Hi All, I have a 200R4 tranny and my engine turns pretty fast at 75 MPH. I havent checked the gear yet, but does anyone have a rule of thumb for engine speeds at MPH with different gear ratios? I would like to find a gear that still gives some performance, but also allows me to cruise on teh highway without turning the engine so fast. Currently, my engine turns 2500 at 65 MPH in OD. 3000 at 70 ish. I am running this in a Monte SS. Thanks, -Jon
My 455 turns at about 1500 RPMs at 65 and around 2000 RPMs at 75+. Are you sure the OD is working? I think my rear gears are like 2.93 or something like that. I know I should really have about 3.50 or so, but this is how it was when I got it.
I count the shifts and I feel all 4 gears. I dont see the RPM's drop once the TC would hit lock up, but it may be happening so quick, I can see it on the tach. I am gonna do a count of rotation on the rear end/yolk to determine what gear I have, but my guess is its a 3.73 or even higher. Great for around town, but I want a compromise. Thanks, -Jon
To calculate: Overall Gear Ratio from Tire Size Gear Ratio = rpm x tire diameter/mph x 336 RPM From Tire Size RPM = mph x gear ratio x 336/tire diameter The 4th gear (OD) ratio for the 200-4R is .67 Other useful automotive math fourmulas can be found at ModernMuscleCars.net
So per the useful calculation below, if I have 3000 RPMs, a 27" tire, and I am going 75 MPH, my gear ratio is probably 3.23. (3000*27)/(75*336) = 3.214 Is that a correct interperetation of your formula? -Jon
I have a 3.73 rear gear and a 2004R. I run about 2300 rpm's at 70 mph now. It used to be 3300 rpm's with my th400.
:TU: Yes. Now you can play with tire sizes and rear axle ratios to see if you come up with a RPM range more to your liking.
i have a friend with a 67 elky with a 327 ci , 700r4 , and 3.43 gears. the 3.43 gear works great for him.
I really appreciate the help! Now if I can just get the cruise control working. Gotta have cruise on a "cruiser"....
Highway RPM'S Hi, just got back from Salem. I run a 3.73 with a 2oo4R& 3.73 gears. I run at 2200 at 70. Got 15 MPG. I also have a lock up converter. JOE My tire size is 295/15
I think ward is right. With a 3.73 you will be running higher rpm's on highway speeds no matter what, but a 3.23 should give you lots of room on top end.
I run a 3:73 with a 200r4 (thats 3 of us on this thread) and it is a very good combination. Runs about 2200 rpm at 70 mph. Get about 14 mpg. I know of a convertable 455 72 GS with a 3:42 that got 20 mpg highway driving. I set mine up with a manual switch for lockup and it is like having a 5th gear. Drops about 300 rpm. Make sure you have a good cooling system if you run OD on the converter. Stock setup is the converter is locked in OD. My GN runs a 3:42 with a smaller tire and turns 2000 rpm at 70. You do not feel the converter lockup in OD. Did those chebbies use a 3:73 to try and keep up with a GN?
