smooth. The torque of the motor makes getting going real easy. Third gear is a blast.
 

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I had lunch with Lloyd Butfoy last week. We were literally laughing at the Superformance guys who are specifying ridiculous gear ratios like this for their gearboxes. Lloyd doesn't care personally--he will build a gearbox with whatever ratios the customer wants. But he would prefer that his customers were happy with the final result, and to that end he has tried to convince people that they are making a mistake by specifying such tall gears, but most people just won't hear it.

The reality of the situation is that nobody, and I mean NOBODY who buys one of these cars will ever drive it at 200 mph on the road, yet most customers are making HUGE sacrifices in day-to-day, real-world performance in order to have bragging rights that they have a "200 mph car".

The ratios on this dataplate indicate the maximum lunacy. Yes, with a 26.5 inch tire, the combination of the .642 fifth gear (normal is .705) and the 3.77 ring and pinion (normal is 4.22) will yield 195 mph at 6000 rpm. But again, what is the likelihood that any of us will ever have the opportunity or desire to achieve that?

With the 'normal' gearing (that is, 'normal' until some early Superformance customer convinced everybody else to go off into the wilderness with their gear ratios), 6000 rpm will deliver 160 mph. Arguably that should be fast enough; few race tracks in the USA are long enough to even allow shifting into 5th gear anyway. But having 'low' gearing like this will radically increase REAL performance, i.e. acceleration.

About the only people who would have a 'need' for taller gearing would be those who plan to run their cars in open road races, i.e. the Silver State race in Nevada, etc. Perhaps if somebody was planning on doing a lot of long-distance driving (and who buys a GT40 for *that*?), the .642 fifth gear combined with the standard 4.22 ring and pinion would be a reasonable compromise.

As another datapoint, Lloyd pointed out that the great delays in ZF delivery have been largely due to the specification of this lunatic gearing (delays in getting 3.77 ring and pinions made); he told me he can deliver gearboxes with 'normal' gearing in much less time.

Remember, you don't need 200 mph gears to brag to your buddies that you have a 200 mph car! Everybody knows that GT40s will go 200 mph, so you might as well TELL them that, regardless of what gears are in the gearbox. But when you then spank them coming out of the corners because you have proper (i.e. lower) gears, you will be all smiles. Having somebody in a Ferrari 360 ACTUALLY eat your lunch at a track day because you can THEORETICALLY go faster than he can is no fun at all.

As an aside, the demand/supply curves for ZF gearboxes are getting closer together; Lloyd told me that the turnaround time from order acceptance to gearbox completion is now in the three-month timeframe (for orders accepted today, with a 3.77 ratio) and potentially less for a 4.22 ratio (since he has those ring and pinions on the shelf, apparently). His facility in Texas is completing and shipping about one brand new ZF per day, and Lloyd himself is reconditioning and shipping about four used gearboxes per week.

As another aside, if somebody wants to go completely the other direction, I will have access to a lightly used 3.20 ring and pinion soon. This was purchased from Lloyd by a Pantera buddy in the UK who insisted he wanted to go 200 mph in his Pantera, equipped with 24-inch tall tires. He has since discovered that he literally can't drive the car in 5th gear most of the time because the gearing is simply too tall, and he is driving everywhere in 3rd and 4th gear; meanwhile his acceleration is severely blunted, even though he has a 550 hp Windsor stroker. I will be getting him a 3.77 from Lloyd pretty soon (the existing batch is already spoken for by Superformance customers!), which actually is the perfect ratio for his car, since he has 345/35-15 rear tires that are only 24 inches tall. That will leave his 3.20 surplus to the cause, and it could be had fairly reasonably if somebody had Bonneville aspirations for their GT40....
 
More: I failed to note that 1st, 2nd and 3rd gears on the new gearboxes are also different--they are all lower than the 'standard' gearing, meaning that this new gearbox is an extremely wide-ratio unit, with a lower first (perhaps necessary with the tall ring and pinion) and higher 5th.

I've posted this link here before, but it bears repeating. There is an excellent Excel spreadsheet for ZF gearing on Mike Dailey's PanteraPlace website; once you download it, you can change all the variables (tire size, individual gear ratios, rear end ratios) to see what the speeds will be in each gear, at each RPM. The spreadsheet is actually set up for a six-speed gearbox; simply ignore the right column.

I actually saved it to my computer, then centered the columns so that they lined up under the headers so it made more sense.

Here's the link:

Pantera gearing
 
Actually, in re-reading your post I have a question:

The 'normal' shift pattern for a ZF is for reverse to be up and to the left, first gear down and to the left (dogleg), and then 2nd through 5th in a normal H-pattern. Is that not what your car has, and if not, why not? Is this a Superformance alteration from original specification, or what? Do you have a cable shifter or a rod shifter? Center shift or sill shift? Do the cars with rod shift in the sill have the 'proper' shift pattern?
 
Hey Mike Drew, glad you and Lloyd had a laugh. It sure is funny.

The day to day driving of this car is excellent. Not sure why you consider Dennis Olthoff a lunatic - he seems to be spec'ing this gearing in combination with the engine he suggests. Probably more lunacy though.

I have cable shift on the center console - is that okay?

I don't have any friends that know much about GT40s so I haven't been able to brag at all. Most people just like the car for what it is.

If you have questions regarding the SPF product (i.e. rod shifting), then contact them - maye they can make it "proper" for you. They seem far from lunatics - nice people really.

I am sure you will enjoy your car.

Regards,
Mike
 
I had lunch with Lloyd Butfoy last week. We were literally laughing at the Superformance guys who are specifying ridiculous gear ratios like this for their gearboxes. Lloyd doesn't care personally--he will build a gearbox with whatever ratios the customer wants. But he would prefer that his customers were happy with the final result, and to that end he has tried to convince people that they are making a mistake by specifying such tall gears, but most people just won't hear it.

The reality of the situation is that nobody, and I mean NOBODY who buys one of these cars will ever drive it at 200 mph on the road, yet most customers are making HUGE sacrifices in day-to-day, real-world performance in order to have bragging rights that they have a "200 mph car".

The ratios on this dataplate indicate the maximum lunacy. Yes, with a 26.5 inch tire, the combination of the .642 fifth gear (normal is .705) and the 3.77 ring and pinion (normal is 4.22) will yield 195 mph at 6000 rpm. But again, what is the likelihood that any of us will ever have the opportunity or desire to achieve that?

With the 'normal' gearing (that is, 'normal' until some early Superformance customer convinced everybody else to go off into the wilderness with their gear ratios), 6000 rpm will deliver 160 mph. Arguably that should be fast enough; few race tracks in the USA are long enough to even allow shifting into 5th gear anyway. But having 'low' gearing like this will radically increase REAL performance, i.e. acceleration.

About the only people who would have a 'need' for taller gearing would be those who plan to run their cars in open road races, i.e. the Silver State race in Nevada, etc. Perhaps if somebody was planning on doing a lot of long-distance driving (and who buys a GT40 for *that*?), the .642 fifth gear combined with the standard 4.22 ring and pinion would be a reasonable compromise.

As another datapoint, Lloyd pointed out that the great delays in ZF delivery have been largely due to the specification of this lunatic gearing (delays in getting 3.77 ring and pinions made); he told me he can deliver gearboxes with 'normal' gearing in much less time.

Remember, you don't need 200 mph gears to brag to your buddies that you have a 200 mph car! Everybody knows that GT40s will go 200 mph, so you might as well TELL them that, regardless of what gears are in the gearbox. But when you then spank them coming out of the corners because you have proper (i.e. lower) gears, you will be all smiles. Having somebody in a Ferrari 360 ACTUALLY eat your lunch at a track day because you can THEORETICALLY go faster than he can is no fun at all.

As an aside, the demand/supply curves for ZF gearboxes are getting closer together; Lloyd told me that the turnaround time from order acceptance to gearbox completion is now in the three-month timeframe (for orders accepted today, with a 3.77 ratio) and potentially less for a 4.22 ratio (since he has those ring and pinions on the shelf, apparently). His facility in Texas is completing and shipping about one brand new ZF per day, and Lloyd himself is reconditioning and shipping about four used gearboxes per week.

As another aside, if somebody wants to go completely the other direction, I will have access to a lightly used 3.20 ring and pinion soon. This was purchased from Lloyd by a Pantera buddy in the UK who insisted he wanted to go 200 mph in his Pantera, equipped with 24-inch tall tires. He has since discovered that he literally can't drive the car in 5th gear most of the time because the gearing is simply too tall, and he is driving everywhere in 3rd and 4th gear; meanwhile his acceleration is severely blunted, even though he has a 550 hp Windsor stroker. I will be getting him a 3.77 from Lloyd pretty soon (the existing batch is already spoken for by Superformance customers!), which actually is the perfect ratio for his car, since he has 345/35-15 rear tires that are only 24 inches tall. That will leave his 3.20 surplus to the cause, and it could be had fairly reasonably if somebody had Bonneville aspirations for their GT40....
Here are the gear ratio of some other performance cars…

Ford GT- 6th .625 with a final drive ratio of 3.36 (265 mph)

Dodge Viper. 6th .50 with a 3.07 final drive (318 mph)

Chevy Corvette 6th .57 with a 3.42 final drive (244mph)

None of those cars will ever be able to reach the speeds that the gearbox ratio is capable of. So why did Ford, Dodge and Chevy waste time and money setting them up to run that way?

Why don’t you go and get a job at one of the big three? It seems you know a lot more then their engineers do. At least you should give them a call and tell them how much you and Lloyd are laughing at how stupid they are, maybe then they will fix their flawed gear ratios.

Or maybe you don’t really have a clue after all. Did it ever occur to you that large V8s (and V10) don’t like high rpms? Did it ever occur to you that cruising on the highway at over 3000 rpm is not very desirable for v8s? Apparently it occurred to Ford, Dodge, and Chevy, but I guess that fact is still eluding you, which is why you’re not working for them.

Just out of curiosity what trans and ring and pinion are you running in the cobra in your sig? Hopefully it’s not one of the Tremecs with that big overdrive 5th (or 6th) otherwise you might get labeled as a hypocrite.

Just so you know if you cant tell by the tone of my post I think your post was a little rude to Spyder Mike…
 
Just to add a little more.

With the gears provided with a 26” tall tire we have at 6000 rpm

1st 50mph
2nd 76mph
3rd 108 mph
4th 146 mph
5th 191 mph

5th @ 2500 rpm = 80mph

rpm drop between gears shifting at 6000 rpm

1st-2nd 2000rpm drop
2nd-3rd- 1750 rpm drop
3rd-4th- 1580 rpm drop
4th- 5th- 1414 rpm drop.

That looks like just about as perfect set up as you could get SpyderMike, nice choice.
 
Thanks to DBLDREW.
You hit the nail on the head.
We specked a 3.77 for highway use. Our first tests were with 4.22 gears. They are terrible. May work with a low torque 8000 rpm screamer, that is useless in traffic or below 3500 rpm.
We ran VIR Soth Course the last 2 days. Gear ratios were perfect using 3rd, 4th and 5th. 2nd at Oak Tree if traffic was ahead. Hardly "stupid" ratios.

Also using the ratios as an excuse for the slow rate of build is laughable. We have had every possible excuse - most not related to ring and pinions.
I would also love to see these new production numbers actually getting to us.
Currently they are shipping 2 a month. The backlog is growing. Maybe Lloyd should check where all these boxes are shipping, cause we aint seeing them.

Regards
Dennis.
(I will climb in under a rock now for safety.)
 
Hey Dennis!

I am finally putting some driving time on my car and I love it - thanks again!

The car is running great and is very drive-able.

Regards,
Mike
 
Wow,

Sure glad you folks don't carry shotguns with you!

For me, when (and if ever) I get a GT-40, I would like to be able to take it out on the freeway, and be able to do 85-90 MPH in a short burst in 5th gear when I got the urge. My thoughts would be 5th gear @ 1,000 RPM = 28 MPH, with the 4.22s. Maybe I need to do Mike Drews Pantera Link for further investigation.
 
I would love to have taller gears in my CAV. I believe I have a Ring and pinion that is in the high fours and at 70 I am running close to 3000rpm. Itis great for short bursts, but hard on the ears on the highway, a 3.77 would be perfect.
 
I will need to agree with Dennis on lead time. I am in no way saying anything bad about RBT. I will wait for the quality and a good product. I can not imagine having to spool up build capacity on such a unique product.
With that said, I was told in November that production would be ramped up significantly in January and I was looking at a 3-3 1/2 month lead time. I ordered two boxes on November 11, 2006. We are now at 6 months and some change and from talking with Llyod I am still 2-3 weeks out. (hopefully!!).
Again, PLEASE do not flame me for my comments! I am not trying to flame anyone else, and if given the opportunity to order from RBT again, I will in a heartbeat. But I do not see the quoted production numbers either.
 
I just got back from 2 days at vir in gt40p2124 and I can tell you that the gear ratio Dennis selected is absolutely perfect for steet or track. lower gears would increase the number of times you shift on the track my car with the fe hits the 6400 rev limter in 4th gear at the end of the straight after oak tree, any shorter gears puts me in 5th with one more shift. The lower gears would tend to light up the tires much like my cobra does with 373 gears and 3550 tremec. light cars with high horsepower and low gears make no sense to me but what do I know? Sounds like we have some bench racers with no real gt 40 seat time.
Jerry Douglas superformance gt40p2124
spf mk3 with gears that are way tooo low.
 
Here are the gear ratio of some other performance cars…

Ford GT- 6th .625 with a final drive ratio of 3.36 (265 mph)

Dodge Viper. 6th .50 with a 3.07 final drive (318 mph)

Chevy Corvette 6th .57 with a 3.42 final drive (244mph)

None of those cars will ever be able to reach the speeds that the gearbox ratio is capable of. So why did Ford, Dodge and Chevy waste time and money setting them up to run that way?

Why don’t you go and get a job at one of the big three? It seems you know a lot more then their engineers do. At least you should give them a call and tell them how much you and Lloyd are laughing at how stupid they are, maybe then they will fix their flawed gear ratios.

Or maybe you don’t really have a clue after all. Did it ever occur to you that large V8s (and V10) don’t like high rpms? Did it ever occur to you that cruising on the highway at over 3000 rpm is not very desirable for v8s? Apparently it occurred to Ford, Dodge, and Chevy, but I guess that fact is still eluding you, which is why you’re not working for them.

Just out of curiosity what trans and ring and pinion are you running in the cobra in your sig? Hopefully it’s not one of the Tremecs with that big overdrive 5th (or 6th) otherwise you might get labeled as a hypocrite.

Just so you know if you cant tell by the tone of my post I think your post was a little rude to Spyder Mike…

You raise some valid questions.

The big manufacturers put massively tall gears inside their transmissions because they are deeply concerned about fuel economy. The government has CAFE (Corporate Average Fuel Economy) standards which they, as a corporation, must meet. Recall that GM puts skip-shift in their manual transmissions, even in the Corvette, where they will automatically shift directly from 1st to 4th gear unless the computers sense a certain level of throttle demand. This is another instance where the engineers have introduced a horrible idea (from our perspective, as performance drivers) and sacrificed driver control to meet bureaucratic necessities. Does anybody here really think that this is a good thing, and would you want your GT40 to be equipped with this GM-engineered ‘feature’?

Too, many new car customers like to cruise long distances at extremely low rpm, so a tall highway cruising gear is pretty much standard equipment on most cars now. In most cases, there is a HUGE jump between the first four (or five) gears and the single, tall overdrive top gear. Too, they tend to put extremely low gearing on the lower gears, so that the car will be able to get out of its own way when it is launched. My first experience driving such a car was with a 5.0 Mustang; first gear was so deep that you had to shift before you got halfway across the intersection, yet fifth gear was so tall that you could get decent gas mileage, and cruise on the freeway at 2000 rpm or so. It was far from optimum for performance driving, but it worked okay on the street.

It felt pretty weird to me, as most of my driving experience was with Panteras (my Pantera was my first car, purchased as a beater at age 22; prior to that I had only ridden sport motorcycles, which may have shaped my opinions too). Both the Pantera and the motorcycles had close-ratio transmissions.

Big V8s don’t like “high” rpms, but 3000 rpm isn’t “high”. In fact, most aggressive camshafts don’t even ‘turn on’ until something above that number. Remember too that during the 1960s, most musclecars were equipped with 4:11 ring and pinion gears, and a 1:1 top gear. They were engineered to last forever spinning quite a bit faster than 3000 rpm on the highway. It wouldn’t necessarily be pleasant on the freeway, but that wasn’t their mission.

When I bought my GT350 clone, it was equipped as Shelby had built them, with a 3:89 rear end and a four-speed toploader with 1:1 4th gear. It ran great, but it did drive me a bit crazy, and as I intended to do a lot of long-distance driving in it, I changed it to a 3:25.

It has a close-ratio gearbox, which made the idea of launching from a standing start laughable at that point. Until it gets rolling, it really doesn’t go anywhere in a hurry. The tall rear end also screwed up its racetrack performance; I found that at Sears Point, Laguna Seca and Thunderhill, I would normally be one gear lower than anybody else on the track in any given corner, and they would kick my butt on corner exit even though I had decent horsepower. However, it was a compromise I was willing to make because I drove so many freeway miles in it.

In retrospect what I really should have done was convert it to a 5-speed and kept the 3:89 (or perhaps a 3:50; I haven’t really considered the question carefully yet), since I took it to Europe for a few years and ran it on their tracks (Spa, Nurburgring etc.) which are typically much longer and faster than ours. I found on the slower bits I was faced with the same performance problems as I was in the USA, but I would still hit 6000 rpm in 4th gear on the straights and then just buzz along, needing more/taller gears. But if I did put a five-speed in it, I would not keep the stock T5 gearing (with a super-tall 5th cruising gear), opting instead for something in the .080 range so it would be a useable gear on the track.

The point I’m making is that I know first-hand about making compromises in gearing choices, and in fact I have suffered to varying degrees because of the choices I have made. My goal here is to keep people from inadvertently doing the same thing.

You asked about my Cobra replica—it has a close-ratio toploader and a 3:54 rear end (it came to me that way). It has a 569 hp 427 side-oiler, and spins about 3500-4000 rpm when I’m cruising with freeway traffic—arguably too high. It is top-speed limited by the low-ish gearing (which, by the way, is exactly the same gearing they originally came with). However, it is positively electrifying on a back road or a race track. I think I get up to about 5500 rpm in 4th gear at Thunderhill on the front straight—perfect for a big block. And it’s pretty damn snappy on the freeway too; no need to downshift that puppy, just flex your ankle and you’re GONE.

Gone, that is, until you reach 130 mph or so, and then you’re just making noise on the rev limiter while the Mercedes or whatever whooshes past you. :>)

My Pantera (and thus ZF) track-driving experience is limited; even though I’ve owned it 17 years it’s been in bits for most of that time. I have only driven it on one track (Spring Mountain, in Pahrump NV), which is very tight and technical, mostly 2nd and 3rd gear; I only got partway through 4th gear (with a 4:22) once per lap, and that track is strictly a 2nd/3rd gear proposition if the gearbox had a 3.77 in it.

With respect to the SPF cars, by looking at my initial and second posts you will note that I originally failed to realize that 1st-3rd gears were considerably lower than original, which would restore much of the performance that would otherwise be lost by fitting a 3.77 ring and pinion. Too, a 500+ hp big block can tolerate taller gears than a smallblock can.

I’m sorry if SpyderMike took offense at what I wrote, or if anybody else thought I was being rude. I meant no offense or insult to any individual; I’m just offering a bit of a reality check about gears. When I consider a GT40, I tend to think of it strictly as a driving, performance car, i.e. an open track or backroads car. I recognize that other people might have other thoughts in mind for theirs, i.e. long-distance touring, or just cruising to the local hot rod café, and if that’s the case, then for them, gearing which provides relaxed highway cruising is a higher priority than outright performance.

So let me qualify my earlier statements and say that IF you are primarily looking for supreme dominance on an American racetrack, or IF you bought the car principally so you could enjoy driving it on twisty mountain roads, and IF your engine is capable of spinning to, say, 6000 rpm, and IF you are equipping it with standard-height (26 inch) tires, then you would almost assuredly be better off and happier with a Pantera-spec gearing setup, i.e. 4:22 rear end, and a closer spacing of all five gears with a 2.23 1st and a 0.705 5th

But, if you are putting 24-inch tall 345/35-15 tires on the car, or if your big block runs out of puff (or wants to come apart) at anything about 5000 rpm, or if you plan on driving hundreds of freeway miles on a routine basis, or if any number of other variables, then perhaps more relaxed gearing would suit you better.

Ultimately, I hope that everyone will consider the question carefully, and actually get the kind of gearing that suits THEM and their individual needs and desires, rather than just going along with the herd. If you haven’t already purchased your gearbox, take my advice, and Dennis’ advice, and Lloyd’s advice, and spend some time with the gear calculator program, and consider the performance characteristics of your chosen engine, then YOU make the decision that’s best for YOU. That way, you can guarantee that you’ll be as happy as can be, and you will enjoy your car to the maximum extent possible.

And isn’t that what it’s all about?
 
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