Why do Gearbox Upgrades Negatively Affect Stats?

Case in point - Porsche 356A mildly upgraded to D500 on stock transmission, with a launch stat of 7.4. But add a street gearbox and the figure plummets to 4.2, or 4.7 for the race upgrade. There are lots of cars like this but I’ve never understood why - yes you’re adding an extra gear so 1st would be shorter, but how would that affect off the line performance? Or is it just a quirk that wouldn’t really make a difference in races?

It is just a quirk. There can be weight difference if I am remembering that upgrade right, but some cars it also puts different gearing in. this different gearing sometimes can be well improper to your current tune as most people probably tune to.

A shorter first gear throws down more torque so traction “drops” even though it doesnt. Once you re-adjust the gearing, you will find no difference. I usually avoid race transmission unless I have to tune the gearing vs just the final drive.

Probably because the car doesn’t have enough torque to overcome the long gear ratios that the race transmission naturally has. You’ll need to go into tuning, and shorten the gearing to improve acceleration.

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Sometimes it is the reverse though - the stock gearing has a tall 1st which means you don’t spin the wheels on launch (especially on older cars with only 3- or 4-speed manuals) and can get going reasonably fast before having to shift, when you upgrade the transmission and 1st becomes shorter you get more wheelspin plus the gearchange (which is slow) comes sooner and you lose more momentum.

He was talking about low powered cars. They need to have a decent power to weight ratio for an untuned race transmission to have better acceleration. Otherwise it accelerates like a train without tuning.

Those stats are based on the “stock” gearing of the new transmission, which if you didn’t tune WOULD be slower. If you tune it, it will be fast, regardless of stats given at upgrade.

You instead compare your 0-60. -100 times for example instead of the “acceleration” and “launch” numbers. You will see there that tuned the other transmission is faster than the stock times, on the stock transmission.


Because the manufacturer(stock) gearbox is designed specifically to be the best for THAT car, when you put in the racing 6 speed, it’s a generic final drive and tune, and may not be optimal for the job the car was intended for out of the factory. with the right tuning setup I assure you it will only get faster.

ie my lancer evolution IV i own in real life has a Final drive of about 4.8x which is pretty high, means you go from gear 1 to 4 lightning fast then cruise in 5th, if you added a 6 speed at a ratio of about 3.3 yes you gain a 6th gear and top speed, but youll take far, far longer to reach your top speed. with higher torque due to a higher final drive ratio your top speed will take a hit, but youll generally reach it much faster.
in the evo’s case(along with many rally cars) they only need 5 gears due to how strenuous rally tracks are, there’s no point adding a sixth if youll never use it due to constant downshifting, just becomes a pain at that point.

Except in many cases, the race transmission is lighter. A fabulous example is the current vandura event. 4 speed default. Race transmission soed make it a six speed. But it gives it the four speed gearing by default and then tacks on two additional gears. So the stats look like they drop, but only because the default installed gearing is so terrible for how I have it built. Tweak the gearing and is fine.

It also only makes it a six if by default it is less than six. Ten speeds stay ten, which is quite annoying. High gear count cars, the last gears all get zeroed out because the shift points are so darn close so will fake gear it as a different count. Unimog and the new Type D regalia are great examples. The Type D is hilarious because with the large tires, there is no way to have a useful 8th gear really. The quad side by sides are similar. Too many gears.

Lowers PI when they have weak engine but slap on a powerful swap and you’ll see stock transmission restricting the car…