anyone know how to figure this out?

[GI Joe]

How many RPMS would the engine turn at 70mph at a 1:1 engine tranny ratio with a rear tire size of 28.7" OD at both 3.73:1 and 3.55:1 rear differential.
Thanks

 

[shawn13]

http://www.ringpinion.com/Calc_RPM.aspx This might help.

 

[PenguinGT]

There are a few different calculators online that can do that for you.

 

[Rypper1]

How many RPMS would the engine turn at 70mph at a 1:1 engine tranny ratio with a rear tire size of 28.7" OD at both 3.73:1 and 3.55:1 rear differential.
Thanks

Right at 2900 with the 3:55's and 3050 with the 3:73's.

 

[don_w]

This is a helpful little Excel chart I threw together a couple years ago:

http://www.2005stang.com/gallery/albums/userpics/10330/RPM_vs_Speed.xls

 

[rog06gt]

Dave,
28.7” OD non loaded = 2910 RPM @ 70 MPH with 3.55
28.7” OD non loaded = 3058 RPM @ 70 MPH with 3.73
Approximately 28” OD loaded = 2983 RPM @ 70 MPH with 3.55
Approximately 28” OD loaded = 3134 RPM @ 70 MPH with 3.73
http://www.5speedtransmissions.com/gear_calculator.html
Cheers

 

[GI Joe]

This is a helpful little Excel chart I threw together a couple years ago:

http://www.2005stang.com/gallery/albums/userpics/10330/RPM_vs_Speed.xls

very cool...Thanks

 

[GI Joe]

I've been wonderinf if I can live with 355's or 373 on the street with a 3 speed auto........................

 

[rog06gt]

I've been wonderinf if I can live with 355's or 373 on the street with a 3 speed auto........................

I know one thing is that at that RPM (3000) you would be ready for a street fight anytime...LOL!!!
Kind of high no? why not 4 speed auto with electrical overdrive, ie; 3 speed manual ratchet + 1 switch for OD (4th 0.70 ratio) no converter lockup...that would be about 2350 RPM @ 70 MPH with 3.73 on the electrical OD...just a tought...
Oupps, forgot about converter slippage (no lock up) add 5-10% to RPM depending on how tight it is...
Cheers