Tranny Gear Ratio's

[Albrecht09]

Whats up...just a quick question I've been wondering about.. I've never been a fan of the gear ratio's Mitsubishi chose to use on some of their transmissions on a few of their vehicles, but now that I got my car to DD status and have been driving it on the highway and such, I'd say this ones the worst yet. With my 2000 3G V6, first gear was essentially useless. It was geared for way to much torque rather than speed. Even on an inclined hill from a stand still, Id start out in second a lot of the time...but my complaint with my 98 GST now is between 4th and 5th gears. Is it normal for 5th gear to seem like it honestly was just an extension of 4th when you first shift? Here's what I mean:

Driving, getting on a ramp to get on the highway, in 4th gear, ~3.5-4k RPM, shift into 5th, and RPM's literally only drop 200-300. I thought my 04 Sunfire was bad (500-600 RPM difference between 4th and 5th), but this seems just ridiculous...What is the reasoning for this?

 

[AllShallPerish]

I dunno man, It would be SOOOOOOOO nice to be able to cruise in 5th on the highway and stay under 2500 rpm..

I just took a road trip that was 2500 miles round trip. 90% of that drive i had cruise control set to 80 MPH which keeps me at about 4k rpm. I still got 30 MPG, i just kept thinking out much more MPG we would get with taller gears.

 

[Redslayer]

I dunno man, It would be SOOOOOOOO nice to be able to cruise in 5th on the highway and stay under 2500 rpm..

I just took a road trip that was 2500 miles round trip. 90% of that drive i had cruise control set to 80 MPH which keeps me at about 4k rpm. I still got 30 MPG, i just kept thinking out much more MPG we would get with taller gears.

This x1000 >.>

I always wondered what kind of gas mileage I could achieve if 5th gear wasn't so short. I'm almost always at around 3k+ when I'm on the highway.


Car should of been a 6 speed .

 

[Fehrion_sit]

has anyone called dogbox transmissions, or Road Race Engineering or shep to see if they have seen or done something about that?

 

[scottyhops]

i know on 420a they take dodge neon gears and swap them over and in 5th is able to cruise a lot better. but i have not heard of anything. they really should have made these 6 speeds. even though my friends evo cruising 90 is at 3k

 

[Boosted DSM 32]

Ive always complained about how short dsm gear ratios are but lately ive been thinking, and they came from the factory with short gears so the cars are made to drive at the high rpms thats just how they were built i dont think the lower rpm would do anything maybe 1mpg better but to me thats not worth it the automatic transmissions are at super low rpms even going like 90 but the 5 speed is just built to be that way idk why im always hesitant to go 50 mph so im at 2500 rpm but remember its not going to do anything because it was built that way

 

[Chrispy0530]

I myself can't stand the short 5th gear that the GSX has. My girlfriends Auto 3rd gen GS Spyder cruises at around 2,600 RPM at 70. While in my DSM it's roughly around

has anyone called dogbox transmissions, or Road Race Engineering or shep to see if they have seen or done something about that?

As far as I know, Shepard is only able to offer the taller 5th gear from the EVO III. Which bumps the final drive down a bit, but I still wish one could be made a lot taller.

 

[DSM1G90]

Prob why the 3000GT has such a pitiful 1st gear is that the 6G72 V6 doesn't have the torque output as does the 4G63 at a certain RPM - it's an "oversquare" motor.-bore larger than stroke. 4G63 is a good designed motor 85mm bore with 88mm stroke ..almost square - revs up quick and has decent torque to match.

Hardly any "V" piston engines are undersquare than their 4 or even 6 cyl straight cylinder setup has. Yet, on the plus side, the "V" motor can get the revs up very quickly, why they're good off the line.

Chev's 327 is a good example: 4 inch bore, 3 inch stroke - jumps off the line in a heart beat, but lousy in pickups. Thus GM took the motor and increased it to a 350 -same bore but longer stroke to get it more square. Now, a slight reduction off the line but got some torque out of that motor.

Old Chev pickups with a 292 straight six in a 4x4 chassis in low gear setting can prob out pull the new stuff that is now due to the massive low torque that motor had .. almost 300 ft lbs at only 2100rpm.

Old Flat top "V8's and 12's" of yesteryear definitely had the long stroke for the low rpm torque output, but these motors were not designed for high revs.

 

[Albrecht09]

Ya, I figured I wasnt the only one ashamed of their 5th gear. I mean, I thought I've seen it all till this...literally cruising at 3500 rpm in 4th, quickly shift to 5th and as soon as the clutch disengages without changing speed at all, RPMs are at 3300. MAYBE 3250. Even with the output of the motor what it is, that seems way to short to me.

 

[DSM1G90]

Course, you have to realize that the final drive ratios are high: 4.15 for turbo and 4.22 for NT's.

Average with 4cylinder cars is in the high '3's .. like 3.70 to 3.82. That is why your RPM's are sitting close to 3500 at 80mph -for both auto and manual DSM's

ALSO, why you're now seeing 6 and up to 8 speed automatics -to get the RPM's down for better fuel economy from smaller motors.

4 Cylinder motors cannot produce torque like their torquy V8 "big brothers" which can use final ratios down to the high "2's" for automatics and the most popular being the 3.08 on a 4 speed.

So, I live with it: Put the cruise on 80mph with tack at 3500 and love my 28mpg on the freeway.