65RFE to 66RFE swap for more towing and drivability

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Hemi395

Senior Member
Joined
Mar 18, 2013
Posts
8,965
Reaction score
15,598
Location
Cape Cod MA
Ram Year
2013
Engine
5.7 Hemi
Yeah looks like this is the best bet....
 

Hemi395

Senior Member
Joined
Mar 18, 2013
Posts
8,965
Reaction score
15,598
Location
Cape Cod MA
Ram Year
2013
Engine
5.7 Hemi
Any of the RFE trans are going to require special care both in maintenance and driving style. However I think a lot of the bad rep the RFE gets is because people tune their Cummins with 300hp tunes and blow the 68. Before 8 speeds came out, people were doing similar with Hemis/545s. Its just not a good trans platform for modified motors.

I do a drain and fill on my trans annually and a filter change every other year. So far, **KNOCKS ON WOOD**, after 9.5 years and 86k with 12k of that towing my camper all over the US, my 65 is still going strong.
 
OP
OP
Steve White

Steve White

Junior Member
Joined
May 23, 2021
Posts
23
Reaction score
46
Location
52404
Ram Year
2014
Engine
5.7
I have read into all of the comments and I have even checked in the parts catalog and the 545, 65 and 66 RFE transmission from 2011 to 2019 all use the same valve body. There is a new separator plate that has a gasket molded to that helps to seal the valve body up more. There has also been cases of the valve body leaking internally and causing fluid pressure loss and that is also causing the clutches to burn up. This is probably the most common problem for the reason they burn up. Almost every 66 that i have seen that has burned up is due to overloading of the actual vehicle itself. Like using a 1500 for a plow truck or hauling stuff its not rated for. The difference is in the software to them and the solenoid pack. The failure that these transmission use to have was the accumulator plate on the side would break the bolts and the accumulators would come out and would burn the transmissions up or make them shift very poorly. What happens in the 66RFE is the with added clutches and heavier loads they haul, and they have 1/2 inch transmission cooler lines, more fluid will go thru certain parts of the transmission and will cause the valve to wear in the valve body. Sorry i dont get on here much to update this but I have been busy. I also have found out that you would need a transfer case out of a 2500 with a 5.7 and change the driveshaft yoke on the rear drive shaft and shorten it about 2 -3 inches. and also get the front driveshaft from a the same truck. I will post pics of the valve body when i go thru hopefully later this week.

I know alot of people are doing the 8 speed swap but there is a lot more to do for that swap. Im sure everything bolts right in and lines right up but you have to changed cooler lines, the cooler itself and also have to run fluid that is almost 30 bucks a quart.
 

DILLIGAF

Senior Member
Military
Joined
May 28, 2016
Posts
4,216
Reaction score
7,551
Location
Canada
Ram Year
2012
Engine
5.7
You dont need the special fluid at all. Lots of guys running Valvoline. and the 8 speed swap is already all figured out by SGA :)
 

Jeepwalker

Senior Member
Joined
Sep 8, 2017
Posts
3,137
Reaction score
3,330
Location
WI
Ram Year
2012 Reg Cab, 4x4
Engine
5.7 Hemi
There are quite a number of owners who are accumulating high miles on their original RFE's w/o problems. I agree with Steve, regular maintenance and stay within the design intent. Even snow plowing ...you have operators who wait that extra (but meaningful) partial-second when shifting between F & R, for the tranny to shift into gear, like you're supposed to. Then you have operators who either don't give a crap or don't fundamentally understand transmission shifting. If ya shift and 'bang' the tranny all day long, it's goiing to kill a tranny lot quicker. But some operators do that...
 
Last edited:

TheEnder

Senior Member
Joined
Aug 12, 2017
Posts
2,088
Reaction score
1,634
Ram Year
2013
Engine
4.7L V8
So I have been contemplating doing the 65 RFE to 66 RFE conversion on my truck and am looking for some tips if anyone has actually done it or not. Programming wise it should be pretty easy as it was available on the 3500 dually with a 5.7 in 2014 as well. So with that being said I am going to be posting what the differences are between these transmissions as I am at the dealer and happen to have a spare 66 RFE laying around and am rebuilding currently.

First big difference between these transmissions that i have found is the gear ratios are completely different.
65 RFE 66RFE
1st 3.00:1 1st 3.23:1
2nd 1.67:1 2nd 1.83:1
2nd gear prime 1.50:1 3rd 1.41:1
3rd 1.00:1 4th 1.00:1
4th 0.75:1 5th 0.81:1
5th 0.67:1 6th 0.62:1
REV 3.00:1 REV 4.44:1

I have looked up in the parts catalog as I have that access (which is nice to have), There is no difference from the torque converter to the center section of the transmission. Everything that is different for these transmission is the same in the input clutch hub. Same Valve body, torque converter, and transmission pump. The biggest difference is when you get into the planetary's of the transmission. The 65 RFE has 5 pinion plaentary gears as the 66 has 6 pinion planetary's. there is two more clutch disc in the 4c clutch and the Low reverse also has two more clutch disc in them.

I know from experience that the week point of the RFE transmission is the input clutch assembly. This is where all the clutches burn up and I am almost positive that it is caused from either lack of maintenance or someone just not caring when there vehicle is overloaded. Anyway. I will post pictures later but was curious what everyone was thinking on this change.
Im curious about this.

I did the 8hp swap halfway through on my 4.7. I was about to get the wiring but then I was informed I would also need a new pcm to make it work, issue with that being that no other pcms work as the 4.7 was never optioned with that. So it's kinda dead in the water for now, I might take apart the trans and put it into my 300 as it's getting 6.4 swapped.

The truck is a 2WD and the programming for it would be easy with the 66RFE using HPTuners. I like the slightly shorter 1st and slightly taller final drive as that would help better account for 4.10s or 4.56s. My buddy has a trans from a 2500 bighorn hell give me to test out too.

Is the tail shaft from a 2wd 66rfe compatible with a tail shaft from a 2wd 65RFE?

Apologies for bringing back up a dead thread too :)
 
Top