Ok, im going from a 2.73 open rear to a 3.23 posi, disc brake rear...255, 40's on the back..What kind of real world difference will I see in launch, and all around driving??? Motor is stock, with all the free mods, and full exhaust.SFC's going on this week, or next..Thanks guys, Tom

 

changing tire size is like changing gears, the increase in tire hight brings the final drive ratioback down (not much going from a 245 to a 255 though so don't worry)
you will have better acceleration without too much detriment to top speed, and hwy gas milage.
with a 3.73 I get 8-10 mpg hwy and cruise 80 at about 3000-3200

 

Thanks T/A Tom....I am not changing the tires at all...They are the same ones I have on the rear right now....I sure hope the gear, and posi will make a difference...I mean the car runs pretty decent for a 2.73 gear, but I want more..I am going to probably go to a 3.42, or the gear you have...Are you pretty happy with the 3.73???????? I think with the motor I have right now 3.73 might be a little much...Ideas??

 

I went from 2.73 to 3.42 and I am more than happy, once you get 3.42 3.73 is not that much of a difference. Youll feel a large difference in 3.42 are you changing out the carrier or just the gears. I swaped the whole rear when I did mine. I have a power point that breaks it down pretty easy. If you want it drop me yoru email.

 

kjvail1204 Im changing the whole rear end out, because it has disc brakes...The gear is a 3.23...Would love the power point thing, will PM you now with my addy...Thanks, Tom

 

a 3.42 tbi with stock motor will walk away from a lightly modded 2.73 TPI car.
if you have the 3.23just run that for a while and see how you like it.
do you drive on the highway much??
and what is powerpoint ?

 

I dont drive on the hiway alot, it is 13 miles to my job..I kinda want stop light fun, and the every now, and then trip to the strip...Have a score to settle with a young chick in a forth gen bird too....lol....Power point is a program for gear ratio, MPH, and tire sizes if I remeber right....I can hardly wait..I just hate being without my car for even a day, and im sue it will take me a day or two doing it after work...Damn will I ever grow up??? Tom

 

changing the whole rear axle is pretty easy i can do it in about 2.5 hours with air tools.
The 4th gens are pretty fast, it takes a lot of work to a 3rd gen to geat one.
insult to injury that it's a chick. but any chick at the strip driving an american car gets a thumbs up from me. is she hot?

 

I wouldn't recommend going any lower than 3.73's unless you're running a T56 6 speed trans. 3.42's are probably the best compromise for good acceleration and still being able to cruise along on the freeway. 3.73's will be slightly better out of the hole, but probably not enough to choose them over 3.42's. 2.73's suck a s s no matter what car you put them in!

 

How true.

JamesC

 

Its just a slide show, pretty much covering everything you'll need to have and look for in order to make this swap go smooth. If your still interested let me know. If not I understand that as well.

 

Am still interested.........FOR SURE....Thanks, Tom

 

I have 3.23's stock and it makes a big difference for my little 305. I can walk away from my Uncle's mildly built carb'd 327 with a 5 speed and a 2.73 rear. But, if we race any longer then a 1/8 mile he catches me.(darn TPI!!!) You will definatly like the new rear-end.

 

8-10 mpg with 3.73s!? great, im swaping my rear as we speak so that powerpoint would help

btw, sorry to hijack but how do you correct the speedo? any links

 

You'll need to swap some speedo gear(s):

https://www.thirdgen.org/forums/tran...en+gear+sleeve

JamesC

 

thanks is that for the 700R4 as well?

 

My bad. The above drive/driven gears are for the T-5. The concept, however, is the same. You might try a search.

JamesC

 

for everyone that would like a copy of that slide show Ill send it just PM me your email addy. Again its not top notch but ill send it. If you can get me more pictures of things I might have left out and anything you think I should add let me know.

 

my pal the mechanic,said that to correct the spedo there is somthing called a DRAC that needs reprogramed. although i know nothing about this.
from a 2.77 to a 3.73 my speedo changed 15 mph. and i can do the math.

 

I could be wrong, but I bet your mechanic is thinking of the GM cars with OBDII computer systems like the newer fourthgens have. I know on those, you can use gadgets like the Hypertech Power Programmer to re-calibrate the speedo.