What gear ratio should I run?

[OrangeCrush1970]

Currently, I have a TH350 running to 4.10 gears in my 12-bolt rear end with 265 / 75r15's (30" tires). I have read that a safe operating RPM range at highway speeds for a small block is between 1800-2800 RPM’s…Im up around 3000 to 3500+ RPM’s. This is my daily driver and I just don’t want to beat my 350 to death. I would also LOVE to see some better mpg’s. Can anyone suggest the best gears to run in our trucks? 3.73’s or 3.55’s? I’m not towing anything, not doing any off roading and my truck is not working on the farm anymore.
Thanks guys-

[webfoot]

I vote for 3.55s.

Have you tried searching online for an RPM calculator, these would be very helpful in making your decision.

[OrangeCrush1970]

Originally Posted by webfoot

I vote for 3.55s.

Have you tried searching online for an RPM calculator, these would be very helpful in making your decision.

I did just look and I found this website:
http://www.intercotire.com/site63.php

""Good "rule of thumb" calculation is to mutiply .12 by your tire diameter.
(.12 X 30" = 3.6)""

YOU THE MAN WEBFOOT!!!

[crazy longhorn]

Originally Posted by webfoot

I vote for 3.55s.

Have you tried searching online for an RPM calculator, these would be very helpful in making your decision.

If you find a 3.55 gear for a 12 bolt truck rear, let me know where! All I have seen are 3.07/3.42/3.73/4.10/4.56. IMO, a 3.73 is a good all around gear.......if you run a lot of hyway with no OD, go 3.42.....more intown, & just a little hyway, I would go 3.73. Your weekend warrior is for sure more fun with 4.10's tho.....L

[webfoot]

I'm new to the truck scene, in fact this is my first one ever. Didn't know that 3.55s weren't available till now! FWIW mine has 3.73s and it does fine on the highways.

My "weekend warrior" actually has 3.31s in it - does well on the highway and the motor makes it fun from a stoplight.

[crazy longhorn]

Originally Posted by webfoot

I'm new to the truck scene, in fact this is my first one ever. Didn't know that 3.55s weren't available till now! FWIW mine has 3.73s and it does fine on the highways.

My "weekend warrior" actually has 3.31s in it - does well on the highway and the motor makes it fun from a stoplight.

It would be a bunch more fun with 4.10's tho.....

[OrangeCrush1970]

It's great with 4.10's, I just worry about the longevity of my engine. I dont know, maybe I shouldnt mess with it, but I would like to get a little more push out of my top end on the highway.

I have to admit though, I upset alot of stock mustangs and rice burners...up until I hit the 60 mph mark that is!

[Psycho71]

I can say one thing for sure; If you like the way your truck runs now, you'll never be happy with any gear less than the 4:10's. (Maybe the 3:73's, but I doubt it). If ya wanna see, go pull a plug wire and drive it around the block. It'll run better than that of course, but it won't feel like it to you. You WILL miss the 4:10's every time you see a ford. But you might be able to pass a few more stations.

The obvious solution is to O/D the truck. You would spend alot more money for the tranny. But you'd then have the best of both worlds. Monster first gear, and lower r's on the freeway (or higher sustained mph if your like me).

Yet another solution would be to buy a motor stand, a good block, and buy a peice at a time until you have a fresh motor on the stand to drop in at the first sign of trouble (or earlier). Another advantage to this method is that each motor will progressively get faster and faster as you freshen them up with beter & faster parts each time. It sounds crazy, but I've seen it happen many times, and it works.


Jay

[lilred67]

3.42's

[Cannon007]

3.07 since its your daily driver, your gas mileage will go from 10mpg to 18mpg on the highway, but if you have the money then get an Overdrive and change to a 3.73 rear. the 4l60(TH350 with OD) or 4l80(TH400 OD) have 3.08 1st gears which will be like have a 4.56 rearend on a TH350. the OD is a .72 gear and will be like having 2.49 3rd gear on a TH350 or something like that, but anyway best of both worlds man! If you can afford it go for that, plus you can get a nice one built with a good little stall converter in it for harder shifts and more punch off the line with a bigger stall.

[BCOWANWHEELS]

3.08 for sure for a driver

[69heavychevy]

Originally Posted by Cannon007

3.07 since its your daily driver, your gas mileage will go from 10mpg to 18mpg on the highway, but if you have the money then get an Overdrive and change to a 3.73 rear. the 4l60(TH350 with OD) or 4l80(TH400 OD) have 3.08 1st gears which will be like have a 4.56 rearend on a TH350. the OD is a .72 gear and will be like having 2.49 3rd gear on a TH350 or something like that, but anyway best of both worlds man! If you can afford it go for that, plus you can get a nice one built with a good little stall converter in it for harder shifts and more punch off the line with a bigger stall.

i thought the 4l60 was a 700r4

[C10-Driver]

I agree with a couple of the posts above... Either a 3 speed with 3.07's or a 4 speed and 3.73's.

[Bus Ted Knuckle]

If you are looking to lower your RPMs on the highway, you will want to go 3.07.

[ChevLoRay]

Keep the gears you have, but swap the transmission to a 700R4. You'll still have a deep first gear, but lower your cruising RPM's to something you'll feel better about.

[scatesracing]

While we are spendinng his money how about 4.56 and a six speed .......5th and 6th are both over drives. my buddys vet is just above idel a 65mph in sixth stock gears 94 vett???????????

[WorkinLonghorn]

Don't mean to sound like a wise-A** here but the cheapest way to reduce your RPMs on the freeway is the method I use;DRIVE SLOWER. I have 3.73s with a stick and 31" tires so so I'm a bit lower than you,but I just drive 55-60 and never exceed 2500 RPMs. You will get better MPG and won't have to change a thing on your truck.

[ChevLoRay]

...something about wind resistance that affects any vehicle, huh? Click and Clack said the effect grows at an exponential rate as we exceed 50mph. Slowing down does save fuel, but at the risk of becoming ticketed for "impeding traffic" negates the desire.

[WorkinLonghorn]

That's what the right lane is all about.Anyway,I'm ancient now,don't have the same "need for speed" as I used to.But still like getting better mileage and being a bit safer.

[71Chevy4-speed]

I like the 3.73's in my 85 but I do have a 700r4 with 31's, my 71 had 4.56's and 31's SM465 trans and I miss those deep gears. I'd suggest 3.42's if you planned on giving the motor a little umph in the lower rpm range. Otherwise 3.73's

Originally Posted by 69heavychevy

i thought the 4l60 was a 700r4

Your correct, the 4l60 is the 700r4, technically 82-86 is called 700r4, 87-up 700r4's are called 4l60's and 93-up electricly controled is obviously the 4l60E, my guess is trying to get away from a name known as junk. The 4l60 isn't a turbo 350 with OD its a different animal, T.V. cable v.s. vacumm modulator, different gear ratio's etc.

[67shortie]

I run 3.42's in mine with a 31" tire, 70 is about 2700 or so.

[mnunn454]

Originally Posted by C10-Driver

I agree with a couple of the posts above... Either a 3 speed with 3.07's or a 4 speed and 3.73's.

Yup!!
Agree completely.


I have a TH700 in my Elky with 3.55's and it's PURRRRFECT. Great both in low and on the highway. My truck has a TH400/3.73 and it's a little too low (numerically high) for my taste. And one of these days, if I don't sell it first, I'll stick a 700R in it too to get a better ratio in low and a better highway cruise RPM as well.


Also, 3.55's were available, but only in passenger car axles. Closest to it for our truck axles is the 3.42 (which is a real nice all around gear for stick shifted SBC on the street).

[OrangeCrush1970]

a friend found me both 3.08 and 3.73 for a great deal, now I just need to make up my mind. The 3.08's are very appealing to my pocket right now with the way ga$$ is. I think I may go w/ the 3.08's and bump back down to 27 or 28" tires.