I have an 84 Trans Am with a 700R4. I was driving up a hill (not too steep) and noticed that the transmission would shift up to overdrive instead of staying in 3rd gear. I was only going about 30-40mph. As soon as it shifted into overdrive, the car seemed like it only had a tiny 4 cylinder motor and was struggling to go uphill. I think the RPM was pretty low at about 1500rpm. If I manually shifted it into "D", it would regain its power. If I shifted back to "OD", it went right back into overdrive and crawled up the hill again. I don't remember it ever doing this.

It was pretty hot out today (got up to 95*F) and since my fan sensor kicks in pretty late, my temperature gauge was about a line above 220 most of the time. Could this have anything to do with the weird transmission behavior? Did the transmission overheat?

 

To be on the safe side, always bring it back a gear. Check the TV cable to see if it has loosened, reset the TV cable so that it is tight or within a 1/16" of being tight at WOT.

 

Pardon the ignorance, but how and where do I adjust the TV cable? Is there a proper procedure? Ive never done this before so I dont know.

 

I thought I heard this was a common problem and barring any actual cable problems and such you may be able to fix the condition with the TransGO shift improver kit.

 

I think it was just the transmission overheating. I went up the same hill today and it didnt have the problem of the other day. Today the temperature was cooler and I the temp gauge was under 220 when I went up the hill.

I guess its time to install the 200F-on 185F-off fan switch I bought to prevent this from ever happening again. If that doesnt work, maybe an external transmission cooler will do the job.

 

I found out today that it is actually the torque converter that is locking up when this happens. A second after the transmission shifts to 3rd or 4th (not sure which one), the torque converter locks up and the tach goes down by about 200 RPM. I kept pressing and releasing the brake while this was happening and the torque converter kept unlocking and locking accordingly.

It have also noticed this problem when driving on level ground going about 30-40mph when the engine temp is above 220F. This problem only happens when the engine gets above 220F after idling at a stop light for a long time (I think the temp gauge is fairly accurate since I have a 180F thermostat and the temp gauge normally stays at what appears to be 180F). Since it only happens when the engine is hot, it leads me to believe that the transmission is overheating too.

The weirdest thing is that the torque converter NEVER locks up during normal conditions like it should. Apparently it only locks when the transmission is very hot. What would cause it to only lock during these conditions? If the torque converter locked like it should maybe I wouldnt get 14mpg highway like I currently do

 

Is it the original transmission?

 

Im not 100% sure but I think so (I got this car May 2006). I had all the transmission seals replaced last summer since it was leaking fluid constantly and also had new 3-4 frictions put in. The guy at AAMCO told me the trasmission was in good condition (other than the worn 3-4 frictions) and that it should last a long time if not abused, which I dont considering I rarely get the engine above 3K rpm) The engine just turned 96K miles.

 

Some 700R4s have a temperature switch to force the TCC to lock if the fluid temperature gets too hot. One for an 84 wouldn't have had this though. If the transmission has been changed though, then anything is possible.

 

Hmm... how can I check if the transmission is original? Where is the code imprinted on it?

The first owner had it until 2002 and it had about 86K miles. If the transmission was changed it must have been when he had it. The second owner only put about 200 miles on it from Feb 06-May 06.

 

give me the 9 digit number on the passenger side of your trans just above the pan. (E.G. 9TAY0M12N)

 

4YG160BT (only 8 digits) That was the number above the tab on the passenger side of the pan towards the back.

I also found these numbers on the transmission casing:
MD8 (near the front passenger side of the transmission casing)
T4 (on the transmission casing above the middle of the pan)

 

Definately check your TV cable adjustment. That would cause the 3-4 shift when going uphill. I just got one with a huge ordeal over that cable. I was adjusting it wrong. Trans was shifting bad, so I got a Transgo shift kit, and Super Rebuild kit. Rebuilt the trans. Burned up 3-4 clutches after about 100 miles because I did the same thing wrong with the TV cable. Rebuilt trans again, this time I used the Beast shell, 13 vane pump, and the springs for the 3-4 apply piston. Trans still shifting a bit funny, so after a few hours of reading I have the TV cable adjusted correctly and the car drives like a dream.

http://www.tvmadeez.com/article/index.html

That explains the whole principle behind the TV valve and it's operation of basicly the entire transmission.

 

Thanks TZFBird, that site seems very useful. I'll follow the directions there to adjust the TV cable.

I no longer think it is shifting from 3rd to 4th. I found out yesterday that the torque converter was locking and I think thats what was happening all along. Would a bad TV cable adjustment cause the torque converter to lock when it shouldnt?

 

4YG160BT

4 = 1984
YG = 700R4
160 = day of year built
BT = second shift

 

Thanks for decoding the number. Looks like the transmission could be original from the number then.

Would it be possible for a temperature switch to have been retrofitted at some point to make it work like later 700R4s that came with one originally? Having a temperature switch would explain why it is locking the torque converter, but since the transmission is from 1984, it may not even have a temperature switch which would bring me back to square one.

 

It's possible. Maybe it's worth dropping the pan and having a look.

 

I checked out the TV cable adjustment and the cable slider (the plastic tube that is pushed toward the transmission) was all the way toward the mounting bracket. I pushed the D shaped button and pushed the cable slider just in case there was a millimeter or two left. Then I rotated the throttle linkage to WOT and I heard clicks. The cable slider is now out about 1 centimeter where it was completely flush with the mounting bracket before. I took the car out for a drive and noticed that the shifts are smoother and quicker. I'm going to be making a 40 mile drive tonight so Ill see what exactly changed.

 

that sounds like your TV cable was definitely out of adjustment.

 

do you think a bad TV cable adjustment would prevent the torque converter from locking up? Now that I adjusted it, it would be nice if I finally get lockup.

 

The converter lockup is controlled by the ECM. You'd have to start by looking into either the signal going to the solenoid, or checking the solenoid to see if it is still good. No idea how you would check it though.

 

To check to see if your lockup works, make the following switch and verify that the convertor locks.

https://www.thirdgen.org/torqueswitch

 

Just a FYI. Some early year 700R4s you could NOT leave the plug on the trans unplugged. Later ones you can as a way to make the TCC not operate. Unfortunately I dont have a TCC pressure switch/TCC circuit diagram on hand. All my stuff is 85-86 and 87-up. Just in those years though was a handfull of wiring routes. Some do lockup in 3rd and in 4th, others jus in 4th. If you dropped the pan, got a good picture of the wiring and the color bands off the pressure switches, I might be able to help out on at least which setup you might have. Maybe someone else already knows. But 84 is prior to any that Ive experienced.

 

I am able to make the TCC lock up by using a switch on the ALDL port so that verifies the solenoid is working. I guess the problem lies in the wiring between the ECM and the solenoid. I'll have to check that. If the wire from the ECM were OK then the problem would be the ECM right?

 

it is possible the ECM is bad but for simplicity you could just manually lock the converter via the ALDL switch.

 

That switch is pretty sick! I have a stick car so I cant try it, but if I had an auto, I would be leaving the switch on the whole trip on the highway. You will get better fuel economy, and it will be easier to hold a speed.

 

I drove about 50 miles yesterday and the TCC never locked while driving on the freeway. I hooked up a light bulb between connector F of the ALDL port and 12V(ign) at the fuse panel to see when the TCC locked. I went off the freeway for bit and the engine temperature went above 220F after being stopped at a light. When I sped up, the TCC locked. It only locked for less than 30 seconds because when I sped up the air flow cooled the radiator and the temp went back down. That was the only time during the whole trip that it locked.

 

There would be no point. The ECM would already be locking up the TCC, so the switch would be redundant.

 

Thats the problem, though. The ECM never locks it as it should.

 

Yes, you need to look into that, then.