Steve White
Junior Member
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.
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.