Ford 8F35 maintenance tips: Planetary failure and no-pressure conditions - Transmission Digest

Ford 8F35 maintenance tips: Planetary failure and no-pressure conditions

Our shop has had several vehicles come in with the Ford 8F35 transmission having planetary failure. Apparently, there was a run where the pinion needle bearings had a hardness problem (see Figure 1).

Figure 1.
Figure 1.

Ford has a bulletin out (bulletin number 22-281), which provides a part number for this planetary assembly: the part number is JM5Z-7N473-C and costs about $160.

The first time we worked on one of these, a no-move due to a no-pressure condition came up after we installed it. We could tell there was a pump-related problem as it wasn’t sucking up any fluid. When we pulled it apart, we found that the chain came off the drive gear. Both the drive gear and chain were damaged (see Figure 2).  

Figure 2.
Figure 2.

We already had the tools we needed to assemble this correctly; we just didn’t know it. We had purchased a special tool kit from eBay to rebuild this transmission. This kit includes an installer/sizer tool for the stator seal located at the base of the stator support shaft shown in Figures 3 and 4.

Figure 3.
Figure 3.
Figure 4.
Figure 4.

Figure 5 shows how the pump is assembled with the chain and drive gear. 

Figure 5.
Figure 5.

There is nothing that keeps the drive gear and chain in position, which allows for it to drop out of position when installing the torque converter. 

We use the sizing tool as an alignment tool to maintain its position as seen in Figures 6 and 7.

Figure 6.
Figure 6.
Figure 7.
Figure 7.

We also use a turbine shaft seal protector (seen in Figures 8 and 9).

Figure 8.
Figure 8.
Figure 9.
Figure 9.

Having both tools in place allows us to lower the converter housing onto the main case, without damaging the seal on the turbine splines, while holding the drive gear and chain in place (see Figure 10).

Figure 10.
Figure 10.

Now comes the next step, which is also very important. Before removing the tools, position the transmission so the torque converter can be installed vertically (as seen in Figure 11), not horizontally. If you position it horizontally, you stand the chance of knocking the drive gear and chain out of position, especially with a used chain having a bit more slack in it than a new chain. 

Figure 11.
Figure 11.

The part number for the tools needed is 307-764. This number includes the two tools used to install the seal onto the stator shaft and the sizing tool once the ring is positioned into the groove. The turbine shaft seal protector is part number 307-765. Alternatively, you can use tape over the splines, as you can see in Figure 10. 

Another tip: the pump drive gear and chain from a generation three 6T40 will interchange with the 8F35 if you need one (seen in Figure 12).

Figure 12.
Figure 12.

Read more columns from our Shift Pointers series here. 

Craig Sarokoff is the lead tech at AAction Transmissions in Florida.

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