I have a 92 RS with the 305TBI it only has 26000 miles on it and the engine is in graet shape. Im going to be putting in 3.73 gears. Can anyone tell me the top end speed with the stock 2.73 gears is and what my top speed will be once i have the 3.73 gears???

 

Go here, and see for yourself.

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George P. Lara
1994 Z28 LT1 T56
1984 Z28 High Output
Member: SCCA, SCFB, SC3GFB

 

i'd guess you didn't lose much on top end if it changed much at all. more to consider when running top speed after a gear change of that much is the driveshaft speed. always something to be considered when top speed is a thought.

 

Depends on your horsepower. Simple mathematics would suggest your <current max speed>*2.73/3.73. But this is only valid if your engine is hitting maximum rpms with 2.73s.

If your engine is running out of breath way before max rpms in top gear with your 2.73s (which it probably can't), then you will probably get a higher top speed than the simple formula above would suggest. In fact, you might go faster if you can get closer to your redline with 3.73s than 2.73s.

I remember a motorcycle I owned years ago could go faster in 5th gear than in 6th gear...just because 6th gear was too tall.

But the next factor is how much horsepower you have and what your objective is. For racing, many guys find 3.73s too low for 3rd gear and it forces them to upshift into 4th. They prefer 3.45s because they can pull 3rd while still in the traps.

In high speeds and enough horsepower, you may run out of gear with 3.73s because you could pull a taller gear and not see your maximum top speed. This is highly possible when you get into the 400 hp range. Optimally, you want to be near redline in top gear when you can't go any faster.

[This message has been edited by Glenn91L98GTA (edited October 23, 2000).]

 

I think a few of us missed a very important clue. Your top speed before was 110. Your top speed now will again be 110. You'll have to disable the speed limiter on the car, unless yours came with the 16x8 rim option like the Z28s.

Otherwise, you'll still need to change the VSS gears for your speedo to read right. If you leave it thinking you have 2.73 when you have 3.73 you'll be going about 15-20mph slower than what it will read.

Top end with 2.73s is virtually unlimited. The 3.73s aren't too bad either. But if you were going for ultimate racing top speed it has been my experience that most cars have either between 3.42 and 3.55 if it's a chevy OR a ford. Those 3.73s should be ok for top end runs, and certainly great for off-the-line punch. It all comes down to how much power you're getting from the car. With 170 factory rated horsepower I'm not sure what kind of top end you'll get - but at least with the 3.73s you'll be higher into the RPMs.

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1991 RS LT1
every imaginable bolt-on, ungodly LT1 355, and 12 pounds of intercooled boost on it's way in '01

2000 C5 Coupe
black/black 6-spd, optional polished rims, first run 13.056 @ 109.52 stock

"So what DOES the back of a Mustang look like?"

 

But with the 170 factory hp, will 3.73 pull harder?? Plus, if you do switch out gears, you have to mess with your speedometer?? How do you get rid of the speed govener??

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Godti
'89 Trans Am (Red)
305 TBI 5spd

 

Changing the speedo gears is not a big deal the "driven" gear is a snap to get at, the "drive" gears requires you to disconnect the driveshaft and pull off the "tail" from the tranny to remove the "drive" gear on the output shaft. Easily done in 1-2 hours (4 hours if you are slow and unsure of how to do it).... but do able.

As for torque, effectively you will increase your torque "effect" by 3.73/2.73 due to the extra multiplication of the rear gears. Remember your "actual" torque produced by your engine will remain the same...only the "effect" will increase.