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New to this so please excuse my mistakes. Am old enough that the computer stuff is not my best field. Now to the problem for those of you who might be able to suggest ideas to solve my problem. I changed the transmission fluid and filter on my 77 C6. Also replaced the O ring on the modulator as well as the vacuum line. have since replaced the modulator with new. The problem is that when taking off, it will upshift right to 3rd. it shifts through all gears manually however and also downshifts. additionally, it will not kick to 2nd from 3rd with wide open throttle. Was working fine until the fluid / filter change and modulator O ring change. I did find a very small pin, about the size of a u-joint needle bearing on the floor when cleaning up , but no idea if it came from the trans. any ideas would be most appreciated. I reside in Alaska and my F150 is my wood hauler so need it running asap. Live 200 miles from the nearest shop so just taking it to the shop is unreasonable. Thanks to all of you in advance for your help.
Welcome to FTE. Mark hit the nail on the head 100%, remove modulator and put the pin back in.
Otherwise my normal trans troubleshooting recommendation is...Check the vacuum modulator and the line that goes to it. Check the line for kinks or other problems, make sure it hasn't come off. If the line checks out, take the line off where it connects to the modulator. If trans fluid leaks out, its bad. If no fluid, it still could be bad. They're simple to replace, disconnect the vacuum line, remove one bolt that holds the clamp in place and the modulator comes out. It has an o-ring seal.
Modulators are identified by the color of the stripe. Pretty much the "go to" one is the black stripe. If they don't show that one in the catalog, go with the green stripe. Avoid the pink stripe. That one is a dual diaphragm version that has two vacuum line going to it. If by chance you have one of these, replace it with one of the other two and use the vacuum line that goes to direct manifold vacuum, cap the other line. When you pull the modulator out, be careful. There is a pin that goes in the modulator. Sometimes it comes out with the modulator, sometimes it stays in the tranny. If it comes out, don't lose it.
Sounds to me like you found the pin on the floor that should be inserted in the buisness end of the modulator as it's put on the transmission. If you just found it after this last total replacement, it likely just fell out of the old one.
Welcome to FTE. Mark hit the nail on the head 100%, remove modulator and put the pin back in.
Otherwise my normal trans troubleshooting recommendation is...Check the vacuum modulator and the line that goes to it. Check the line for kinks or other problems, make sure it hasn't come off. If the line checks out, take the line off where it connects to the modulator. If trans fluid leaks out, its bad. If no fluid, it still could be bad. They're simple to replace, disconnect the vacuum line, remove one bolt that holds the clamp in place and the modulator comes out. It has an o-ring seal.
Modulators are identified by the color of the stripe. Pretty much the "go to" one is the black stripe. If they don't show that one in the catalog, go with the green stripe. Avoid the pink stripe. That one is a dual diaphragm version that has two vacuum line going to it. If by chance you have one of these, replace it with one of the other two and use the vacuum line that goes to direct manifold vacuum, cap the other line. When you pull the modulator out, be careful. There is a pin that goes in the modulator. Sometimes it comes out with the modulator, sometimes it stays in the tranny. If it comes out, don't lose it.
Hope I have figured out how to properly post and reply. I sure appreciate your prompt replies! Yes, I knew there is pin for the modulator as it did come out when I replaced the o ring. Am not sure if it can be inserted the wrong way but reinserted it and it feels as though there is a seal that it slides into. that pin, as I recall, is about 3 inches long and about 3/16 in diameter. The pin I found on the floor was only about 1/16 diameter and 3/4 in long. I really suspect you are right in assuming that the modulator is the culprit. It does appear that the rod is to short to enter all the way into the modulator body although dont know if it is supposed to contact the diaphram. Will check the vacuum, with a gauge, to make sure I have ample vacuum to the diaphragm, as well as your other suggestions. Once again, thank you all for your assistance!
Hope I have figured out how to properly post and reply. I sure appreciate your prompt replies! Yes, I knew there is pin for the modulator as it did come out when I replaced the o ring. Am not sure if it can be inserted the wrong way but reinserted it and it feels as though there is a seal that it slides into. that pin, as I recall, is about 3 inches long and about 3/16 in diameter. The pin I found on the floor was only about 1/16 diameter and 3/4 in long. I really suspect you are right in assuming that the modulator is the culprit. It does appear that the rod is to short to enter all the way into the modulator body although dont know if it is supposed to contact the diaphram. Will check the vacuum, with a gauge, to make sure I have ample vacuum to the diaphragm, as well as your other suggestions. Once again, thank you all for your assistance!
That "about 3 inches long and about 3/16" diameter" seems way-way too big.
