Forum Discussion

puma_28db's avatar
puma_28db
Explorer
May 18, 2013

3.21 vs 3.55

Ram has built a number of 1500s, 5.7 hemi's with the new 8spd trans. Some or most of them have the 3.21 gears. The tow rating is about 2,000lbs less than the same truck with 3.55s regardless if the truck has the 6 or 8 speed.

1. Would the 8spd have more/better lower gear ratios than the 6speed?
2. With the trucks frame and engine the same, is the only facter changing tow rating the axel ratio?
3. Would towing the extra 2,000lbs with the 8spd/3.21 combo adversly affect the trans?
4. Yes tow/haul would still be used. does the 2 extra gears in the 8spd make up for the 3.21s in the rearend?
8spd with 3.21. 6speed with 3.55
1st. 4.71 vs 3
2nd. 3.14 vs 1.67
3rd. 2.1 vs 1.5
4th. 1.67 vs 1
5th. 1.29 vs .75
6th. 1 vs .67
7th. .84
8th. .67
5. Would the 8speed be suited to pull better with the lower gear ratios?
Tow Vehicles
  • BenK's avatar
    BenK
    Explorer
    May 18, 2013
    With today's close ratio automatics, the diff can now be a MPG ratio

    Close ratio to allow the ICE to spin within it's most optimal range and
    also has double over drive

    What really matters is the 'effective' ratio at the tire contact patch to pavement

    So your posted tranny gear ratio's is out of context without the diff ratio
    and the simple math is to factor both the 3.21 and 3.55 to see them side by side


    My dream manual tranny is a NV4500 and here are it's ratios and might even
    change my 4.1's to something in the 3's...along with an inline over drive

    1st 6.34 1993 or 5.61 after 1993
    2nd 3.44
    3rd 1.71
    4th 1.00
    5th 0.73

    reverse 6.34 (1993) 5.61 (1994 on)
  • bmanning's avatar
    bmanning
    Explorer
    May 18, 2013
    Looking at the ratios you've posted I would think the 8sp would have a pretty big advantage at getting a load moving...the 4.71-3.14-2.1 first 3 ratios seem pretty well suited to getting from 0-40mph which IMO is the real-world performance that's most important.

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