View Full Version : Transmission troubleshooting
Hay I need some serious help here!
I had a blown seal in my water pump and after running the engine way too hot the water drained out, and I limped it home, smoking and hissing. I saw a bubble coming out of the cylinder head, so... I replaced the head gasket, the valve cover gasket, the water pump/gasket, a couple of hoses and had to monkey the carburetor around to get it running again. After ALL of that I get it up and running, take it out on the road... and it WON'T shift into second! It's an automatic tranny in a '74 4 dr straight 6 250. Any help would be much appreciated.
make sure you didnt mess up any of the vacuum lines that run to the vacuum diaphram on the tranny.
Hi, thanks for the advice,
The only vaccum lines I thought might be switched caused the engine to not run when I switched them... The only thing I messed with that might affect the transmission is this linkage hooked up to the carb that gets pressed when the gas pedal is practically floored, some sort of overdrive I guess. It seems to switch the engine to a lower gear, but that's only on freeways and such, for normal street driving I don't think it even engages. I had 5 vac hoses and they all seem to be in the right spots, I have a Chilton manual, but the diagrams they have for the vaccum lines is incomplete, and their advice on the transmission is: don't mess with it. Any other ideas?
I'm not trying to insult you, but if you continue to run any car after loss of coolant there can be damage in many areas.
The transmission oil is cooled by the radiator. So expect that the trans has overheated as well.
The trans has no overdrive. The linkage to the carb kicks the trans backward one gear when invoked.
As K.M. said, there could be some damage internally on your trans. First thing is to check that your kickdown rod going to the trans is not forcing the lever on the trans to the rear. Some applications have a small spring siimiliar to a throttle return spring that holds the lever foward. Normally if the lever is rearward and engaging the kickdown valve, the trans will shift into second but not into third or drive position. My guess is that you fried the trans fluid and either the governor valve or the 1 to 2 shift valve in the valve body is stuck. Could be several other problems associated with the valve body also. Pull the dipstick on the tranny and see if the fluid is a nice redish color or a dark brown(burnt) color. Smell the fluid and see if it smells burned.
If it is burned then there is only one solution and that is to pull the tranny and rebuild it. Heat is the death of automatic transmissions, thats why a good aftermarket external cooler should be added for longevity. You could try changing the fluid and filter but my guess is it would not help in this case. Change out the vacum modulater valve, it may be the culprit if the fluid looks and smells ok. If you have ever fried something in a frying pan and left it there too long, you probably have had to scrape a nasty fried mess from the bottom, same thing happens to the trans fluid when it gets extremely hot as yours did. That crust is on the very intricate slide valves that control each gear change and they will not move. Also seals and clutches suffer the same fate in overheating. Sorry to make the bad diagnosis but have taken apart many C4's etc. that suffered the same fate and it is not a pretty sight, almost as bad as those trannys that have gone 100,000 miles without the fluid and filter being changed at regular intervals. Anyway let us know what you find out.
The tranny fluid is still a nice clear red and seems fine. So the "overdrive" is actually the kickdown rod? It seems to just spin on the bolt, not really interacting with the other part of the mechanism. Sorry, I'm just starting out as a junior grease monkey, and I don't know anything about transmissions. I'll try to be as descriptive as possible though. I realize I probably blew every seal in the engine, and I've almost replaced them all, but if the trans got cooked, is rebuilding the only way to free it up, or could I soak or spray it with something to try to loosen it? I have a mechanic friend whose been helping me along, but some things just stump us both. I actually got the carb working again by noticing the electric solenoid wasn't connecting to the accelerator plate... just luck and a little research. So the tranny was fine when I brought it home, could something have terribly wrong after it cooled? We could put a new one in, but I have a feeling it's something much simpler. I'm still at work now, but I'll do some more poking around after I get home, and keep you guys abreast of the situation. Oh yeah and thanks a whole ton for the suggestions... keep 'em comin'
Oh p.s. I can still manually shift into 1st and 2nd, but I'm assuming it's a bad idea to drive it, or is it?
Ok trouble, I checked the fluid while it was running instead of just checking it like my friend did, and found some pretty good aeration, light colored with bubbles... The Chilton manual says to have it professionaly inspected, but I know of only one place that won't ream me for bringing it in. Is is just a gasket problem perhaps? I could probably deal with that... or am I just going to have to let a professional take care of it? :( Thanks again!
Judging from what you've posted (no offense), you are best off having it professionally done. Automatic transmissions aren't for the novice. :(
Your transmission does not have an overdrive, it's a 3-spd.
When the engine overheated the engine went south too. Which can cause damage down the line. Bearings, lifters, seals, piston rings, and pistons all need good oil to keep the engine running. Your engine might have been tight when you tried to restart it and needed cooling down to loosen back up. Watch for engine problem signs in the next few weeks.
The trans got hot from the water heat and threw the torque converter. The flywheel put heat into the converter which is full of fluid and the heat hurt the fluid. If even for a short time it damaged the trans. Might just be a rubber seal in the trans leaking now, but the clutches and bands felt that heat to.
Have a pro check the trans.
Yeah thanks for the advice, I'll probably just do that. I'll be back when I've grown up a little. Thanks again.:cool:
Sorry we gave a tonge lashing of sorts. Stay with it, were not that bad! We could have reccomended you ride a horse into battle like they did in Afganhistan. Incredible to see that in this day and age.:D Good luck with the car.
So after all that wonderful and invaluable information (i'm not being sarcastic, i mean it) about my transmission it turns out Will was right the whole time. I just had no idea where to transmission vac lines were. I took it to a shop, called back 2 hrs later and the dude said he'd already fixed it! Now he says I need to do the brakes, but I knew that already. :D Anyway good lookin' out guys, and don't worry I can appreciate all your experience and I don't take anything personally, I have a pretty good sense of humor. Speaking of which I may post some pics of my beast in its different inCARnations :rolleyes: hehe sorry. Be Back soon!
Glad to hear you got it fixed, sometimes us old gear heads look at the worst of senarios when trying to diagnose a problem. We have seen most of the real grenaded trans and engines in our day so we sometimes tend to think of simple problems in a more sarcastic overview than most. I want to say "atta boy and good job" to Will for showing me a thing or two. Also four stars to you for taking it to a pro. The real lesson here is that you are never to old to learn and in your case, you have also learned. I bet you know where those vacumm lines go now, huh? Great job by all on this board in helping out. :) ;) :cool: