"Sport" Transmission Gear Ratio

I really wish we could see the values/ratios for components/features that are not tunable…

I am in need of the gear ratios for the “Sport” transmission upgrade found in older cars like the '70 Challenger, the '69 Camaro, etc. This is a 5-speed transmission and appears to be something like the Tremec TKO with 2.87, 1.89, 1.28, 1.00, & .82 gear ratios, but it’d be nice to have some sort of confirmation of this.

google search the old car for an old road & track article and it will detail the transmission gear ratios. there are plenty of ways to search the internet for the information you seek.

He’s not asking for the cars’ stock gear ratios, though; he’s asking for the gear ratios for the generic 5-speed “Sport Transmission” upgrade Forza uses for most cars with fewer than 6 gears.

OP: Best bet is to install the Sport transmission, check top speed in each gear at a given final drive, then try to replicate those speeds with a Race transmission set to the same final drive. Check several cars this way and you should be able to suss out whether they’re all using the same gearing and, if so, about what that gearing actually is.

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This was my backup plan. I was hoping to find the info elsewhere, but it doesn’t seem most people even understand what is being asked…

The “Sport Transmission” only unlocks the final drive ratio and reduces the shift time. The gear ratios or the number of gears are not changed, so the cars stock gear ratios are identical to the gear ratios of the “Sport Transmission”.

So you can search for the original gear ratios of the car and hope that they are correct in Forza, check the top speed in each gear and use engine speed, tire dimension and final drive ratio to calculate the gear ratio for each gear or replicate the gears with a race transmission.

This varies from car to car. For most modern cars, yes, you’re correct (And what a stupid thing that is. The differential ratio is set by the ring & pinion gears in the rear differential, which should be tied to the “sport” differential upgrade, not the transmission.); you just get the “stock” transmission with the unlocked rear diff. But in older cars - like almost all the muscle cars in the game - you get a whole new transmission. For instance, the '70 Challenger goes from it’s stock 4-speed to a generic 5-speed when you go to the “Sport” upgrade. If you stay below that, you retain 4 gears. If you go to “Race,” you get a fully-tunable 6-speed in that same car. In the Hellcat Challenger, you keep an 8-speed for all upgrades levels…

You’re right, I didn’t know that.

Assumption: If a car has less than 5 gears, the street and sport transmission will change the transmission to 5-speed and also change the gear ratios. I’ve tried that with four cars ('70 Challenger, Dodge Super Bee, '70 Chevelle and Pontiac GTO) and at least for them it works like that.

To answer the question about the sport transmission gear ratios: I have a capture card and I took screenshots of both the sport and race transmission and the gear ratios of the first five gears are identical (at least for the four cars I mentioned above). So the sport transmission gear ratios are 2.89, 1.99, 1.49, 1.16 and 0.94. Of course it would be nice to always see the values.

You can check out both screenshots here:
1970 Dodge Challenger Sport Transmission
1970 Dodge Challenger Race Transmission