Overdrive

[Andrew]

Hello all
I'm considering putting a 4 speed overdrive from passion performance in my 70 coronet rt. it's a 500" non ported Eddie heads mild Hyd roller 6 pack 3:55 rear. My guess is that it will hurt my 1/4 mile time. Is that a given?

 

[q-ship]

Depending on how tall your rear tires are, I doubt it will have any negative effect.

As long as you are not reving much past your power band in third as you cross the stripe, you should pick up a 10th or so by not having to shift to 4th.

Even with air shifted, computer controlled autos, the quickest NA cars are running 2 speed powerglide based transmissions.

My guess is that if your car can hook even a little bit, you will be quicker.

Decades ago I went from 5.57 rear gears to 4.88. Stock Hemi 4 speed, 3,600 + lbs, Professionally built Hemi engine, and went from 11.20's to 10.90's by eliminating the 3/4 shift! .... scary 7300+ trap RPM vs. 6800, but MUCH quicker. --- (Ultimately went 10.20 flat with nitrious@ 7600 RPM) .. I only point this out because parts back then were noware near as strong as even the "junk" parts nowdays, so pushing RPM today is much safer than years gone by.

 

[Andrew]

Great answer. Thank you.

 

[696pack]

I have that tranny in my 66 Charger with a 523 stroker and Dana with 3.54 gears.
The first three gears are very close to a torqueflite so you run the 1/4 in 3 gears and just use 4th for highway.
GREAT trans!

 

[696pack]

Here are your number for Passon 4 speed overdrive.

http://www.passonperformance.com/images/stories/passon_documents/Passon_Overdrive_Flyer_20091109.pdf

 

[Darter6]

Running one in a 73 Cuda 451 stroker 3.73 gears. Very happy with it. We took it on the Hot Rod Power Tour a few years ago and got 20 mpg highway. Like said above 3rd is 1 to 1 so for drags you will never need 4th.

 

[68 HEMI GTS]

with out the torque multiplication of the auto & a torque convertor the more forward gears you have in a manual the better for drag racing ET.