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Ford 9 inch 3.55 driveability?

Discussion in 'The Hokey Ass Message Board' started by louder50, Jun 19, 2012.

  1. The last rearend I bought at a you-pick yard I paid $50 for complete drum to drum with a fairly recent brake job. I know it's been a couple years but their prices haven't gone up that much. Maybe that's the way to go.

    Of course, a 9-inch may not leap out at you right away, but unless you intend to pound the snot out of it most anything that's the right width and wheel bolt pattern should be fine.

    I think the drivability has pretty well been covered; it all depends what you're going to do the most in the car and what you expect from it.
     
  2. bhurlin
    Joined: Nov 14, 2008
    Posts: 62

    bhurlin
    Member
    from Texas

    Can anyone tell me what model and years you are pulling the rear end out of. (8") for a Model A Sedan or Pickup

    Bill
     
    Last edited: Jul 1, 2012
  3. amadeus
    Joined: Dec 27, 2006
    Posts: 321

    amadeus
    Member

    1957-60 F100 Truck is PERFECT for the wider Sedan Bodies; lenght drum face to drum face I believe it to be 62''
    This is the rear end I have in my 29 Sedan,LOOKS PERFECT!
     
  4. TRIK3R
    Joined: Mar 19, 2011
    Posts: 49

    TRIK3R
    Member

    I'm running a 3.25:1 9" in my 350/350 MGB 225/50/15, 3200 rpm@ 60, highway sucks but yeah it's still a blast.
     
  5. 40FordGuy
    Joined: Mar 24, 2008
    Posts: 2,907

    40FordGuy
    Member

    3:55 is a good all around,....Ford put countless numbers of them in small block F100 and F150 pickups. We drove our then- new 72 F100 all the way across country, did just fine.

    4TTRUK
     
  6. 40FordGuy
    Joined: Mar 24, 2008
    Posts: 2,907

    40FordGuy
    Member

    Rice Rocket,....... Hi,, neighbor !

    4TTRUK (Also in Citrus Heights.)
     
  7. I'm running a 9" with a 3:55 - 4l80e - 31 tall tire. The 502 run's around 2100 rpm at 70/75 mph.

    http://www.ringpinion.com/Calculators/Calc_RPM.aspx

    Transmission Gear Ratio Chart

    1st 2nd 3rd 4th 5th 6th
    GM TH200-4R 2.74 1.57 1.00 0.67
    GM TH350 2.52 1.52 1.00
    GM TH400 2.48 1.48 1.00
    GM TH700R4 3.06 1.63 1.00 0.70
    GM 4L60/4L60E 3.06 1.63 1.00 0.70
    GM 4L80/4L80E 2.48 1.48 1.00 0.75
    GM 5L40 3.46 2.21 1.59 1.00 0.76
    GM 5L50 3.45 2.21 1.59 1.00 0.76
    GM 6L80 4.03 2.36 1.53 1.15 0.85 0.67
    GM ALLISON 1000 (5 SPEED) 3.10 1.81 1.41 1.00 0.71
    GM ALLISON 1000 (6 SPEED) 3.10 1.81 1.41 1.00 0.71 0.62
    DODGE TF727 2.45 1.45 1.00
    DODGE TF904 2.74 1.54 1.00
    DODGE TF 909 2.74 1.54 1.00
    DODGE TF 999 2.74 1.54 1.00
    DODGE 30RH 2.74 1.54 1.00
    DODGE 32RE 2.74 1.54 1.00
    DODGE 32RH 2.74 1.54 1.00
    DDOGE 42RE 2.74 1.54 1.00 0.69
    DODGE 42RLE 2.84 1.57 1.00 0.69
    DODGE 44RE 2.74 1.54 1.00 0.69
    DODGE 45RFE 3.00 1.67 1.00 0.75
    DODGE 46RE 2.45 1.45 1.00 0.69
    DODGE 47RE 2.45 1.45 1.00 0.69
    DODGE 48RE 2.45 1.45 1.00 0.69
    DODGE 545RFE ('03-'05) 3.00 1.67 1.00 0.75 0.67
    DODGE 545RFE ('06 & UP) 3.00 1.67 1.00 0.75 0.67
    DODGE 68RFE 3.23 1.83 1.41 1.00 0.81 0.62
    DODGE G56 ('05-'07) 6.29 3.48 2.10 1.38 1.00 0.79
    DODGE G56 ('08 & UP) 5.94 3.28 1.98 1.31 1.00 0.74
    DODGE NAG1 3.59 2.19 1.41 1.00 0.83
    FORD C4 2.46 1.46 1.00
    FORD C5 2.46 1.46 1.00
    FORD C6 2.46 1.46 1.00
    FORD 4R44E 2.47 1.47 1.00 0.75
    FORD 4R55E 2.47 1.47 1.00 0.75
    FORD 4R70E 2.84 1.55 1.00 0.70
    FORD 4R70W 2.84 1.55 1.00 0.70
    FORD 4R75E 2.84 1.55 1.00 0.70
    FORD 4R75W 2.84 1.55 1.00 0.70
    FORD 4R100 2.71 1.54 1.00 0.71
    FORD 5R55E 2.47 1.87 1.47 1.00 0.75
    FORD 5R55N 3.25 2.44 1.55 1.00 0.75
    FORD 5R55S 3.22 2.29 1.55 1.00 0.71
    FORD 5R55W 3.22 2.41 1.55 1.00 0.75
    FORD 5R110 3.09 2.20 1.54 1.00 0.71
    FORD 5R110W 3.09 2.20 1.54 1.00 0.71
    FORD 6HP26 4.17 2.34 1.52 1.14 0.87 0.69
    FORD 6R60 4.17 2.34 1.52 1.14 0.87 0.69
    FORD A4LD 2.47 1.47 1.00 0.75
    FORD A4LDE 2.47 1.47 1.00 0.75
    FORD A5LDE 2.47 1.87 1.47 1.00 0.75
    FORD AOD 2.40 1.47 1.00 0.67
    FORD AOD-E 2.40 1.47 1.00 0.67
    FORD AODE 2.84 1.55 1.00 0.70
    FORD AODEW 2.84 1.55 1.00 0.70
    FORD AXOD-E 2.77 1.54 1.00 0.69
    FORD E4OD 2.71 1.54 1.00 0.71
    FORD TORQSHIFT 3.11 2.22 1.55 1.10 1.00 0.71
    FORD M1HD 3.38 2.06 1.30 1.00 0.79
    FORD M5HD 4.11 2.37 1.42 1.00 0.77
    FORD M5HD-W 5.72 2.94 1.61 1.00 0.76
    FORD M5R2 3.75 2.32 1.43 1.00 0.75
    FORD M5R2-C 3.42 2.16 1.34 1.00 0.75
    FORD M6HD-6 5.79 3.31 2.10 1.31 1.00 0.72
    FORD M50D (2.3) 3.97 2.34 1.46 1.00 0.79
    FORD M50D (5.0) 3.35 1.93 1.29 1.00 0.79
    FORD M50D-R1 (2.3/3.0) 3.72 2.20 1.50 1.00 0.79
    FORD M50D-R1 (4.0) 3.40 2.05 1.31 1.00 0.79
    FORD M50D-R2 3.91 2.24 1.49 1.00 0.80
    FORD M50D-R4 3.38 2.06 1.30 1.00 0.79
    FORD RICARDO 6 2.61 1.71 1.23 0.94 0.77 0.63
    FORD T45 3.37 1.99 1.33 1.00 0.67
    FORD T5OD ('92-'98) 3.35 1.93 1.29 1.00 0.78
    FORD T5OD ('99-'05) 3.35 1.99 1.33 1.00 0.68
    GEO TRACKER 3.65 1.95 1.37 1.00 0.86
    LAND ROVER R380 3.69 2.13 1.40 1.00 0.77
    LAND ROVER R380 ('94-'97 DISCO, '94-'95 D90) 3.32 2.13 1.39 1.00 0.73
    NISSAN PATROL (5SP MANUAL) 4.56 2.63 1.52 1.00 0.84
    NISSAN PATROL (4SP AUTO) 2.78 1.54 1.42 1.00
    SUZUKI SAMURAI ('89 & DOWN) 3.65 1.95 1.42 1.00 0.80
    SUZUKI SAMURAI ('90 & UP) 3.65 1.95 1.42 1.00 0.87
    SUZUKI SIDEKICK (3SP AUTO) 2.40 1.47 1.00
    SUZUKI SIDEKICK (4SP AUTO) 2.83 1.49 1.00 0.73
    SUZUKI SIDEKICK (5SP MANUAL) 3.65 1.95 1.38 1.00 0.86
    TOYOTA A43D 2.45 1.45 1.00 0.69
    TOYOTA A44D 2.83 1.49 1.00 0.69
    TOYOTA A340E 2.80 1.53 1.00 0.71
    TOYOTA A340F 2.80 1.53 1.00 0.71
    TOYOTA A340H 2.80 1.53 1.00 0.71
    TOYOTA A343F 2.80 1.53 1.00 0.75
    TOYOTA A440F 2.95 1.53 1.00 0.72
    TOYOTA A750E 3.52 2.04 1.40 1.00 0.72
    TOYOTA A750F 3.52 2.04 1.40 1.00 0.72
    TOYOTA U140E 3.94 2.19 1.41 1.02
    TOYOTA U140F 3.94 2.19 1.41 1.02
    TOYOTA C50 3.55 1.90 1.31 0.97 0.82
    TOYOTA C52 3.17 1.90 1.31 0.97 0.82
    TOYOTA C56 3.17 1.90 1.39 1.03 0.82
    TOYOTA C59 3.17 1.90 1.31 0.97 0.82
    TOYOTA C60 3.17 2.05 1.48 1.17 0.92 0.73
    TOYOTA C65M 3.17 1.90 1.39 1.03 0.82 0.73
    TOYOTA C150 3.55 1.90 1.31 0.97 0.82
    TOYOTA C151 3.55 1.90 1.23 0.89 0.73
    TOYOTA E153 3.23 1.91 1.26 0.92 0.73
    TOYOTA E350 3.54 2.05 1.33 0.97 0.73
    TOYOTA E351 3.54 2.05 1.33 0.97 0.73
    TOYOTA G40 3.93 2.33 1.91 1.00
    TOYOTA G52 3.93 2.33 1.45 1.00 0.85
    TOYOTA G54 4.45 2.40 1.41 1.00 0.80
    TOYOTA G57 3.70 2.02 1.37 1.00 0.85
    TOYOTA G58 3.93 2.14 1.40 1.00 0.85
    TOYOTA H41 5.30 2.84 1.63 1.00
    TOYOTA H42 3.56 2.29 1.41 1.00
    TOYOTA H55F 4.84 2.62 1.52 1.00 0.85
    TOYOTA J30 2.76 1.69 1.00
    TOYOTA R150 3.83 2.06 1.44 1.00 0.84
    TOYOTA R150F 3.83 2.06 1.44 1.00 0.84
    TOYOTA R151F 4.31 2.74 1.93 1.00 0.83
    TOYOTA RA60 4.17 2.19 1.49 1.19 1.00 0.85
    TOYOTA RA60F 4.17 2.19 1.49 1.19 1.00 0.85
    TOYOTA RA61F 4.17 2.19 1.49 1.19 1.00 0.85
    TOYOTA S51 3.54 1.96 1.25 0.95 0.73
    TOYOTA S54 3.29 1.96 1.32 1.03 0.82
    TOYOTA V160 3.83 2.36 1.69 1.31 1.00 0.79
    TOYOTA W46 3.95 2.14 1.38 1.00
    TOYOTA W55 3.57 2.06 1.38 1.00 0.85
    TOYOTA W56 3.95 2.14 1.38 1.00 0.85
    TOYOTA W58 3.29 1.89 1.28 1.00 0.78
    TOYOTA W59 3.95 2.14 1.38 1.00 0.85
    AISIN AR5 3.75 2.26 1.37 1.00 0.73
    AISIN WARNER AW30-40 2.80 1.55 1.00 0.75
    AISIN WARNER AW4 2.80 1.53 1.00 0.75
    AISIN WARNER AX-4 3.93 2.33 1.45 1.00
    AISIN WARNER AX-5 3.93 2.33 1.45 1.00 0.85
    AISIN WARNER AX-15 3.83 2.33 1.44 1.00 0.79
    ALLISON 545 3.45 2.25 1.41 1.00
    ALLISON 1000 (5 SPEED) 3.10 1.81 1.41 1.00 0.71
    ALLISON 1000 (6 SPEED) 3.10 1.81 1.41 1.00 0.71 0.62
    BORG WARNER AS-8 2.40 1.46 1.00
    BORG WARNER SR4 4.07 2.39 1.49 1.00
    BORG WRNER T4 4.03 2.37 1.50 1.00
    BORG WARNER T5 4.03 2.37 1.50 1.00 0.86
    EATON-FULLER FS-4205A 8.05 4.35 2.45 1.48 1.00
    EATON-FULLER FS-4205B 6.99 3.78 2.13 1.28 1.00
    EATON-FULLER FS-6305A 7.22 3.89 2.22 1.39 1.00
    EATON-FULLER FS-6305B 7.22 3.89 2.22 1.27 1.00
    EATON-FULLER FS-5406A 9.01 5.27 3.22 2.04 1.36 1.00
    EATON-FULLER FS-5406B 9.01 5.27 3.22 2.04 1.36 1.00
    EATON-FULLER FSO-6406A 7.05 4.13 2.52 1.59 1.00 0.78
    EATON-FULLER FSO-8406A 7.05 4.13 2.52 1.59 1.00 0.78
    GETRAG 238 4.23 2.53 1.67 1.23 1.00 0.79
    GETRAG 260 3.83 2.19 1.40 1.00 0.81
    GETRAG 260 ('03-'04 CTS ONLY) 3.57 2.04 1.34 1.00 0.82
    GETRAG 360 5.53 3.02 1.60 1.00 0.77
    GETRAG F234 3.58 2.02 1.35 0.98 0.69
    MUNCIE SN420 7.05 3.58 1.70 1.00
    MUNCIE SM465 6.56 3.58 1.70 1.00
    MITSUBISHI FM156 3.72 2.20 1.50 1.00 0.79
    NP260 3.09 1.67 1.00 0.73
    NP435 CLOSE RATIO 4.78 2.39 1.37 1.00
    NP435 WIDE RATIO 6.69 3.34 1.79 1.00
    NSG370 CLOSE RATIO 4.46 2.61 1.72 1.25 1.00 0.84
    NSG370 WIDE RATIO 5.01 2.83 1.79 1.26 1.00 0.83
    NV1500 3.96 2.37 1.49 1.00 0.83
    NV2550 3.85 2.25 1.48 1.00 0.75
    NV3500 CLOSE RATIO 3.50 2.14 1.39 1.00 0.73
    NV3500 WIDE RATIO 4.01 2.33 1.39 1.00 0.73
    NV3500HD 3.50 2.14 1.39 1.00 0.73
    NV3550 CLOSE RATIO 3.50 2.14 1.39 1.00 0.73
    NV3550 WIDE RATIO 4.01 2.33 1.39 1.00 0.73
    NV4500 ('93-'94 GM) 6.34 3.34 1.71 1.00 0.73
    NV4500 5.61 3.04 1.67 1.00 0.75
    NV4500HD 2.61 3.04 1.67 1.00 0.75
    NV5600 5.63 3.33 2.04 1.39 1.00 0.73
    PEUGEOT BA-10 3.39 2.33 1.44 1.00 0.79
    SPICER 3053/3053A 5.02 2.78 1.62 1.00 0.79
    TREMEC 109MM 5.81 2.94 1.61 1.00 0.77
    TREMEC T-5 CLOSE RATIO 3.50 2.14 1.39 1.00 0.73
    TREMEC T-5 MEDIUM RATIO 3.76 2.18 1.42 1.00 0.72
    TREMEC T-5 WIDE RATIO 4.03 2.73 1.49 1.00 0.72
    TREMEC T56 CLOSE RATIO 2.66 1.78 1.30 0.74 0.50
    TREMEC T56 WIDE RATIO 2.90 2.07 1.43 1.00 0.84 0.57
    TREMEC T150 2.99 1.75 1.00
    TREMEC T176 3.52 2.27 1.46 1.00
    TREMEC T177 3.82 2.29 1.46 1.00
    TREMEC T178 3.00 2.08 1.47 1.00
    TR -3450 3.82 2.31 1.42 1.00 0.83
    TR-3650 CLOSE RATIO 3.38 2.00 1.31 1.00 0.67
    TR-3650 WIDE RATIO 3.77 2.00 1.31 1.00 0.67
    TR-4050 CLOSE RATIO 5.81 2.94 1.61 1.00 0.77
    TR-4050 WIDE RATIO 6.16 3.11 1.71 1.00 0.76
    WARNER T14 3.10 2.60 1.00
    WARNER T15 3.00 1.83 1.00
    WARNER T18 4.02 3.09 1.69 1.00
    WARNER T18A 6.32 3.09 1.69 1.00
    WARNER T19 CLOSE RATIO 4.00 2.40 1.40 1.00
    WARNER T19 MEDIUM RATIO 5.11 3.03 1.79 1.00
    WARNER T19 WIDE RATIO 6.32 3.09 1.69 1.00
    WARNER T84 2.94 1.94 1.00
    WARNER T85 3.17 1.92 1.00
    WARNER T86 2.80 1.69 1.00
    WARNER T90 (JEEP CJ) 2.98 1.66 1.00
    WARNER T90 (PICKUP) 3.44 1.85 1.00
    WARNER T98 6.40 3.09 1.69 1.00
    ZF S5-42 CLOSE RATIO 4.65 2.60 1.53 1.00 0.77
    ZF S5-42 WIDE RATIO 5.72 2.94 1.61 1.00 0.76
    ZF S5-47 CLOSE RATIO 4.14 2.37 1.42 1.00 0.77
    ZF S5-47 MEDIUM RATIO 5.08 2.61 1.53 1.00 0.77
    ZF S5-47 WIDE RATIO 5.72 2.94 1.61 1.00 0.76
    ZF S6-40 2.64 1.80 1.29 1.00 0.75 0.49
    ZF S6-650 5.79 3.30 2.10 1.31 1.00 0.72
     
  8. Stick Shift
    Joined: Oct 2, 2005
    Posts: 2,558

    Stick Shift
    Member
    from LENA IL

    I think 3:55 would be good. I run a 3:73, 350 turbo with 28.5 tall tire. Heavier car and I use to cruise it down the highway 65-70 mph. I love the 3:73.
     
  9. 6-71
    Joined: Sep 15, 2005
    Posts: 542

    6-71
    Member

    I ran a 10 bolt 2.73 camaro rear in my 39 chevy for many years, 6-71 blown 400 small block,turbo 400 trans. and fairly tall tire. It was great,with the low end torque of the blown engine and the cruising ability of the tall gears. I changed to a 9" Bronco rear end with 3.50 gears,and dont like the rpm's at cruising speed. sort of like driving around in second gear.
     
  10. coolbreeze1340
    Joined: Aug 18, 2009
    Posts: 1,340

    coolbreeze1340
    Member
    from Indiana

    429, C-6, 3.50 (I believe) and I do not like it on the freeway. 3300 RPM at 70-75 mph sucks after the first hour on the road. I am currently looking for a OD set-up but there is nothing cheap about putting an OD trans behind a built BBF! I might go ZF-5 speed if I can find a decent one and figure it all out. I would love to stay auto but $3000 for the swap is too rich for my blood!
     
  11. attorney1
    Joined: Sep 12, 2009
    Posts: 13

    attorney1
    Member

    My 66 Hertz appears to be turning at almost 4000 RPM at 70 mph with a 3.50 9 inch rear and 4 speed Ford Toploader. The engine is a late model 5.0 roller cam and roller rocker engine out of a Fox body Mustang. Am I in danger of blowing up the motor on a say, 300 mile round trip to Road America for the vintage races in July? From all that has been posted, I am leaning toward a 3.0 rear end or 2.73 if I can find it. At Summit Racing, the lowest I could find was 3.0 from Richmond Gears...Maybe the tach is wrong (original Cobra tach to the car) or the gear on the speedo is reading wrong.

    Richard E.
     
  12. go-twichy
    Joined: Jul 22, 2010
    Posts: 1,648

    go-twichy
    BANNED

    I think they went home.
     
  13. Gene Boul
    Joined: Feb 9, 2006
    Posts: 805

    Gene Boul

    3.55s are what early 9" rears came with. If it's really a 9" with those gears, they're probably really old....

    I have a 9" out of a 57 PUP it is a 3:00!
     
  14. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 5,260

    2OLD2FAST
    Member
    from illinois

    About a million yrs. ago I had a '57 chev. w/a 283 & 4-speed w/ 4.88 rear gears , at 65mph I was turning in excess of 4 grand , drove 700 miles up & back to the parents cottage 5 times a summer for 2 years, never blew up but it could be why my hearings not so good. With gas at $.32 a gal. , I didn't worry about mileage.

    dave
     
  15. Judd
    Joined: Feb 26, 2003
    Posts: 1,894

    Judd
    Member

    Dump the t350 for a 700r or 200r with 3.50 gear. you'll have a tire burner that rolls 70 MPH at 1800 rpm or so. My Galaxie with t-5 and 3.50 gear runs 1800 at 70 MPH and will burn the tires all the way through first and second if I wanted to. My Comet has 4.57 gear and will do 70 at 3,000 on the interstate with the .64 5th in my tremic t-5.
     
  16. Jay Tyrrell
    Joined: Dec 9, 2007
    Posts: 1,631

    Jay Tyrrell
    Member

    Put an overdrive in it. I am running a 4:44 with a 5 speed transmission (tremec) 1-4 gear is awesome slip into 5th with that .64 over drive with a 29 inch tire gives me 1900 rpm at 65 miles an hour. Loving the combo!
     
  17. need louvers ?
    Joined: Nov 20, 2008
    Posts: 12,903

    need louvers ?
    Member


    Figured with a 26 tall tire I calculate that you should be running at about 3166RPM for 70mph. If your tach isn't off, the only other thing I can think of is you rear is loaded with 4.11s instead of 3.50s. That would check in at 3717 @70 mph. Depending on the condition of your engine you probably won't blow it up, but after my Tremec in my avatar Plymouth, turning anything over about 2400 on the freeways drives me completely mental! And out here, 85 is the common freeway speed.

    Seriously, the best money you could spend on your car would be a Tremec TKO 500 or 600. They have a top loader pattern so you should be able to pretty much slide one out and one back in without too much fanfare. Even with the theoretical 4.11s it would net you about 2582 rpm at 70 mph, plus give an even better of the line launch do to a deeper first gear. Call it win win.
     
  18. sixpac
    Joined: Dec 15, 2002
    Posts: 553

    sixpac
    Member
    from Courtenay

    Turbo 350 29 inch tire 3.55 9 inch posi. Model a sedan love it. I do most town driving the car weights 2400 lbs with me in it. 300 hp 348 6x2 holley 94s all work.
     
  19. Pontiac Slim
    Joined: Jan 16, 2003
    Posts: 1,188

    Pontiac Slim
    Member Emeritus

    Guess this ain't the place to say it.... but I will! Ran 4:11s/full spool in a 455 Pontiac/31 Ford with 29" tires for 5 yrs. Yes do run all over New England via I-95. Its a hot rod, simple as that...Ended up brake'n both axles so put my spare in, 3:73s/posi and I hate it.......Guess it depends what you built the car for....
     

    Attached Files:

  20. mustangmike6996
    Joined: Apr 7, 2013
    Posts: 147

    mustangmike6996
    Member
    from the D

    3.73s are great for short trips but 3.55 seems to be right on the money for an average car/mild build
     
  21. DeepRoots
    Joined: Dec 23, 2011
    Posts: 31

    DeepRoots
    Member

    my 63.5 Galaxie has 4.10 rear gears with 25.5inch tall tires.
    Ain't scared of 3800rpm cruising. The downside? the 429 gets 6-8mpg

    I've got a gear vendors in the shop I'll eventually hook up. I'll probably miss the noise and get some 4.56 gears :p

    either way everything is a trade off.... get used to the acceleration of 4.10's and 3.25 rear will be annoying. Get used to 3.25's and you'll hate sounding like your in nascar driving 70mph. for myself, it is a fun car meant for fun things. If I had to drive it to work everyday, I'm sure a more highway friendly gearset would find it's way into the rear.
     
  22. fordor41
    Joined: Jul 2, 2008
    Posts: 1,018

    fordor41
    Member

    I'm running SBF,C-4 2.75's with 235/75/15's on the rear, in my 3400# '41 Ford Fordor and get an easy 22 MPG. I get smoked at a light but I love passing gas stations!
     
  23. Don's Hot Rods
    Joined: Oct 7, 2005
    Posts: 8,319

    Don's Hot Rods
    Member
    from florida


    Need louvers is right, something doesn't compute on you turning 4 grand at 70 mph. I am running 4.30 gears with a 29 inch rear tire and am only cranking 3,500 at 70 mph. Either you have some VERY short tires or your tach readings are wrong. Tire height does make somewhat of a difference in the rpms a car will turn, but not that much as you describe. You might have 3.90's or deeper in there.

    Don
     

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