FMX-pert Needed

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1973 Mustang Convertible 351C restoration project
I rebuilt the transmission because it had morning sickness. I put it back in and there is no engagement in D. Car is on jacks.

Reverse Yes

First Yes

Second Yes. It shifts from 1 to 2 in the 2 position.

D Nothing. Even if I shift 2 to D at 30+ mph nothing. It is like putting the car in neutral. It worked a couple of times and then nothing.

All seals, clutches, front band are new. Vacuum modulator is new. The one-way clutch appeared to be working during assembly.

 

Bentworker

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Are you positive the linkage is adjusted correctly?  Might as well check simple stuff first 

 

knn

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We had similar problems when we replaced our C4.  For us, it was a misalignment between the detents in the shifter and the detents in the transmission (and of course alignment with the neutral safety switch).  

I know this isn't the way you're supposed to do it, but what worked for us was...

  • loosen shifter linkage
  • manually put the transmission in drive (count off the clicks)
  • put the shifter in drive
  • tighten the linkage

Oh yeah, then fiddle with the neutral safety switch until you can get the car to start in P or N and the reverse lights to come on in R.

Hope this helps,

Nick

 
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1973 Mustang Convertible 351C restoration project
We had similar problems when we replaced our C4.  For us, it was a misalignment between the detents in the shifter and the detents in the transmission (and of course alignment with the neutral safety switch).  

I know this isn't the way you're supposed to do it, but what worked for us was...

  • loosen shifter linkage
  • manually put the transmission in drive (count off the clicks)
  • put the shifter in drive
  • tighten the linkage

Oh yeah, then fiddle with the neutral safety switch until you can get the car to start in P or N and the reverse lights to come on in R.

Hope this helps,

Nick
I put the shifter in D and put a bungie on it to hold it there. Then I loosened the adjustment bolt and put the transmission in 1. Then I counted 2, D.

I will try it your way and see if that helps.

 

knn

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I put the shifter in D and put a bungie on it to hold it there. Then I loosened the adjustment bolt and put the transmission in 1. Then I counted 2, D.

I will try it your way and see if that helps.
Like I said, I know that wasn't how you're supposed to do it, but after a LOT of foul language I decided to focus on the gear that I cared about (D) and see if all the other pieces would just fall into place.

Good luck,

Nick

 

Bentworker

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If the linkage does not magically fix it you may have a piece of dirt or a burr hanging up something in your valve body.  D applies both the front and rear clutches - I think.

The Superior Bench Buddy brushes are worth their weight in gold.

https://www.monstertransmission.com/Superior-Solutions-Bench-Buddy_p_11400.html#.YWRLQyRHaEc

Dropping the pan and valve bodies isn’t that bad, except for the bath in transmission fluid.
I just had the valve body completely apart. I had to use emory cloth on a couple of the valves but they all moved freely when I reassembled it. 

 

Bentworker

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If you don't have to do something twice occasionally on a 48 year old car you are very lucky.

I usually repair in a  "pain in the ass hierarchy" 

Least pain in the ass = linkage

Mildly painful = dropping the valve pan and valve body for a second check

Most pain in the ass = pull the transmission and take it fully apart looking for cut / blown seals, damaged frictions or hard parts.

 

Fabrice

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I know after 

Dropping the pan and valve bodies isn’t that bad, except for the bath in transmission fluid.
ahaha, yeah and you regret the first time you do it that the container supposed to receive the oil is at the wrong place or not wide enough :D

I now replace any pan going down with one with a drain plug. So far did not need use any of these but I know the time will come!

 
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Here is an Update:

I added two more quarts to bring it to the full 11 quarts. It now has Drive. I took it for a ride in my neighborhood.

The 1-2 shift is crisp. The 2-3 shift was a little slow (mushy) at first and then after a few minutes it stopped shifting into third altogether.

I now believe it has an incorrect dipstick and/or tube because it still shows as overfilled. I may try adding another 1/2 quart.

To sum it up: It now engages in D and has a nice 1-2 shift. It will not shift into third.

Opinions/ideas? Vacuum modulator?

 

Bentworker

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What does the fluid look like?

My guess is still something valve body related.

 
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