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3000 RPM AT 60 MPH?
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BIG-A
New User
| Posts: 44
| Joined: 12/07
Posted: 03/04/08
06:57 AM
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DOES THIS SOUND RIGHT FOR A 3.23 GEAR? I HAVE 28" TALL TIRES AND MY FACTORY TACH READS 3000 AT 60. BOUGHT THE CAR 7 YEARS AGO AND WAS TOLD IT HAD A 3.23. IM ABOUT TO BUY A REMAN. 489 CHUNK AND AM TRYING TO DECIDE ON WHAT GEAR? I WAS WANTING AT LEAST 3.73 BUT HOW MANY RPM WILL THIS ADD? OH YEAH ITS A 383 AND A 727.
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RBolig
Moderator
| Posts: 658
| Joined: 12/03
Posted: 03/04/08
07:09 AM
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It doesn't sound like you have a 3.23 gear to me. Are you sure your tachometer is right? It almost sounds like you have a 3.91 or 4.10 gear already.
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Some people are like Slinkys; they're not very useful, but fun to watch when pushed down the stairs.
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BIG-A
New User
| Posts: 44
| Joined: 12/07
Posted: 03/04/08
09:53 AM
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THANKS FOR RESPONDING. MY TACH SEEMS TO BE RIGHT AT IDLE ITS @800 RPM AND WHEN UNDER HEAVY ACCELERATION IT SHIFTS AROUND 6000. THESE SEEM RIGHT TO ME SO I FIGURED IT SHOULD BE CORRECT WHILE AT A STEADY SPEED. WHAT DO YOU THINK ABOUT TRANS GEARING? IF ITS A TRUCK OR RV 727 DO YOU THINK THE FINAL GEAR MAYBE DIFFERENT THEREFORE CAUSING MY REAR RATIO TO SEEM DIFFERENT? THANKS FOR THE HELP
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72Demon
New User
| Posts: 1
| Joined: 03/08
Posted: 03/04/08
10:08 AM
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No. The 3.23 should run 60 @ 2500 rpm. The 3.73 should run 60 @ 28-2900 rpm. A 235/60-15 tire will need close to 3000 rpm with a 3.91 rear gear to make 60 mph (3500 @ 70). Speedometer gear for this combination should be blue and have 38 teeth. Typically one tooth changes the speedometer reading by 2-3 mph. This assumes the tachometer, speedometer & odometer are working correctly.
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RBolig
Moderator
| Posts: 658
| Joined: 12/03
Posted: 03/05/08
07:21 AM
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Big-A, I don't believe the final gearing in the transmission varies from truck to car.
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Some people are like Slinkys; they're not very useful, but fun to watch when pushed down the stairs.
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BadFish
Moderator
| Posts: 307
| Joined: 01/07
Posted: 03/05/08
07:44 AM
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All TorqueFlites without overdrive have a one to one final ratio.
Sounds like you have 3.91 gears to me, jack the car up and turn the wheel one revolution, the rear end yoke/drive shaft should turn 3.91 (nearly four) times.
If the rear really is 3.23, I'd suspect a tach inaccuracy.
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duster367
New User
| Posts: 11
| Joined: 12/07
Posted: 03/16/08
02:42 PM
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This makes me think I thought I had a 4:30 for years but I'm turning around 4000 to go 60. Is it posible that I have a 4:56?
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RBolig
Moderator
| Posts: 658
| Joined: 12/03
Posted: 03/17/08
06:27 AM
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Duster, Yes, it's possible
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Some people are like Slinkys; they're not very useful, but fun to watch when pushed down the stairs.
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moparmike
New User
| Posts: 10
| Joined: 03/08
Posted: 03/25/08
10:54 AM
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My Bee has 3:23's in the rear and I'm at the same RPM cruising down the freeway. I think my speedo is close compared to other traffic. I do have 225\70
14's on it. I'm thinking it's because my tires are small. Glad I didn't install the 3:91's like I planned. My next set of tires will include a taller size on 15"
1969 Superbee WM23
440-6, 727, B-5
1977 D-150 Adventurer
2001 Durango 4X4
2006 2500 CTD
They don't call me Mopar Mike for nothing!!!
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drmopar
Guru
| Posts: 847
| Joined: 02/08
Posted: 09/02/08
08:58 AM
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Your either in second gear or your tach is hooked up as a 6 cy.
I have 4.30 gears and run a L/60/15 I cruise at 60 mph at 3000 rpm.
The other possiblty is you already have a steeper gear.
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AdamR
User
| Posts: 78
| Joined: 09/08
Posted: 09/30/08
06:30 PM
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What do you have for a torque converter ? A high stall unit will slip more at cruise. Especially if its a cheap unit or has to much stall for your application.
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fishy68
New User
| Posts: 24
| Joined: 11/07
Posted: 11/11/08
10:06 PM
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Somethings not right. With a 3.23gear and 28" tires you should only be turning barely over 2500 rpm at 60 mph. And that's figuring you using a automatic with 8% calculated torque converter slippage which is really high like a cheap converter has. If you have a manual trans. you should be only turning approx. 2350 rpm. Before you buy something you may already have I'd get a buddy over and jack that thing up and spin the wheels exactly one turn and count the turns of the yoke to see what gears are really in there. I'm betting on 3.91's.
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liletn
New User
| Posts: 1
| Joined: 04/09
Posted: 04/09/09
11:58 PM
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I also have a gearing question.. currently a 440 with 727 in 1972 charger running a set of 2.45 gears...... (wish i was kidding, a little too fast) ... i am putting a 8 3/4 under it but not sure what gears to use.... it is mostly just cruising around town, but occasional jaunting on interstate and i dont want the engine screaming to keep up with traffic... i think 3.23 or 3.55, any thoughts or experiences welcome
...also planning on putting a powertrax unit in, but not sure how it will handle
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64fury
New User
| Posts: 11
| Joined: 04/09
Posted: 04/18/09
05:53 PM
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I have a 64, 383, A/T, Fury coming in a couple of weeks that has had the rear end ratio changed (I'm assuming) since the speedo seems to be about 10 mph fast when I test drove it. When it arrives I'll do the tire rotation trick to see what gear it really has.
My question is this. I want a sure-grip rear end and I don't think this car has it. Is it easier to swap out the 3rd memeber or can I modify the stock 8-3/4 472 rearend and make it a sure-grip?
Butch
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Cudadon
User
| Posts: 101
| Joined: 02/08
Posted: 04/18/09
07:18 PM
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2325.6 Rpm = 168 x 3.23 x 60 / 14.
All 8-3/4s can use any of the sure-grips if you use the matching carrier bearings.
Don
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