Can you change/upgrade the final drive ratio

[kaganader]

I think this is a newbie question so I will post this here. I was pondering on this idea, since there is a market for the evos to change the final drive ratio down to a 4.11, 4.28, or 4.00 from there stock 4.53:1. Can we also do this for our setup. I'm thinking about changing my setup to a 2.3L 1.5 rod ratio and would only rev it to 7800-8000 compared to the 8700-8900 I'm doing now. Setup now makes mid 500s and low 400tq, next setup I would like to keep around the same top end but have it come in sooner, to make a more usable powerband.

Reasons for this

• I do not want to sacrifice mph per gear by shifting lower in rpms
• I want to pull the VE down to have a broader powerband
• I would like to keep as much mph in every gear in comparison to where I revved the 2.0
• I would not rev the 2.3 as I do the 2.0 due to cylinder wall wear and rod ratio

 

[Bud92gsx]

Evo 3 5th gear.

 

[kaganader]

Evo 3 5th gear.

I miss wrote the title of the thread, I meant to say Final drive ratio not final drive gear...

 

[Bud92gsx]

Right sorry I should have elaborated.


The evo 3 5th is taller...Commonly upgraded for gas milage on the highway. http://www.dsmtuners.com/forums/drivetrain-tech/333313-10-taller-5th-gear.html

So take a look,even tho it might not help you at all.

 

[kaganader]

Right sorry I should have elaborated.


The evo 3 5th is taller...Commonly upgraded for gas milage on the highway. http://www.dsmtuners.com/forums/drivetrain-tech/333313-10-taller-5th-gear.html

So take a look,even tho it might not help you at all.

Yeah thanks for that, mpg isn't a problem on the highway, forced open loop and cruising at 15.5-15.7 gets me quite good mpg when cruising. I'm looking to see if the final drive ratio can be change as they do with the evo 8-10. on an evo8 going from 4.53:1 to 4.00:1 at 8000rpms in 3rd gear would be a difference of 13mph (95mph to 108mph on the 4.00:1 final drive ratio)

With the 2.3 it naturally will make more torque down in lower rpms and reach piston speeds of 26.0 m/s at 7800rpms (stock 2.0 does so at 8863rpm) so there is a big difference of rpms I can use. to counter that I would like to see if we are able to change the final drive ratio so that I can meet or get close to the same mph at 7800-8000 that I was getting at 8700ish rpms.

If not, it is what it is then.

 

[boost97gst]

I know what you're getting at i think. Similar to how rwd v8s just swap in taller gears in the rear(3.55 to 4.10 for example)? Simple as that.
AWD will be far more complicated. You have front and rear diffs and a whole bunch of stuff i dont know about. TMZ would be who i would call if i were serious about this.

 

[kaganader]

I know what you're getting at i think. Similar to how rwd v8s just swap in taller gears in the rear(3.55 to 4.10 for example)? Simple as that.
AWD will be far more complicated. You have front and rear diffs and a whole bunch of stuff i dont know about. TMZ would be who i would call if i were serious about this.

Exactly Boost97gst! I see it being done on Evos, GTRs, of course fbodys, mustangs and the like. So I'm researching and looking if it has ever been done on DSMs before. Evos 8-10 only change the final drive ratio of the front differential and leave the rear alone.

 

[TimIacobucci]

Tranny gear ratios for DSMs

If you could find the parts from a ggsx, mitsu did make the gear sets you are looking for so it does exist. Those would give you a 3.937 final drive.

The other problem is the difference in the transfer case ratio between the 1g and 2g. If you got the matching set of front and rear diff gears you still would have about a 1.5% taller ratio in the rear. That's not allot so slightly shorter tires in the back might fix it.

If you could actually order a new ggsx front ring gear and front output shaft I think you could swap any earlier 1g tcase if its 23 spline. Or even a 22 if you can get the rear output shaft with it.

If you could actually find a ggsx transmission though it would be best to try and swap your 2g guts into that case and run a 1g tcase with it. The center diff and intermediate shaft need to match, I think the manual awd front and rear ouptut shafts are all splined the same so they should fit the 2g center diff. That would give you the 2g primary ratio and the ggsx secondary and tcase ratio to match the new rear diff ratio.

Also the rear diff carrier between the manuals and automatics interchange, I know the 1g's ring and pinion interchange, not sure if the 2gs ring and pinion does as well but I would imagine if the carrier does then the ring and pinion likely do to, if that's true you might also be able to use the non ayc rear diffs from the evo's as well. I can only vouch for the 1g ring and pinion though. ALL of those rear diff carriers interchange though.

If that is true it would mean you could pick from any of the 1g/2g and possibly even the none ayc evo rear diff ring and pinions.

Of course that still leaves you to match the front. The awd front differential also interchanges between the manual and auto, not the fwds though. I doubt the front ring gear and front output shaft would interchange between the manual and auto though. So some of the pieces of the puzzle are there to swap auto stuff too. I'm just mentioning this because if you actually had a custom gear set made for the front you could make it to match the stock ratios you could actually find for the rear.

Considering the rarity of the ggsx stuff that seems like the only relatively practical route to accomplish what you are saying.

 

[pacn91]

I havent gotten far in my home work on this, but I was wondering if this could be done on a fwd.