3.90 Final Drive Ratio - Gauging level of interest

[BlackICE]

I have a company doing 4.11's and 3.90s. I dont know how far you have gotten with this Kendall but you may want to wait till i see what pricing is going to be on them. The 4.11s are being done first and supposed to be done soon.

Why 4.11? The 3.9 seem plenty low too me, especially if you have up the HP and torque. It's my understanding the lower the ratio the lower the efficiency too.

 

[B.M.F.]

4.11s are the lowest gear set possible for the GT cause the ring gear is so big. I'm gonna build a na 5.0 coyote motored ford gt and it will benefit from the slightly lower gear and I'm gonna run the 4.11 for the mile also. My motor turns 8800 tho.

 

[PL510*Jeff]

If I remember correctly, Steve Millen asked Riccardo to do a 4.10.

Engineering said the "tallest" ring gear the case physically allowed would be the 3.90.

 

[B.M.F.]

If I remember correctly, Steve Millen asked Riccardo to do a 4.10.

Engineering said the "tallest" ring gear the case physically allowed would be the 3.90.

We have already got the 4.11 figured out! So it will fit with out any or very little internal case modifications.

 

[SMOKDU]

We have the 3.90 gears in one car and the stock 3.3 in the other, both cars are otherwise identical, Whipples, exhaust, brakes, short shifter…
The stock geared car is as most everyone knows is long legged; getting 0-60 without a shift will do that. The torque the GT has masks this as to not be a real issue and as we know most people are very happy with the car as is. The 3.90’s surely aren’t for everyone but once you drive one it’s obvious why they have their place. On the road it seems to always be in the heart of the torque curve, a very responsive car in any gear at any speed. Sure my fuel economy took a small hit but my right foot does more damage! How many drive a GT like a prius? On the track it is fantastic, everything it does for the streetcar is exponentially better there, I really can’t overstate how much I enjoy it. Running the mile does require a shift into 6th 400’ from the finish, so not so good but that’s a rare occurrence and it did get me over 210. The stock geared car is still pulling 5th and is the winner there.
As for the cost Kendell is in the same ballpark as the originals. This isn’t ordering a ring and pinion off the shelf, per unit cost, as before, is going to be up there, frankly building only 20 sets I would think most vendors would consider a waste of time so its going to cost you.
The gear change is one of, if not the best mods made to the car, it isn’t seen or heard but it’s felt and it makes me smile.

That is great that you can test side by side. I wish I could drive both like you can. Because I do not track the car and do agree the 3.90 or higher gears would be much better pushing out of the turns than 3.30 gears. I used to run 4.11 gears in a drag car but the car was a high 8800 RPM 1/4 mile car that was an automatic. What do you think about the extra shifting in a roll from say 60 to 130 would be like. both shifting at 7000k rpm would net? if the 3.90 gears would net me a faster time I would change. sorry I am not a road racer but I will go from a dig or a roll but that's in my blood. If I have to get away I will do turns.:eek

 

[dbk]

To me, you buy the 3.90s if you like running on a road course for the reasons Sandman stated, or because you just like the opportunity to shift more. I doubt it would be an assist in a 60-130 roll race for a car with a lot of power. With the stock gears you're making one shift around 90 mph, with the 3.90s you're shifting twice. Ditto for the drag strip if you're crossing the traps around 130-135 mph.

 

[SMOKDU]

To me, you buy the 3.90s if you like running on a road course for the reasons Sandman stated, or because you just like the opportunity to shift more. I doubt it would be an assist in a 60-130 roll race for a car with a lot of power. With the stock gears you're making one shift around 90 mph, with the 3.90s you're shifting twice. Ditto for the drag strip if you're crossing the traps around 130-135 mph.

That is what I thought but if I had two cars with the same setup and only the gears different I would know for sure... hint hint Sandman. I can send you my v-box for some testing for us.

 

[BlackICE]

That is what I thought but if I had two cars with the same setup and only the gears different I would know for sure... hint hint Sandman. I can send you my v-box for some testing for us.

His cars are already setup with vboxes.

 

[sandman]

To me, you buy the 3.90s if you like running on a road course for the reasons Sandman stated, or because you just like the opportunity to shift more. I doubt it would be an assist in a 60-130 roll race for a car with a lot of power. With the stock gears you're making one shift around 90 mph, with the 3.90s you're shifting twice. Ditto for the drag strip if you're crossing the traps around 130-135 mph.

DBK nailed it.

 

[BlackICE]

Dave is right about the 60-130 races and on the 1/4 mile.

For the 60-130 runs

With the 3.9 gears I would start off in 3500 in 3rd go to 4th at 5756. I would forego 2nd since I shift too slow.

With the stock gears you would start of in 2nd at about 4147 and end up in 3rd at 6500.

 

[33Bravo]

Dave is right about the 60-130 races and on the 1/4 mile.

For the 60-130 runs

With the 3.9 gears I would start off in 3500 in 3rd go to 4th at 5756. I would forego 2nd since I shift too slow.

With the stock gears you would start of in 2nd at about 4147 and end up in 3rd at 6500.

Awesome! This is good.. Really good!

Could you share the formula? Many thanks!

 

[SMOKDU]

Awesome! This is good.. Really good!

Could you share the formula? Many thanks!

Great stuff and I can see if you had a centrifugal blower or turbo that liked RPM I would do the swap. Great chart

 

[B.M.F.]

To me, you buy the 3.90s if you like running on a road course for the reasons Sandman stated, or because you just like the opportunity to shift more. I doubt it would be an assist in a 60-130 roll race for a car with a lot of power. With the stock gears you're making one shift around 90 mph, with the 3.90s you're shifting twice. Ditto for the drag strip if you're crossing the traps around 130-135 mph.

The only problem is with big turbos (Big Enough to make 1300+rwhp) they do not spool at 3900 which is 60mph in second. You do not have enough hp at the hit. same thing im running into with my combo. IM maybe 100-200hp right now from spinning the tires at 60mph in second. which is about 800whp from a roll. Remember i dont make the tq right there that a twin screw does. Im just gonna spray my car for a brief second for now till my gears are done!

 

[Gulf GT]

To me, you buy the 3.90s if you like running on a road course for the reasons Sandman stated, or because you just like the opportunity to shift more. I doubt it would be an assist in a 60-130 roll race for a car with a lot of power. With the stock gears you're making one shift around 90 mph, with the 3.90s you're shifting twice. Ditto for the drag strip if you're crossing the traps around 130-135 mph.

Agreed, it's for road course driving, and I think general spirited street driving. If you want a dragster, its not for you.