Transmission and rear end gear ratios

[austinjjesus]

Hey guys, I’ve fallen into the trap of doing research on the internet. Im building (hear me out) an E36. I’ve got a mildly cammed 5.3 built for it and I’m probably going to end up going t10 since I have one readily available. And no I can’t afford a tkx or t56 so the t10 I have is a 2.64 first gear and the rear end in the car is a 3.91. I’m not worried about highway mpg because it’s pure track/fun car. I’ve read a lot of contradicting info that I can’t wrap my head around. I’m afraid it’s not going to launch hard and that’s really what I want first and foremost. Somebody help explain!!
Little PFA ;)

[Hotwire]

You can use this calculator to figure out your rpms and shift points.

https://www.blocklayer.com/rpm-gear

5.3s aren't know for a lot of torque so you'll have to put a little rpm to your launch but you should have plenty fun with it.

[austinjjesus]

Thank you for this. The cam I have is advertised to make 400+ in a 5.3 but the car will probably weigh 2500 pounds ish with me in it. I’m just more worried about is being a pig because of the ratios. I’ll be honest, the combination of rear end ratio and trans ratios are way over my head lol

[Mkelcy]

Rear tire size?

[austinjjesus]

Rear tire size?

285/35/18

[Mkelcy]

I've got an LS376/480, a 2.66 first gear T56 in front of a 3.70 rear end. My overall first gear ratio is 9.84, and I can light up my 295-35-18's all the way through first and second gears in a '68 Camaro. You'll be at about 10.24 overall first gear ratio in a much lighter car. I think you'll be fine.

[austinjjesus]

I've got an LS376/480, a 2.66 first gear T56 in front of a 3.70 rear end. My overall first gear ratio is 9.84, and I can light up my 295-35-18's all the way through first and second gears in a '68 Camaro. You'll be at about 10.24 overall first gear ratio in a much lighter car. I think you'll be fine.

If you don’t mind, can you explain the math behind that?

[Mkelcy]

My combo - 2.66 x 3.70 = 9.842; your combo - 2.64 x 3.91 = 10.322. Our rear tire heights are about the same. I have more torque and weight, you're lighter with less torque. I think you'll be okay.

[austinjjesus]

Ahhh understood, thank you

[mmosley]

My combo - 2.66 x 3.70 = 9.842; your combo - 2.64 x 3.91 = 10.322. Our rear tire heights are about the same. I have more torque and weight, you're lighter with less torque. I think you'll be okay.

agree - you have a light car, the 2.64 will be just fine, it will also make for more time in first gear which is good for a track car. you also wont get as much rpm drop shifting to 2nd. This combo will be just fine.

[austinjjesus]

agree - you have a light car, the 2.64 will be just fine, it will also make for more time in first gear which is good for a track car. you also wont get as much rpm drop shifting to 2nd. This combo will be just fine.

Thanks for the input!! That also makes me feel better