3.91 gear question

[dekan513]

if i go with one just wondering what the car run rpm wise at say 65 mph i dont want to be driving and it running 3500 rpm in 6 th gear anyone have a video of them driving their car with a gear ratio around this size

[rick john]

DEKAN,I just got my 3.91 installed last week and your 3.91 will only increase your r.p.m's by about 200 rpm's... believe me do it, you won't be disappointed. in sixth gear you'll go from cruising at 1700 or 1800 to 2000... trust me worth every bit

[dekan513]

sounds like a happy camper to me i think i may do it did u do lpe or whatever they r and if u dont mind pm how much things costed for complete kit

[bmorecam]

I used to turn 2k rpm doing 70mph, now I am right under 2500 rpm. I have a V6 tho.. just remember that low gears are a low rpm mover. Don't expect to see a big difference in the higher rpm.

[UCI CamaroFan]

I don't want to start another thread on this same topic, so I will ask my question here too. Do 3.91 gears with a supercharger (with maybe around 500 rwhp) need any other suspension mods to keep from breaking? How is traction with this combination?

[Bad70supreme]

These cars need suspension mods even when stock! The gears will make traction worse to a point, you need some good rubber out back to really make it stick with or without suspension work. Either way gears would be a great upgrade, I plan on doing 3.91s at some point also. You will feel a huge difference in the butt dyno, almost like you added a 100ft lbs of torque!

[NinoSS]

Originally Posted by Bad70supreme

These cars need suspension mods even when stock! The gears will make traction worse to a point, you need some good rubber out back to really make it stick with or without suspension work. Either way gears would be a great upgrade, I plan on doing 3.91s at some point also. You will feel a huge difference in the butt dyno, almost like you added a 100ft lbs of torque!

I was always under the impression that gears make a car faster period. There are some here that say they slow you down on the top end? I would like to see before and after 1/4 mile runs in the same car (similar conditions) to see how they really work in these cars. I think I am ready...

Convince me...

[Big Daddy Kane]

I know with 3.91 gears and a supercharger, my car doesn't get traction. But thats with street tires. I love the 3.91. Not too steep in my opinion. I actually think the 3.73 would be a waste.

[UCI CamaroFan]

Originally Posted by Big Daddy Kane

I know with 3.91 gears and a supercharger, my car doesn't get traction. But thats with street tires. I love the 3.91. Not too steep in my opinion. I actually think the 3.73 would be a waste.

How would this be corrected? With drag radials?

[flht99b]

Originally Posted by rick john

DEKAN,I just got my 3.91 installed last week and your 3.91 will only increase your r.p.m's by about 200 rpm's... believe me do it, you won't be disappointed. in sixth gear you'll go from cruising at 1700 or 1800 to 2000... trust me worth every bit

I installed AAM 3.70's in my LS3 M6 trans car and after the speedo re-calibration turn 2,000 rpms at 80mph in 6th. The 3.91's should turn another 175 to 200 rpm at 80mph.

Ed M.

[Slickcas]

With my new 3.91's I just took the car out and at 2,000 rpm I was running 75mph with the stock 3.45's I was going 81mph at 2,000 rpm. So not a big change and you will be under 2k if you cruse ar 70 or so on the interstate like I do(Illinois 65 is speed limit) But man the car feels so much better.

[NinoSS]

I would like to see two M6 cars with otherwise similar power, one with .391's and the other with .345's race from a roll. This way you could definitively see the difference the gears make.

[swiftkart]

Originally Posted by NinoSS

I would like to see two M6 cars with otherwise similar power, one with .391's and the other with .345's race from a roll. This way you could definitively see the difference the gears make.

When the new 1LE (3.91 Gear) comes out you will be able to see that or read about it in the mags.

[SUX2BU]

Originally Posted by dekan513

if i go with one just wondering what the car run rpm wise at say 65 mph i dont want to be driving and it running 3500 rpm in 6 th gear anyone have a video of them driving their car with a gear ratio around this size

Originally Posted by rick john

DEKAN,I just got my 3.91 installed last week and your 3.91 will only increase your r.p.m's by about 200 rpm's... believe me do it, you won't be disappointed. in sixth gear you'll go from cruising at 1700 or 1800 to 2000... trust me worth every bit

Everyone in here needs to Google "MPH gear calculator"

Originally Posted by NinoSS

I was always under the impression that gears make a car faster period. There are some here that say they slow you down on the top end? I would like to see before and after 1/4 mile runs in the same car (similar conditions) to see how they really work in these cars. I think I am ready...

Convince me...

Originally Posted by NinoSS

I would like to see two M6 cars with otherwise similar power, one with .391's and the other with .345's race from a roll. This way you could definitively see the difference the gears make.

It's amazing how misunderstood gears are on here.

The easiest way to describe what gears do is imagine two cars with the exact same amount of power racing each other. One can only use gears 1-5 and the other can only use gears 2-6. Obviously if the both cars can get traction then the car that can use 1-5 will win. If traction is a hug problem, then the 2-6 car will win. Now this is an exaggerated gear difference, this example would be like the comparing 3.45 gears to 2.37 gears.

The best way to choose your gear for racing down the 1/4 mile is figure out what mph you want to cross the traps at and choose a gear that will get you there right before your RPM redline.