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JnJnKatiebug's avatar
JnJnKatiebug
Explorer
Feb 08, 2017

Differential ratio vs transmission gears

Don't know if the subject line says what I want to ask. Without going into the exact numbers here is the question. I have been towing my TT with my Tahoe. It is a 6 speed transmission. I tow about 64 to 65 mph in 5th gear at 2000 to 2100 rpm. Works well on level highway and when I hit a grade I drop down to 4th and about 2700 rpm and maintain the same speed. I might also add that with the Husky Centerline hitch it is a one handed pleasant drive. (I weighed the rig and I am within all the weights, so let's not go there please)

I just got a new company pickup and I am allowed to tow my camper with it. It is a Chevy Silverado, same 5.3 engine and 6 speed transmission but higher differential gears. It will run 64 to 65 mph in 4th gear at about 2100 rpm.

I read on here all the time about getting the lower geared differential for towing but why can't you just make up the difference with the transmission?
  • BenK's avatar
    BenK
    Explorer
    Feb 09, 2017
    When you do start looking for a new TV...take this thread in context of 'that new' truck...it all depends on what is 'stock' for that model/year/etc

    Then you need to gather that TV's tranny gear ratios vs tire rev's per mile vs diff ratio

    If it has one of these new high number of close ratio gears...they typically have a very low (high numeric) first gear.

    Plus double OD, with the 2nd OD mainly for using it as a car. Tow/Haul normally will NOT allow it to go into that 2nd OD...and again, dependent on the ICE torque/HP curves

    IF it has a really low 1st (high numeric), then the weight you are considering will play. If you are going to be very close to the OEM's specification ratings limits...then consider a lower diff ratio (higher numeric)...but know that 'car' MPG will be lower

    Trade-offs in everything

    Then personal opinion. Mine is to have a really low diff ratio (high numeric) for the kind/type of driving style 'I like'...

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