Cummins automatic trannys

[Dusty]

Yeah FAR too many people think you can just throw a tune on a modern diesel and hammer away on it.

It's not like the old days when transmissions were built to handle vastly more power than the engines they were coupled to could put out in stock form. You used to be able to take a 350 out of a car, put a 502 big block with the same (or a similar) TH400 transmission, and things would hold together. You can't do that today.

These days they keep costs in mind 95% of the time, so the transmissions have been redesigned to handle what the stock setup can put out and that's about it. It allows them to use less expensive materials to keep their costs down and profits up. Then when you throw a tune on it and grenade the trans, they can deny the warranty claim.

On really ANY modern driveline, if you're going to start making big horsepower and torque, more than the engine was rated for, you HAVE to spend money on the rest of the driveline. That means big upgrades to the transmission, probably the transfer case, and you may want to look into the gearing too just to be safe. ONLY after that can you be somewhat sure you can shred the tires without blowing up something expensive.

I have a friend in the transmission repair business. A while back when at his shop I noticed he was just installing an Allison in to a GMC. I said to him that I didn't think Allisons ever broke (they have a beefy power drive architecture). His reply was, "If it has a valve body it will break."

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 111770 miles.

 

[truck2014]

Myself and my brother both had HO cummins, I went manual out of the gate he went auto. He went through 3 transmissions but he towed heavy. He traded his baby in on another ram but this time he went manual as well. If you never want to worry about a transmission, just get a manual end of story. However, clutches aren't that cheap for a Cummins manual transmission either, but hey it isn't a perfect world. I did love the manual, but my knees didn't, and I ended up getting rid of the truck because of aging knees.

So he went thru 3 Aisin tranny’s ??? Wow , that’s something, that had to be some heavy towing .

 

[Burla]

So he went thru 3 Aisin tranny’s ??? Wow , that’s something, that had to be some heavy towing .

Not 100% sure on that, to be honest I can't even remember if it was a 2500 or 3500 it was over 20 years ago. I think it must have been a 3500 and another 3500 that he switched to, as he really towed heavy, heavier then 95% of the public for sure, so no way was it a 2500. It was first year of HO, he had to drive to AZ to buy it because they were outlawed in CA that year. Whatever transmissions were avail back then. Dodge paid for the first one and flat out told him they weren't paying for anymore, as it was a business truck and technically they shouldn't have paid for the first one, just good customer service back then. Talk about a pain in the ****, towing farm equipment well over 20k pounds and losing the truck not once but 3 times. Just flat rattle some folks, he was prized enough to never go auto again this much I can tell you.

 

[Choupique]

20 years ago

I think that would have been the 4 speed which was a POS behind the cummins.

It's damned aggravating for the average farm dude to not be able to get a regular dodge dually Cummins 6.7 (250hp ish) with a regular 8 or 10 speed medium duty Trans that'll last forever with 30k lbs behind it. The torque wars have gotten ridiculous. Nobody needs to rip 35k lbs up a 7% grade at 75mph with a one ton pickup.

I know 1200 ft lbs is what'll sell trucks, but damnit I just want one that will drag my boat around till I die of old age without dumb stuff happening. Shame I'm in the minority in the pickup truck market. The power is cool and all, but reliability is all that matters to me.

 

[truck2014]

68rfe is fine if it hasn't been beat on. I tow with mine in 5th gear unless pulling long and flat and light. 6th gear is a little bit dinky. With a load, 3.42's behind it and a big motor in front of it, full retard downshifts for 6th to 4th like it will do, and dropping into 6th right before another grade to Downshift again is bad for it.

I never liked the logic in tow haul mode. It'll shift to 6th past 65mph basically no matter what, and try to hold it up to 25ish lbs of boost on a grade, and then go full throttle down to 4th and obviously accelerate like mad, and then start upshifting again. It's kinda ******** if you don't lock out 6th while towing.

Definitely lock out 6 , have since day 1 towing , no sense gear hunting . I run all day towing my fifth wheel in 5 . It stays there unless some fairly steep grades then it shifts to 4 , and pretty much stays there until the top .

 

[Choupique]

run all day towing my fifth wheel in 5 . It stays there unless some fairly steep grades then it shifts to 4 , and pretty much stays there until the top .

That's the right way to do it. Towing at speed is a work problem. RPMs are not a bad thing and the delta in fuel economy will be negligible. More engine speed = less torque for the hp required. More air flow, more oil flow, more coolant flow, more fan speed. It's better for everything. More parasitic losses in the engine are offset by the high fuel burn as the engine nears peak torque at lower RPM. I know at some speeds and loads, I get equal or slightly better fuel economy in 5th than I do in 6th. The engine can rip out loads of torque while the whole truck falls apart around it but that doesn't make good sense. It's a turned up medium duty engine wrapped in a light duty package. I think we all just wish the most expensive parts of it (transmission, body, etc) would be as overbuilt as the engine is for the application.

 

[2003F350]

I never lock out my OD gears, haven't regardless of what truck I've owned and never once had transmission issues. If it needs to shift out of them it'll do so. I just set the cruise at 65 and let 'er run.

Pulled a 10k fifth wheel with my '99 F250, 7.3 auto all over the state. Only time it DIDN'T run in OD I was pushing about a 20 mph headwind, it pretty much stayed in 3rd, on a tuned truck that turbo whistle got kinda annoying but it got the job done, no heat issues.

Pulled that same camper with my '03 F350 6.0 auto. Held OD better, would drop to 4th on big hills but no issues with heat or trans slippage. Put over 100k on that truck as a daily driver. No tune, no delete, no bulletproofing on that truck, only issue was rust.

Switched campers and trucks and got an '04 F350 dually, 6.0 auto, to pull our 42' Cyclone tri-axle toy hauler (18k GVW I think? Big heavy camper). Tow/haul didn't lock out OD, so it would shift into it on flat ground. Pulling grades it would shift to 4th, I don't believe it ever went to 3rd pulling a grade in this state. Ended up tuning and bulletproofing that truck because I was pulling heavy with it, only issue I ever had was failed injectors. Pulled like a freight train.

Got away from the toy hauler and got a smaller lightweight travel trailer (same one as now) and pulled it with the Wagon. It would go into 6th on flat ground, preferred 5th while pulling smaller hills, big hills would see it drop to 4th and scream at 3k+. Wife thought it was going to come apart, but she was used to the lower-revving diesels I had previously. Again, no issues with heat, no valve body issues, no wiped out cam/lifters, probably the best truck I'd owned to date. MAP sensor and 110k saw me needing a new truck.

Picked up my '22. First trip with the camper was at about 2k miles on the clock, ran across the state on a mix of expressway and state highways (55-65 mph). Once we got to speed I don't think it ever shifted out of 6th. Even pulling the bigger hills up north it only built 10 lbs or so of boost and stayed in 6th. Haven't seen over 180 on the trans temp.

If you're pulling really heavy all the time in the hillier parts of the country, by all means lock out 6th if you feel you need to. But they've got these trucks set up to protect themselves in their stock form. They are built for people to just get in and drive whether you're pulling or not. I do agree that there should be an even more de-tuned version of the CTD, as not everyone needs the 850+ ft lbs of torque even the SO has, most could get away with something closer to 500/600. With the exact same trans behind it, it'd last forever. Of course, they can't sell new trucks if the old ones don't break.

 

[nlambert182]

Cab and chassis trucks are detuned.

I lock mine out of 6th as well, but I do it more for my peace of mind than anything else. In 6th gear with a load it's pushing a lot of boost. I never allowed my previous 3500 to shift into 6th pulling 16.5k lbs. There was no need.

I let my 2500 shift into 6th on flat ground this past weekend pulling the TT and monitored the boost gauge. It liked to live in the 20psi+ range.

Totally not necessary and it builds a lot more EGTs than needed. Locked it back in 5th and hovered around 3-4 psi most of the time. I still stayed right in the 1,800 rpm range, so right in the power band. Truck pulled flawlessly. The truck will manage itself no doubt, but I like to help it where I can. Plus, as Choupique said... it keeps it from doing a 6-4 downshift while on the exhaust brake on a steep hill. A little less shock on the transmission and driveline.

Those "Allison" transmissions that so many harp on are absolutely not as robust as people think. A "real" Allison is stout though not without it's flaws, but the Allison branded GM transmissions do fail at a higher rate that the real thing. As do the Aisins, the 10 speed Fords, and any other auto you can think of. The 68RFE is actually a pretty well thought out transmission. I've always been happy with all of the ones I've owned.

 

[ajparry89]

I appreciate all this convo guys. But just to be clear, I have not accused or suspected the 68 tranny of being a bad tranny. The one that I thought was not as great was the one in the 3rd Gen. I was mostly looking at 3rd gens because of budget. So, I am now going to try and find an older 4th gen. But I appreciate all the input and convo, just hope nobody thought I was accusing the 68 or anything. I think maybe some others did.

I just wont be able to afford something newer than 12-14 years old or less than 200k. thats a lot of time and mileage for mistreatment to happen to any tranny, so I was just hoping to find a manual instead. Plus, I do like shifting myself. I understand there is no need for a manual nowadays, that the autos out perform and the technology is way advanced. I am an automechanic by trade.

 

[nascar72]

You may have to go to an emissions state to get a stock or undeleted truck. I know here in MA that's all you can find because everything has to pass emissions. Very rarely do I even see a deleted truck here and usually they're from a different state.

Pre emissions trucks are extremely common here for that reason, I see lots of 12v Cummins and older Powerstrokes.

Pre 2008 cummins trucks I believe had the 545RFE in them for a few years and before that it was 48RE.

545RFE trannies were used only on gassers. The Cummins had the 46 and 48RE on the 3rd gens.

 

[Hemi395]

545RFE trannies were used only on gassers. The Cummins had the 46 and 48RE on the 3rd gens.

Yeah I wasn't 100% sure on that one, thanks!

 

[nascar72]

Yeah I wasn't 100% sure on that one, thanks!

I had the 545 on my '03 1500 and now have same tranny on my '08 2500 gasser. Beside some occasionnal torque converter shudder, it runs just fine. Been driving it that way for about 25k miles with once a year towing my 8500lbs 5ft wheel camper and still runs fine. Changed the fluid twice along with both filters and when towing I don't even bother with TOW/HAUL mode, I'll just put it in O/D OFF all together. And also to prevent the TCC shudder, I just let off the gas a bit when I feel it about to kick in.

 

[Choupique]

hoping to find a manual instead

Good luck bud. They are uncommon and grossly overpriced when they do hit the market. I'd personally rather just buy one with an auto and rebuild it if necessary. The 4 speeds aren't horrible expensive to rebuild, and the selection of trucks to pick from will be better.

I say that as someone who would pay 10% more for a stick shift. From a purely logical perspective it's stupid. These days you've got to REALLY want one to get it - either grossly overpay for it or do a custom build and deal with the reliability issues that come with that. Just get an auto and not worry about all that.

 

[truck2014]

2018 was the last year for the manual trans with a Cummins. There just was not much demand for them because for the most part people are lazy.

Lazy never had anything to do with me going to an auto. Back in the 70's early 80's it was always manual, couldn't live without a clutch . Had a 68 Ford single cab 4x4 stick shift , bought it used in the mid 70's. Great truck , if I remember it was the 360. My boys were getting big ,needed something different , single cab truck was not working . Around 1983 , sold the ford , bought a used 74 Jimmy 350 , auto . It was what we needed at the time , didn't like the idea at all that it was an automatic . That Jimmy was great for the family , and a hunting machine back in those days , didn't know what I was missing . Chained all four I could push some snow in the mountains hunting . Only drawback that I saw it didn't have the same compression, coming off some steep hills hunting, still not bad in 4 low . I kept that 74 Jimmy until 1995, bought my first new truck in 1995 a Chevy auto , 1500, 350, extended cab . Have never had another manual since that 68 Ford, and never the slightest desire to have another manual .

 

[Choupique]

never the slightest desire to have another manual .

I really wish my truck was a stick shift. My car is, and despite all the eye rolls I get I still enjoy driving it after ~180k miles. I genuinely enjoy driving them and everything I owned would be a stick shift if I was king of the world.

That being said, they just don't have a place in the world anymore. Lean manufacturing practices and the EPA aren't conducive to driveline options, and very few people actually want them. The reality is that people buying new trucks (the only ones the manf makes money on) want the comfort and bells and whistles and gizmos. If there was enough demand for them they'd still be built. My wife can't drive one, has no desire to attempt to learn, and it's hard to logically explain why she should. People unwilling or unable to buy brand new don't get to influence product offerings with their wallets and will forever be stuck with what the new market wants.

 

[buckeyexx]

Traffic and stop lights keep me from buying a manual these days. Seems like a stop light is installed every 100ft or so and the traffic is just as crazy and I'm not even really in the city limits. If not for that I would own one.

 

[2003F350]

I really wish my truck was a stick shift. My car is, and despite all the eye rolls I get I still enjoy driving it after ~180k miles. I genuinely enjoy driving them and everything I owned would be a stick shift if I was king of the world.

That being said, they just don't have a place in the world anymore. Lean manufacturing practices and the EPA aren't conducive to driveline options, and very few people actually want them. The reality is that people buying new trucks (the only ones the manf makes money on) want the comfort and bells and whistles and gizmos. If there was enough demand for them they'd still be built. My wife can't drive one, has no desire to attempt to learn, and it's hard to logically explain why she should. People unwilling or unable to buy brand new don't get to influence product offerings with their wallets and will forever be stuck with what the new market wants.

The move away from manuals has also been manufacturer driven. If they can take the 'human component' out of any of the vehicle's systems, they will, because it allows them more freedom to meet standards and regulations. For instance, EPA regs dictate certain mileage requirements. They're achievable with a manual, but many people won't shift at the 'appropriate' times to hit those numbers, but an automatic will because the computer told it to. Lane keeping sensors and adaptive cruise (two features I loath) are an effort to keep vehicles in the proper lane and avoid accidents. Automatic shutdowns and power reduction in diesels due to lack of DEF or a full DPF are intended to prevent you from running a vehicle that's creating more smog than it 'should.'

It's also why there's a push for autonomous vehicles that we don't even drive. We just get in, program a destination, and let the vehicle do the work. It's all about making sure you get where you're going alive and reducing accidents. Is it necessarily better that way? For some people, sure. For others, they're still good enough drivers that no, they don't need it. But frankly, in my travels, I'd say fewer than 10% of the country can still drive properly, respectfully, and safely.

 

[ajparry89]

The move away from manuals has also been manufacturer driven. If they can take the 'human component' out of any of the vehicle's systems, they will, because it allows them more freedom to meet standards and regulations. For instance, EPA regs dictate certain mileage requirements. They're achievable with a manual, but many people won't shift at the 'appropriate' times to hit those numbers, but an automatic will because the computer told it to. Lane keeping sensors and adaptive cruise (two features I loath) are an effort to keep vehicles in the proper lane and avoid accidents. Automatic shutdowns and power reduction in diesels due to lack of DEF or a full DPF are intended to prevent you from running a vehicle that's creating more smog than it 'should.'

It's also why there's a push for autonomous vehicles that we don't even drive. We just get in, program a destination, and let the vehicle do the work. It's all about making sure you get where you're going alive and reducing accidents. Is it necessarily better that way? For some people, sure. For others, they're still good enough drivers that no, they don't need it. But frankly, in my travels, I'd say fewer than 10% of the country can still drive properly, respectfully, and safely.

Also so the government can control one more aspect of your life.

 

[truck2014]

Traffic and stop lights keep me from buying a manual these days. Seems like a stop light is installed every 100ft or so and the traffic is just as crazy and I'm not even really in the city limits. If not for that I would own one.

Thats one aspect of a manual , boat ramps , steep hills ,they all factor in for the negative on manuals . Has it ever been fun ,when you got a car sitting on your back bumper on a steep incline at a stop sign or whatever ,and you want to start out smoothly . I have zero nostalgic feelings about shifting , sitting at lights , stop signs , backing up an RV , slipping the clutch etc etc .

 

[truck2014]

I never lock out my OD gears, haven't regardless of what truck I've owned and never once had transmission issues. If it needs to shift out of them it'll do so. I just set the cruise at 65 and let 'er run.

Pulled a 10k fifth wheel with my '99 F250, 7.3 auto all over the state. Only time it DIDN'T run in OD I was pushing about a 20 mph headwind, it pretty much stayed in 3rd, on a tuned truck that turbo whistle got kinda annoying but it got the job done, no heat issues.

Pulled that same camper with my '03 F350 6.0 auto. Held OD better, would drop to 4th on big hills but no issues with heat or trans slippage. Put over 100k on that truck as a daily driver. No tune, no delete, no bulletproofing on that truck, only issue was rust.

Switched campers and trucks and got an '04 F350 dually, 6.0 auto, to pull our 42' Cyclone tri-axle toy hauler (18k GVW I think? Big heavy camper). Tow/haul didn't lock out OD, so it would shift into it on flat ground. Pulling grades it would shift to 4th, I don't believe it ever went to 3rd pulling a grade in this state. Ended up tuning and bulletproofing that truck because I was pulling heavy with it, only issue I ever had was failed injectors. Pulled like a freight train.

Got away from the toy hauler and got a smaller lightweight travel trailer (same one as now) and pulled it with the Wagon. It would go into 6th on flat ground, preferred 5th while pulling smaller hills, big hills would see it drop to 4th and scream at 3k+. Wife thought it was going to come apart, but she was used to the lower-revving diesels I had previously. Again, no issues with heat, no valve body issues, no wiped out cam/lifters, probably the best truck I'd owned to date. MAP sensor and 110k saw me needing a new truck.

Picked up my '22. First trip with the camper was at about 2k miles on the clock, ran across the state on a mix of expressway and state highways (55-65 mph). Once we got to speed I don't think it ever shifted out of 6th. Even pulling the bigger hills up north it only built 10 lbs or so of boost and stayed in 6th. Haven't seen over 180 on the trans temp.

If you're pulling really heavy all the time in the hillier parts of the country, by all means lock out 6th if you feel you need to. But they've got these trucks set up to protect themselves in their stock form. They are built for people to just get in and drive whether you're pulling or not. I do agree that there should be an even more de-tuned version of the CTD, as not everyone needs the 850+ ft lbs of torque even the SO has, most could get away with something closer to 500/600. With the exact same trans behind it, it'd last forever. Of course, they can't sell new trucks if the old ones don't break.

I never lock out my OD gears, haven't regardless of what truck I've owned and never once had transmission issues. If it needs to shift out of them it'll do so. I just set the cruise at 65 and let 'er run.

Pulled a 10k fifth wheel with my '99 F250, 7.3 auto all over the state. Only time it DIDN'T run in OD I was pushing about a 20 mph headwind, it pretty much stayed in 3rd, on a tuned truck that turbo whistle got kinda annoying but it got the job done, no heat issues.

Pulled that same camper with my '03 F350 6.0 auto. Held OD better, would drop to 4th on big hills but no issues with heat or trans slippage. Put over 100k on that truck as a daily driver. No tune, no delete, no bulletproofing on that truck, only issue was rust.

Switched campers and trucks and got an '04 F350 dually, 6.0 auto, to pull our 42' Cyclone tri-axle toy hauler (18k GVW I think? Big heavy camper). Tow/haul didn't lock out OD, so it would shift into it on flat ground. Pulling grades it would shift to 4th, I don't believe it ever went to 3rd pulling a grade in this state. Ended up tuning and bulletproofing that truck because I was pulling heavy with it, only issue I ever had was failed injectors. Pulled like a freight train.

Got away from the toy hauler and got a smaller lightweight travel trailer (same one as now) and pulled it with the Wagon. It would go into 6th on flat ground, preferred 5th while pulling smaller hills, big hills would see it drop to 4th and scream at 3k+. Wife thought it was going to come apart, but she was used to the lower-revving diesels I had previously. Again, no issues with heat, no valve body issues, no wiped out cam/lifters, probably the best truck I'd owned to date. MAP sensor and 110k saw me needing a new truck.

Picked up my '22. First trip with the camper was at about 2k miles on the clock, ran across the state on a mix of expressway and state highways (55-65 mph). Once we got to speed I don't think it ever shifted out of 6th. Even pulling the bigger hills up north it only built 10 lbs or so of boost and stayed in 6th. Haven't seen over 180 on the trans temp.

If you're pulling really heavy all the time in the hillier parts of the country, by all means lock out 6th if you feel you need to. But they've got these trucks set up to protect themselves in their stock form. They are built for people to just get in and drive whether you're pulling or not. I do agree that there should be an even more de-tuned version of the CTD, as not everyone needs the 850+ ft lbs of torque even the SO has, most could get away with something closer to 500/600. With the exact same trans behind it, it'd last forever. Of course, they can't sell new trucks if the old ones don't break.

I owned ,and towed with a 99 Superduty 350 7.3 for nearly 16 years . I did everything that was fairly practical to that truck ,bagged it for towing a fifth wheel . AIS intake ,DP tuner , 4"turbo back exhaust . 6.0 intercooler ,and tranny cooler , gauges to monitor boost ,ETG's , and transmission temp . Great truck ,just didn't have it towing a bigger fifth wheel in the mountains . Locking out OD on it , with the head winds , steep grades etc ,it was in third a lot of the time , no need to lock it out of fourth . It didn't take a whole lot with towing to kick that truck out of fourth . Did okay towing 9-10 K , not great , but jumping up to much over that ,that 7.3 fell on its face . Plus that 4R100 transmission was one of fords worst .