V6 and 8 Speed Transmission (Driving Habits)

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wildneg

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So per my other post (will not go into details), I ended up needing a full size truck and gas mileage. I ended up with the V6 3.6 w/ the 8 Speed. It is a 2018 Ram 1500 crew cab with 4x4. Blue sport if that makes any difference. It also has the 3.55 just in case I need to tow the trailer from time to time.

So driving up north for work once a week (and every other Thursday), my trip is about 170-190 miles round trip. It is pretty much all expressway. I know I read reviews about the engine's torque and slight inclines, depending on RPMs/Speed I am running, will downshift to keep speed. I notice it a lot and I'm OK with it.

I find myself driving in a few different ways and curious if any of them will lower the life of my drivetrain (transmission, rear end, converter).

Scenario One
I drive with cruise control on because it takes some stress out of my leg. It spends the time in 8th gear until I hit some inclines that are big enough to start bogging down the engine slightly, forcing it to downshift to 7th. A few hills will bring it down to 6th for a short time to maintain the speed as well. I can tell when it is going to down shift because the real time MPGs hits about 17 and can't keep up the speed (giving more throttle).

I do not have the exact number of times it down shifts, but it is a lot. Much much more then the GMC 2.8L Diesel I had. Though that was a 6 speed and it had close to 400 ft/lbs of torque which was available much lower in the RPM range. Completely understand the difference between the two trucks and I'm ok with it. I would guess the truck could down shift into 7th ... 30 times? Down into 6th maybe 5 times or so.

Scenario Two
I do not use cruise control. I can see/tell that I’m approaching a hill. I usually have the realtime MPG displayed on the dash cluster display. So I will try maintaining the speed I want, slowly pressing more on the pedal as I climb the hill. As the MPGs start dropping, at about 18MPG, I will start releasing the pedal some. Basically I’m keeping it in 8th gear by giving it as much pedal as I can before it shifts down to 7th. I will not keep the speed on the hill but it slowly decreases, maybe by 2 or 3 MPH. I basically get back up to speed once I am over the hill. Sometimes I can have it drop 4 or 5 MPH. Just depends on the hill.

This method, I know it isn’t shifting as much but I feel like I’m just working that 8th gear much more. Trying to get every bit of power through 8th without letting it free up some more torque in 7th.

So between one and two… Is one where it shifts more often really going to harm anything? Or is two going to stress anything by me trying my hardest to just keep it in 8th gear? I wish cruise control would do this for me, keep it in 8th… but I’m OK doing it either way.

I may be thinking too much into this. If I have no worries and either way is really fine, then I will try out both and see which ones net me a little better MPG. Right now, three tanks, I’m just over 20MPG on two of them and under 20MPG on one. The one under 20MPG was due to me letting it idle a lot because I was running an ozone machine through to clean the smell inside. Worked great.

Any input would be greatly appreciated! I have a feeling I’m over thinking this though… I always do. I just want to keep it running as well as it can for as long as it can. Thanks all!
 

ramffml

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Where's the fun if you can't over think it? :)

CC sucks. It has one mission, keep you at a permanent speed. As you've discovered (and its even worse when towing), you have far better control over your truck by cruising down (increasing speed) and coasting up (bleeding speed) hills as needed.

You will definitely notice more shifts, not just v6 gas vs diesel's torque but also 8 gears vs 6, these transmissions are designed to keep you at the optimum RPM and will shift often to put you there. But as long as you don't care about holding your speed to an exact fixed number, you can have much better experience without CC.

Edit: And don't overlook the gear limiter either, on bad hilly sections you can set it to 7th (for example) and save a lot of up/down shifting from 8th, either with or without CC engaged.
 

PolarisCobra

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I am trying to do the opposite of overthinking this. What is the harm in the transmission shifting a few more times? Seems to me that is what it is designed to do. I would not think it will substantially shorten the life of the system, and we need not worry about it.

Does anyone have any data that says different?
 

gfh77665

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The question you pose is not really about the truck, its about you. What do you like best? Believe it or not, vehicles are made to serve us, not the other way around.
 

Yardbird

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I never shift to drive and leave it there. I always select the right gear for the road speed and terrain. Much better performance on rolling hill 35 mph (4th gear) and 40 mph (5th gear) roads. 6th gear for 45 to around 60, then 7th for everything else.

I consider my truck a 7 speed, as with 3.21 rears, 20" tires, and a V-6, 8th gear is useless at any speed unless going downhill.

Didn't want 3.21, but the exact truck I wanted at the price I wanted came up, just had 3.21 gears.

No problem. I always select my gears in anything I drive anyway, and with 3.21s it hasn't changed 2 to 3 gears before 25 mph. I have a V-10 to pull with, so there's that as far as pulling.

I average 19.5 to 20.5 mpg local, and 22 - 23+ on trips.
 

crash68

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I may be thinking too much into this.
Yeap, your thinking way to much into this. Set the cruise and enjoy the ride, if you listen to old farts who stuck in the past they'll have you believe that all trucks should be carbureted with manual transmissions.
These ZF 8HP transmission are pretty much bullet proof, very few reported problems. There one that was into the 700K mile range that most of those miles were towing trailers across country.
 

star_deceiver

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The 8HP and 845 are smarter than all of us. They’re never in the wrong gear. They don’t upshift further than they should, nor at inappropriate times. The only time I select a certain gear is when I have a long downhill and I’m trying to hold a slower speed without riding the brakes.

And if this truck could have been optioned with a stick shift, I would have gladly paid extra for it!
 

HunterCat

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You can also use the Tow/Haul button and this should give a better experience with less shifting on a hilly drive (I think this is suggested in the owners manual). I think you're fine regardless but you can try a couple of methods during your drive while watching the transmission temp gauge to see if there's any actual difference.
 

Random_Walk

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I have never used CC on the truck since I got it. Ever.

Then again, I drive on some wicked twisty roads with variable inclines/declines, so keeping speed is a tad impossible. I might try using CC the next time I find myself on any serious stretch of I-5 or such... I average around 20-21mpg. :)
 

EdGs

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deleted

Sorry, just realized I was in the v6 section, posted about my hemi. Blame it on old age.....lol
 
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