66rfe vs 68rfe

So, 66 is in the 6.4 Hemi and 68 in the Cummins and they are different trannys but share gear ratios.

For those that have driven both is the spacing in the diesel more natural than with the gas? I'm among many other posters I've read who am not too happy with the tranny on my 6.4. The longer I drive this truck the worse it seems to get (I know it learns so maybe I'm causing the problem to some extent).

It's gotten to the point where it waits so ridiculously long to downshift that the truck starts to convulse and shake like it's going to die. Then, an abrupt down shift and if I'm not careful the rear wheels start to break loose. The truck may not be acting any differently but it's just more annoying now that it's the rainy season again.

I'm annoyed enough with this truck that I'm about to the point of buying something else. I really like everything about the truck but the tranny. Will I be happier with these gear ratios mated to a Cummins versus the Hemi? fwiw, I've owned a diesel before and am pretty sure I know the answer.... just looking for some confirmation.

So has yours been declining since the rebuild steadily? Just curious if a tuner would help over ride the horrid shift points and liven it up?

The only irritation I have is this trans programming. It hasn't caused me enough stress to think about being rid of it, but it's annoying as hell. I did relearn my driving a bit too and that's helped a pile. I get a bit more punchy on the throttle coming out of turns etc and it has made a difference in the shifting. Do the 6 speeds actually "learn" I wonder?

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I don't think my complaints are the result of the rebuild. It's got other problems related to that incident that I'm working through. Or, more to the point, hoping would just cause the thing to blow up again

I think after nearly 3 years with this truck I'm just getting sick of the crappy shifting. It just seems that for a 40K truck with a new engine offering and some hype Ram could have done A LOT better.

To be honest I'd likely jump to the Ford or Chevy/GMC but I like the rear coils on the Ram and I have a bunch of parts I'd be hoping to swap to a new Ram - 5th wheel hitch, air bags, running boards, tonneau cover.

And today was just a crappy driving day - rainy, lots of tight turns and steep hills in neighborhoods. Most days the shifting is only a minor annoyance.... other days it's worse. I also just get sick of driving a 3/4 ton truck sometimes. The family truckster (minivan) is just so much easier to drive.

Coming from a 2014 1500, pray to god every night that you'll never have to experience the 65rfe. Coming to the 66rfe is a damn blessing.

I went through a period when my trans was doing some of the same things. Perhaps not as bad as you're describing, but I could feel a slight "shudder" going up an incline on the highway.

For some unexplained reason, it went away.

Yesterday I had my truck in to the dealer for its semi-annual oil change, and I had mentioned this strange shifting that I had experienced. They performed an update on the tcm. As I drove home (it's only about 15 mins) it actually felt great. Time will tell if suppose, but my trans seems to be working like a champ right now!

The 68RFE behind the Cummins still has its issues when it comes to shifting. The issue I have is due to the truck shifting into 5th and 6th earlier than I would like. It doesn't bog the engine down by any means, but I just would like it to not shift to 6th on back country roads where the speed limit is 50-55mph. This is easily fixed by taking out 6th in these situations.

When the the DPF is close to needing a regen and you are going up hills while having your cruise control set at low 60 mph speeds. The truck will want to hold 6th for too long causing you to loose about 4 mph from what your cruise control speed. When it finally drops down to 5th it puts a big load on the engine to catch back up. I have found that one way to deter this is to tap the throttle right before the hill to get the turbos spinning so it can power through without needing to downshift. This is not needed when the engine is no where near a regen since the turbos spool up quick enough due to less back pressure.

Other then that, the trucks shifts perfectly fine and the ratios are damn near perfect for the low end torque of a diesel. I still don't know why Ram didn't make the ratios shorter in the 66RFE. I would bet that the ratios of Ford's 6R140 in the Superduty would make a world of a difference in the 6.4L.

I noticed the same issues with my 6.4...holding higher gear too long then an abrupt downshift. I installed a Hemifever Tune and the truck shifts much better now. It holds the lower gear longer, doesn't hesitate to downshift, shifts are much more positive and with the extra torque and HP it really doesn't need to downshift as much when pulling a load. The tune made it perform the way Ram should've done it to begin with.

Mchurch52 said:

I noticed the same issues with my 6.4...holding higher gear too long then an abrupt downshift. I installed a Hemifever Tune and the truck shifts much better now. It holds the lower gear longer, doesn't hesitate to downshift, shifts are much more positive and with the extra torque and HP it really doesn't need to downshift as much when pulling a load. The tune made it perform the way Ram should've done it to begin with.

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I agree with everything said here, it's a world of difference. Almost forgot just how bad it was until I restored the stock trans tuning temporarily. Then it's immediately obvious how much the HF tune helps address the trans tuning. The Edge 2600 stall TC was a big improvement as well, with no loss of drivability thankfully.

Still, if FCA/Ram doesn't install the 8 speed (or some derivative) on the next generation in place of the 66RFE then they are absolute fools.

Mine isn't that bad, but Ive noticed crappier shifting patterns with my truck since they flashed my computer last week with some recalls. It's started bogging some like when you don't downshift a manual car and it starts jumping.

I noticed the same since the latest flash/update. The first two days it seemed better but now it is definitely worse than it was originally. It bogs a lot more now.

SouthTexan said:

I still don't know why Ram didn't make the ratios shorter in the 66RFE. I would bet that the ratios of Ford's 6R140 in the Superduty would make a world of a difference in the 6.4L.

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Yep - As I drive this truck I often feel like a good engine has been wasted on a crappy tranny. I can see how the ratios are much better suited to the low end torque of the diesel.