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-   -   Help Me Understand Transmissions (http://www.ramforumz.com/showthread.php?t=149017)

Parkersdad 07-31-2013 11:32 AM

Help Me Understand Transmissions
 
I have a 2011 Hemi with the 5 speed transmission. I keep wanting to trade simply because of the 8 speed transmission. I pull a 5500 to 6000 pound trailer 10 to 12 times per year and half of that in the mountains. My truck does well but will the new 8 speed help me? Sometimes even empty if at the wrong rpm's my truck will not gear down and haul ass. Can someone please clear this up for me?

Thunderhorse 07-31-2013 11:57 AM

The 8 speed's ratios are spaced better than those of the 5 speed so you will have more available power while you are towing. It is also a tougher transmission with a higher torque rating than the 5 speed, and will get you better mileage.

Go test drive an 8 speed and you will see what I mean. Granted you won't be towing but you will still get a feeling for the better power availability with the 8 speed. My dad has the 5 speed in his '09 and the difference is night and day. The 8 does a much better job of keeping the engine in its power band, and the lower 1st gear makes starting with a load easier.

Graygoose 07-31-2013 12:03 PM

8 speed keeps the truck in the optimal gas mileage rangs, while lower ratio will help on gas mileage, dont know if it can justify trading in and possibly spending alot more cash.

What gear ratio does your '11 have?

Parkersdad 07-31-2013 12:16 PM

Quote:

Originally Posted by Graygoose (Post 1164157)
8 speed keeps the truck in the optimal gas mileage rangs, while lower ratio will help on gas mileage, dont know if it can justify trading in and possibly spending alot more cash.

What gear ratio does your '11 have?

Mine has the 3.92 gears

snrusnak 07-31-2013 12:20 PM

8 speed will be better, but not worth trading IMO. The biggest difference would be starting out power. The 8 speed is geared lower so will pull from a stand still better. The spread of ratios is also better but I don't think that'd be as noticeable. The final ratios are the same, so no difference cruising(other than a little difference in parasitic loss as I'm sure the 8 speed is more efficient).

Graygoose 07-31-2013 12:59 PM

Quote:

Originally Posted by Parkersdad (Post 1164167)
Mine has the 3.92 gears

Lucky, I'd keep what you have honestly.. :) But thats just me :wavey:

huntergreen 07-31-2013 08:29 PM

i would like to see how the 8 speed holds up for a few years before i get one. sit tight for a bit op.

Gantman 07-31-2013 08:51 PM

I just wanted to say, that 1st gear of a 4.71 gear ratio mated to a 3.92 rear gear sounds like a kick ass combo for your use.

wolfman01 08-03-2013 07:02 PM

Quote:

Originally Posted by snrusnak (Post 1164170)
8 speed will be better, but not worth trading IMO. The biggest difference would be starting out power. The 8 speed is geared lower so will pull from a stand still better. The spread of ratios is also better but I don't think that'd be as noticeable. The final ratios are the same, so no difference cruising(other than a little difference in parasitic loss as I'm sure the 8 speed is more efficient).

I have to say sort of. I've driven an 8 speed auto and can attest that the 8 speed is much more willing to let you have that top ratio at moderate speeds. My "6" speed will not readily let me have "6th" gear until 62 - 63 mph in many cases. I've often had to accelerate up to that speed to get my truck into the top gear before letting it cost back down to the 60 mph that I try to keep to in my truck to maximize fuel economy. Once there, it'll hold until 57 mph before a forced downshift will occur.

The 8 speed will happily give you 8th gear @ 55 mph, letting you waft along in MDS mode at 1100 RPM. IIRC, 60 mph was also about 150 RPM lower, so there had to be something different between the two to allow for the slight drop in RPM over my truck.

Yeah, I know I'm a geek for trying to hypermile a truck, but what can I say. I have been able to squeeze as much as 24.7 mpg out of mine, and I think I still have enough room to push it to the 25 mpg mark, as that figure came in despite having to engage in a high speed flat out run to get around a huge piece of oilfield equipment, the pilot vehicles, and a short train of people not wanting to pass, and fighting with the construction zone in Cheyenne WY at the Flying J.


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