I have been talked into keeping my C4 trans, however the rear end in my 73 is too slow. The car was a 6cly from the factory and is now a v8 302 bored .40 over big cam headers, preformer rpm with a 650, when I get up to about 85 it seems to be turning way too many rpms. Long story short I need a new rear looking for something I could grab at a pull a part or somthing of that sort would love to bust a 100mph in this car and not feel like I'm going to blow my motor.
if it's a stock ratio rear, then you are not going to do much better than that. Not sure about the sixers, but it should have a 3.00 or 2.79. You would need to go lower than that to gain more top end speed. or run a much taller tire.
you will need to figure out what gear ratio is in the rear end. you can do this by jacking up the rear of the car and puting it on jack stands. now take some white out or nail polish or a paint pen of some sort. mark the location of the yoke on the front of the diff to front of the diff. mark each wheel to a mark on the backing plate of the diff. put the trans in nutrual. now rotate both wheels togther 1 full revolution till the marks line back up with the backing plates. at the same time count how many times the mark on the drive shaft passes the mark on the front of the diff. if you have 3.00s the mark will line back up on the third revolution. if you have 2.80s it will not line back up but be about 3/4s of a turn. if it goes past 3 turns then see where the mark stops and that will tell you what ratio you have. puting a taller tire on the rear will increase the top speed that you can go. it has the same effect as puting a numaricaly lower gear in the rear. you really need an over drive trans to achive what you want.
oh and also a tach to know how many rpms you are really turning at those speeds. ive had cars that just have a loud exhast resonance at the rpm that they end up crusing at that makes them think that there engine is reving high.
yeppers. I meant numerically... didn't want to throw in the terminology. I should've been more explicit. my first reply used words like taller and shorter... but I figured that would lead to confusion... and here we are. Either way, sounds like AOD is the way you want to go.
