6spd v 8spd trans??

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GeneM

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So I recently purchased a 2016 RAM 2500 with the 6.4 Hemi and 6spd and I'm wondering if I should have spent the extra money and got a '19 or newer truck with the 8spd? Sadly I'm learning more and more about these trucks kinda after the fact and now I'm wondering if I should just sell the '16 and find a new one with the 8spd?
If so, what makes the 8 spd so much better, seems like maybe it's more stout and helps with MPGs a little? What else about the newer truck is so much better that it's worth the extra $$$$?
 

turkeybird56

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IMHO, 8 speed just a better built trans and runs soooo smoothly. But as to the exact science and gearing, that is a lil outta my wheel house. I'm sure more versed PPL will chime in. I have new 5th Gen with the 75 trans basically same, had a few things "tweaked" by ZF.

 
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GeneM

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So I should add that I came from a 2020 RAM 1500 EcoDiesel and yea I really thought it's tranmission was excellent however it was not without flaw. That said, is it really worth the thousands of dollars I would have to spend to jump into a newer truck? Guess I should have done more research but at the end of the day I really only wanted to spend so much money and the truck I landed on hit those targets minus the trans...
 

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So I should add that I came from a 2020 RAM 1500 EcoDiesel and yea I really thought it's tranmission was excellent however it was not without flaw. That said, is it really worth the thousands of dollars I would have to spend to jump into a newer truck? Guess I should have done more research but at the end of the day I really only wanted to spend so much money and the truck I landed on hit those targets minus the trans...

No.
 

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what makes the 8 spd so much better, seems like maybe it's more stout and helps with MPGs a little?
The biggest noticeable difference with the 8spd aside from a shift knob is the gear stagger. The 8spd has more consistent jumps in gear ratios, this is really noticeable while towing and hauling. It's not that the 66RFE is a bad transmission but the 8spd is more refined. As for fuel economy, it's a 7K lbs cinder block there's not much fuel economy hopes... LOL.
As for the shift knob, there some people just whine like two year olds about it. After a few weeks it's no longer strange.
 

62Blazer

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For a 2500, the 8 speed starting in '19 has a much lower first gear and tighter split in ratios in the first 5 gears. Basically, on the 6 speed you have first gear through direct drive (1:1) is 4 gears, while on the 8 speed first through direct drive (1:1) is 6 gears. On the 8 speed, 2nd gear is about the same as 1st gear on the 6 speed. The combination of the lower 1st gear and tighter splits makes the truck feel peppier/faster on take off. However the highway cruising gears are almost identical. This means the top 3 gears on both trans, which are the gears you will be in when cruising down the road at highway speeds. On a 6 speed that would be 4th, 5th, and 6th which are almost identical ratios to 6th, 7th, 8th on an 8 speed. With an empty truck it's unlikely you would shift down more than that unless maybe climbing a mountain pass.
I was shopping for a new truck when the 19's with the 8 speed became available and test drove several. I did wind up buying a '16 with a 6-speed because it only had 24k on the odometer and was $20k cheaper. Yes, the 8 speed made the newer models feel stronger during acceleration from a stop (exact same engine and gear ratio) but I'm cheap and decided the 8 speed wasn't worth $20k. Does the 8 speed shift better....from test driving I can't say it was noticeably better. Maybe if I drove one more now I will say that. Some people claim it tows a lot better. From a stop it should feel better, but on paper there isn't any real reason it would feel stronger at highway speeds because the top 3 gear ratios are the same. But have obviously never towed with an 8 speed truck.
More reliable? I mean, we will see. Maybe they are? Everybody claims that but keep in mind that the 8 speed 2500 trucks are "only" 5 years old meaning there is simply not a lot of older high mileage trucks running around. The national average annual mileage on a pickup is under 12,000 miles. This means the average '19 2500 only has 60,000 miles on it. On the other hand I think the 66RFE was introduced around 2013 in the 2500 truck? So you are talking 11 years at an average 132,000 miles, or over the double the mileage. Of course you would see more failures reported on an older truck! My last comment is that failures or issues are blown way out of proportion on the internet. That is because anybody with an issue will jump on every Ram related forum they can find and complain their transmission failed. However nobody just randomly makes a post saying "hey, just wanted to let you know my trans has not failed....". Again, maybe the 6 speed failure rate is higher than typical but you can't confirm that based on browsing the internet. Let's say 1/2% of Ram 2500 6 speed trucks have a trans failure. Ram sells almost 500,000 Ram 2500's annually (not sure exactly how many are 66RFE trucks), but let's say 200,000 of them are. Even though only 1/2% have problems, that is still 1,000 trucks with issues. Now each person makes 3-4 different posts on different forums and Facebook groups and seems like a LOT of trucks have issues....even though it's only 1/2% of the total. Then on top of that, anytime somebody asks the question about the 66RFE you get 20 people reply back that they are junk and will explode and kill a bus full of nuns. Not because they personally have had a trans failure, but simply because they read a post 3 months ago about a guy who did have a trans failure.
 

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So ask yourself why it took so long to make it in the 2500. Not that the rfe is a great transmission because it isn't, but if you ask me this is a lateral move at best with a real commitment if you want to service it. BTW, you can build an rfe as well, plate upgrade with tune and address other weaknesses because the main weakness on rfe is in valve body and solenoid. As far as mileage, I think the 8 speed wins by a lot. My 545 which I don't like because of the added fact of gear ratio never seen 165f even towing. Gear ratio is another consideration, if you want to have an rfe in the best efficient power bans you need 3.92's or more aggressive based on tire size. Some of the weaknesses if the rfe have to deal with how many rpm's it takes to get into gear and outta gear. If you have 3.55's with the 545 it means you will have a lot of bogging and low rpm issues. If you have a 66 or 65rfe with 3.92's not so much at all bogging, and if you want to save fuel it is as easy as slowing down on the freeway.

 

turkeybird56

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The biggest noticeable difference with the 8spd aside from a shift knob is the gear stagger. The 8spd has more consistent jumps in gear ratios, this is really noticeable while towing and hauling. It's not that the 66RFE is a bad transmission but the 8spd is more refined. As for fuel economy, it's a 7K lbs cinder block there's not much fuel economy hopes... LOL.
As for the shift knob, there some people just whine like two year olds about it. After a few weeks it's no longer strange.
yeah, SOMETIMES I end up adjusting the radio or the heater temp, LMAO. 7K, oh I hope not. My GVWR is just under 6K, and it still suks fuel outta the gas tank like it is an old GM 396 motor, if I do not pay attention to the skinny pedal, hee hee. (and the speedometer).
 

Burla

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Plus why did Cummins not get the 8 speed until 2025? We don't even know how that will work out yet. RFE's been handling Cummins for quite a while now. My brother did go through a couple rfe's but that was with the HO so I believe it was a 4 speed, cant remember for sure. Now he made a great move that solved it, he went to a manual after that. Mind you he towed equipment many of us haven't even ever seen, stuff you need a permit and police escort in most places.
 

Nickx86

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So I recently purchased a 2016 RAM 2500 with the 6.4 Hemi and 6spd and I'm wondering if I should have spent the extra money and got a '19 or newer truck with the 8spd? Sadly I'm learning more and more about these trucks kinda after the fact and now I'm wondering if I should just sell the '16 and find a new one with the 8spd?
If so, what makes the 8 spd so much better, seems like maybe it's more stout and helps with MPGs a little? What else about the newer truck is so much better that it's worth the extra $$$$?
I had a 2016 and I was going to regear to 4.56 to help with the less than stellar first gear. However I never had the chance since my truck got totaled and bought a 2022 with the 8 speed. If you got a great deal on the 2016 then keep and run it, maybe gear swap down the road. My 2016 was a solid truck for me
 
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GeneM

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Yea, I really don't think getting a newer truck and spending a ton more $$$ is worth it. The '16 I picked up has only 56k miles on it and is in excellent condition and has a color I really like. Is it perfect, nope but to get the "perfect" one would cost another 30K and I'm to cheap for that.
 

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There's also practical considerations in what truck is available to buy and at what price, as OP notes.

I waited at least a year to pick up (pun intended) a decent used 3/4 ton with the 6.4L Hemi. I wasn't going to wait for a ZF 8 speed, I took the 66RFE 6 speed it had. If I had known more, I would have put in the upgraded valve body BEFORE I tuned the damned thing, but that's water over the dam. A new valve body requires a complete PCM re-learn. I changed trans oil to Red Line C+ ATF, changed twice, and it shifts great.

I would have preferred 3.92 axle as well, but they made most of these trucks with 3.73 axles, so it is what it is. Now it's paid off and running good.

Would I do this again? Yes, knowing how bad the competitors were at the time (GM AFM oil pumper engines, Ford ecoboosts failing).

Now it's on to a new set of exhaust manifold logs that won't warp and leak!
 

HarryN

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Plus why did Cummins not get the 8 speed until 2025? We don't even know how that will work out yet. RFE's been handling Cummins for quite a while now. My brother did go through a couple rfe's but that was with the HO so I believe it was a 4 speed, cant remember for sure. Now he made a great move that solved it, he went to a manual after that. Mind you he towed equipment many of us haven't even ever seen, stuff you need a permit and police escort in most places.

I believe that part of the reason is that they had to change transmissions completely to deal with the torque.

The 8 speed transmission in the 2025 Cummins version 2500 / 3500 is supposed to be much stronger to deal with the ~ 1 000 ft lbs.
 

Wild one

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Plus why did Cummins not get the 8 speed until 2025? We don't even know how that will work out yet. RFE's been handling Cummins for quite a while now. My brother did go through a couple rfe's but that was with the HO so I believe it was a 4 speed, cant remember for sure. Now he made a great move that solved it, he went to a manual after that. Mind you he towed equipment many of us haven't even ever seen, stuff you need a permit and police escort in most places.
The Cummins market is pretty small in comparision to the other trucks they make,so there wasn't a big push by FCA/Stellantis and ZF to build an 8 speed capable of handling it's off idle torque.
I don't know the production number differances,but i'd hazard a guess they'd be lucky to build 10% of Cummins equipped trucks in comparision to the amount of 5.7 and 6.4 trucks they build,so it's not a big enough market to justify the R&D and manufacturing costs
 

Treburkulosis

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I never had any complaints with my 6 speed in my 12 1500. I kept in tow haul to keep the MDS from kicking in, but I had a 5.7 Charger R/T with a 8 speed I can see the love for them. I did enjoy how it shifted, but I hauled some heavy loads and my 6 speed had no issues. My 6 speed is still going strong. The neighbor across the street now owns it. It’s got close to 170k on it now, and I listen to it shift often when he leaves in it. It still sounds smooth. I did take really good care of it though.
 

HEMIMANN

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The Cummins market is pretty small in comparision to the other trucks they make,so there wasn't a big push by FCA/Stellantis and ZF to build an 8 speed capable of handling it's off idle torque.
I don't know the production number differances,but i'd hazard a guess they'd be lucky to build 10% of Cummins equipped trucks in comparision to the amount of 5.7 and 6.4 trucks they build,so it's not a big enough market to justify the R&D and manufacturing costs

So why didn't they fix the poor cam oiling for all those Hemi's?

Huh? Huh? lol
 

Docwagon1776

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I never had any complaints with my 6 speed in my 12 1500. I kept in tow haul to keep the MDS from kicking in, but I had a 5.7 Charger R/T with a 8 speed I can see the love for them. I did enjoy how it shifted, but I hauled some heavy loads and my 6 speed had no issues. My 6 speed is still going strong. The neighbor across the street now owns it. It’s got close to 170k on it now, and I listen to it shift often when he leaves in it. It still sounds smooth. I did take really good care of it though.

1500 is different, though. Drive a 1500 6 speed and 8 speed back to back and it's there but not a huge difference. Do the same with a 2500 and it's *much* more noticeable. It's a big difference on initial acceleration, interstate speed kickdown to pass, and general smoothness. I'm fine with the 6 speed 1500. I would not have bought a 6 speed Power Wagon. I don't know what objective numbers are for 55-75 acceleration but it feels so much more effortless.
 

Wild one

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So why didn't they fix the poor cam oiling for all those Hemi's?

Huh? Huh? lol
I think it'd be easier to get the winning numbers to the next lottery,then getting that question answered "truthfully" ;) But if i was to hazard a guess,it was probably cheaper to warrenty the small percentage of hemi's that had cam/lifter issues with-in the warrenty period,then re-tool the block or go with a better quality billet cam.
Once you're past the warrenty period,they could care less about the issue,as it's now a "you" problem to fix,not a "them" problem,:rolleyes:
I still remember when the trucks had a 100,000 mile warrenty,instead of fixing issues,they backed the warrenty down to 60,000 miles,so it became a customer issue and not a corporate issue that they'd have had to deal with;)
 
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