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Ford 6F50 and GM 6T70: Similar but Different

Tuesday, October 28, 2014 - 07:00
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The 6F50 and 6T70 transaxles were developed as a joint effort between Ford and General Motors. Because this was a joint effort, as you can imagine, many of the internal parts are very similar or almost identical but will not interchange. The solenoid body for example contains the TCM with GM’s 6T70 (Figure 1) whereas Ford does not (Figure 2). The solenoids are controlled by an external PCM. Ford uses a total of seven solenoids to operate the transmission (Figure 3) while GM’s Generation 1 6T70 uses four pressure switches and eight solenoids to operate their transmission (Figure 4). They also number their solenoids differently but I labeled them according to their operation for ease of identification. 

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Both GM and Ford use the same firing order of the solenoids. The extra solenoid (SS2), GM uses for a reverse engagement. Ford handles it differently eliminating the need for this additional solenoid. With having an external PCM, monitoring solenoid computer commands or solenoid resistance checks can be made at the pass through connector (Figure 5).

The near closeness of the valve bodies between the two transmissions make them similar but they are totally different.  

I am going to start at the top and work down from the solenoid body. Once you remove the solenoid body the first thing you come to is the Upper Plate Assembly (See Figure 6). The plate shown is for a 6T70. The difference here is the 6F50 does not have the aluminum block and the two feed holes circled. The aluminum block is used as a spacer behind the internal TCM and the holes are for the additional solenoid that are only used by GM.

The next piece we come to is the Channel Plate (See Figures 7 and 8). First look at figure 7. This is the top side of the channel plate. The area circled in the worm tracks is where the passages are different for the additional solenoid on the 6T70. Also notice that there is the Ford or Hydra-matic Logo on the casting depending on the manufacturer. Now look at figure 8. This is the bottom side of the channel plate. Here you’ll find there are three solenoid feed accumulators that are only used on the 6T70. The 6F50 channeling is the same but it is not machined for the accumulator pistons.

Moving down, the next piece we come to is the Upper Valve Body (See Figures 9 and 10). For the most part this section is identical between the two manufacturers. If you look at figure 9 you’ll see the valve line ups out of their bores. They are both the same for 

the 6F50 and 6T70. Figure 10 shows the difference in check ball usage between the two units. Ford uses two less then GM however the Ford casting is machined for the additional check balls.

The last piece we are going to look at is the Lower Valve Body (See Figures 11 and 12). Here the only difference is the 4-5-6 accumulator used on the 6T70. All of the other valve line ups are the same for both units.

A quick word about the upper and lower separator plates on these valve bodies. They both use bonded gaskets and because of the different check ball and solenoid feed accumulator usage on the 6T70 they are both different.

To sum up, over the years there have been some minor changes to the valves and springs on both the 6F50 and 6T70 but in the end you’ll find they are both similar but different. 

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