So i have ported polished 416 heads on a carbed 91 rs. It is basicly set up for high end power, i have no real low end power at all. from idle to 1500 i have nothing....bad launches and all.

so here is my delima. 3.42 or 3.73. this is a daily driver , also an automatic.

What GM cars/trucks came with 3.42 and what came with 3.73s?

 

I had both in my car...............3.42 were cool, but 3.73's rule.......don't kill you mpg either. 70@2500

 

Get a 3.73. Will helpwith no low-end grunt. 3.42 will make your launches WORSE than 3.73.
Options when I ordered my car were 3.23 or 3.73. I believe 3.42 came along later. (87-89)I could be wrong.

 

Well i know that 3.42 wont give a better launch than a 3.73. but im wondering if the 3.73 will travel too fast through my power range and hurt more than it will help. That is why isuggested the notion of a 3.42

At what guesstimated MPH will i be at by 5500 rpm in first gear with the 3.73 Vrs the 3.42


i was thinking 27 with the 3.73
and 30 with the 3.42

Just a guess.

 

With my 5-speed, 1st gear tops out at about 40 MPH.

 

really? i hit 40 in first with my 2.73s and 700r4

 

1st gear on that 5-speed is almost a "granny". I can take off from a complete stop in second.

 

http://www.f-body.org/gears/


That will tell you everything you need to know about tranny/rear/MPH relationships.

 

I would do a torque converter change long before I would do a gear change. A 9.5" TC with the right stall will work with either gear and you will save money and give you more of a performance gain. A 3.42 to a 3.73 gear change is almost imperceptible by itself.

 

i have a 2500 stall tc.