Monthly Archives: March 2019

Rebuilding my first automatic transmission a 45rfe .

This is my first attempt at fully rebuilding an automatic transmission, I have messed with valve bodies and entire trans replacements in my teenage years but after the Dakota ate its second transmission I realized that rebuilding one was was something that I needed to master as I had no control in the quality of rebuilt replacements and junkyard specials were not holding up.

I pulled the first transmission out a few years ago because it started shifting extremely hard with the 2-3 shift it had a transgo HD2 shift kit and line pressure mod.

Once the front pump was removed, taking apart the transmission was extremely easy, I did the entire thing with one straight blade screwdriver and a dental pick.

Everything inside the first old transmission was perfect except for this planetary reaction plate that cracked… that explains the hard shifts, I got 80K out of this transmission.

No clue on why the transmission was designed with so little material around the area that cracked.

The second transmission was a used one out of a Durango, I left it unmodified, it lost all gears going up the back-way to crown king after overheating, I got 30K out of it.

Here you can see that the 4th clutch had a major failure, the snap ring that holds the spring plate came off and the transmission started to grenade itself by lathing the 4th clutches, retainer, thrust bearings and ring gear. You can see friction material from the clutches were all over the place, there were chunks of metal in the pan and metallic, burnt fluid everywhere.

This is a cracked reaction plate, it looks to have been damaged for quite some time.

There have been some variations and changes between the models of 45rfe, 545rfe and 66RFE transmissions throughout the years.

The first version was the 45rfe, it came out behind the 4.7L in the 1999 WJ Jeep Grand Cherokee and was used in the Rams, Dakotas and Durangos. In 2001, for Jeep the transmission was changed to include 5th speed and called  the 545rfe, the only difference is the transmission control module that uses a kickdown for the other gear.

In 2002 there was a change across all models with the pump fluid pressure spring, all post 2002 transmissions run at a higher pump pressure, this may throw a code when a later year TCM is used with a pre 02 transmission or vice versa.

In 2005-2007 there was a change to the front pump, this new pump has a seal in the cover of the transmission, an updated pressure spring and internal plate that solves the no move issue if you let your vehicle sit for a while and it does not build pump pressure. Chrysler got rid of two bolts that were leaking fluid back into the transmission. I used the updated front pump for my rebuild.

In 2012 there was a major change to the transmission with the introduction of the 65RFE and 66RFE. This FRONT HALF of this transmission IS IDENTICAL IN EVERY WAY to the 45rfe and thus can use the same front pump and torque converter, most other parts will not interchange. The new transmissions have an improved torque converter that is 1″ larger in diameter then the older units.  Larger torque converters have a better mechanical advantage, hold more fluid and are easier to cool and have more clutch capacity. This generation also used crappy plastic valve body pistons to cut down noise.

Many torque converter rebuilding companies, MOPAR and transmission builders I contacted said that the two torque converters are NOT INTERCHANGEABLE IE: WILL NOT FIT IN A 45RFE /5-45RFE TRANSMISSION. I was laughed and told that they were physically completely different. I ignored the advice of the “professionals”, studied diagrams and schematics of the design changes and purchased a 2017 Ram torque converter for my build, it paid off as it physically bolted to my 2001 Dakota’s flex plate slipped into the updated front pump and never hit any areas of the casting of the 2001 45rfe.

To rebuild the transmission I used a Mopar master kit, which contained borg warner clutches. I then purchased molded pistons, the updated “white” mopar solenoid pack with slider, new Sonnex aluminum valve body pistons, 66RFE torque converter, new style front pump, 545rfe TCM from a 04 grand chero car, steel filter nut upgrade (to replace the plastic one).

I was able to scrounge parts from the two failed transmissions to rebuild one good one.

To rebuild the transmission I followed this video, it is in Spanish but if you are not blind it should not matter. Make sure to install the snap rings in the correct direction, many are tapered to fit into specific machine grooves in the transmission. Be sure to measure and adjust your clutch clearance as well.

I used a cheap transmission press to remove and install the springs and assemble goo to hold components in place.

Luckily my transmission worked perfectly the first time I bolted it up in there, take your time, mark directions and positions of all snap rings, thrust bearings and plates before you remove them and reinstall them in the same direction.