So, ever since my EJ22/Rx trans swap, I've been very unhappy with the gear ratios. so over the last few days, I've done a bunch of research on gearing, and what all came with what, and what I found was rather suprising.

 

this is all from an '89 FSM

 

first off, an N/A EA82 D/R 5MT

1st: 3.545

2nd: 1.947

3rd: 1.366

4th: 0.972

5th: 0.780

Final Drive: 3.90

Lo Range reduction: 1.592

 

EA82 turbo FT4WD 5MT (RX or GL/-10)

1st: 3.545

2nd: 2.111

3rd: 1.448

4th: 1.088

5th: 0.871

Final Drive: 3.70

Lo Range reduction: 1.196

 

Myth: Because of the final drive, the turbo trans would yield lower rpms at cruise...right?

 

well, punch those numbers into a gear calc (like the one on Subarubrat's Website). using the stock tire height of 23", cruising at 75 mph with a turbo trans means 3500 rpms, while using an N/A trans, means 3300 rpms.

 

BUSTED

Makes perfect sense - the EA82T makes more efficient power at higher RPM. And it needs all the help it can get

 

I guess you could swap the gearset with a regular D/R.

 

GD

Makes perfect sense - the EA82T makes more efficient power at higher RPM. And it needs all the help it can get

 

I guess you could swap the gearset with a regular D/R.

 

GD

 

haha, you beat me to it....here's my idea for a solution...

 

 

listing of common EJ gear ratios:

http://www.nasioc.com/forums/showthread.php?s=&threadid=181343

 

also, gen 1 legacy gearing from my '92 FSM

FWD 5MT

1: 3.545

2: 1.947

3: 1.366

4: 0.972

5: 0.738

FD: 3.70

 

AWD 5MT

1: 3.545

2: 1.947

3: 1.366

4: 0.972

5: 0.783

FD: 4.111

 

 

So, inspired by Beefaru's el sweeto hybrid transmission, and the fact that I had a couple RX transmissions, and a legacy 4.111 AWD trans fall into my lap (and assuming, since he's got a forester 5-speed...that other EJ gears can be used). plus the EA82 N/A D/R trans I already have (although I did promise to sell it to a buddy....). Here's what I'm going for:

 

EA82 N/A or AWD Legacy 1-4 (same ratios, I'm leaning towards the Legacy ones...assuming they're stronger)

FWD Legacy 5th

EA82 N/A lo range

RX center diff and final drive (the guy who's giving me the RX trannies seems to think a Mazda 323 GTX viscous locking center coupler could be used....he's got one...so I plan on finding out...).

 

This would give me:

1: 3.545

2: 1.947

3: 1.366

4: 0.972

5: 0.738

Final Drive: 3.70

Lo range: 1.592

 

which would mean, on stock tires (ignoring the fact that I'll probably be on bigger ones), this means that in 5th Hi, at 75, the engine would be turning a relaxed 2900 rpms.

 

And, when lo range is engaged, it would be like having a final drive of 5.9:1. Which means, in 5th Lo, 5k rpms would be 78 mph. Which would work out perfect for even the fastest of courses.

 

AND, still keep the locking center diff. While I have it all apart, I would really like to put in a front LSD. but that'll depend on the cashflow at the time

uh, do that to mine too plz

i figured that out a long time ago. crazy huh, better low end and better high end and better low range, what was the point of the turbo tranny. oh well

lower compression at lower rpms is no doubt a reson for the shorter gears in the turbo. A n/a motor has thump and go from the jumpy 1st all the way through...

I have had the 3.7 to 3.9 and noticed nothing , even after paying attention to difference. Here is another calcc site for gears that can include transfer reduction:

 

http://www.4lo.com/calc/gearratio.htm

 

The 3300 at 75 is quite accurate on n/a d/r trans. I have closer to 24 inch and it rides around 3000 at 75 (very "tall" for a little engine!) at 25 inch, my particular setup is in "gear heaven" for my highway cruising. The oem engine needs a bit more air, but thats about it.

 

The swap is worth it, if you do. The turbos are so easy to get outrageous power over oem numbers.

after talking with Shawn while he was digging through the trannies, I believe the biggest obstacle is the pinion gear/shaft. they are different lengths and possible milled a bit differently on the shaft as well...

FYI, the Turbo pushbutton 4WD tranny has the same gearing as the N/A 5spd D/R just with a 3.7 final drive ratio.

 

Same goes for the Turbo pt4wd 5spd D/R, except it has a 3.7 final drive and the 1.2 low range.

 

Meaning the PT4WD Turbo trannies have the highest 5th gear.

after talking with Shawn while he was digging through the trannies, I believe the biggest obstacle is the pinion gear/shaft. they are different lengths and possible milled a bit differently on the shaft as well...

 

yea, I suspected that. but with this setup. I'd be using the 3.7 pinion and ring gears. along with the RX center diff....so that shouldn't be a problem....if I can get the 1.6:1 lo range gears to work, I don't see any reason to lower the final drive.

 

 

according to my FSM, all turbo 5MT models had the same gearing. whether part or full time, single or dual range. all had 3.7 final drive and 0.871 5th gear. it may have been different in other years....but it appears not in '89.

according to my FSM, all turbo 5MT models had the same gearing. whether part or full time, single or dual range. all had 3.7 final drive and 0.871 5th gear. it may have been different in other years....but it appears not in '89.

It must be a year basis then. My 86 FSM says all turbo trans have the same gearing as the N/A 5s D/R. However, in 88 that's not the case as I just checked out. The S/R PT4WD trans has the same gearing as the FT4WD trans. So yeah, its a yearly thing.

It must be a year basis then. My 86 FSM says all turbo trans have the same gearing as the N/A 5s D/R. However, in 88 that's not the case as I just checked out. The S/R PT4WD trans has the same gearing as the FT4WD trans. So yeah, its a yearly thing.

 

yep, they didn't start the FT4WD 5MT until '87...so maybe that's when they adopted the different gears...