Ford FMX shifting trouble.

Joined: October 29th, 2017, 10:31 pm

November 7th, 2017, 9:36 pm #11

Sorry it took a while to answer. Been really busy Working. I work with cars and rebuild transmissions for living btw.

I Checked shifter lever positions the manual valve correctly. There is some slack on shifter it self, but detent bullet and plate locates every position correctly.

Valve body issue is what i think too. Valve body has been apart multible times. Nothing is stuck and everything seems to be in order. I have small pick that i use to check valve movements. I have couple of cruise o matics that i am working right now too, and as there is lots of similar parts on their valve bodies, i have compared them to this FMX valvebody and found nothing odd.

I am thinking that fault in the valve body has something to do with manual valve bore or passages to 1-2 shift valve. Main difference between Drive position gear 2 and Manual 2nd gear is that in manual gear 1-2 valve and 2-3 valve are cut off by manual valve. So i am thinking that fault may be a result of bore wear somewhere from the manual valve to the 1-2 shift valve. I have Sonnax vacuum pressure tester, but i can`t pinpoint what i should look for. I know how much vacuum drop i should see from good bores but i don`t know if it actually could be the reason for malfunction.

So i am thinking that my next move is to get known 69 mustang valvebody that is know to work and compare it to my customers valvebody. The thing that bothers me is that everything worked before it was taken apart first time.




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Joined: October 29th, 2017, 10:31 pm

June 2nd, 2018, 11:15 pm #12

Hello everyone.

Took some time because winter and all the work hassle, but finally got around to working with the problem transmission. Now i have replaced the valve body and pressure regulator assemblies with known good ones and exactly the same fault persists. There is no change, so the fault could not be in the valve body. Anybody has any ideas for the next move?
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Joined: November 18th, 2004, 4:20 am

June 3rd, 2018, 2:24 am #13

Better take it apart. Something is not fitting fight.
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Joined: October 29th, 2017, 10:31 pm

June 3rd, 2018, 2:13 pm #14

Hello Stuart. Appreciate your input. Do you have any idea what i should look for? I have pulled it apart before and allthou i did find one thing that had some wear on it, and i replaced it, it had no affect for the fault. But i was very careful to look every single part and looked for hair cracks and everything that i could figure, still did not find anything. Pressure tested everything and all worked fine.

I will be happy to go over again whole thing, if there is something that i could look for. But as i did not find anything as i went thru it earlier with extra attention to every detail and still not find the fault, i am afraid that it will happen again. I have built a lot of transmissions so i know that every little thing counts. And i also know that i am just missing something.

Next step is that i will try new modulator. What is your oppinion, could some weird sticking issue cause this kind of behaviour?
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Joined: November 18th, 2004, 4:20 am

June 3rd, 2018, 6:01 pm #15

I imagine you did but curious. Did you test fit each ring? Especially the small ones on the intermediate shaft. Also in the rear housing. 
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