Good rear end gearing for daily use???

I have a 350/350 combo in my 52 3100. Its all stripped down right now so I figure now is the time. I got the rear out, not sure of the gears in it now, havent checked yet but it would scream at about 3K at 55-60 on the highway. What would be a good ratio to put back there so I can cruise up around 70? I know a 700R would be the hot set up but its not in the budget right now. Thanks

 

You don't say which rear axle you have so gearing would depend on what's available. Somewhere between 3:08 and 3:55 would probably work OK.

 

I would say 3:00's or there abouts. I have 3:50's in my '51 and I cruise at 65. My '49 has 2:74's and I can cruise at 70-80.

 

Depends on rear tire size but generally 2:73s to 3:08s with the TH350 for comfortable highway running. You can run more gear with a taller tire. I used to stick with 3:55s tops with a 14" tire and 3:73s tops with a 15", but I was not making any long highway runs. I would consider keeping your gear and putting in a 200r4, same overall size as the TH350.

 

You won't find 3.0ish gears for the original rearend, and you didn't say what other modifications you're making, or if someone already changed the rearend. Kind of hard to make good recommendations. But yeah, 3.0 or thereabouts is good for normal driving.

 

Gear it to run about 2000-2400 @70. Use the tire size/gear ratio calculators.

 

Sorry guys, its a 10 bolt chevy back there. And I am running a 255/60/15

 

3.08 would be good, you might even want to go with the 2.73 (or whatever it was in the 8.5"?). Beware you'll lose some acceleration ability....

 

yeah I figured that but I aint looking to race anyone. Donw the road when I finally do the motor and 700R I will be able to gear it down again.

Thanks everyone.

 

Well keep this bug in your ear.... You can pick up a good used REBUILDABLE 700R4 for around $75 bones. A rebuild kit is right around $80 with steels and clutches. Im not an expert by any means but im two ******s in and they are both working great. Its easier than you think to rebuild!! ESPECIALLY a 700. Just food for thought.

 

I like anything from 3:55 to 3:90 (depending on the vehicle) for local driving and get some good throttle response as well. The last one I drove had a 3:90 and I'd bolt on taller tires for road trips, mark up my tach face to correspond with the MPH. 80 MPH would be ~ 4k on the tach, 60 MPH was 3K and so on.

Bob

 

After having a couple 4:11 cars, I started using 3:50 rear ends. I have a 350 engine, 350 turbo trans, and the 3:50 rear is a 9" from an early Bronco. It pulls good off a stop, and can run 80mph or so without the guts flying out of the engine (I'm thinking @ 3,500 rpm).

 

X2

There's lots of websites that will give you all the numbers you want.

here's one: http://www.car-videos.net/tools/spe...o7=&Redline=5500&Increment=500&B1=Recalculate

 

I run 3.55's in my 55 with a th350. Good, all-around gear. I'm at about 2400rpm at 50 on a 28" tall tire.

 

Might have 3.73s in it now? Might want to check, before you get too far along...***uming it's not a posi, turn one axle exactly two turns while making sure the other one does not move at all, and count the number of times the pinion yoke turns. The number of turns is the ratio, for example 3 and 3/4 turns would be 3.73 ratio

 

I agree along this line. If you have to purchase gears, and install them in the rear, you should be able to find a good used 700R4 or 200-4r for similar cost, then have low gears AND overdrive for highway cruise.

 

i run a 3.27 in my 58, i set the cruise at 80. i also have a 700r4 so adjust that for overdrive. i have no tach, but my truck sounds like it lugging at 55mph.

the rearend came out of an 86 trans am and came with disc brakes. i believe the camaro had drum brakes on the same 82-92 rearend. the rearend in your truck is 62'' wide, so is the 82-92 camaro. lot of good info on rearends on chevytrucks.org scroll down.

 

a good all-round gear is 3.73 it will give you good seat of the pants feel and cruise good on the interstate. I use it for a baseline, 3.90 or 4.11 for faster accelleration and 3.50 or 3.08 for top end driving.

Remember GM put 3.08 and 3.73 behind 700Rs and turbo 350s so its not an unproven concept.

Hope that helps
MrC

 

If it IS a "posi" (sorry, mopar guys like to call them a "Sure Grip" ) you can simply get both wheels off the ground and with the transmission in neutral, rotate one of the tires exactly one full revolution and count how many times the driveshaft rotates.

Speaking for myself, I've found that somewhere in the "low to mid three's" is about the best all around gear. I have 3.23's in one car, and 3.55's in another. A lot of it depends on your tire size though too. I agree with using one of the online calculators. Having your engine screaming at 70 mph for an all day cruise gets tiresome.

Maybe when you get out of the budget crunch and have a little extra $ to play with... what I love about a Chrysler 8-3/4 or a Ford 9" is that you can have as many different gear ratios around as you can afford. I have a set of 3.91's in a 5 gallon bucket for the occasional trips to the track, and have the 3.23's in the car for the road trips and general cruising around. Last time that I counted, you had to unscrew and re-screw 24 nuts & bolts to change out the center section in an 8-3/4. With an air ratchet you can do it in an hour! When I moved to Virginia when my fiance and I were engaged, I'd run around with the 3.91s in the car for two weeks and then put the 3.23's or 2.76's in it when I'd go to Pittsburgh to see her. Soon as I'd get back the 3.91s went back in. (I was a single guy living in an apartment... I was bored, ok?)

I've also borrowed some other ratios just to try them out (I had a set of borrowed 4.56s in the car for ONE day! With G60-14s on the back, the 340 was screaming at 45mph...)

 

My vote is 3.42. If you need a rearend now get one from a wrecking yard from a 4x4 S10 Blazer. They also have 3.08, 2.73,and 3.23 readily available.

 

Great information guys, thanks. I am gonna look into the 700R/200R and rebuild. Not sure if this makes a difference but here is the rear out of the truck, I just had time to take a quick phone shot during lunch. Also when I turn one wheel the other wheel turns in the same direction, that makes it a posi correct? Bare with me, I am a bike guy, getting this deep in cars is new to me.



here is how the truck sits now, I will also update my build thread with better shots tonight. A few shady modifications going on there.

 

What is the power band of your engine? These numbers are a good ballpark number for about any small block.

I like a 3.26 gear with a 28" tire for my small block. That puts me in the 2500 to 3000 range on the highway. My engine likes to run in the 2800-3200 range as far as cruising speed. If your engine likes to run @ 2200 than a 3:1 gear with a common light truck tire is good but if your sweet spot is 3500 then you are going to want to run a steeper gear.


No one can make a good suggestion to you without knowing all the variables. Operational RPM range, and tire diameter are the very least you need to know. You can add to that list if yu want to get it to the knats ***.

 

Sounds like you have a posi. If it's a 3.73 you might need to change the posi case to a different one to go with lower gears, so you would probably be better off going with an overdrive transmission like a 200-4R or 700R4.

As you've seen, everyone has their own opinion about what's the right thing to do....

 

Absolutely, thats why I came here to ask. I want to hear the options and opinions and also learn what will help me make my own in the future. I really appreciate the help.

 

Just an opinion, But in todays world i wouldn't consider building a car without an overdrive. You will spend basically the same to put gears in your rear axle as you would the trans... Nothing makes a bigger difference in performance or fuel consumption.

 

I was thinking the same thing until I found a 350 turbo for $60. Guess my cheapness won.

 

I didnt realize these transmissions could be had for cheap. I was figuring on spending around $1000 or so. I think I am going that route and finding a 700R. Is there a certian year to look for? I remember reading something about 1985 for some reason. I'll do a search, I am sure this topic has been brought up before.

 

Look for one that's newer, but not so new that it has the electronic control. The older ones all had a single 4 pin connector for the converter lockup, but the 93-up 700s are called the 4L60E and are completely controlled by a computer, with a big fat wiring harness. The electronic speedo has a two pin connector (?) at the back where the speedometer cable would be. Some can be easily converterd (or used with an electronic speedo), but you should figure that out before you buy.

The 200-4R are mostly the same for all the years they made them, but some are better than others, and if you start with a lame one, you'll need to spend some money beefing it up.

But yeah, that's a subject for a whole other thread.

And some of us don't ride the "gotta have overdrive" bandwagon, I don't have it in any of my old stuff. OD is for my wife's late model ****.

 

Play with the numbers here and decide for your self.

http://www.project33.com/tiresize.cfm


3:73's and a 700r4 with a 28 or 29 inch tall tire is a nice combination-but you may want something different for a truck

 

I ran 3.08's in a 41 Ford sedan with a 350/350 and 14 inch tires. It still had respectable power from a standing start, great top end and plenty of p***ing power at 65-70. Gas mileage wasn't bad either.