Rear differential ratio

Sep 12, 2021 4:48 PM - 192 Views Create A New Thread

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Espanola, NM

selecting rear diff ratio
Hello, out there, haven't posted in a while. Have sorted out most of the problems with my 37 Plymouth 2 door, only thing remaining is installing a puller fan and shroud as car starts getting hot in city traffic. The car has a 350v8 with a turbo 350 transmission, looking for suggestions as to what rear diff ratio would be the best for highway driving, the car does 60mph with the RPM's at 2000, I am thinking that maybe a change of gears to a taller ratio would be better, any and all advise appreciated.

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  • martymtz
    Sep 16, 2021 at 10:16 AM

  • Thanks for the info on gear ratio, I will be attending the last show and shine of the season, I will find out what aluminum radiator they are using. I am going to buy a cooling concepts fan with shroud next spring as temps here are dropping off, also changing rear diff gears in the spring.

  • 32 Dodge
    Sep 15, 2021 at 7:32 PM

  • Highway gears? 308
    As far as electric fans go---- Cooling Components Electric fan with built in shroud.

    I have a lot of Engine tucked into a small space. No more cooling problems with this fan.

  • GeneF
    Sep 15, 2021 at 7:09 PM

  • Do you know where they are getting the aluminum radiator, and which one? I might be up for investing in one...

  • martymtz
    Sep 15, 2021 at 10:21 AM

  • I believe that there is just not enough radiator core surface area to provide adequate cooling at low engine speed, have attended a couple of show and shines and everybody has the aluminum shroud with the puller fan, or have replaced the walker radiator with a new aluminum radiator to prevent overheating. Marty

  • GeneF
    Sep 14, 2021 at 5:14 PM

  • I don't know. Heck I had a 5 or six blade fan, and a shroud before too. I took my side pods off the hood, and it is sooooomuch better. I kinda think there is no place for the heat to go. What do you think?

  • martymtz
    Sep 13, 2021 at 10:10 PM

  • I am going with a cooling components shroud and a 2500cfm fan, I also have the heavy duty Walker radiator. I am going to pull the 9" Ford differential ball to find out what ratio I have and change the gear ratio to lower highway engine speed, but will be doing this in the spring. Question, why can you not keep the temps on this cars from creeping up in city driving with the engine driven fan?

  • GeneF
    Sep 13, 2021 at 7:09 PM

  • Marty, in the end it is nice having something that is not a Chevy, or a Ford. It makes it just that little bit special.

  • GeneF
    Sep 13, 2021 at 7:06 PM

  • fan

  • GeneF
    Sep 13, 2021 at 7:06 PM

  • Be careful, I have a 36 Plymouth, and the car is heavier than it appears. 350/350THM 3:73. Mine turns fairly hard at 70 MPH

    I have a colling components shroud with intigrated 2-speed fan, behind a super heavy duty walker radiator. Lover hose is flexible aluminium, so it does not collapse. The wiring for the fan is all 10Ga, and the dakota digital temp gauge control is inside under the dash. The ground does NOT GO TO THE FRAME! Too much carbon, and Cooling Componenats recomends against ground to the frame.

    Oh, and asses if you need the bypass pin in the water pump or not...hope ya know about that.

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