OK folks got a crazy one here, this is on a 1993 vette and has to do with the automatic transmission. When starting up the car and start driving all gears work as they should and a good lock in each gear. However after between 10 to 15 miles of driving in town stop and go when the overdrive locks into gear after 5 to 10 seconds it down shifts back to 4th gear. If you give it a little gas the Overdrive will kick back in but again will drop down to 4th when it gets to the new speed. None of the gears slip or shift crazy in any way. Could this be the TV cable out of adjustment or could it be electronic with the lock up? Oh one other thing in the morning when the outside temp is lower it takes longer for this to start than say in the afternoon when the temp is higher so the driving temp seems to have something to do with it in some degree. Any help or advice would be great, thanks.

 

That really sounds like a problem with lockup. A 4 speed transmission shifts three times because it starts off in first. But there "feels" like a 4th shift because the lockup clutch comes on.

Make sure you are shifting through all the gears when this happens, so we know if you are dealing with the lockup clutch or some other problem.

If you have three shifts from a stop and can pull it into 3rd and back to 4th and feel a solid engagement, then it is probably the lockup clutch.

 

PS: On the older units you can hold your foot steady on the gas at highway speed, and feather the brake just enough to turn the brake lights on, and you should see and feel the lockup clutch switch off. You will notice an increase in rpm when this happens.

If you then remove your foot from the brake, you should feel the clutch come back on an see the tach drop.

Edited to add:

PS: I don't think you have a TV cable in 93. We're talking about the 4L60E, right?

 

PSS: If it IS the lockup clutch, you're going to need a scanner that does data streaming.

Sure, you can point to point check the whole car and do test lights and 6 months worth of silliness, but the scanner will answer the big question very quickly: Is this in the controls, or inside the unit?

With a scanner you can see things like the TPS, which affect lockup. You can see if the computer is commanding the converter to lock, or unlock, depending on what it sees the various sensors on the car doing.

It is a good thing to have anyway? So, maybe this is your excuse to buy one!

Cha-ching!

 

Yes it is a 4L60E and it does have a TV cable, it is connected to the ASR that has the throttle cable and the cruse control cable. I have see the adjustment procedure for this car . Anyway here is the story. When I an going 45 MPH the RPM is 11 hundred, when the OD drops out the RPM goes up to around 13 hundred RPM, if I drop the gear down to drive the RPM goes up to around 15 hundred RPM, still the same thoughts? Thanks for you help

 

It can't be both. If it is the 700R4/4L60, it is a hydraulic unit and has the cable. It will run down the PS and come through the case near the dipstick.

The "E" in 4L60E stands for "Electronic." There is no cable on these. They have a large, round connector over the pan, behind the dipstick, on the passenger's side.

Of course I can't see it from here. I wish I could drive it, I could tell you in a second. But it sounds like the converter clutch is dropping out.

There are a number of reasons for this. One could be that it is functioning perfectly, and the computer is commanding it to turn off.

Reasons why it might do this are things like faulty sensors. The TPS, the brake light switch, etc.

If you want to try and confirm if it is the converter clutch, driving steady at highway speed, hold the throttle in the same place, then take your other foot and feather the brake pedal. You should see the clutch unlock when the brake is touched, and lock back when you remove your foot from the pedal.

If you don't see this, and you are solidly in gear (no flaring, slips, etc.) it's the tcc clutch.

Do you have a scanner that data streams? This would be wildly handy. Otherwise you are kind of chasing your tail. The first thing you need to know is: Does the clutch unlock because the computer is commanding it to unlock?

If so, then you're looking at sensors on the engine.

If not, then you're looking at the trans, the solenoid, etc.

 

PS: One thing you should definitely do is pull codes.

 

No, 93 was the last year for the 4L60(not E)/700R4.

In 93, they started to call the trans a "4l60"

 

 

I had a similar issue on my 85, which is essentially the same transmission that you have. You can test this theory of the torque converter clutch by unplugging the electrical harness as it goes into the transmission. This turns off the ability to activate the torque converter clutch. this will not hurt your car to run around with the torque converter clutch disengaged. However, you should not drive for an extended period of time on a highway at high-speed's in this configuration. This can hurt your transmission. if you were driving in stop and go traffic on the way to work you could do that all day long. The best way to handle it is to simply drive for a short period of time to confirm the condition. Don't leave it in this configuration for very long.

if you have positive identified the torque converter clutch mechanism as the issue, the next thing to check is the torque converter clutch filter inside the valve body of your transmission. If this filter becomes plugged up, it can mess with the engagement and disengagement of the torque converter clutch. The plugged filter effectively obstructs the pressure circuit. google this filter and location.

The next thing to check would be the actual torque converter clutch solenoid which is an inexpensive part accessible as soon as you remove the transmission oil pan. swap it out for a new one.

note that swapping out the solenoid is easier then checking the filter, you may try that first. But a filter can be cleaned for free. That's why I put it first. But it is a lot more involved to get to the filter iirc.

first things first, unplug that electrical harness on the outside of your transmission, on my 85 is located on the driver side it's a bit tricky to reach if you have big hands, but it can be done, I used a long flat head screwdriver to help me gently manipulate The retainer tabs on the plug.

 

At 45 in forth you are at threshold for TCC so ECM commands TCC on. The engine load is too high because engine "lugs" and ECM turns it off. That is not unusual in a 92-93 with 2.59 and there wasn't a revised chip to correct it.(All about fuel economy) If that is your only problem: don't drive in a way engine is lugging at 1100-1300 rpm.

 

Maybe I'm not understanding here.

I think what you are saying is the torque converter is not locking up. Is that correct?

Fourth gear in the 700r4 is overdrive. You have 1st, 2nd, 3rd, OD and then TC lockup. So I just want to make sure we are all on the same page.

 

The op's post is very confusing. He states the tranny goes into overdrive, then drops down to 4th gear (which is overdrive). He must mean lockup.

 

Going off post #5 in OD or 4th gear with 2.59 axle when TCC engages RPM will be around 1100 at 45 mph. ECM turns TCC on and off depending on MPH and engine load. TCC or Torque Converter Clutch will turn and off and can be confused for transmission shifting. The 700r4 shifts 3 times to get to overdrive, but many times torque converter clutch engagement is felt. RPMs drop giving the impression of a 4th shift IF OP can drive 45 mph in D or 3rd gear with no adverse concerns occurring I doubt there is a problem with transmission. Changing prom to one calibrated with higher engine rpm/mph engagement could correct it but would reduce fuel economy.

 

Or keep it in 3rd for city driving.