• Register Today It's free! This box and some ads will disappear once registered!

4R70W Rebuild Diary - Part 7 - Forward (main) Planetary and Sun Gear


EF Tranny Guru
Moderator Emeritus
February 8, 2003
Reaction score
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
This is where we start to separate the men from the boys. The main planetary for this transmission is a massive thing.... I did a thread a while back detailing a comparison between the 4R70W and the A4LD/4R-5R. HUGE difference.

In the thread linked in post #8 in the first thread in this diary (www.tccoa.com in their techincal thread portion - transmissions 101) Jerry W. talks about the differences in the gear sets between the AOD, AODE and 4R70W. I doubt there are a lot of AOD gearsets floating around out there still. The heavy duty models according to Jerry W (from about 6 years ago) come from the 5.4 liter transmnission.......for the 4R70W. The part numbers he gave are:

Planetary: XL3Z-7A398-AA (list $235)

and for the sun gear: XL3Z-7A399-AA (list $100)

I bought a planetary that had a listing of XL3Z-7A398-BA... which would be a newer model than he describes (fair enough - FORD is constantly upgrading in production runs.) That said, for a retrospective look at these planetaries, I recommend his dissertation for a discussion of the differences going back in time. (Mainly materials used in the planetary). The model of planetary I purchased is clearly a newer one than he describes but I cannot tell you the differences.

This planetary weighs a bunch. It also serves as the reverse drum (the band applies to it's body) and is serves to pilot other pieces. This is kind of the heart of this transmission.

Each end has a bushing. On one end (I'll call it the front end) is a small one, and on the other much larger one... ID wise. I now possess about 5 of these, one of which is brand new (and going into THIS transmission.) What I have found is interesting.

Generally speaking the gears in all of them look good and there are no obvious issues there. The large end bushing is .. in most... ok. The smaller "front" end (as I refer to it) bushing is toast is almost ALL of the used ones I have. I think there is a message in that... if you plan to reuse this planetary (which is not a bad idea based on price alone) you might want to pay close attention to the front bushing and maybe replace it with new ! Also check the splines on the front end in the "snout" - this is where the planetary engages the diect clutch hub, in effect linking it directly to the direct clutch frictions (show in the direct clutch thread in detail).. These can wear.

Ok, enough talking, let's look. Here is the new planetary (notice the nice clean bushing in it - remember that "good" is not necessarily shiny... like pennies these get discolored but work just fine):


Here is the front end bushing in the new one closeup...


Here it is in a "used one" .... nasty - ridges throughout the width:


(Like I said more or less commonplace... I will maybe post an appendix thread on refurbishing these planetaries.)

The rear bushing in this new one is a little discolored but if I polish it a little will be pristine. Oddly, even when the other bushing is damaged this one seems to look pretty good on the used ones. Curious.


Here is a look into the "backside".... notice the ragged shaped place in the casting....


That is for the one way roller clutch (FORD calls it a "planetary clutch")... shown here... it consists of a carrier, some "accordian springs" and some rollers...


This piece is FORD P/N C3AZ-7A089-A and lists for $12.89. Replace it on rebuild. Cheap insurance. I always like to replace one way clutches in rebuilds.

Here it is being installed


and installed


Notice how the rollers are held in place with the accordian springs. This is a common design. If you look you will see a "torrington' built into the bottom of this planetary... for? The sun gear.


(I am noticing that newer FORD parts are starting to bear bar codes on them...like the torrington in the Planetary had....) I have no issues with reuse of the sun gear.. but there are a few places to check. First the obvious... how do the gears look? Here is new for comparison:


And the end splines? Check them for any damage (not common). There is also a bushing in this puppy.... and it also gets damaged. I am wrestling with how to replace it.. (ain't easy). I have 3 used ones and they all need it replaced - take heed... that bushing is a problem child!

This also uses a torrington on it.... here it is being installed...


and all together


I am now installing it into the planetary, with a little twist to get the gears to mesh..


And here it is all engaged


A couple things to remember about this planetary in our tranny.

1) it serves as the drum for the reverse band. So it gets grabbed by the band... (nice because the thermal mass of the planetary is pretty large...) on a used one I will try and capture the outline of the double wrap... showing where it rode on this planetary shell...


can you make out the lines on the inner spaces on the cuts in the band? Try here:


See those two faint lines? (by the way the roller clutch was sliding out of the planetary here, it sits flush, in case you wondered.

Oh and...

2) Notice that this tranny is getting all NEW here... worth about $350! (Have you been adding up the prices of the "new" parts going into this rebuild/ remanufacture?)


I have been attempting to fathom out the diferences betwen the 4R70W and the 4R75W. A member here, BENT BOLT, a FORD tech reports that the main difference as far as he knows is in an upgraded planetary and sun gear, that uses a thicker torrington. The part numbers and prices are:

Sun Gear and Torrington: 4L3Z-7D234-AA List: $195

Planetary: 4L3Z-7A398-AA List: 420.

These parts are reverse compatible. They should up the torque handling by about 8% over the 4R70W.

Ok that's it for this thread in the Diary. (for now - I reserve the right to further update it.)


EF Tranny Guru
Moderator Emeritus
February 8, 2003
Reaction score
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
Refurbishing the Planetary Bushing

The smaller bushing on the planetary for some reason is like the canary in the mine... when evrythign ele looks good, it will often be scored. A new one is cheap - under $2. So why not replace it. It is pretty easy, let's walk through this.

First off you will need a pilot bearing puller. HF has one for $20, often on sale for half that, and it's pretty stout. It is perfect for this pulling job. Insert in in the bore and expand it to grasp the bushing...Then pull up on the engaged 3 legged puller and the bushing will start to come up and out...



Once it is out.... the new one can be put on a bushing driver (HF makes a set for about $10) or if you have the BW 1354 Transfer Case toolset the driver in that set is a perfect fit...and drive the new bushing back into the now empty bore.. drive it no more than about 3/16 below the top of the bore.

pic coming

Voila, good as new....

ps. That back large bushing almost NEVER is bad! Good thing! Not sure how to drive THAT one.


Hauls the mail.
Elite Explorer
June 17, 2004
Reaction score
City, State
Knoxville, TN
Year, Model & Trim Level
98 Limited AWD