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Discussion Starter #1
Hey all

I got the 2.41 open....yeah yeah... I KNOW!

But i have a question about 2.41's and 3.73's

My 2.41 likes to keep real low rpms, it dont usually get over 2,000-2,500, unless i punch it. Now would a 3.73 act any differnent on the same acceleration?

Lets say you do a 0-60
2.41- @ lets say 3,000 rpm @ 10 seconds
3.73- would 3.73 be the same for the same time of 10 seconds?

Also for any high gears (2.41) people-

Does your 2.41 tend to keep ya at low rpms? I dont got overdrive so i imagine i would be real low with OD.

Thanks guys- kinda wanted to clear this up in my mind
 

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I just went from an open 2.41 to a posi 3.08. I love the acceleration but if you dont have an overdrive tranny I would not go any lower than 3.08. I don't have a tach but the shop that did the install calculated that I am running about 600 rpm higher at any speed. When we go to Pismo this week I will check highway mileage but around town with my new 350 I am getting 10 mpg! I am saving to swap my th250 tranny for a 200r4 overdrive unit.
RTT:beer:
 

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Discussion Starter #3
Agree, you run maybe 2,700 rpm on the highway with no overdrive.

I run [email protected],500
[email protected],450

I would consider a 3.08 or 3.11 swap, 3.73 is for racing in my opinion. Mine is a daily driver.

So just wondering, are the rpms the same on acceleration? Its troubleing me
 

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If you have 2.41 gears , 15 inch tires and were running at 2500 with a th350 tranny you should be running at 46.3 mph but if you ran 3.73 gears with 15 inch tires and a th350 tranny you should only be running 29.9 mph , these are just rough numbers i put into a speed program ,tire size and tranny gear ratio will alter these speeds but it shows the difference beween the 2 rear ends in proper ratio , having had 4;10 and 3;73 gears I wouldn't recommend them for a daily driver without an overdrive transmission , but boy are they fun ,lol
 

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I think those speed programs are using TIRE size, not WHEEL size. I used one and my 255/60-15 tire is approx 25.6 inches while the wheel is only 15 inches. Made a big difference when trying to calculate my axle ratio - using the 15 inches my ratio was an unheard of low number that didn't even exist in any GM chart.

just my .02
 

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if you are using this for an everyday driver. i wouldn't recomend the 3.73 without an overdrive tranny. I do have 3.73 with a 3 speed automatic and at highway speeds the motor is really turning. My car is not a daily driver so I can deal with it. Its a fun gear at the stop light though.
 

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When I got my '87 Choo Choo, it had the 2.41 posi in it. No acceleration at all as far as I was concerned behind the stock 305 carburated (LG4) motor.

I installed an '87 Monte SS 200R4 trans with the 3.73 posi rear and a '88 IROC 305 TPI motor.

Right now it shows ~2600 RPM @ 65 MPH. Cruises nice, not over revving and gas mileage isn't too bad either, ~22 MPG highway.

It is very perky pickup now.

I am very happy with the performance and was not expensive to do. Between the hooker headers, exhaust, motor rebuild, tranny rebuild, and all considered, cost me ~$2500.

Bruce
 

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ok here ya go i run 373 gears with a th350 trans and everyone is right, they are a blast around town but after about 20 minutes on the freeway it gets old quick...... but this isnt my daily driver either so i can deal with it and when i do take it to dallas and further i just pop in some good tunes and ease on down the road :beer::secret:
 

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I did the same swap, 7 1/2-2.41s to 8 1/2-3.73s and boy did it wake up the car. I'm running with a 700R4 so the overdrive is the only reason I went with 3.73s. I'm not sure how accurate the factory tach is but with 27'' tires (255/60/15) I'm doing 65 mph at around 3000 rpms on the highway.
 

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For a quick, rough estimate, simply divide 3.73 by 2.41. You get about 1.5. If you divide 2.41 by 3.73 you get about .65.

Now, if you were running 60 MPH at 2000 RPM with 2.41 gears, multiply 60 * .65 and you'll see, with 3.73 gears, you'll be running 39 MPH at 2000 RPM.

Or you can figure the new RPM at 60 MPH by multiplying 2000 * 1.5. You will now be running 3000 RPM at 60 MPH.

These are fairly close to actual numbers.

Pretty much says that you need OD with 3.73 gears to keep the RPM down.

Jack
 

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With 3.73s your rpms are going to be higher at any speed than with the 2.41s. Currently, it takes 2.41 rotations of the driveshaft to turn the rear tires once. With 3.73s it will take 3.73 rotations of the driveshaft to turn the rear tires once. I have a 2004r with overdrive, with 2.41s at 65 mph I could run the car under 2 grand, which it hated, it would lug and feel significantly under powered. With 3.73s I run just under 3 grand at 65.

In this day and age with gas prices and such, I really wouldn't put 3.73s in a daily driver behind a th350, it will be fun but be pretty harsh on the wallet. Stick with 3.42s or numerically lower, like 3.23s, or 3.08s. The rest wouldn't be much of an upgrade if you're looking for a performance upgrade.

Swapping in a drum to drum unit is simple and straight forward, but will still be a lot of work especially if it's your first time taking on something like that. Mine took 3 days, ORDER NEW TRAILING ARM BOLTS BEFORE HAND! PB blast everything for a week, order any new brake parts you might need, fluids etc. If you take the route like I did, you will spend more then a hundred bucks for all the extra parts. In the end it is totally worth it, and so far the best thing I have done for my cruck. Good Luck!
 

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I went from 2.73's to 3.23's and I could still tell the difference, especially when I can scratch in 3rd gear with my little 305. That is mostly because of the shift kit however. @ 70 mph I am doing 2500 rpm and @ 55 I am doing 2000. This is with 215/70-14 tires and 2004r tranny. To me that is about perfect and I get 20 highway mpg. I am thinking about swapping to tbi and see if I can get it up to 22 or so.
 

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I have a Muncie 4 speed and run 3.70 gears in my ford 9", I was running a 65 series tire and running 2800 rpm on the highway at under 60 mph.... I later changed to a 275/60/15 drag radial which actually lowered my cruising rpm down to about 2500-2600 at 60-65.... Remember the height of the tire will change your final drive ratio
 
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