Hey guys i got 3.42's out back w/ an open rear and ive heard that taller gears would put down more tourque down low. Would like 4.11s in a v6 be feasable? Any upsides or downsides.. Thanks .. its an auto by the way w/ a mostly stock engine

 

You can... I find 3.42's to be more than enough, though, myself.

Might try 3.73s?

 

I think that 4.11's would be bad because you would rev too high when cruzing on the highway. not so bad for the motor, although i don't know what the effects of long term revs are on a motor, but you'll get HORRIBLE gas milage. The 3.73's are a good choice for a little more umph. just remember that you'll have too change the dirve gear in the transmission for the speedo so that you get the right read out on the dial.

 

Horrible is a relative term.

I have 4.10's, tranny slip, and a cam with my 302 and get 14 mpg. All things considered, I think I get damn good mileage.

 

That's true, but your final trans gear is higher in your Mustang. I figure that with the V6 with a stock trans and 3.42 gears, I am running about 2500 RPM at 70 on the freeway, If I went all the way down to 4.10's I would probably be well into the low to mid 3000 RPM range at cruze. That's a horible place to be if you're trying to save on gas with your daily driver.

 

What's your final trans gear?? My AOD has, if I remember right, a .68:1 Overdrive. 2500 at 70 is pretty high for only 3.42's....you must be right about the final gear! My car does about 2600 at approx. 70 mph (this is going by the seat of my pants and averaged traffic speeds only, because my speedo doesnt work). Does 1600 cruising at 45 mph.

 

4.03
2.37
1.49
1.00
.76

There are the gear ratios for a 1988 5 Speed tranny. See, you're pullin' a 0.68 final OD gear with the 4.10's, but we are running the 0.76 ratios with 3.42's. If we were to run any higher than 3.73's, we would easialy be into the mid to upper 3000's on the free way, but we'd get there in one hell of a hurry.

 

At 2500 RPM, the wheels should be spinning about 962 RPM in 5th gear with 3.42's. (RPM/tranny drive/Rear Ratio=wheel rpm)

With that known, you can work backwards and get what you'll be running with different rear gears.

RPM = Wheel RPM * Rear Ratio * tranny drive ratio

RPM = 962 * 3.73 * 0.76
RPM = 2727(A little higher than stock gears)

With 4.11's in the back:

RPM = 962 * 4.11 * 0.76
RPM = 3005

Ok, so it's not as high as I thought it was, but when you add 500 RPM to a motor daily for any length of time, it's gotta mess up the mileage. I apologize for the bad numbers before, but I was just lazy and didn't want to figure out exactly what they were.

 

4.10's if you never drive over 50 miles one way... Otherwise 3.73's with posi.