1973 Comet 250 inline 6, 3 speed (C4) auto column........ Car starts out in 3rd and stays in 3rd, when decelerating it doesn't downshift. I can shift it manually upshift and downshift. What can be the problem ???
If modulator vacuum is disconnected trans will not upshift. With that condition, can manual shift 2nd and maybe shift to high around 70+ mph. In 50+ years I've never seen a C4 that is "hung" in high gear.
So I crawled/slid under car vacuum hose connected to modulater but I can't see where it goes but low and behold there's a hose just hanging there by modulater. My question is where does the hose connect to from modulater, manifold, carb. ?
The hose will connect to a spot on the manifold that has constant vacuum, or any place below the base of the carb. Some modulators had 2 ports to hook hoses too and perhaps yours was one of those and somebody replaced the modulator with a single port type. It looks as they may have ran another hose to replace a bad hose and just left the old hose in there. Have you checked to see where the hose that is connected to modulator goes now ? At any rate plug the hose that is just hanging as it may be a vacuum leak
There is a steel line connecting to manifold and appears to run back to tyranny, right before the bend down along firewall there was another steel line uncapped so I ran a hose from it to a capped vacume port on vacume advance and still same issue, as far as the hose on modulater it disappears. Behind the tyranny cross member. So I can not detect where the steel line goes or the hose from modulater. I think what I will do is run a hose from modulater directly to manifold and see if there's a difference. If there is none then can I assume the modulater is bad ? I really appreciate any and all of your input ! By any chance can you tell me what years are compatable for instrument cluster ? I assume it's 71 thru 73 ?
From what I have read about the clusters 71-73 will work but some have said late 73 models it changed to a cluster with a different size plug ? If I was to search for one I would look for a 71-73 . My knowledge with transmissions and how they function is very limited so to avoid giving you bad advice I will deffer the answer to that question to more experienced people. I do know that if you take the hose off of the modulator and it has transmission fluid in it then it is bad . Personally I do not think it is a problem with the modulator and you will end up having to pull the pan and possible change the valve body but that is just a guess, hopefully a wrong guess. Good luck and keep us posted on what you find so we can all learn something
I'm down with that !!! Its all about being honest and sharing knowledge and information with each other !!!!
do you know if it has been sitting for a long time? sometimes if you baby it you can drive out some of the quirks... keep an eye on all the fluids. good luck
