shortest gearing available (OEM)

[Paddy1337]

So, my trans has to be rebuilt before I can race this year. If I can find a better option to start with for my use, it would make much more sense to do that, especially if it's already working.

So, for rally, I'm looking for the lowest gearing I can, but want to keep things cheap so I'm ruling out custom gearsets. I don't care if I'm in 5th gear on stage, that just means the car is going to pull great.

I'm not a DSM/GVR4 guru, so I get lost when reading about matching the diffs to the trans- so I'd greatly appreciate dumbing down your response to my level. I wish I could just swap a final drive and be done like my Evo /ubbthreads/images/graemlins/wink.gif

 

[Paddy1337]

I just want to make sure I'm not being confusing. I hear people use different terminology with gears (high low tall short).

I want a lower (numerically higher) gear; to increase my RPM for a given speed.

 

[cheekychimp]

I don't know about a lower final drive but a lower final ratio does exist! But I'm afraid I'm dangling a carrot without much assistance in being able to reach it. I have an ex rally car box in my daily that states it is a 4.3 final ratio. That's shorter than the JDM RS 3.909 boxes. It has shorter ratios 1st through 4th but 5th is a bit of a jump since it appears to be 'equivalent' to the stock 5th gear in terms of speed at a given rpm.

I tried to find out what I could regarding the box and I found nothing apart from an archived thread from a Mirage or Colt forum I believe talking about a frankenstein box that also had a 4.3 final ratio. I think very likely whatever the builder of those boxes discovered probably has something to do with the combination of parts in my gearbox.

Your best bet probably is either a JDM RS 3.909 box or an EVO III drivetrain especially with some proper plate LSDs. I also have a couple of excel files showing speed at given rpms for different gears for different configurations. One is a maximum speed per gear chart that you can experiment with by inputting different ratios, the second gives the various ratios achievable using combinations of 1G/2G/VR4/RS EVO III/GGSX drivetrain parts/transfer boxes etc.

If you need either chart, PM me with an email address and I'll send them to you. I will at some point crack this gearbox open and freshen it up. If I can get part numbers or any other info at that stage I will post them up, but unfortunately I have very few facts available to me at this stage to verify the validity of the 4.3 final ratio box, other than the seat of the pants experience. This thing hauls ass through second and third and requires quick shifting on the highway on a pull away from the toll tunnels.

 

[Paddy1337]

appreciate the help. PM coming.

I must have been mistaken, because in my limited research the Evo3 I thought gave the opposite of what I wanted. I'll do mroe digging /ubbthreads/images/graemlins/wink.gif

 

[BENE38A]

im not a wealth of knowledge on gears but if i were rallying i would go for an vr4 rs gearbox and if your serious about it an evo 3 rs box as above with an lsd, evo 3 stuff is strong and holds good power rs meaning rally spec so you cant go wrong, i guess finding one stateside would be hard? i wouldnt know where to start but if you found part numbers for the evo stuff you could put it in your 6 bolt box, i have an evo 3 rs gearbox on my 6 bolt and it works.

 

[BENE38A]

its 3.909 stuff so you will need a diff too

 

[cheekychimp]

Did some more digging ... look what I found



I wonder if any of these are FWD parts that can be mixed and matched? I haven't even started looking at those 4.3 and 4.9 ratio boxes to see what they came out of ...

Might also be worth seeing if Merrill Performance are still about. I have this as a PDF and will send it on with those Excel files for ya!

 

[Paddy1337]

Now that's definitely food for thought. I'll have to feed info like that to guys I know who really know these transmissions. Possibly one of my weakest points on cars if I had to say.

thanks!

 

[cheekychimp]

You're welcome, but it does look as if these are FWD boxes. The problem is going to be the rear ring and pinion gear to match the final ratio in an AWD car. I'm going to have to crack the rear diff I suspect to find out what the story is back there as well.

Edit: I suspect that given the interchangeability of Mitsu parts, there are probably a few unicorn parts about that do work. The 1993-1995 Mitsubishi Galant VR4 had a completely different engine and gearbox to these cars but the rear ring and pinion is a 3.909 ratio which fits the E39A rear diff and works with the 3.909 ratio RS boxes. It wouldn't really surprise me to find out that some later model AWD Galant, Diamante, RVR etc Japan only model has a 4.3 ratio rear ring and pinion that works with some of these parts. But finding it will be a bitch!

 

[CutlassJim]

I believe the shortest first gear for a AWD box is the Galant first gear. It's also the weakest though. The close ratio box's that people sell are a DSM 1'st and 2nd, Evo3 3rd and 4th, and DSM 5th. That or Evo 2nd and 3rd and DSM 4th and 5th. If you wanted to make all that even closer you could get a shorter final drive as well. But I'd think the car would be slower because you have to shift so much. Just make more torque and stop being a nimby.

 

[Paddy1337]

i won't be using first gear much, and even then it's on gravel, not a drag strip. Getting the ratios matched up would certainly be nice, but it's just the final ratio that I'm really concerned with.

through a dinky restrictor, I'll take all the gearing advantage I can. Because extracting reliable power through that thing is going to suck.

 

[Wizardawd]

USDM GVR4 1st is slightly taller than a DSM 1st, but as you mentioned, weaker. EVO3 1st is even taller in first, yet stronger than the DSM 1st. Usually rally boxes are setup as having a fairly tall 1st gear, then very close gears from there. 100mph top speed at the rev limiter in 5th.

Wiz

 

[Paddy1337]

"100mph top speed at the rev limiter in 5th."


^^ exactly. That's really what I'm looking for here, is to change the overall ratio.