I have a '71 Cutlass that I'm planning on warming up, performance wise, and need to change the axle ratio.  It is the SX model that came stock with 2.52 ratio. As you may know this gear sucks for anything but highway cruising. I want the car to have  bit more gear to get up and go for the occasional drag-strip run or back roads scramble.  The car has a 455 that I plan on souping up to put out closer to 600 lbs/ft torque (465 stock) and 400+ HP (320 stock).  I've been told to go with nothing less then 3.73 gears (by hard core drag racers). I am affraid to go over about 3.42 and was wondering if it will make that much of a highway driveabilty issue going with the 3.73?
Car will only see around town driving and the as mentioned occasional back roads sprint...

I had 4.56 on my last jeep

I personally would go 3.73's but wtf do I know.

If you plan on making this a highway rig 3.42 or 3.55 is where I'd want to be.

How about 3.73's to 4.10's and you find yourself a tranny with another gear.

I would go with 3.73's in your case.  You mentioned that most of your driving will be around town and 3.73's would be perfect for that.  Where they hurt you if if you do a lot of highway driving, you'll be running a lot of RPM's around 70-75 mph, est around 2500-3000, which really isn't that bad..  I had 3.42's in my 96 Impala and highway driving was still fine, but I wish I had gone ahead and got the 3.73's.  

Bill3508

My truck has 4.56 gears and cruises just fine at 80mph.

Quoted: My truck has 4.56 gears and cruises just fine at 80mph.

and you can beat just about anyone off the line

If you're running the Turbo 400, then 3.73s probably won't make you happy if you're ever on the highway.

Big inch engines don't need a ton of gear and I doubt that anyone who says to gear the hell out of it is running a big Olds, Pontiac, or Buick.

A lot of the 455 Poncho street strip cars run 3.55s and run pretty quick (low 12s - high 11s).  I don't think you'd be disappointed with the 3.42s, unless you go to the track and try to use tall slicks - then it may bog off the line.

Also, don't overdo it on the converter either.

Not a dedicated drag racer.
stock type converter/stall, tires are 255/60/15 and the tranny of choice will be a built 400

the vehicle

What size tires are you gonna run in the rear? Just read it.  What is the stock tire size?

With the 255x60x15's, that tire is 27" tall, meaning it's 85" around, making 746 rev/mile.
With a 2.52 ratio you're moving 33.75" per turn of the drive shaft, making about 1,900 engine rpm at 60 mph with a TH-400 tranny.
3.42's move you 25" per driveshaft turn, making about 2,550 engine rpm @ 60 mph.
3.73's put you at about 2,800 engine rpm @ 60.
Just food for thought.

keep in mind 3.73's are the typical TRUCK ratio with 31" tall tires- just the typical full size truck setup

i wouldnt go anything lower than 3.55's unless you plan on setting records at the track.

and all these guys running 4.56 gears in their trucks... probably have 35"+ tires!!  i had 35"s on my last 3 trucks with either 3.73 or 4.10 gears... and i know your car probably wont be running 35" swampers

Quoted: If you're running the Turbo 400, then 3.73s probably won't make you happy if you're ever on the highway. Big inch engines don't need a ton of gear and I doubt that anyone who says to gear the hell out of it is running a big Olds, Pontiac, or Buick. A lot of the 455 Poncho street strip cars run 3.55s and run pretty quick (low 12s - high 11s).  I don't think you'd be disappointed with the 3.42s, unless you go to the track and try to use tall slicks - then it may bog off the line. Also, don't overdo it on the converter either.

+10,000

Had a buddy w/a 72 Skylark, he ran a 455 Buick w/3.31 gears and a 3000 converter. It ran 12.0s.

3.42s.You'll be happy!

OK, repost your message on www.442.com/

I have a 72 Cutlass with a 455 and TH400.  My rear tires are 295/50 - 15's.  I have the 3.42 gears and I would not want to go lower.  On the highway, it cruises around 2000-2500 rpm.  Remember, these Old's are low RPM engines. Go with the higher ratio gears (that means lower number) and you'll be happy.  If your putting out 600 lbs/ft  you dont need the gearing to get you moving.

rpm = (mph x final gear ratio x 336) / tire diameter

A 700 OD tranny will give you lots more options.  Sticking with the T400 I would not go below 3.42.   With the 700 I would go with a 4.11 and buy a set of 9" slicks for the strip.  Should run low 12's high 11's at which time they will make you put in a roll bar if it is an NHRA track [ 11.99 and quicker requires roll bar ].  I will enclose a pic to show that I have a bit of a clue

ETA:  What I meant by go below was that I would not go lower { higher numerically } than 3.42.  I would use a 3.42 or 3.23.   I had a 68 GTO with a 3.23 that was a pretty good compromise between out of the hole and highway topend. These are torque motors.  The Camaro below had a 4.88 that was too low for the cam/carb/intake and actually slowed the car down [ which was good as the footbrake cutoff was 13.00 and the car would run 12.60 with a 600 holley ].

rj

You should be alright with a 3.73 though If I have my choice, I'd go with a 4.10 or above....

3.73 (gears) ring and pinion is actually "livable" and can be driven daily contrary to popular belief......

+3.42

Spend money on the Convertor{3000-3500} and it will hardly make difference at the track. Big engines don't need much gear with a good convertor.

3.73 is too low if you want to cruise it on the freeway,

like others have said all of my trucks have had 373's and even with big tires it still sucks

I would go 342 or even 308 if you do alot of highway.

by questioning driveability one of my concerns was will 3.73s make much of  diff with the engine temp?  I am running a 4 core radiator, mech fan and shroud. Considering twin electric fans though.
BTW, the drags will strictly be a past-time. I am not building a drag car. The car is going to be basically  set-up as G-machine.

3.42s or 3.55s will be plenty with a 455 and that kind of torque, real similar to my TA with 455

Quoted: by questioning driveability one of my concerns was will 3.73s make much of  diff with the engine temp?  I am running a 4 core radiator, mech fan and shroud. Considering twin electric fans though.

Running a higher rpm constantly will create more heat.  How much I can't say.  The electric fans will make no difference at speed because the radiator is receiving all the air forced through the grille and the radiator.  I think the twin electrics will help speed up the cooldown once you are back to stop and go.  The biggest thing is keeping the shroud in place so the air goes through the radiator, rather than around it.

Nice Cutlass, BTW.  Good Luck with it.

My 66 Mustang has a 3.50 final drive ratio and can just about stay in the lower part of the power curve at 60 MPH in 5th (0.67 OD).  Also, around town  (@40 MPH) 3rd gear is too high and 4th bogs at just over 1200 RPM.....SO...... I'm swapping to a set of 4.11s this spring.  OD on the highway will actually be at an RPM that has some useable power and I will be able to cruise around town likewise in 4th gear.

I say go w/ no lower than 3.73 without OD or you'll won't be able to hear your radio or CDs on the highway.  Or bolt in a newer GM OD 4-spd auto and run 4.11s.

Miami makes a good point.

Your OD ratio will determine the "driveability" on the highway, so don't overlook that.

unless someone makes an adapter the only OD tranny option is TH200 of which very few were made and their survivability is high;y questionable. I am unsure of the add on OD units so any advice there were be useful as well.

Here's more to think about...

650HP capable TH200-4R

If I was sinking a lot of $$$ into the car, and already had plans to upgrade the tranny, I would opt for a HD rebuilt 700-R4.  They are quite capable trannys, as long as they have high quality components.  The OD would be a godsend if you opt for the 3.73 or lower (numerically higher) gears.  I rebuilt mine in a 86' 4x4 a few years ago, using aftermarket parts from a place named premier performance out of CA.  The kit cost $600, the rebuild labor cost $250.  I put it in and took it out.  I also upgraded to a deep sump pan from B&M, and the largest cooler they made.  I had a SB 400 in front of it, 3.73 gears with 33" tires.  The tranny held the 400's torque just fine.  Google can probably show you some great place dot get 700R4's from.

Quoted: If I was sinking a lot of $$$ into the car, and already had plans to upgrade the tranny, I would opt for a HD rebuilt 700-R4.  They are quite capable trannys, as long as they have high quality components.  The OD would be a godsend if you opt for the 3.73 or lower (numerically higher) gears.

not much chance of finding a 700 to fit an Olds block

Quoted: Here's more to think about... 650HP capable TH200-4R

thanks Tom

Quoted: not much chance of finding a 700 to fit an Olds block

Damn I dropped the ball on that.  DUH.
I think somebody makes custom housing for this.....

I run 4.11 on my ranger, but I run 33x12.5 tires. this give me a good mix with the 4.0. I have several gear sets in my garage, from 3.40 to 4.56. No they are not cheap, but I can change as money and tire size calls for. I have left the 4.11's in for the last three years as it give me the best mix for the engine and tranny and tire combo. You must make the choice on what you want, stump pulling power, or top speed over a distance.  With what you have stated the higher gears of 3.73 would be the max you would want to run, as you have the C.I. to make up for gears.
Unless you are running illegal street races against a similar setup most will be running 350's or less. Your C.I. will make up for the diff.
When I was into drag racing we ran from 4.11 to 5.56  based on the track conditions, and compition.
Most of the young kids who are into straight line racing are now using riceburners, and they generate massive H.P.  but not torque. Cubic Inches create torque, a big block does this every day and it is nothing for it. The ricers will only last a short time running maxed out.
You have a nice ride what I would suggest is to find the specs. from the hottest of that model. Why re make the wheel?
That year make and model was cover in one of the "hot rod" type mag.s. If you can go online you can find the reactions to mods. you are looking at. she listed
Now if you want to F.U. a possible classic car look and a late model fuel injection and computer for this.
But before you do that google car sales and classic cars and listing make model and year and engine size, you may find that people will will pay much more then it is worth to you.
For example my mother's sister had a  1968 VW she thought is was only worth about $3000.
After she listed it with my help, she sold it from a guy from MD for $17000, and her drove to pick it up.
On the same kind of note my next door neighbor has a 1978 camero Z with the 4 speed hurst he was going to sell it to his daughter for $1000 to use as a daily driver. One owner low miles records etc.
He posted a questional note from my computer as to value, the last I will buy it now was $30,000
Think before you tinker

Quoted: I run 4.11 on my ranger, but I run 33x12.5 tires. this give me a good mix with the 4.0. I have several gear sets in my garage, from 3.40 to 4.56. No they are not cheap, but I can change as money and tire size calls for. I have left the 4.11's in for the last three years as it give me the best mix for the engine and tranny and tire combo. You must make the choice on what you want, stump pulling power, or top speed over a distance.  With what you have stated the higher gears of 3.73 would be the max you would want to run, as you have the C.I. to make up for gears. Unless you are running illegal street races against a similar setup most will be running 350's or less. Your C.I. will make up for the diff. When I was into drag racing we ran from 4.11 to 5.56  based on the track conditions, and compition. Most of the young kids who are into straight line racing are now using riceburners, and they generate massive H.P.  but not torque. Cubic Inches create torque, a big block does this every day and it is nothing for it. The ricers will only last a short time running maxed out. You have a nice ride what I would suggest is to find the specs. from the hottest of that model. Why re make the wheel? That year make and model was cover in one of the "hot rod" type mag.s. If you can go online you can find the reactions to mods. you are looking at. she listed Now if you want to F.U. a possible classic car look and a late model fuel injection and computer for this. But before you do that google car sales and classic cars and listing make model and year and engine size, you may find that people will will pay much more then it is worth to you. For example my mother's sister had a  1968 VW she thought is was only worth about $3000. After she listed it with my help, she sold it from a guy from MD for $17000, and her drove to pick it up. On the same kind of note my next door neighbor has a 1978 camero Z with the 4 speed hurst he was going to sell it to his daughter for $1000 to use as a daily driver. One owner low miles records etc. He posted a questional note from my computer as to value, the last I will buy it now was $30,000 Think before you tinker

   

sorry, Ive been at the hospital for the last two days, wifey poo fell and broke her elbow slipping on the ice.                                      This is the "PLAN".
          The car is an SX Supreme with very few options and had been wrecked/repaired and repainted by E. Sheib.  I paid book value for the car three years ago. (not a 442 or convertible so is not worth anywhere near the 15K+ those are advertised at) The car is basically identicle to the one I sold in 1981 for 500U$.  I purchased this one for the sole purpose of applying some modern technology to make it better (comfy interior) stronger (major chassis upgrades) faster (aluminum heads and intake/fuel inj and roller everything + four w/disc brakes) ect ect ect.  I have no thoughts of ever selling the car but will keep all initact but unused original pieces in storage.

bump for the day crew

I guess I dropped the ball on the 700 tranny to Olds too [ being a bowtie guy ].  If you have ever seen a Buick GN reel off some unreal times at the dragstrip you will know that the 200 is pretty stout.

When I was just out of high school I was an oil change / floor sweep flunky at an Olds dealer ship. Couple of drag racers worked there .  I had a 65 Galaxie with a 4bbl 390 factory 4sp [ slow turd but I didn't know any better ].  This 442 shows up for an oil change. I go out to test drive it after I am done. GD !!!!! What a JET !!!!!  I come back and get Harold "What the hell is this thing ?"  1970 W30 4sp.  Surely the fastest stock vehicle I ever drove.  [ 4 wheels,  I worked at a Kaw/Suz dealer the next year starting 73 ]

{ 67 GTO just drove by in real time }.  

Go here for more tranny info:


www.442.com/oldsfaq/oftswp.htm

rj

preciate all the response I'm gonna jerk the rear axle assy out next week and take it in for an overhaul + locker + 3:42/3:55s

I fixed the link.  Be careful with the locker in the rain. First time I drove a posi in the rain [ at all actually ]  it  jumped out from under me. 68 Petty blue Road Runner.  This was in 73.   Fortunately nobody was coming , I was going pretty slow and it just did a 1/2 spin in the middle of the road. Eye opening experience .  Chaz [ rip ] would have killed me if I had bent his car.

rj