I have a 69 coupe with a built 427, Muncie M20, 255-60-15's on the rear. I have a GM 12 bolt rear with Eaton posi and 3:36 gears ( I believe).
I'm turning 2200 rpm's at about 40 mph. I'd like to go a little higher so I can drive on the highway if I need to.
Please explain gear ratios, is 3:73 higher or lower thatn 3:36?? etc.
Thanks in advance
JZ

3.73 is lower. Put in 3.55 or 3.73 and a Tremec TKO 600 5-speed.

If you are turning 2,200 RPM at 40 MPH you probably have 3.73 or 4.11 gears already. How many RPM's at 55 MPH?

If you are turning 2,200 RPM at 40 MPH you probably have 3.73 or 4.11 gears already. How many RPM's at 55 MPH?

You can get a Overdrive trans or switch to some 3:08s though Jody would suggest no lower than 3:42s so you dont stress your clutch.

Thanks guys. New trans is out of the question. It's a Yenko clone and I stayed pretty much with the correct stuff. Besides I just paid $1000 for the "new" Muncie.
Isn't there a way of telling what gears you have by turning the wheels and counting the yoke rotations?

yes,mark the tire and count how many rotations on the drive shaft- it takes to make
the tire go one revolution.little over 3 turns probably a 3:08 little over 3 1/2 turns
probably a 3:55 or 3:73.
unless you want to take the cover off and count both teeth and divide them into each other.most ring gears have the numbers stamped on them..

Isn't there a way of telling what gears you have by turning the wheels and counting the yoke rotations?

You calculate how many times your rear wheels turn for one turn of the drive shaft. Do you have posi traction?
What is the diameter of your rear wheels and what RPM are you turning at 55 mph? That will give us a pretty good indication of your rear gears.

Thanks guys I'll get some more info today.

I'm running a 427 with a 4-speed and 373 12 bolt possi.... I cant wait until i put a 5-speed in it.