question about gears w/ an auto tranny

[some_guy]

first i'll apologize if this is something that's been asked ad nauseum and prostate myself for forgiveness heh, since the search didnt turn up anything.
first off, can anyone tell me what cruising rpm @ 65mph are supposed to be for a stock gearing setup with an automatic? mine are right around 2k normal hiway.

2nd, what kind of rpm at the same cruising speed could i expect switching to a 3.55 or 3.73?

background: i bought this car this weekend, and im not that familiar with the 4.6L setups.
thanx

-rob

 

[prsrizdgt]

Best I remember, my 65mph rpm is 2500 in overdrive. I think the rpm goes up about 250 for every 5 mile per hour increase. 2750 @70....3000 @75

 

[some_guy]

thanx

 

[01mgvert]

I put 4.10s in my automatic, and the rpms went up about 600 rpms. Do the 4.10s. You won't regret it.

 

[BuffaloZone]

I also vote for the 4.10's - to me, 3.73 (and especially 3.55) seem like a waste...for now. After I get my KB Supercharger installed I *might* think that the 4.10's are too much, but then again with an automatic the 4.10's might be pretty fun.

 

[01MachGT]

only reason I went with 3.73s is cuz I plan to supercharge. 3.73s are nice on the NA setup but 4.10s would have been better if I were to stay NA

 

[some_guy]

01mg, so 2600 give or take,, @ 65,, in 4th.. that'd feel like runnin 60 or so with the OD off ..lol dang, they give you that kinda power in 4th?

 

[BlackenedSVT]

On a side note, i wouldn't do rear end gears in an automatic. I really didn't feel a difference in my 98GT auto, even when i went from 3.27's to 4.10s

I mean i would SEE a difference when i would pass cars easier on the highway, and sometimes from a launch. But i really didn't FEEL a difference driving around or launching by myself with the auto trans. I dunno, maybe its the whole 4spd with O/D thing.

Not to mention it messed up my speedo a lot. I 'hear' you could get them fixed, but my STEEDA 31 tooth chip or whatever that i bought (speedo-chip, not performance chip) never fixed it. So goodluck with all that. I just wouldn't do gears in an auto again...pesonally.

EDIT: People always told me (on here): "if you have an automatic, don't go with anything less than 4.10s." I guess i know why now...because you dont feel a difference. Maybe 4.30's would have been better?

 

[some_guy]

thanx all,, i'll keep it in mind