Won't shift into 3rd gear
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Trailering
Joined: Jul 2013
Posts: 24
Likes: 2
Won't shift into 3rd gear
Hello gents
I have a custom 1978 f150 stepside . The previous owner put a 460 7.5 liter engine in it from a 1977 lincoln connected to a 3 speed auto transmission.
The truck had some revving issues which mentioned it would not rev above 3000 rpm. But that's fixed now.
However then the transmission stopped shifting into third.
Any ideas why that might be?
I changed the oil and it was not Burnet but was not fresh, a so cleaned the filter.
Still didn't shift into 3rd.
Aprreciate your input
Sam
I have a custom 1978 f150 stepside . The previous owner put a 460 7.5 liter engine in it from a 1977 lincoln connected to a 3 speed auto transmission.
The truck had some revving issues which mentioned it would not rev above 3000 rpm. But that's fixed now.
However then the transmission stopped shifting into third.
Any ideas why that might be?
I changed the oil and it was not Burnet but was not fresh, a so cleaned the filter.
Still didn't shift into 3rd.
Aprreciate your input
Sam
Hotshot
Joined: Apr 2009
Posts: 14,333
Likes: 247
From: Stanley, VA
That's going to be a C6 transmission. Check the vacuum modulator and the line that goes to it.
Check the line to make sure it hasn't become disconnected and check the condition. Look for kinks or breaks in the steel line and check that the rubber hoses on the ends are in good shape.
If the line checks out, pull the hose off of the modulator, if fluid leaks out, its bad. If no fluid drips out, it could still be bad.
Changing it is easy. One bolt and one hose. The modulator pulls out, careful, there's a pin in the end of the modulator. Sometimes it comes out, sometimes it doesn't. If it does come out, don't lose it, you'll need to install it in the new modulator.
Check the line to make sure it hasn't become disconnected and check the condition. Look for kinks or breaks in the steel line and check that the rubber hoses on the ends are in good shape.
If the line checks out, pull the hose off of the modulator, if fluid leaks out, its bad. If no fluid drips out, it could still be bad.
Changing it is easy. One bolt and one hose. The modulator pulls out, careful, there's a pin in the end of the modulator. Sometimes it comes out, sometimes it doesn't. If it does come out, don't lose it, you'll need to install it in the new modulator.
Senior User
Joined: Oct 2014
Posts: 130
Likes: 1
From: Pilot Mound, Iowa
x2 on the modulator.... May also want to check/adjust the intermediate band. My C6 went from 1st to 3rd, band was really loose. After band adjustment, New modulator, and vacuum line, shifts like new.
Jeff
Jeff
Senior User
Joined: Oct 2014
Posts: 130
Likes: 1
From: Pilot Mound, Iowa
A quick search will get you more info than I can type. There is a bolt and lock nut just above the linkage on the side of the trans. You need to loosen the lock nut and tighten the bolt to ( can't remember the torque setting) then back it out 1 1/2 turns(??) then tighten the lock nut. This band is second gear.
Jeff
Jeff
Hotshot
Joined: Apr 2009
Posts: 14,333
Likes: 247
From: Stanley, VA
Like Jeff said, the band adjustment is just above the manual linkage on the driver's side of the transmission, see the picture below.
To adjust it, first, Ford recommends replacing the lock nut with a new one because this is a sealing nut but you can usually get away with reusing the same nut.
Clean the threads of the stud sticking out. Hold the adjustment stud with a wrench and loosen the lock nut, then tighten the stud to 10 ft/lbs. Then back off the screw exactly 1 1/2 turns. Hold the stud to keep it from turning and tighten the lock nut.
To adjust it, first, Ford recommends replacing the lock nut with a new one because this is a sealing nut but you can usually get away with reusing the same nut.
Clean the threads of the stud sticking out. Hold the adjustment stud with a wrench and loosen the lock nut, then tighten the stud to 10 ft/lbs. Then back off the screw exactly 1 1/2 turns. Hold the stud to keep it from turning and tighten the lock nut.
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Trailering
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Joined: Apr 2009
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From: Stanley, VA
Glad it was one of the "cheaper" fixes.
Mountain Pass
Joined: Aug 2024
Posts: 132
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I realize this is an older thread but it's the most helpful one I've seen on the vacuum modulator. My 66F100 which i've owned less than 2 weeks came to me with a 460/C6 swapped in and I got zero info on what it came out of. runs good, trans shifted ok but but the upshifts occurred at very low speeds. No kickdown either. Fluid proper level, nice and red / not burnt.
1st step was adjusting the kickdown cable which they may as well have left on the shelf. It looks like the same Lokar setup I installed on my 68 charger. It was adjusted so poorly that even full throttle would not pull on it. I got that resolved and it kicks down now, even at part throttle which I like.
Then I found this thread checked vacuum modulator. plenty of vacuum with engine running. I adjusted it and now the upshifts are occuring at higher speeds/rpms. I may look into the band adjustment. I'll have to buy a different torque wrench for that. Mine is huge and I don't think it will fit down there.
1st step was adjusting the kickdown cable which they may as well have left on the shelf. It looks like the same Lokar setup I installed on my 68 charger. It was adjusted so poorly that even full throttle would not pull on it. I got that resolved and it kicks down now, even at part throttle which I like.
Then I found this thread checked vacuum modulator. plenty of vacuum with engine running. I adjusted it and now the upshifts are occuring at higher speeds/rpms. I may look into the band adjustment. I'll have to buy a different torque wrench for that. Mine is huge and I don't think it will fit down there.
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