Chris Melia said:
Hi DBLdrew
again interesting comments, we agree the sixth gear option is without merit and also note the Ford GT has 28.9" ZR tires, with this large wheel and tire combo the 3.77 final drive gives you a top speed of 203 Mph in fith gear at 6500rpm.
Well that is another option, but I didn’t know that you could run such a tall tire in most gt40s
The question is especially for guys that want to drive their cars on the street with the odd hill climb speed trial and track use, why not get the best functional use from the gear set?
I agree, but if the car sees road use 95% of the time then I believe that the design should lean more towards being more road friendly. But anyway most hill climbs they won’t go into 5th anyway, (and probably not even 4th) so I don’t think gearing more highway friendly will have much impact on the “weekend warrior racer”
There has been much comment on the poor performance of the GT40's in the quarter mile speed events, seldom do they achieve better than 12 seconds in the quarter. I put this down to tall gearing and I think this is more relevant for a street driven car with the occasional track day.
Well with drag racing the hole shot is very important, so if people are babying it to save the trans or to try to keep the tires from going up in smoke, then the E.T. will suffer a lot. I don’t think that having a low enough first gear is the reason most replica gt40s are not getting any faster then a 12 second ¼ mile.
It’s all about putting the power to the ground, and believe it or not having a lower gear ratio makes it harder to do that. Think about it this way tack it up in 1st gear and dump the clutch, what happens? Well if you don’t blow up your trans your tires go up in smoke. Now tack it up in 4th gear and dump it (both from a dead stop) and what happens? Well you would probably break something, maybe burn up a clutch, but even if you managed not to break anything you won’t be spinning your tires. So anyway back to my point, if you are spinning your tires in first gear, lowering your gear ratio will only make it easier to spin your tires.
Bottom line is unless those guys are running Drag Slicks where they are maximizing grip, then having a lower gear ratio isn’t going to help them much for the ¼ mile.
I also think that running the trans with a tall final drive like 3.4 would exert higher torque loads on the gears and could promote reduced life expectancy.
Well then wouldn’t I have the same problem with running the taller tires like you suggested? After all the true Final Drive ratio is in fact the tire diameter. The problem with going with such a tall tire like the Ford GT uses is getting it to fit and having it maintain the 60s look that so many want to maintain.
I really think you should offer a few more choices on your final drive. Just search through the threads here looking at how many people have talked about custom ring and pinion (crown wheel and pinion for those across the pond) for the Audi, and Porsche transaxles, or the custom 5th gear options. I think there is a lot of people who want a more streetable trans and not having options for them might be a big mistake. If you want to keep just having 2 final drive options then maybe split the difference like going with a 3.90 and maybe a 3.50 for instance.