I have a 71 Ford 302 and C4 in my 53 F100. Finished my all new brakes yesterday so I felt comfortable running it with the driveshaft again. Before I hooked up the driveshaft the tail would spin when I put it in gear. After driveshaft hookup nothing in gear. 4 quarts of tranny fluid later and D,2,1 all work great and will move the truck. However I have no reverse nor does the engine seem to be under load when in reverse. Today I removed the driveshaft again and when in reverse the tail shaft spins. Driveshaft back on and still no load or movement. I realize the smart thing to do is remove the tranny and have it gone thru but like most men I prefer a more difficult and less costly approach to my vehicles. I am basically just shifting it by hand using the stub arm on the tranny. Doesn't seem to be too much external on the tranny to screw with. Any ideas on what to try or look at?
Has it been rebuilt or is it an older trans? An old used car salesman's trick is to drop in about a cup of brake fluid into the tranny to make it work. I've seen this trick do some interesting things to transmissions. My former father-in-law bought an old Falcon once and it wouldn't move in any gear but first. He added a cup of brake fluid to it and after a day of just moving it around the yard, the trans freed up and worked perfectly. Worked that way for 6 months and then gave up the ghost.
The tailshaft will spin in every range except Park. Try driving it (or running it on stands) to see if it shifts to 3rd gear (shifts twice) while in drive. If no shift or engine revs, it sounds like the reverse-high clutch is not engaging.
Lo (or 1) would not work as the band is LO/REV band. Lo works on his trans according to the thread originator.
Call this guy http://www.broaderperformance.com/ He knows his Ford transmissions. I'm not sure how far he is from you but when he was in Massachusetts I had him rebuild my cruise-O-matic and he does good work.
Tightening down the band has a method. Tighten it down to 10 ft.lbs of torque, then you back the screw 3 1/4 turns and tighten down the locknut. If you have 1 and no reverse, then the reverse/hi clutch is the next check. I believe there may be a pressure port for the rev/hi clutch apply. If so then you may want to hook up an oil pressure gauge and see if there is pressure when in Reverse.
Do you have vacuum set up - I just read something that if you don't have vacuum then reverse won't work??????
There are 2 vacuum lines going into a modulator on the back of the pan. But I thought that vacuum was for up/down shift. The modulator is leaking tranny fluid, maybe I'll replace that and see what I get.
A bad vacuum modulator won't cause reverse to not work. The clutches/bands that apply in reverse are the ,lo-reverse band and the reverse-high clutch. Have you driven it enough to know if you have high gear? If it, does then you problem will be with the lo-reverse band. Also the lo-reverse band can be malfunctioning and you will still have low gear as it's purpose is only to provide engine braking in manual low gear. HTH
Are you sure you have the tranny completely full. Reverse is the first gear to not work when fluid is low, in my experience. Joe
Had my trans sitting dry for a while after rebuild. Turns out that three valves in valve body were sticking when I took the valve body to the shop. Freed them up and like magic I now have reverse!!
Low will still work with a broken reverse band. However, you will have no engine braking in manual low. What I would do is start out in manual low (1), accelerate to 10 -15 mph and let up. If the rear band is working you will have engine braking like a stick transmission. If you just coast when you let up, the problem is the low band, or the rear servo. On a C4, to get reverse you apply the front clutch and the low/reverse band. The front clutch is also applied in high gear. If it were bad, the transmission would slip if you apply power without downshifting when in high gear.
You could at one time buy a reverse band that bolted together (trans does not have to come out} for a c-4. If that proves to be the problem.