Rear Gear Top Speed

SupraSean

SPRASEAN MTHRFKR
Mar 3, 2009
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Pittsburgh, PA
My car (92 7mgte was auto, now converted to 5 speed) Tops out 5 gear at 6k rpm at around 145-150 ish.. I thought for the longest time that i had a 4:11 Gear Ratio. I Through my info into the vin lookup at work and it says i have a 3:73. How is it possible that im topping out that low on such a wide gear? My actual question is of you guys that have the same 3:73 rear, what do you top out at?
 

hvyman

Dang Dude! No Way Man.
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Apr 17, 2007
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I went to 165 plus a little one time.

If you google mph calculator can see what your gearing should take you too but also need power to get to those speeds.
 

SupraSean

SPRASEAN MTHRFKR
Mar 3, 2009
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Pittsburgh, PA
Is it possible that the speedo gear in the trans is reading wrong since its a 5speed? i would imagine speedometers have different gear ratio's to accomodate rear end gear ratio's. Im wondering if i was going alot faster than the speedo said.
 

Turbo Habanero

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Apr 28, 2009
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SupraSean;1804741 said:
My car (92 7mgte was auto, now converted to 5 speed) Tops out 5 gear at 6k rpm at around 145-150 ish....
the redline is 6500 correct?

There was a tread awhile back talking about this and a r154 with 3.73 and 18inch wheels would go all the way to 180 plus with a 6500 redline
 

Carl Johansson

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Dec 19, 2009
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easy to do the calculations on line about potential top speed. you can determine the ratio by just jacking it up and spinning the tire and counting the rotations. You also need tire size for the calculators. But the issue is really how much power it takes. drag goes up as the square to the speed. it becomes a monster at high speeds, the vast majority of your Horsepower is used up pushing air out of the way! In the land speed world the saying is that it takes 7X as much power to make 2X the speed. ie if you can make 100 mph with 100 horsepower, you would need 700 HP in the same car to reach 200 mph. You can actually run the car through a calculator if you know CD and frontal area. Frontal area pretty easy to guestimate, measure up the side, then across the width, think of it like if the car punched through a wall in a cartoon. The shape the car leaves, thats the frontal area.
you can go over to Seldom Seen Slims website - landspeed . com for calculators and alot of guys who know this stuff cold!

anyway with frontal area and coefficent of drag you can easily calculate how much horsepower you need to reach any specific speed. i can tell you that most guys way overestimate their cars top speed, and some of em even lie about it - make stuff up. I doubt the 180 speed given here, unless the guy is putting out about 550 hp at the wheels
 

Turbo Habanero

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Apr 28, 2009
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The 180mph speed is where you will run out of gear..

I was not saying I have gone that fast or I have the power to go that fast just that the transmission and gearing will slow it to reach there.
 

Poodles

I play with fire
Jul 22, 2006
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Bit soon than that with everything stock on a 7M and R154

Auto will go a bit higher because of the gear ratios. It wouldn't be hard to go higher with taller tires or increased rev limit, but of course you need the power to get there...
 

Turbo Habanero

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Apr 28, 2009
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So what do the gear ratio's allow the car to achieve poodles?

Let's say

R154 with 3.73 and stock wheels.

If one had the power of course to hit rev limit of 6500rpm
 

te72

Classifieds Moderator
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Mar 26, 2006
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SupraSean;1804741 said:
My actual question is of you guys that have the same 3:73 rear, what do you top out at?

SupraSean;1804793 said:
Is it possible that the speedo gear in the trans is reading wrong since its a 5speed? i would imagine speedometers have different gear ratio's to accomodate rear end gear ratio's. Im wondering if i was going alot faster than the speedo said.
Really useful Toyota specific calculator:

http://akb.norbie.net/Public/Gearing.aspx

Stock 1j rev limit of 7200, 3.73 gear, R154 trans, 275/40/17 tire, puts my car's theoretical top speed at about 195. No way in hell would she do that at current power level, and I'm thinking of going with the 3.91 gear for the other shell for a closer spread of gears anyway. Relatively stock a Mk3 should be able to clear 150 pretty easily. You have the right idea at the speedometer gear in the transmission being different for different rear diff ratios. Let's just say 4.10 transmission speedo gear and a 3.73 diff gear make for a horribly inaccurate speedometer. ;)