devestator_x

iTrader: (1)

Ok, so my trans just started to jump out of lockup. It was jumping back and forth for about a day, then did it much less frequently while staying out of lockup 90% of the time. Right now as it is, it only locks up after driving for a few miles at the same speed.

So looking at the wiring diagrams, looks like there are 3 main things that can be faulty and tell the clutch not to lock. The ECU, the brake switch, and the clutch itself.

How difficult is it to diagnose which part is faulty? I have no CEL codes, so I assume the ECU is working correctly.

I have very basic hand tools and basic car knowledge, which is why Im posting here for help.

framedoctor

This is a very simple system. You should see a plug on the trans with 3 wires in a white 4 wire plug. There should be a purple wire that shows bat+ with ign on, and goes dead with the brake applied. That's why the converter unlocks when you hit the brakes. The tan/black wire is from the ECU and turns the solenoid on. This wire also goes to the ALDL. The last wire is green/white and tells the ECU when the trans is in 4th gear.
The first thing I'd check to see if you have power on the purple wire. If you do, then make a jumper to ground the tan/blk wire in the ALDL. With the engine off and the key on, ground the tan/blk and you should be able to hear the TCC solenoid open and close. If not, you can test drive it and see if it locks the converter. My money would be that you have a faulty solenoid. They are pretty cheap and aren't difficult to replace, but you do need to drop the pan. Also a good time to replace the fluid and filter.

devestator_x

iTrader: (1)

Thanks for that...going to try to get under there tonight. Hoping its something I can actually repair myself, the solonoid would be a little beyond my capabilities (non-level driveway and not having anything proper to lift the car with) Hoping that grounding the wire creates a temporary solution.

It did lock up for a good chunk of the ride to work this morning though and only unlocked when I had to slow down for traffic, so thats an encouraging sign.

What i really need to do is data log the whole thing and see everything thats going on.

fireburdluvr85

check what Ur CTS is reading. Every yr mine reads -40 in summer and iI lose my tcc til I change my CTS. That's if by grounding the aldl u can get it to lock to verify the solenoid is good.

vetteoz

iTrader: (13)

Could be as simple as a bad connection on a worn out brake switch that drops out the power to the solenoid intermittently from vibration
or even the brake switch itself simply being out of adjustment

devestator_x

iTrader: (1)

I appreciate all the advise guys. I have rigged up a toggle switch inside the car to eliminate the ECU from the equation by grounding the tan wire at the aldl. 30 test runs if the key on but car not running and 30 distinct clicks from the solenoid, so I think the solenoid is good.

I havent had the opportunity to test drive the car with the switch yet, but now I know if it drops out this time around, fault will most likely be in the brake switch. If it doesnt, then its most likely an ECU issue.

Will update further after more driving has been done, like after Mondays commute to and from work.

I will say that on Friday I had to report to jury duty which required a 23 mile highway drive there and 23 miles back at 70+mph. Once I got up to cruising speed, it did lock and stayed locked until I exited the highway, so it's intermittent at best, which is obviously one of the hardest things to diagnose, because the results are never consistent.

devestator_x

iTrader: (1)

Ok, just got back from a quick trip to the gas station. So the solenoid is working flawlessly. When the switch is on, it locks up and stays locked the entire time (even in 3rd gear) Turn off the switch and poof, no more lock up. So the problem lies either in the ecu itself or wire leading from the ecu to the junction before the aldl (since we now know that the circuit from the aldl to the solenoid is good)

How do I go about solving this? Once again I dont have any fancy equipment. If I had a data logger, this would be much simpler.

devestator_x

iTrader: (1)

I think I narrowed down the problem this morning. The car was acting normal, even without using the switch. I noticed the speedometer wasnt jumping around like it normally does (the cable is a bit sticky sometimes) well half way to work, it starts sticking again and suddenly the ecu stops locking up the tcc. The switch took care of lockup, but the point is the ecu stopped doing it on its own.

Is it safe to say if I replace/relube the speedo cable, the ecu will lock up the tcc again? It is an original 1983 mechanical speedo, but maybe the vehicle speed sensor reads off the speedo?

vetteoz

iTrader: (13)

The vehicle speed is probably the most important input to the ECM for when it activates the TCC.
If that input is flaky ,would certainly account for your problem

IIRC ,
on cable speedo cars ,the VSS input to the ECM comes from the buffer box in the cluster

devestator_x

iTrader: (1)

Thanks Vetteoz. I removed the upper speedo cable and found it to be pretty tacky inside. I need to buy some proper grease to the job correctly, but for now some wd40 did clean out the insides a bit. I also learned the easy and the hard way to do this. Unfortunately I chose the hard way... by disconnecting both ends and pulling the entire housing out of the car. What a bear to get back up into the dash board.

This coming weekend I will pull the inner cable out again and properly grease it. I need to pull the cluster out and clean the connectors again anyway. Yanking it out tonight brought back an old issue from last year where turning on the lights kills all the gauges. Luckily I know the fix for this, just ran out of time and daylight to fix it this evening.

Will update again after tomorrows test drives to and from work to see if even that tiny bit of lubrication from the wd40 helped at all.

devestator_x

iTrader: (1)

Well, even though WD40 isnt the best lubricant in the world, it was enough to free up that sticking cable. Everything is working smoothly and how it should. Ran 12 miles through stop and go traffic to work, quick 5 mile trip to the bank and back, then 12 miles home and not once did I need to use my make shift TCC switch. I am going to leave it in until the weekend because we all know as soon as I pull it out, thats when it will start malfunctioning again... murphys law.

So, I'd like to thank everyone that gave advise on how to narrow down the issue and give me a few ideas to steer me in the correct direction. Never would have guessed the speedo cable could cause the ecu to get confused and in turn not operate the transmission correctly. Hopefully someone else who may have this issue will see this thread and save themselves some headache trying to find the gremlin.