Just wanted to get information about gear changing in mustangs.
I finally drove my 66 for the first time ever around my area and the gears in my c4 never change. The fastest I went was 35-40 miles and hour, which I'm guessing is around 70kmh or so. Both on the green dot and the dot above.
This seems strange to me. I know that the c4 only has 3 speeds, but going that fast should at least change gears automatically at least once.
And before someone says its the vacuum modulator, I had a look and it seems connected. Not sure if the person that rebuilt it has tightened it too much though. Maybe it needs to be adjusted backwards to let more vacuum occur? I have no idea hahhaa
With very little throttle it should change fairly early.
If the C4 is similar to the AOD, from memory, the reverse clutch is actually supposed to be engaged for 1st gear to operate.
If reverse does not work, then it's possible your reverse clutch is not engaging, so you're actually starting off in second gear.
That might explain why it's not changing gears.
IMO you really need that box looked at properly, or replace it.
No I am not sure, but it voids warranty if I go somewhere else and on top of that, taking it to someone else will cost me at least 500 bucks to open the damn thing up and make a diagnosis. And I don't have that kind of money lying around hhahaha
If you believe mustang monthly, then the C4 seems to have a Low/Reverse band, the same as the AOD.
So my guess is that you either have an issue with the low/reverse band (or the servo that actuates it), or the reverse clutch/drum.
If you got up to a decent speed and it didn't change gears, my first guess would be that the band is not engaging.
For reverse, you need both the drum and band actuated. For first gear, you just need the low band actuated. Without the band actuated, you have second gear.
This is exactly what happened to mine when I first put my gearbox back in. I took the pan and valve body off and found that the low band was slightly out of alignment and the actuator could not engage it.
40mph is over 60kmh, so if it was sticking in first, it would be revving pretty hard. Stuck in 2nd gear at 60.. not so bad.
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