Rearend gearing

I have 2.56 in it now, stock. What I want to know is what gear would be equal to my driving in drive now, when I'm in overdrive with the new gear. I've tried to ask some people and I think they where confused. Another way to say it is I want the RPM when I'm in drive now to be my overdrive RPM. Hopefully that doesn't screw up anyone. Thanks for all the Help.

It depends on your overdrive gear ratio. Divide your present gear ratio by the overdrive ratio. Example: If your overdrive is .7:1, divide the 2.56 by .7 (2.56/.7=3.66). The closest ratio would probably be a 3.73 in this case.

3.73s are a pretty big jump. I dunno how a Caprice will act to it, but I know that F-bodys way diferently when they go to 3.73s, and they have like 2.8s stock. Expect to see a huge change in acceleration

Thanks for all the help. I'm kind of leaning towards 3.42. Does anyone think that would be a noticable difference? Also, how big of a difference in accleration is it from 3.42, meaning noticable at all? Again thanks alot for the help.

Well I have 2.56s in my 86 and 3.42s in my 89. Now the 89 does have a L05 vs the LG4 of the 86. But the 89 pulls ALOT harder. It just does everything with less effort than the 86. I don't think it's all in the gears, but they certainly help.

you will notice a huge difference by going with the 3.42s.

my brother had 3:73's on his Impala, it is probably the fastest thing you can do to your car, you will notice a nice improvement for just one part.

on those Lt1's with the computer retuned it will actually go faster then the stock 155mph speed limiter, people say it goes to about 158 or so now. So it doesn't kill your top end, actually it improves it, and your first gear where they are real dogs is helped out a lot.

How bad does a jump from 2:70's to 3:42's affect gas milage? I was thinkin new gears, but I heard they kill your milage.

Id check your ratios again

look up the rpo code

when you exceed 3.23 on that carrier, you need a different carrier to get to 3.42

How bad does a jump from 2:70's to 3:42's affect gas milage? I was thinkin new gears, but I heard they kill your milage.

Without adding an overdrive, gearing your car down will hurt your highway gas mileage. I couldn't give you any exact figures, but I can give you an example.

I used to own a '76 Impala 8-passenger wagon with a 350 and 2.93 or 3.08 gears. I never broke 15 mpg on the highway even though I kept it under 70 most of the time. I just bought a '71 Kingswood Estate with a 402 big block and an unknown gear ratio, although I know it's geared much higher than 3.08, since it moves out slow and upshifts at higher speeds than the '76 did. Even with the bigger engine, the highway mileage is well above 15. At some point, I plan to add an overdrive transmission and 3.55 gears. I will be restoring the car first, so it will be a while before I can make the mods and track the mileage.

Dan

Are you sure about changeing the carrier? I sure hope your wrong for my sake. I guess I'll have to check up on the myself or find a junk car with a 3.42 or something. If I change my whole rearend to a 8.5, what else would I need to do? New driveshaft, Different springs and shock, Control arms?

I highly support the use of 3:73s. My car pulls like a mofo off the line and will lay the smack down on most any mustang. Im running a LT1 w/ exhausts and i love it. The 3:73s make a big difference. The only downfall is that your speedometer will read too high. Go to pcmforless.com and get your pcm reprogrammed and it will fix it right up.

You have an LT1 in that Caprice? You sure it's not just a 5 ltr?

I have a 1992 9c1 with the 5.0 (form which fed92sled was created) and a 1994 9c1 with the 5.7. The 92 is for sale by the way.

I wasn't sure about the carrier. Any tips on a good ratio with the overdrive? Let me know.

I get fairly good milage w/ the gears I have now. I think 3:73s are good street gears. I didnt actually install them so i dont know what all has to be done. The previous owner replaced them. I plan on replacing my posi eventually so i will be learning all about that kind of stuff.

Sorry man, I didn't realise that you had 2 of them. You have any pics of the LT?

If you go to www.impalassforum.com and look at my profile, I have a pic of the 94. Its black so it looks almost like the 92. Someone should buy my 92. $1500.

im not flaming anyone but......saying f bodys had 2.8's is like saying all mustang's were 5.0's

the 2.5 f bodys had 3.73's
the auto 2.8's had 3.73's and manual's han 3.42's(untill 84)
when all 2.8's had 3.42's

the 5.0 f bodys could have anything from 2.73 to 3.42's

3.08 being the most common.

dollar for dollar the gear swap is the best mod you could do.

thats my next step, gonna go 3.73's since im going to a turbo 350 trans,
but 3.73 is all the more you wanna go with the 700-r4, and more than that and you will have trouble keeping it from spinning when launching the car.

Well, I know I defently will have to change my carrier. Should I just go to a bone yard and try to find a 7.5 that will work, or should I just go ahead and change it to a 8.5. And also what all is needed to change it to a 8.5? Is the springs, control arms, and shocks still going to work without changing anything on them? Thanks for the Help.

3.73 was optional with the v-8s and v-6s in the third gne f-bodies i have had several stock 5.0L f bodies iwth 3.73 rears, 3.08 was most common yes,

B body saw 2.41, 2.56, 3.08 and 3.42,

2.41 common late 77-79 with 3052bbl and 200c
2.56 comomn about all years, and 3.08 too,

all crap ratios horrible for any dirving except for highway fuel saving

find a way to get 3.42 or 3.73 and it will wake up your car, if you have 2004r or 700r4 then you wont hurt gas mileahe with 3.42 or 3.73

deeper gears such as 3.42 and 3.73 make the engien run higher RPm at slower speeds than 2.28 and 2.56 and 3.08 do, higher RPm means more power output, and at take off the 3.42 or 3.73 car will always get goiing faster than the car with lower 3.00's ratios

high gear ratios are 2.28-3.08

lower gear ratios are 3.42-up

tall are 2.28 and 3.00's

short are 3.42 up


its kinds ocnfusing til you learn it

if you want to make the car perform better with the crappy taller ratio and cant afford to have axle changed then get a 1500 stall torque converter, leave it in after you get axle changed, it will make car take off even faster due to increased rpm;'s at low speeds, you will be tkaing from top end and placing more power at low end this way, trade offs,

engine performance increasing always involves trade offs



good luck