In the process of building a new motor for my 63 Nova , it currently has 3.90 gears in the rear end with a 26 inch tire . The motor is going to be super charged with close to 600 hp +/- . I already know its going to run out of gears with the 3.9s and about perfect would be 3.55s . How much affect on the 1/4 mile time would going to a little taller gear to make it a little more freeway freindly be , like going to a 3.00 ? I am estimating low 10s in the 130s mph
03-20-2008 04:53 PM
What do you have for a trans? An overdrive trans is a great match with a low (high numerically) gear. The 700R4's big brother, I can't think of it's number designation right now, should be able to handle 600 hp with no problem.
03-20-2008 05:18 PM
Current trans is a th350 with a shift kit and 3000 stall convertor , I was thinking it would be alot less money for rear gears than a trans .
car is a weekender only so its not driven alot . After I get done paying for this motor I want to do a new paint job , so there goes another years worth of Fun money , I was also thinking about bolt on overdrive Like the V02 but its like $1500 , can almost do the 700r4 for that .
03-20-2008 05:26 PM
I thought I read somewhere that a 700R4 wasn't reliable for over 500 hp. It's bigger brother that GM puts in the pickups will take it though. You may save $500 by changing the gears instead of the trans but you'll have a lot less fun, IMHO.
03-20-2008 05:39 PM
rear gear affects on 1/4 mile
with a 3.90 gear it be cheaper to go with higher tires 28" high should work. or you can go to web sites that will give you rpm with these tires and gears in 1/4 mile.
03-20-2008 05:46 PM
when you guys say 700r4's big brother, do you mean the 2004r ? thats the one that they put in regals and cutlasses
03-20-2008 06:01 PM
I think they mean the 4L60 and 4L80E's.
03-20-2008 06:03 PM
ok yea, the truck ones, but I thought those were for the newer blocks only
03-20-2008 06:05 PM
4l60 IS a 700R4
4l60E needs a puter to shift...
same as a 4l80E....
4l80 being a heavier duty trans..
03-20-2008 06:06 PM
It sounds like they are talking about the 4l80e.
03-20-2008 06:09 PM
can they run on a non computer controlled engine? meaning it doesn't need to hook up to the ecu, does it have its own ecu that you can just put in for the tranny itself
03-20-2008 06:35 PM
I am pretty sure they have mods to run full manual on the 4l80e...as long as shiftin all the time doesnt bother you.
They also have controllers priced anywhere from 1000 to 1900 dollars.
Anyway you you try it the 4l80e route is a pricey one.
Either spend it on gas or spend it on an OD transmission. I cant say it will take a long time for the transmission to pay itself off in gas the way gas keeps rising.
Things to ponder for your project.
03-21-2008 07:10 AM
Depends on the engine rpms. my car trapped 135 mph with a 3.90 gear, 26 inch tall tires, around 6800 rpm at the end of the track. This is with a final trans ratio of 1:1.
First you need to figure out what will be your engine's max rpm? Then pick a gear and tire diameter so that it hits the max rpm at the target trap speed.
03-21-2008 10:42 AM
here's some simple gears and tires changes calculators....plug in values till you find what you want