I have this weird problem with my TH350 transmission. At higher speeds and after a little driving I just lose the driving power to the wheels. All of a sudden the engine RPM's go up and the vehicle slows down. There just no power going to the rear wheels. When you let it slow down and hit the accelerator again it usually 'picks' up again. This is very annoying, specially with traffic behind you. This only happends after I have been driving it for a while. Not when I just leave home. It usually happends at speeds above 50 mph. Other than this the transmission is fine. The car drives great but every now and then, without warning the above issue suddenly happends. What could this be? I still need to renew the ATF and transmission filter. I have no idea when the previous owner did this the last time. Could a clogged filter result in issues like this? I hope you guys can help me out.
you could try a filter but i think the seals are worn out had a similar problem with a older trans in a regal it would shift back into drive if i downshifted manually into second then wind out back to drive did this for an hour to get back home
It's unlikely, but you could have a stator problem in the torque converter. If the stator is locked up when it should be freewheeling, the top speed of the car will be restricted to 40-65 MPH, the engine will run hot and gas mileage will be bad.
Well, the top speed isn't restricted. You can go over 60 MPH. It just seems to happen at higher speeds, highway speeds mostly. Driving around town is no problem. Alec296, what kind of seals are you talking about? I'm no too familliar with transmission tech, so I don't really know where these seals are supposed to be and what their purpose is. Can they be renewed in your own garage/driveway with the transmission still installed on the car? Oh one more thing, a while back I checked the ATF level. The engine was not running and cold (had been sitting for a few days). I know these are not the correct conditions for doing this, but it turned out that there was more ATF in it than should be. It was over the full mark. And this was with a cold tranny, so I figured that readings with a hot tranny will be even more when the ATF expands. I was kinda in a hurry and I thought it couldn't hurt that bad, because the previous owner must have driven it like this. But since this problem occurs I'm thinking this might have something to do with it. Just brainstormin though. So, could a high ATF level (and higher hydraulic pressure probably) cause weird problems like this? I think I'm going to drop the pan one of these days. Just to have some clues maybe in what condition this tranny is.
It is completely normal for the fluid level to read over full with the engine off and cold. Some of the fluid drains back from the converter into the pan when the engine is shut off. If you start the engine and go through the gears and then check the fluid with the engine running, it will read low until the trans heats up and the fluid expands. It sounds as if your transmission is slipping and it probably needs to be rebuilt. You can try a fluid and filter change. At this point it can't hurt.
foward clutch apply seal or direct drum clutch seal it holds the fluid in the chamber to engage the clutch if you rebuild you could take out the wave plates and put in flat steels with a really good shift kit it will bark the tires pretty hard trans will need to come out and will be a mess if you dont drain completely best if someone with the right tools did it as the seals do cut easily and there are a lot of springs in the clutch drums it can be done in you garage but i would try to get knowledgeable help you will have to pull most of the gearset and planetary sets out you will need a lot of clean space
Thanks guys for the advice. But I sure hope it doesn't need a complete rebuild ray: Right now I'm thinking of a vacuum leak. There might be a leak at the vacuum modulator. I hope this is the case. That sure is an easier and cheaper fix than a complete rebuild (wich I can't really do myself, so I would need to take it to a transmission shop). I'll keep you guys posted. Gonna check that vacuum modulator first.
The good news will be that a rebuild on a THM400 or 350 doesn't cost 2000.00 like an overdrive trans does-- more like 600-700 or so...
Im pretty sure the characteristics of a leaky modulator are late, harsh shifts. :Smarty: But basically can be just any weird shifting patter. I am going to have to agree with most others on this, your clutches are probably slipping, probably varnished from being driven too hard by someone sometime, or no fluid changing.
Yeah, it might need a rebuild. I kinda get that feeling too. But I haven't checked anything yet. I didn't have any time yet. But I will check the vacuum modulator first. Just to see if this is the troublemaker, or just to eliminate the possibility that this is the troublemaker. One more thing guys, something that crossed my mind. I'm no expert on these tranny issues, so forgive me for saying anything stupid, but I have a posi rear axle, could it be that the fluid in the differential is too low? Somehow I can hardly believe that. But I don't know. Just brainstorming here.
Thinking more and more about it, I think that rear axle thing I mentioned, can't be the cause. It will always transfer some power to the wheels, even if the differential is slipping. I did some more learning on the TH350 transmission, and 2 new possible 'suspects' are: - the governor - the detent cable Kinda looking for all possible causes of this issue, things that not nessecarily point in the direction of a complete rebuild :laugh:
try adjusting the detent cable. I had to do this with my 89 chevy suburban (TH 700R4 overdrive automatic,similar cable ) it made a world of differende in how it shifted
the cable is not the same thing on the overdrive trans is their any reason to believe the cable is out of adjustment? some of the regals and centurys had the cable go to the firewall/to the pedal like the skylarks. not really adjustable but you could put fishing lead sinkers on it one at a time to bring it up some i think your going to find the inevitable , i have dealt with these many times from my cars and fleet work. you could price rebuild kits online you could dump brake fluid in there and if it gets better then you need a trans but you will need one either way as it will mess up seals after they expand
the detent cable is not the same between a regular trans, and an OD ?? don't they operate in the same way? they both control shift points?
you can run a 350 trans without a detent since it can control shifts by vacuum modulator the overdrives if ran without a cable will not be able to control the pressures and will burn itself out withing a few hundred miles, the cable controls everything and without it the trans will be junk, even at idle the cable determines the pressures in the trans a 350 trans can last for many years without a detent cable and still be drivable without destroying itself
alec296 has it right. The cable on a TH350 is a detent cable. Often called a downshift, kickdown, or passing gear cable. It only controls detent operation. When the linkage pulls the cable far enough, the cable begins to move a valve in the transmission that when it moves, it allows oil to act on the shift valves and move them to the downshifted position thereby forcing a downshift if other criteria allow it. Modulator and governor pressure. On a 200-4R or 700-R4 the cable is NOT a detent cable. It is a throttle valve cable, or more commonly called a TV cable. It controls the line pressure of the transmission (controlled by a modulater on a TH350 or 400). If the cable is setup wrong, or not connected, it causes low line pressure which quickly results in clutch failure.
Well, today I checked some stuff and went for a test drive. Turns out I don't even have a third gear! It just doesn't make the 2-3 shift. You can feel the 1-2 shift, but after that it won't shift again. You can gain speed and you can feel the car has enough power left to keep pulling at any speed. But the rpm's are just kinda high. And I can't feel or hear the tranny make that 2-3 shift. Before I went for a test drive I did check the vacuum modulator and adjusted the detent cable. There were no vacuum leaks. I couldn't see, feel or hear anything. The rubber pieces that connect to the modulator at the tranny, and on the other end to the manifold look okay. About the detent cable (mine is located at the acclerator), I grasped that plastic cable sleeve with a plier and pulled it towards me (towards the back of the car). And let it go, it got retracted (wich should be good). And I floored the accelator. Is this the correct method? I quess it could be those seals Alec296 was talking about. You meant the seals from the pumps stator support right? To be honest I have no idea where to find these and what the exactly do. I got this out of that book (TH350 Handbook by Ron Sessions).
Yeah, the governor is still something I need to check. So far it's been untouched. I quess I have to take it out, and see if the weights function as they are supposed to. And see if the valve is moving. It might be stuck. Thanks guys for thinking with me here, preciate it! :beer
I had my vacation, and I've been out of town. But today I finally had time again to look at that damn tranny. I dropped the pan now and i noticed a hole. It looks like something exploded in there or something. I was thinking this is really bad and that this transmission really is junk. A guy that I know had a TH350 BOP transmission laying around, so I went to his place to go and see it and maybe taking it home with me. At his place we turned it over and took the pan off so we could look inside. And just as I wanted to show him where this hole is located on mine, I saw this one has the same thing!! At the same spots! I took photo's of my tranny so y'all can look at it and maybe tell me if this is normal: http://i14.tinypic.com/66c5a1c.jpg http://i14.tinypic.com/4kuu98y.jpg http://i16.tinypic.com/4zeguaw.jpg And here's the other smaller hole, that other transmission had that hole too: http://i14.tinypic.com/6cy16i0.jpg What you can see behind that big hole is the direct-clutch drum right? I hope someone can tell me if this is normal or not. The edges are kinda rough, so it looks like the pieces of cast iron blasted out of there or something. o No: But I find it so weird that this other tranny had the exact same holes at the same spots...
