Rear determination

[dlrshort]

Could someone tell me the way to determine the rear in my C-3 using the ration between RPM's and MPH? I know I saw a tech web site that dealt with that.

Thanks

Dave S

 

[fasterthanu]

Here you go. This site has what you are looking for. Type in your mph, rpm, and tire size, and it will tell you the gear ratio... It will even convert your tires size for ya. type in what it is such as 255/60/r15, will tell you the size in inches that you need. Enjoy!

http://www.geocities.com/4xvan/rpmcalc.htm

 

[AKRAY4PLAY]

Dave,
here is a site on this forum that supplies your answer. http://www.corvetteactioncenter.com/tech/tools/gearcombo.html i believe that all of these numbers are correct if you still have a 1:1 final drive in the tranny. the stock 4 speed manual or three speed autos have a 1:1 final drive. if you have an overdrive tranny, you will need to count the drive shaft revolutions per one tire revolution. for instance, if the drive shaft turns four complete revolutions plus a tad for one tire rev, then you have 4:11 rear end. also 3.5 turns = 3.55 rear, 3&tad = 3.08. you get the idea. Brian

 

[dlrshort]

Thanks, everybody. I worked it out and the closest I calculate is a 4.11 ratio. Does that make sense for my '71 LT-1?

Dave

 

[corvgreg]

Yes that's probably correct. Is your tranny an M21? The 3.70 was standard with the M21 and the 4.11 optional. I just sold my 71 LT1 and it came with the 4.11 rear.


Greg

 

[dlrshort]

Greg, I have the M-20.

Dave

 

[corvgreg]

Dave,

My Vette Vues book shows the M20 had ratios available to 3.70, so the rear ratio probably isn't original. That's a lot of gear multiplication for an M20...you must get a fast launch with that!

Greg

 

[dlrshort]

Greg, I'm pretty sure the entire drive train is original on the car. My bet is the speedometer is off. I'll have to see if I can get under the car and get the #s off.

Dave

 

[Stallion]

That has a 4.11 in the rear!? :eek Wow, I bet she can really jump off the line.