Rear end gears

[gunmetal]

I have a 72 challenger with a 340 running about 400 hp with a auto tranny.  Looking for some advice on what rear end gears I should put in, daily driver that I'd like have plenty of torque to the rear wheels.  I'm being told to put 3.73's in for an all around ratio

[73Chally]

Will you see much highway driving?  If not, I would go up to 3.91s (That's what I have with my 440-6).  If you will be driving on highways on a regular basis, I would look at 3.55s.

[dodj]

Will you see much highway driving?  If not, I would go up to 3.91s (That's what I have with my 440-6).  If you will be driving on highways on a regular basis, I would look at 3.55s.

[MEK-Dangerfield]

Another factor is your tire size. What diameter are they? If you are running some low profile wheels, I would look at 3:55's.

[Katfish]

I went from 3.55 to 3.73 when I changed from 8.75 to Dana.  I'm very happy with the new gears.  Tire size does need to be factored in.

Check out this post, I have a spreadsheet that lets you enter everything for comparison.

http://board.moparts.org/ubbthreads/showflat.php?Cat=0&Board=QuestionAnswer&Number=5413584&Searchpage=2&Main=5412888&Words=cnxt&topic=&Search=true#Post5413584

[gunmetal]

15 inch tires Goodyear T/A's.  Sounds like the 3.73 gears will be fine. I don't want to go so low that the motor runs at 3,000+ rpms at highway speed.

[Moparal]

Check out this site a mod posted for us a few months back. It's fun and pretty close

http://vexer.com/68rt/speed.html

[gunmetal]

That is "AWESOME".  Thank you...