6.4 with 8 speed?

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SKS 800

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In tow/haul mode only 8th gear is locked out.
I had a 2018 6.4 with 4.10’s and now I have a 2021 6.4 with 4.10’s. There is no difference in fuel mileage from the 6 speed to 8 speed.
However, the 8 speed is better than the 6 speed when pulling. I have a 33’ fifth wheel that is 12,000 wet and it pulls well. There’s some good size hills where I’m at and the 6 speed would be in 3rd and the 8 speed is in 4th.
 
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Bearcatrp

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Thanks SKS. Helps me feel better on my up coming purchase. Now to find it before the trade ins drop in price. Missed one by one day.
 

OC455

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My dually has the 3.73 gears, 8sp and the 6.4. If I had the 4.10's it would probably net me another 1600-1800lbs of towing capacity. I'm at 13792 lbs with what I currently have, plus 6292 lbs of payload...

If I was going with a big camper/5'ver I'd get the diesel, but considering I only go within state right now, and I'm not going more than 2 to 3 hours away most times, the 6.4 is fine for what I have. Even if I get a 5'ver it will be a lighter one. (Less than 10k)
 

Firebird

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In tow/haul mode only 8th gear is locked out.
I had a 2018 6.4 with 4.10’s and now I have a 2021 6.4 with 4.10’s. There is no difference in fuel mileage from the 6 speed to 8 speed.
However, the 8 speed is better than the 6 speed when pulling. I have a 33’ fifth wheel that is 12,000 wet and it pulls well. There’s some good size hills where I’m at and the 6 speed would be in 3rd and the 8 speed is in 4th.
In tow haul mode, mine will still shift into 8th in the right conditions. However, I do live in flat Florida
 

Riccochet

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In tow haul mode, mine will still shift into 8th in the right conditions. However, I do live in flat Florida
Same on mine. Also depends on what I'm towing. With my TT it rarely sees 8th, but with my bass boat it'll hit 8th no problem.
 

KKBB

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Same...mine will hit 8th also, but it is only on one stretch of road that is slightly downhill for about 2 miles. After a mile or so it becomes less downhill, but is still downhill a bit and immediately jumps to 7th
 

HEMIMANN

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In tow/haul mode only 8th gear is locked out.
I had a 2018 6.4 with 4.10’s and now I have a 2021 6.4 with 4.10’s. There is no difference in fuel mileage from the 6 speed to 8 speed.
However, the 8 speed is better than the 6 speed when pulling. I have a 33’ fifth wheel that is 12,000 wet and it pulls well. There’s some good size hills where I’m at and the 6 speed would be in 3rd and the 8 speed is in 4th.

Is there a big difference in engine rpm between 6 speed in 3rd and 8 speed in 4th?
 
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Bearcatrp

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Good question. Looking at max torque for the 6.4, looks like 4000 rpms. Is that 4th gear or 3rd gear on the 8 speed? Can’t find a 3/4 or 1 ton worth a crap with gas and 8 speed. Missed one by 1 day. This market sucks. Dealer keeps pushing me to order one.
 

Riccochet

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Is that 4th gear or 3rd gear on the 8 speed?

Both. The whole point of more gears is so the computer can keep the engine in the power band longer. You can stay in the 3500-5000 rpm range easier with 8 gears than 6. So when the trans does up shift you're not lugging as much, or at all, to be in the power.

Gassers make peak torque and power higher in the RPM range than a diesel. And it's not going to hurt that low compression 6.4 one bit.
 

Firebird

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Good question. Looking at max torque for the 6.4, looks like 4000 rpms. Is that 4th gear or 3rd gear on the 8 speed? Can’t find a 3/4 or 1 ton worth a crap with gas and 8 speed. Missed one by 1 day. This market sucks. Dealer keeps pushing me to order one.
Yeah, decent 2500's and 3500's with a 6.4 are hard to find. The chip shortage has reduced most inventories to Tradesman packages, great truck, but not a lot of options.
 

HEMIMANN

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Yeah, decent 2500's and 3500's with a 6.4 are hard to find. The chip shortage has reduced most inventories to Tradesman packages, great truck, but not a lot of options.

I put up a standing internet search for a year until mine popped up. I pounced immediately, and that was before COVID!!! I feel for guys looking now, hence why so many of us are keeping ours, adding fuel to this executive-made fire.
 

Firebird

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I put up a standing internet search for a year until mine popped up. I pounced immediately, and that was before COVID!!! I feel for guys looking now, hence why so many of us are keeping ours, adding fuel to this executive-made fire.
I looked forever for a 6.4 with 4.10 gears. All we had in my area were 3.73's. Mine was a unicorn in 2019
 

Riccochet

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Yup. Spent 3 months watching autotrader, ebay and dealer sites daily. Lucked out and saw mine hit a Ford dealer lot. Immediately called and put a deposit on it sight unseen. Drove 3 hours and bought it.
 
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Bearcatrp

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I keep on looking. Don't want to order and wait 3-4 moths for delivery. Tried to get a dealer to drop the price of a diesel but won't budge. Would go diesel if they drop it 5 grand. Not going to pay $61,000 for a diesel. One thing I have noticed is some 3/4 and 1 ton do not have cab lights. WTF. 1st time I have ever seen a 1 ton with no cab lights.
 

runamuck

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my son bought a new loaded 2500 4x4 ccsb laramie dsl just before the shortage hit dealers. 75,000$ msrp for 63,000. no deals to be had right now. you can get a tradesman gasser for cheap or a dsl for msrp. neither is an option for me
 

retired

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I keep on looking. Don't want to order and wait 3-4 moths for delivery. Tried to get a dealer to drop the price of a diesel but won't budge. Would go diesel if they drop it 5 grand. Not going to pay $61,000 for a diesel. One thing I have noticed is some 3/4 and 1 ton do not have cab lights. WTF. 1st time I have ever seen a 1 ton with no cab lights.
look at that as a bonus....just one less place for it leak lol.
 
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Am at a cross roads trying to decide if I want a diesel or 6.4 with gas. The added maintenance with the cummins and dealing with DEF has me having second thought. Looked at a diesel yesterday, then talked to the maintenance department on service costs. $400 a pop just to service the fuel filters at 15,000 miles so basically every oil change at 15,000 miles. Wow. Thinking 1 ton 6.4 with 8 speed. Has a 50 gal gas tank. I pull a 10,000 lb 5th wheel with my 2017 Ram 2500 CC with 6.4 and 6 speed. Climbing hills going from minnesota to colorado sucked. 4th gear allot of time and some 3rd gear and high RPM's. Will the 8 speed do better? Reading allot of posts on diesel mileage pulling and seems about the same a gas except they can climb hills allot better. If you have a 6.4 and 8 speed pulling 10,000 in hills, please chime in. Can save $10,000 by going gas. Plus can get $3000 more than I paid for my current truck. Thanks.

I went through this same agony in February. I ran a spreadsheet with all the numbers I could find and it took roughly 240k miles to break even on the up front cost of the diesel engine. I came from a Dodge 12v 3500 diesel dually and a 5.7L Hemi 1500. The gas engine gets the job done when towing but nothing compares to towing with a Cummins. Even my old 12v towed 8k lbs at 75mph with no drama so I could imagine the new Cummins would be very nice. If you are pulling a 10k lbs trailer, I suggest going diesel, no question, and you will not regret it.

I ended up going with a Power Wagon, a 6.4L with 4:10s, 8 speed. I think I would have gone diesel if it wasn't for the PW package.
 
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Bearcatrp

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I did it. Just brought home a 2021 Ram 3500, 6.4 w/8 speed, long bed and a 50 gal gas tanks. Just what I was looking for. Got $1000 over what I paid for my 2017 3/4 ton back in 2017. White color is about the only thing sold these days so I jumped. Can't wait for my 1st trip with 5th wheel. Great help on this forum so thanks for all the replies.
 

Firebird

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I did it. Just brought home a 2021 Ram 3500, 6.4 w/8 speed, long bed and a 50 gal gas tanks. Just what I was looking for. Got $1000 over what I paid for my 2017 3/4 ton back in 2017. White color is about the only thing sold these days so I jumped. Can't wait for my 1st trip with 5th wheel. Great help on this forum so thanks for all the replies.
Be sure to post pics, would love to see it!
 
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