Determining Gear Ratios

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Christopher Chirdon

Determining Gear Ratios

Post by Christopher Chirdon » Mon Apr 21, 2003 1:19 pm

Okay, I think I'm pretty confident that the 1993 Tansmission is compatible.
But I need to figure out if the front and rear differentials are the same.

My car : 1993 Legacy 4WD
Donor: 1993 Impreza 4WD

Who do I determine:
-Gearing on the front diff?
-Gearing on the rear diff?

Are there axle codes I can 'decode'? Which are they?

If this is a bare transmission, is this information on the transmission
somewhere?

Would the baisc Impreza use the same rear diffs as the Legacy?

Thanks for everyones' help,
Chris

Mark Ward_

Determining Gear Ratios

Post by Mark Ward_ » Mon Apr 21, 2003 7:29 pm

Look on the transmission near the starter, There will be a sticker starting with TY752.... Post this number and I will post back your gear ratio's or look it up at Josh's page... http://www.surrealmirage.com/subaru/trans_spec.html
Mark

Christopher Chirdon

Determining Gear Ratios

Post by Christopher Chirdon » Mon Apr 21, 2003 10:09 pm

Okay. So, I looked at the rear diff on my 1993 Legacy LE Auto and it is
quite plainly marked 3.90. Thus I definitely have a 3.90 rear end, and
thus a 3.90 front diff. So, as many things are labeled as 'final drive
ratio', what do I have? How can I tell what my 'final drive ratio' is?

I checked out that page; awesomely useful, if only they related that info
to model years/trim levels. And why does it seem like my car is an odd
offering? I mean, on that page, very few are marked as 3.90 but then it is
also labeled 'turbo Legacy models' which mine is not. If course, why would
they put a shorter gear ratio in a turbo? Aren't you supposed to put
taller ratios in a turbo? Better use of power.

It's sad; I'm babbling because I'm tired. I'm tired because my kids wore
me out. LOL. =) At 100PM. How sad...

I'll try to get to the yard tomorrow to see what the '93 Impreza tranny is
stamped.

Thanks to all,
Chris

PS (for Mark) the transmission 'fender codes' (not in the place you said to
look) were as follows:
I'll look the others up tomorrow.

My Car: 1993 Subaru Legacy Auto 4WD
TZ102ZA2AA

1993 Impreza Code:
TZ102ZX3AA

Josh Colombo

Determining Gear Ratios

Post by Josh Colombo » Mon Apr 21, 2003 11:19 pm

The turbo legacy got 3.90 gearing. The 92-93 legacy autos had 3.90
ratio

That is the final drive ratio.

There are few imprezas that have a 3.90 ratio as well, but I think it's
less common. Most had 4.111 final drive ratio.

Subaru did funky stuff and had mixed final drive ratios among years....I
don't know why.

I know I had some confusion about gearing and such....so I'm goin to
explain it to how it was explained to me so I can understand it. If you
already know....forgive me.

The higher the actual final gear reduction number is, the "lower" the
gear ratio is said to be. What that basically means is the larger gear
that connects to the drive shafts will spin 1 revolution, and the gear
connected to the transmission will spin 4.111 times, or 3.90 times. I
don't know why the terminology is backwards....but like I said....a 3.90
gearing is said to be a higher gear ratio or taller gear ratio then a
4.111 ratio which is said to be lower gear ratio.

As for picking a ratio. My FWD legacy has a 3.70 final drive ratio. I
can do 85-90 mph and my revs are at 3,000 rpm. Which for cruising and
such, it's nice. If you want all out acceleration, a lower gear ratio
is going to help. The 3.90 final drive ratio IMO is probably the best
all around gearing subaru has done. 3.70 is a little too high...(not as
high as I guess the 3.545 that the SVX has) and the 4.111 & 4.444 final
drive ratios are just too low. If you're just interested in
acceleration or top speed, one of the other ratios would be better
suited. Like I said 3.90 is a pretty good all around final drive ratio.
But that's my opinion and for my driving needs. Someone else may have a
different opinion and different driving needs.

Josh

Mark Ward_

Determining Gear Ratios

Post by Mark Ward_ » Tue Apr 22, 2003 7:19 pm

Personally, I love the 4.11... It brings the gears together, esp 2nd and 3rd. But it does rev higher on the Highway.
Mark

Mark Ward_

Determining Gear Ratios

Post by Mark Ward_ » Tue Apr 22, 2003 7:19 pm

Hmmm, I only have the info for the manual transmission...
Mark

subaruracer755@cs.com

Gear Ratios

Post by subaruracer755@cs.com » Wed Apr 23, 2003 7:49 am

and 4:44 is QUITE high for highway... i dont know how the autos do it, but in my legacy, the 4:44s i have puts me at 3500 at 70mph. its quite loud, but DAMN fast, its like i have 4.5 gears not 5!!!

Mark Ward_

Gear Ratios

Post by Mark Ward_ » Wed Apr 23, 2003 7:19 pm

It does depend on the actual ratios inside the box... When figuring out final ratio's to the wheel, all gears and finally the actual tires size is used. You could run taller tires to compensate, it would just mess up your speedometer.

Mark

subaruracer755@cs.com

gear ratios

Post by subaruracer755@cs.com » Thu Apr 24, 2003 2:49 pm

so, since i have 4:44 gearing and my 16" 205/55 tires put my RPMs waaayyy too high. does anyone know what size rims are on the liberty RS? or what would I have to get for my car to bring the RPMs down aobut 500 RPM? right now at (what the speedo says) 70MPH i am pulling 3500 RPMs. i want to get back to 3K at 70 (which was what it was with my old tranny and 3:90 gears.

i like the quickness of the car, just the highway cruising sucks.

Josh Colombo

gear ratios

Post by Josh Colombo » Thu Apr 24, 2003 9:59 pm

Get a taller tire....215 or 225.

subaruracer755@cs.com

gear ratios

Post by subaruracer755@cs.com » Fri Apr 25, 2003 8:19 am

215 or 225??

thats wider

Josh Colombo

gear ratios

Post by Josh Colombo » Fri Apr 25, 2003 10:09 am

doh....my bad.....well actually a 225/50 will be slightly taller as well as wider then a 215/50.

ssspoon@aol.com

gear ratios

Post by ssspoon@aol.com » Fri Apr 25, 2003 4:19 pm

Hey Subaruracer I'm no trans person, but you seem to be always into one mod or another. I have always thought it would be nice to have a 5th gear WAAAAAYYYYY taller than fourth, exclusively for highway cruising...not passing...cruising.

Isn't there a way you could swap out that 5th gear for something higher, so you could keep the 4:11's and enjoy all they give you, but then when you're on the freeway in traffic, you just upshift from 4th at 70 and watch your rpm's go from 4500 to 3000?

Yes the gap might be too great for optimal times at the strip, but unless low et's all the way thru 5th is your ultimate goal, you would hardly ever notice it.

Spoon

Bill Covert

gear ratios

Post by Bill Covert » Fri Apr 25, 2003 11:19 pm

Hi Larry, This is BillC.Small car is a company that offers 5mt conversions
for the SVX. They offer a taller 5th gear as an option.The gear is a
.738.stock is .78. I think they use turbo legacy trannies so this might be
an option.Their website is
http://www.smallcar.com/svx/index.htm

subaruracer755@cs.com

gear ratios

Post by subaruracer755@cs.com » Sat Apr 26, 2003 10:41 am

change 5th gear?!!??!

i just got the trannie in!!!!

anyways...

IN OTHER NEWS
i have a 3:90 open rear diff in the housing sitting around doing nothing that needs a home!!! you can have it for $100 plus shipping. its all ready to go!

Douglas Hancock

gear ratios

Post by Douglas Hancock » Sun Apr 27, 2003 1:18 am

Weld it up.

subaruracer755@cs.com

gear ratios

Post by subaruracer755@cs.com » Sun Apr 27, 2003 8:52 am

no no no....

i now have 4:44s in my car, i have NO need for the 3:90 sitting around. why would I weld it up? anyone on this list want it?

Douglas Hancock

gear ratios

Post by Douglas Hancock » Sun Apr 27, 2003 9:32 am

Just kidding.

subaruracer755@cs.com

gear ratios....

Post by subaruracer755@cs.com » Mon Apr 28, 2003 7:32 am

ahhhh

i see...

well yesterday i went past a known place that had one of those speed displays and kept it (my speedo says...) 75... the box said i was doing 70... so its 5mph high, ill just remember that

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