rear gear choice

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Dartsun

Dartsun

Mopar Dude
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I have a 69 dart that im going to put a mild 340 in..has a pretty lumpy cam..also have a 727 with a 2800 stall it came with..what kind of rear gears should I use..I want to use 3.23 posi but should I go 3.55s?
 
do you drive it on back roads? alot of freeway driving at 70 mph?

if it will never go above 50mph except at the track go 4.56's... if you plan on alot of freeway driving and long distance trips stay below a 3.73...
 
It'll be mostly freeway and cruising..is the 2800 stall convertor to much? I was going to use it cause it came with the tranny I bought while back.. trying to keep build cost down some..Thanks
 
It'll be mostly freeway and cruising..is the 2800 stall convertor to much? I was going to use it cause it came with the tranny I bought while back..trying to keep cost down some..thanks
 
Make up two chunks. One with badass gears and one with 3.23s.
 
Dartsun said:
It'll be mostly freeway and cruising..is the 2800 stall convertor to much? I was going to use it cause it came with the tranny I bought while back.. trying to keep build cost down some..Thanks
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Sounds like it will see a fair amount of freeway driving, go with the 3.23. Especially if you will be driving long distances. Anything more than that on the freeway and the engine will be buzzing pretty good. I run a stall converter that size and it does fine.
 
What cam is in the engine? Depending on the powerband of the cam, the only issue I see you having with the 3.23 is if the cam doesn't build much low end power. Then it will be a little lazy at low rpm's.
 
The 3.23's are good city/highway gears. If the cam is really lumpy the 3.55's would be better. Just a note: The '69 340 Dart Swinger came with 3.55's.
 
Use a calculator like this to determine what you can best live with taking into account cam specks, and torque curve of your new engine. If you don’t have a good match between cam rpm range and torque curve, and converter stall speed performance will also suffer.

As for stall speed, after selecting rear gear etc, you will need to select a stall that is under normal cruising rpm, but higher than minimum idle rpm for selected cam. Pick one too low, and car will be a beast in traffic, pick one too high will cause excessive transmission heat, and poor fuel economy.

You can talk to a converter company about selecting a stall speed based on cam, rear gear, tire size, and driving environment. The converter you have may or may not be suitable for your build.
 
Unfortunately I do not know the cam duration..but im thinking the 3.55 sure grip is what ill go with..thanks everyone
 
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