Speed vs RPM

[Rockin302]

Just curious, I have a pretty much stock 90 lx 5.0 coupe with a stock 5 speed transmission. When I'm cruising at 60 mph what should the rpm's be reading??

Feels like the previous owner slapped a set of gears in the car. I'm at around 1800-2000 rpm when going 60 in 5th gear. Is this normal??

 

[PhLoBuS]

3.73's maybe, on my AOD it is around 2krpm when cruising around 60 and I have 4.10s.

 

[5spd GT]

Just curious, I have a pretty much stock 90 lx 5.0 coupe with a stock 5 speed transmission. When I'm cruising at 60 mph what should the rpm's be reading??

Feels like the previous owner slapped a set of gears in the car. I'm at around 1800-2000 rpm when going 60 in 5th gear. Is this normal??

Yeah he has put some gears in or your tachometer is off...

I'm at 2050rpm at 60mph with 373's...

You may have 355's?

I know in my 2000 Gt that I had 327's (stock) and was at 2krpm at 70mph...a nice interstate gear

With my 373's I believe there closer to 2400rpm at 70mph...so I avoid the interstate usually...I hate the constant "high rev" on the engine...its like driving around in 1st gear at those rpms (though it sounds good)...just doesn't appeal to the longevity side of me

 

[Rockin302]

Hmmm, maybe those gears are a cause of my problems with the driveline. If the gears weren't installed properly(backlash, etc...) then it's probably the cuase of all my symptoms!!!

 

[HISSIN50]

Rick, that does sound high (higher than stock). i would jack the rear and count the ratio of wheel rotation to DS rotations. this is your gear ratio.

im turning ~1500 rpm at 60 mph (i dont drive at 60 - dont even shift into 5th till 65, so this is a close guestimate).

 

[4dStang]

What problems?

 

[HISSIN50]

What problems?

here:
http://forums.stangnet.com/showthread.php?t=513271

 

[townethug]

I would say that sounds about right. I dont think that i have gears in mine and at 2000rmp i am doing 70. Isnt there some kinda calc. thing around here that tells you?

 

[Funanin]

sounds like 3:73's to me. anywhere from like 1950-2050 rpms is 3:73's in 5th

 

[townethug]

Here, i still think 3.08's. See for yourself.

http://www.corral.net/tech/gearcalc.html

 

[Rockin302]

Thanks for the links!! So it looks like I have 3:55's in mine.

 

[5spd GT]

Thanks for the links!! So it looks like I have 3:55's in mine.

That is what I thought...based on the rpms you gave at the mph given...

Do what hissin said and count the number of tire/driveshaft spins you get to get an pretty accurate teller...unless you already have...

 

[tHeOnEGT]

townthug,

thanks for that link, i was looking for somethig like that since i brought my car to the track. Since i bought the car my rpm would be 6000 and doing only 100 mph in 4th. The previous owner said it had 4.10's so i figured the speedo or mph was off. Finally took it to the track and was crossin the traps at 103 mph at 6200 rpm. I checked at the gear calculator and low and behold i really have 456 gears. Just like to say thanks. What you guys think 3.73 or 4.10's. Im leaning toward the 373's???????

 

[HISSIN50]

townthug,

thanks for that link, i was looking for somethig like that since i brought my car to the track. Since i bought the car my rpm would be 6000 and doing only 100 mph in 4th. The previous owner said it had 4.10's so i figured the speedo or mph was off. Finally took it to the track and was crossin the traps at 103 mph at 6200 rpm. I checked at the gear calculator and low and behold i really have 456 gears. Just like to say thanks. What you guys think 3.73 or 4.10's. Im leaning toward the 373's???????

was this from your stock tach or aftermarket? i might look for error in that area. also, one can jack the rear end and note DS to wheel rotation to figure the ratio.

good luck.

 

[5spd GT]

townthug,

thanks for that link, i was looking for somethig like that since i brought my car to the track. Since i bought the car my rpm would be 6000 and doing only 100 mph in 4th. The previous owner said it had 4.10's so i figured the speedo or mph was off. Finally took it to the track and was crossin the traps at 103 mph at 6200 rpm. I checked at the gear calculator and low and behold i really have 456 gears. Just like to say thanks. What you guys think 3.73 or 4.10's. Im leaning toward the 373's???????

Yeah go with the 373's...you will lose SOTP feel but the driveablity/mileage/less wear on engine will increase...

Despite popular belief...it is okay to fear the gear...especially if it is daily driven car...

 

[HISSIN50]

The One, not to beat a dead horse, but i would be sure of what you have before you decide - the relative difference will matter. as i recall, i think one can get 3.90:1 gears too, no? might be a compromise bwtween the 3.73's and 4.10's.

 

[5spd GT]

The One, not to beat a dead horse, but i would be sure of what you have before you decide - the relative difference will matter. as i recall, i think one can get 3.90:1 gears too, no? might be a compromise bwtween the 3.73's and 4.10's.

Yep 390 gears are an option...but FRPP doesn't make them so there usually not as popular...I'm happy with my 373's...I wouldn't go up or down on them since I drive it everyday and it provides a good kick...and liveable highway rpms though I try to avoid the interstate if it is for a long distance...

 

[HISSIN50]

Yep 390 gears are an option...but FRPP doesn't make them so there usually not as popular..

thanks for the info and clarification.

 

[Rockin302]

Even with my stock gears (double checked, I have 3:27's) there's a drone at highway speeds, approximately 65 mph. Maybe I should switch out to the 3 chamber delta flows.

 

[HISSIN50]

Rockin, what RPM do you see for that drone? RPM and not speed (as you know) is what determines drone.

you must not have stock mufflers then, right?