Switched to 3.73 gears and not loving it

Discussion in 'High Performance Modifications' started by sinnyz_me, Jul 7, 2018.

  1. sinnyz_me

    sinnyz_me Veteran Member

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    I recently changed out the center section on my 10 bolt with a posi setup from quick performance and 3.73 gears. I had stock 2.41 gears before so really low. However they were nice on the highway. So I drive my car on a 45 minute highway drive for the first time this week with those 3.73 gears and it sucks. I know they are not meant for highway driving but didn’t think they’d be that bad. I was running 60-65 mph and my rpms were 3500-4000. Way to high and just not enjoyable. I want something that I can run decent on the street for burnouts and quick starts at the light but still go out on the highway and cruise. Maybe 3.08 gears? Or upgrade the tranny form stock th350 to 700r4? Maybe it’s the tranny that’s dragging it down. Let me know what you think
     
  2. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    Go with an OD transmission and you will be almost back to your original RPM at highway speeds.
     
  3. camaro71/holland

    camaro71/holland Veteran Member

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    Sounds a tad too high for 3.73 like you have small tires? 26" or something?
     
  4. camaro71/holland

    camaro71/holland Veteran Member

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    Anyway, 3.42 or 3.55 are a good compromise for both off the line performance and highway cruising.
     
  5. djorgensen3

    djorgensen3 Veteran Member

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    When you decide to get rid of the 3.73's let me know. I would like that gear set. It will go nicely with my 700r4.
     
  6. jeff swisher

    jeff swisher Veteran Member

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    I run a tall tire on my rides 29.5" tall and the gear does not bother me so much.
    Quiet exhaust makes you feel better at 4000 rpm also.
    I ran many 4 cylinder and 6 cylinder cars and most would cruise the highway at 400+4500rpm and I got used to that.
    It will not hurt anything to cruise at higher RPM as long as oil pressure and coolant temps stay in check.

    Some math for you to remember.
    336 is a given to make it work and this is for a lock up trans or stick shift so allow some for converter slippage.

    336 X gear ratio X MPH divided by tire diameter = RPM
    336 X 373 X 65 divided by 26 =3133 now allow 10% more for converter slippage and you get about 3500 RPM.

    2.41 x 1.52 = 3.66 basically If you were to stick the 2.41 gears back in the car with your TH 350 stick it in second and go down the highway you would see what a 3.66 gear would feel like.

    I went from a 2.56 to a 3.08 when I was a teen and WOW! huge difference. Very nice gear.
    I have 3.70's in one car and 3.25 in another.. the one with 370 has a tighter converter and pulling my boat both turn within 250 RPM going down the highway.
    Lot of slippage from the vehicle with 3.25 gear.
    Not that you are pulling a 3500 lb boat.

    What we did with the Father-in-laws vehicle was have a complete spare rearend.
    One with racing gears and one with highway gears.
    Took us 45 minutes to swap them out.
    I have 9" fords in my vehicles and gear swaps are pretty quick there also.
    About the time it takes to get packed for a trip i can have gears swapped out.

    Not saying you need that. But maybe an OD would be nice..I scored 2 transmissions and a lot of parts to go with them including extra valve bodies 2004R is what I got.. still sitting in the garage floor.
    I never cared for the 700R4. Too many friends busted theirs.
    I always thought I would run the 2004R or the 4L80 once it came out.
    I tend to beat on my stuff.
     
  7. 1980RS

    1980RS Veteran Member

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    Might have some 2.73's if you are interested.
     
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  8. 450bench

    450bench Veteran Member

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    I'd take the man up on a set of 2.73s...
     
  9. djorgensen3

    djorgensen3 Veteran Member

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    I have a couple sets of 2.73's as well....lol.
     
  10. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

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    If you have the means, an overdrive transmission is the best answer.
    The 4L80E is the toughest, common, one out there.
     
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