Closer ratio trans. - what are my options?

[skivittlerjimb]

Long story short - for the types of events that I do, the gap between 1-2, 2-3, and 3-4 could stand to be shorter to keep me in the power band.
I'm honestly not sure if I have the DSM 1st gear or GVR4 1st gear, but either way, 1st gear is just about perfect for autox and hillclimb starts and I have no need to mess with that ratio.

2nd through 4th could all be shorter and closer together. Having 2nd gear a good bit closer to 1st gear would certainly help with being above the "lag band" around 3200 - 3600 rpm when I run out of first gear in autoxs. At track days, I've definitely noticed the fall off between 2nd and 3rd is also a bit too much and it'd be much better for lap times, less downshifts, etc., if I could leave the car in 3rd more often and rarely have to drop down to 2nd. Also, having 4th gear top out at 7k rpm ~110mph would be ideal, as this is about the maximum speed I'll likely see at a hill climb in VT or elsewhere for that matter. 5th gear is fine where it is and if I were to change the ratio I'd actually go 10% higher with it to get a bit better mpg on the highway. I realize getting spool and power lower down would be a partial remedy, but even a Evo 3 16G being spooled by 9.0 to 1 compression on a 2.0 isn't probably going to spool any lower than 3200 rpm. I might be able to get spool lower than that with a BB turbo but that's bigger money and an Evo 3 16G is really the route I want to go.

So, what are my options? Should I be looking for an overall gear set from some type of tranny that already exists, or will I need to custom order something to my needs from a shop like Jack's or TRE? Ideally I don't really want to mess with the final drive ratio. Right now I have a DSM 4-bolt viscous rear LSD and, I believe, a DSM 1G transmission as well, so if I can stick with that set up and only change the 2nd through 4th ratios to make them overall lower and closer I'd be happy.

I have a tranny in the car that's getting crunchy in 3rd and 5th and two spare trannys on the shelf in the garage. Anyone of these could be a candidate for a full send-off / re-build this winter, and I'm starting to budget for that already. I want to re-build for reliability and strength for sure, with autox, track days, hill climbs, and ultimately tarmac rally (Targa Newfoundland) in mind. I don't launch the car super hard nor do I abuse it trying to shift as fast as humanly possible. Advice?

-Jim B.
280/1000

 

Evo III gears are what your looking for. The Evo 1st gear is taller than the galant but its a perfect match for the rest of them. www.jackstransmissions.com sells them and I think www.teamrip.com does also.

If you go with an evo 1st gear you will need to change your input shaft.

 

[skivittlerjimb]

Definitely seems like it would address the 2-3 and 3-4 shift, and bringing 1st gear higher would help at autoxs for sure. I still need to do my p/s pump mod to get rid of p/s cut out above 6500 rpm, but 11% taller than GVR4 1st gear would give me more head room there regardless.

So there is no shorter 2nd gear that anyone is aware of then? Not that I need this, but figured I would ask anyway. Any GVR4 owners who run the full Evo III gear set and can comment on improvement in drivability / powerband?

-Jim B.
280/1000

 

[Dialcaliper]

The only way to shorten 2nd gear would be to swap in a JDM final drive (3.909:1 rear instead of 3.545:1). This would make *everything* shorter, which might be what you're looking for - With the Evo III gearset (1,3,4,5) it would probably be tolerable (The Evo III actually came with the shorter final drive). With the JDM final, the VR-4 5th gear will stay in the powerband and be a much more usable gear on the track (~4500 RPM at 100 MPH, Redline just above 150 - fine unless you think you'll need to exceed 150 MPH with any frequency), but you'll lose a bit of highway cruising capability.

With plenty of low end torque from a snappy turbo, first gear spaced closer to 2nd, and a double synchro in between, downshifting to first won't be nearly as bad. You might be fine with the USDM final drive.

Also, the JDM final + Evo III 1st will put you almost exactly at the same spot in 1st gear as the USDM VR4 1st.

The closest possible ratios (unless you find a true JDM RS box, which is supposed to be even tighter) would be Evo III 1st, 3rd, 4th, and keep the VR-4 2nd and 5th. If I were to build a race car, I'd use those combined with the JDM final gear - A true close ratio transmission is designed to make all 5 gears usable for a given engine. None of this "Cruising gear" business.

Start talking to Jack, Shep or TRE - any of them can help you out with a similar build.

 

[skivittlerjimb]

I believe there is one person I know of that went with the Evo III gear set plus the actual Evo III final drive as well. He hill climbs a 1G and says if he had it to do over again he wouldn't have gone so short with the gearing. He tops out at 115mph now, is shifting all the time, and at a few hills is bouncing off the rev limiter in 5th. /ubbthreads/images/graemlins/shocked.gif

Anyway, great info. I appreciate it! Will definitely get on the phone with Jack's to talk about it and see what the options are.

-Jim B.
280/1000

 

115??? I go through the traps at 9000ish in forth @ 132mph. He should be much faster than that. I love my ratio, I just need a taller tire.

 

[Dialcaliper]

1G DSM's have a fuel cut speed limiter at 130 mph - if he is running the JDM final drive without changing out for the correct speedometer gear, and he doesn't have a chip or tuning setup that removes the limiter removed, it's very possible he's hitting the limiter at 115, not the actual engine rev limiter.

Quoting skivittlerjimb:
I believe there is one person I know of that went with the Evo III gear set plus the actual Evo III final drive as well. He hill climbs a 1G and says if he had it to do over again he wouldn't have gone so short with the gearing. He tops out at 115mph now, is shifting all the time, and at a few hills is bouncing off the rev limiter in 5th. /ubbthreads/images/graemlins/shocked.gif

Anyway, great info. I appreciate it! Will definitely get on the phone with Jack's to talk about it and see what the options are.

-Jim B.
280/1000

 

[Bimmubishi]

Jim I have another dogbox here with your name all over it! /ubbthreads/images/graemlins/smile.gif

 

[Rausch]

Quote:
I realize getting spool and power lower down would be a partial remedy, but even a Evo 3 16G being spooled by 9.0 to 1 compression on a 2.0 isn't probably going to spool any lower than 3200 rpm.

FWIW I think you could see positive pressures a decent bit under 3200 rpm with some careful parts selection on a 9:1 motor.

A stock engine that is relatively healthy should get you that 3200 number, and the fairly significant bump in compression, plus careful cam selection (Like this: click or this: click ) should net you much better results.

 

[cheekychimp]

Jim did you get my PM. I can send you some Excel sheets to show you where various combinations of 1G, 2G, VR4 and GGSX gears and final drives can get you. Similar to what Dialcaliper mentioned above but you can go through every gear of every box with each compatible final drive and work things through. It's kind of interesting, Teet and I worked out once that the GGSX gear set with one of the final drives (forget which one off hand, but I think it is in the archives) gave ratios almost identical to the Magnus Dogmission.

 

[skivittlerjimb]

Quote:
A stock engine that is relatively healthy should get you that 3200 number, and the fairly significant bump in compression, plus careful cam selection (Like this: click or this: click ) should net you much better results.



Liking the second option you posted for sure. Restrictor plate cams don't seem to make much sense as I have no plans of running SCCA Pro Rally any time in the near or foreseeable future. The 264/260 cams you listed sound perfect and might be a better option to the 272/272 or 264/272 HKS option. Either one of those HKS options sounds like I'd have to sacrifice some 3-4k power for cleaner and more power up to 7k. Have you driven a car with Kelford 1-TX264 set up and can give feedback on drive-ability and power up to 7k?

I went with 9-1 so I wouldn't have to run as much boost to get the same power levels and would get better off boost throttle response and lower RPMs for full spool. So far so good, but with my current crappy Bullseye 38mm flappper door O2 housing I can't see what life beyond 16psi is like. /ubbthreads/images/graemlins/frown.gif Ported Evo III 16G with different O2 housing should let me run 20-22 psi all day with good tuning (DSM link + DSG's dyno) without sacrificing low-end. Going crazy with aggressive cams makes no sense with this option, so the cam option you posted above might be just the ticket before messing too much with gear ratios.

-Jim B.
280/1000

 

[Rausch]

Unfortunately I do not. I spent some time going through all the cam specs I could find (was originally looking to build a stroker, and shoot for max tq) to determine what would be best. At one point I was fairly determined to have Kelford grind a cam with similar specs to the rally spec, but with some minor changes. The idea was to maximize lift as much as possible, and dial in the durations to see a maximum efficiency around that 5252 rpm mark. I wound up with something about 268 intake, and closer to 260-262 exhaust. I never did work out the centerlines, and the ramp angles I wanted to run were quite steep...

I noticed these cams seemed a bit more suited to the range of builds I contemplated, and noted that the lift and durations seemed more suited to building tq.

I only referenced the rally cams to lean you towards something with a shorter duration. Granted you'd lose top end for sure, but it makes for a good reference if nothing else. the 264/260 seems like a very good option, and with a ported Evo III and a good flowing O2, you should be much closer to where you need to be, before digging into the gearing areas.