Best trans for 6.4 heavy duty ?

DEMONIZEDCAT · Feb 4, 2017

I'm looking in to buying a used heavy duty 6.4 L 4×4
What transmission is most reliable?
Used daily on and off and to tow trailers motorcycle
Snowmobile, boat , travel trailer !

Thanks in advance , I'm new to the forum

BBRAM2500 · Feb 4, 2017

Lol you are opening a can here lol id say the ansin is better than the 68rfe but some guys say the manual is best thennnnnnnn you get guys that bullet proof the previous 48re and adapt it to the truck lol so who knows ive had good luck with the 68 on my cummins my father has had 0 trouble with his 48 but i had the 48 in a previous durango and it was junk

Andrew09HEMI · Feb 4, 2017

Don't think the 6.4 Hemi was available with the manual but I'd love to have it just cause I prefer manual transmissions. The 66rfe auto that comes in the Hemi has the same guts as the 68rfe so the gearing isn't great but with a tune it's great.

DEMONIZEDCAT · Feb 4, 2017

Thanks for the info so far

MADDOG · Feb 4, 2017

The 6.4L gas engine comes with one transmission, the 66RFE six speed automatic.

If you are referring to the 6.7L Cummins, a six speed auto is available in the 68RFE configuration.

A manual is also available with the Cummins.

Lastly for the 2014+ 3500/4500/5500 trucks, you can get the Aisin AS66RC.

cattaco · Feb 4, 2017

Can you tune the the 2015+ 66rfe?

MADDOG · Feb 4, 2017

Tuning on 2015+ trucks is done via a blank PCM unlocked by Diablosport and an I2 programmer.

cattaco · Feb 4, 2017

MADDOG said:
Tuning on 2015+ trucks is done via a blank PCM unlocked by Diablosport and an I2 programmer.

Thanks, I knew I'd have to buy a new pcm and tuner, just wasn't sure if the Diablosport allowed tuning of the 66rfe.

MADDOG · Feb 4, 2017

The place to get some better tuning, which will help with shifting, is through a custom tune.

This is not a situation where the entire shift algorithm is replaced. Rather, it's a tweak and a fine tune. Apparently we can't get that deep into the TCM or PCM to affect a huge change.

Having said that I noted that my shifts were firmer, there's no slip, and the custom tune was set up with specific shift points at WOT that I asked for.

cattaco · Feb 4, 2017

Thanks a lot, I've been trying to figure out the transmission tuning for the 66rfe for quite a while.

HvyDuty · Feb 5, 2017

You can get an Aisin transmission with a 6.4L gas engine, as long as its a 4500/5500 Ram. :naughty:

Would be nice to get the Aisins better ratios in a 2500/3500 6.4L. Maybe in the 2019 redesign?

The 66RFE comes from a long history beginning with the 45RFE back in 1999. Proven design and nothing like the older infamous Chrysler trans (adjustable bands etc.)

The 45RFE, 545RFE, and 65RFE automatic transmission for Jeeps and Rams

mtofell · Feb 7, 2017

My 66rfe blew up at 38K while sitting in stop/go traffic on a completely stock truck. After the rebuild it's 95% better. It still shudders every once in awhile and seems to get lost between gears. Needless to say I'm not leading any campaigns bragging about the 66rfe reliability. I'm also logical enough to know that what happened to me is by far the exception rather than the rule.

It's also hard to take coming from my Duramax/Alison on my old truck. 150,000 completely flawless miles.

DEMONIZEDCAT · Feb 11, 2017

Thanks for all comments and info

Best trans for 6.4 heavy duty ?

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