My friend has an LHO 3.1l V6 with the M5 in a 91 firebird and is wonering what rear end gear ratio to get with his new posi.

Which gear ratios would you reccomend and why?

Thanks.

 

I'm going with 3.42, I think you/he could go with a 3.73 or even 4.10. Just keep in mind that the higher/lower you go the lower your top speed will be and the higher the rpms will be at 65mph when your cruising.

 

with the 5 speed, it may not be as bad as my auto but if he ever takes the car to the track, i say 3.73! with my auto (or anyone's auto) only going to 3rd gear at WOT, i had a good 1/8mile car with 4.10s but i went back down to a 3.73 so that i could run the 1/4mile a little better. it ran out of "steam" after the 1/8th. if he doesn't do much real racing with the car and just wants a little more "kick", i recomend 3.42s becuase the car will do better cruising, also. wait, just happened to think that 3.42s are stock in his car (v6, 5spd), anyway...

 

Yea come guys, V6 com stock with 3:42
why they can still get up, good gears.

Best factory mod ever.


last time hotrod did a review and I read it, 3:55 was the best
over-all street strip ratio to use.

 

wait, what, my v6 has 3.42 in the rear already!?

 

heres my question,,,,,,,,,,i'd love 4:11s but the v6 dies to early,,,,,if you put spacers between the upper to mid parts of the plenum(remember someone made 1 inch spacers cant find the post,,,,anyone remember which post it was,,,had pics) this would increase runner length, decrease low end torque, but increase top end horse,,, if you do the spacers 4:11's might make more sense by pushing up the power band,, and the steeper gears would negate the loss of low end torque.............hows that for starting the discussion,,,,,,,,,,,,,,


anyone have that old spacer link ?

 

edit : i know the gears dont push up the power band,,,,worded messed up but you know what i meant

 

nocturnall, no. v6 cars with 5 speed trannies had 3.42s. v6 cars with autos had 3.23s.

a spacer between the upper section of the intake and the mid isn't going to be near enough work to get the higher rpm horsepower that you'd need to run 4.10s. I have extensive internal work done to my motor and couldn't use the 4.10s.

Gumby, its hard to pinpoint "the best gear ratio" for any combo (street/strip,...) becuse what ratio works best depends on your motor, transmission, tire size,... all that plays a huge role in it. besides (as i'm sure you know already) there is no 3.55 for a 7.5" 10 bolt; goes from 3.42 to 3.73.

 

Agreed. The best gear ratio for your car is the one that is matched to your perform best with your setup. You just need to determine what that is.

 

Are you Mr. Obvious or what?

Read what I said again.

I didn’t say it, hotrod did. That the 3:55 gears where the best over all. Plus he didn't say what kind of POSI. Could be a 9 bolt ford for all we know.

And just like aluminum rotors, you can get gears in any size for anything, if you have money.

Stop following me around making obvious inane rebuttals to my post.


Though you are right his 91 doesn't have 3:42,

85-89 was 3:42 for all V6 cars.
85 4 cylinders came with 3:73

 

FWIW he is thinking of making performance upgrades to his car, one of which is installing a posi unit in his current rear. The car as of now is completely stock except for a flowmaster muffler. Besides the typical exhaust and intake mods, are there any mods that could add some performance without breaking the bank(besides free mods: gutting air boxes, etc)? Just want to make sure he isn't wasting his money.

Thanks for the opinions so far, they are much appreciated. Please don't point out the obvious either (Ex: Of course you would pick a gear ratio that best matches a cars perfomance and usage.)

 

any help at all is much appreciated.

 

3:42s

 

I got 2.73's in my rear.. Im guessing thats bad for my V6?? Better gas mileage tho right?

 

maybe a little better mileage cruising. but not too great for city, really.