Its a 79 malibu. Im building a 350 for it as we speak. My transmission is a 200-4r with a .67 final drive ratio. My rear gears are 2.73 ( pulled off the cover and counted the teeth). My tire diameter is 26". So what will my rpm's be at 65 mph (legal speed limit in illinois) and if it's ridiculously low will it be lugging my motor to death. I do have a line on a posi rear end with 3.73 gears out of a 87 monte carlo ss, if I can ever catch the guy. What will the rpm's be at with that rear end? thanks

http://www.angelfire.com/fl/procrastination/rear.html

http://www.csgnetwork.com/rpmcalc.html

Here is one of many listed on Google under RPM calculator. It should help you out.

According to this calculator click (http://www.slowgt.com/Calc1.htm#RPMInGear) your RPM's will be 1536..

hahaha 1500 rpms

hahaha 1500 rpms

It is funny ain't it. My BB idles at 1400!!!!!!

2100 rpm's with the 3.73's

so what you guys are saying is its going to buck and kick with those 2.73's?

so what you guys are saying is its going to buck and kick with those 2.73's?

depending on how your timing curve is set up you will get detonation in OD on throttle cruising that low of RPM. I was cruising at 2200 with a Tremec and getting detonation in 5th with slight on throttle excel. And I have 4.56 gears

so what you guys are saying is its going to buck and kick with those 2.73's?

It all depends on your cam. Mine doesn't "smooth out" until about 3000rpm and I have a 4-speed.
If you have a mild cam and with you running a auto. You should be fine. The converter will soak up most minor bucking. I would go for the 3.73's. Better off line performance and still keep your RPM's down.

hmm I have a comp 268h cam. its has a rough idle

Don't use OD until you change the rear end.

ok I picked up a used posi carrier with 3.42 gears already on it. This is going to be a pretty good combination now correct?

I have a question. When I change the carriers do I use the shims from the old carrier with the posi carrier or use the shims from the posi carrier? Dont worry I haven't taken anything apart yet on the rear end and I kept everything in order on the posi carrier.

Since youre using a completely different carrier and gear, just use them as a starting point, knowing that you will have to adjust more later.