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I have a TH350 with the lock up installed. Had a shop rebuild everything about 6 months ago.. .and install the lock up. Everything has been working like it should. Until this week.. went for a long highway drive... hit the toggle switch to turn on the lock up and watched the RPM drop down a bit like normal.

Then the trans started un locking and locking on its own... back and forth.. every min or so... while I held the gas steady.
What would cause this.. seems happen more once the trans is real hot.

 

some of the forum members are transmission Professionals..

until they have time to read todays posts..

i would like to know.. HOW hot is the transmission getting..

what kind of filter do you have in it.. the nylon screen filter. . or the far superior double sided dacron filter..

there are brass screen transmission filers..
there are nylon screen transmission filters..
there are single sided dacron filter..
there are double sided dacron filters...  used on buick applications.. but fit all TH350s..

PowerTorque - Automatic Transmission Filter Kit  Part # FK122 at Oreilly  

lack of fluid flow will make it do weird things..

you should gather the filter kit and some ATF...  you will get more of an answer soon..  

Why would you install a switch to start with? Just curious.

If it is unlocking/locking it could be caused by brake application, lock up switch in the valve body, cruise control, slight increase in elevation ( lowers vacuum ).  
Journeyman mechanic, transmission builder since 1963.

Are you saying you have the lockup solinoid hooked up to battery voltage through a toggle switch? No computer control?  

Correct....No computer control  

Correct....No computer control  

perhaps.  the oil pressure switch inside the transmission pan is failing...   leaking fluid so it closes then opens... locking and unlocking the torque converter..




or the oil pressure to this switch is not stable do to some other problem..

how about the internal ground connection..???  is the engine and transmission properly grounded to the body and battery negative???

i have a 2 minute test...  with a digital volt meter to verify proper grounding .. a great place to start..

digital volt meter .. set to 20 volts DC scale..   start engine.. turn on headlights..

1.  measure positive to negative battery posts..   14.1 to 14.8 volts is expected..

2. measure negative battery post to engine block...   0.04 volts is expected.

3. measure negative battery post to the body..     0.02 volts is expected.

4. measure engine block to body.. usually firewall... 0.02 volts is expected..

you might have to change the meter setting to 2 volts DC scale for tests 2, 3, 4

if you get more voltage than  the tiny readings on tests 2.3, 4,,  you have a bad ground between those parts.. fix it..



can you monitor the voltage going into the connector..  while the transmission is acting up???

you might want to change the pressure switch and the lock up solenoid on the valve body.. they are both cheep..  you might want to OHM or replace the wiring harness also.. the through the case connectors are usually under 6 bucks new..  depending on where you buy them..

the TCC when wired is usually wired through the second set of connectors on the brake light switch..  i have found these switches intermittent..  when really worn.. or when the brake pedal does not sit tight against the upper stop...

could the power source for your TCC be intermittent??? loose.. falling out of the fuse box...  

Dear HOg,
I just join this forum and see it very heplful. i do not know how to post this in the email for ur solution. If u can help me post this to auto expert to listen to my problem I will appreciate it.
I have SUV car 4runner toyota 4X4 1996 SR5 model with 64,000 miles. It is a 4 speed auto drive.It had a slight accident but has been fixed.All internal elctronics are working but my problem is on the transmission.My gear does not select or shift to higer gears ie gear 3 and 4.It enters drive when enagaged and when u accerelate,it shifts to the next gear  but on further acceleration, it gets stuck on that gear except u de-accelerate.I have changed the fluid oil with toyota T-IV yet the problem is persisting. This just started after the repair bicos before the accident, it was perfect and I was enjoining the vehicle. I do not have cash for change of transmission gear and would not want the mechanic to reap me off. I need ur solution. The reverse is perfect.  

I have this SUV car toyota 4runner 1996 SR5 model with 64,000 miles but it had an accident recently.It is an Auto transmission system with a 4 speed gear.However, the internal electronics are ok and functional and everyother things have been fixed.
The Problem i am having is that it does not shift to higher gears ie gear 3 and 4. It enters drive D smoothly and shift to gear 1 when u accelerate but further acceleration, it won't shift again. When u slow down, it comes to the lower gear, once u move further, it shifts to the next gear but would not select or shift to gear 3 and 4. Meanwhile, the auto transmission fluid has been changed completely with toyota type T-IV. This is my problem and would not want to loose the car just like that. I need ur solution.  

I have this SUV car toyota 4runner 1996 SR5 model with 64,000 miles but it had an accident recently.It is an Auto transmission system with a 4 speed gear.However, the internal electronics are ok and functional and everyother things have been fixed.
The Problem i am having is that it does not shift to higher gears ie gear 3 and 4. It enters drive D smoothly and shift to gear 1 when u accelerate but further acceleration, it won't shift again. When u slow down, it comes to the lower gear, once u move further, it shifts to the next gear but would not select or shift to gear 3 and 4. Meanwhile, the auto transmission fluid has been changed completely with toyota type T-IV. This is my problem and would not want to loose the car just like that. I know u may have some experts over there that specialised in auto transmission and who may be of help when this problem is told to them. At least they can offer solution that will guide me while I asked the local mechanic to work on it.  

Ambrose75:
Dear HOg,
I just join this forum and see it very heplful. i do not know how to post this in the email for ur solution. If u can help me post this to auto expert to listen to my problem I will appreciate it.
I have SUV car 4runner toyota 4X4 1996 SR5 model with 64,000 miles. It is a 4 speed auto drive.It had a slight accident but has been fixed.All internal elctronics are working but my problem is on the transmission.My gear does not select or shift to higer gears ie gear 3 and 4.It enters drive when enagaged and when u accerelate,it shifts to the next gear  but on further acceleration, it gets stuck on that gear except u de-accelerate.I have changed the fluid oil with toyota T-IV yet the problem is persisting. This just started after the repair bicos before the accident, it was perfect and I was enjoining the vehicle. I do not have cash for change of transmission gear and would not want the mechanic to reap me off. I need ur solution. The reverse is perfect.

Please post your question in a separate thread.
You will get much better results.  
Journeyman mechanic, transmission builder since 1963.

Ambrose75:
Dear HOg,
I just join this forum and see it very heplful. i do not know how to post this in the email for ur solution. If u can help me post this to auto expert to listen to my problem I will appreciate it.
I have SUV car 4runner toyota 4X4 1996 SR5 model with 64,000 miles. It is a 4 speed auto drive.It had a slight accident but has been fixed.All internal elctronics are working but my problem is on the transmission.My gear does not select or shift to higer gears ie gear 3 and 4.It enters drive when enagaged and when u accerelate,it shifts to the next gear  but on further acceleration, it gets stuck on that gear except u de-accelerate.I have changed the fluid oil with toyota T-IV yet the problem is persisting. This just started after the repair bicos before the accident, it was perfect and I was enjoining the vehicle. I do not have cash for change of transmission gear and would not want the mechanic to reap me off. I need ur solution. The reverse is perfect.

Again, post in one thread only.

Why would you trust someone on this or any board if you are afraid of being ripped off.

The majority of people answering questions here are mechanics, perhaps they will rip you off as well.  
Journeyman mechanic, transmission builder since 1963.

Ambrose75


to start a new thread... you have to log in.. and there is a menu above to pull down to select which forum to post in.. then you have to click GO on the right side of that pull down menu...


i would think... that since this 96 that you have is OBD2...     you will want to invest in an OBD2 scan tool....  the least expensive version that does most of what you need is the harbor freight 98614..  as most of the toyota  transmissions are computer controlled..  when they stop shifting. there will be a computer code.. usually in the P0700 to P0799 range or above P1000..

the ONLY way to know is by checking the codes...

many people invest 40 to 80 bucks in a code reader..  that will give you codes.. but won't help diagnose the problem...

a scan tool like the 98614 will not just let you access trouble codes.. but let you view the live sensor data so you can work with the proper manual section to trouble shoot what's going on..   this 120 or 130 dollar scan tool is a great investment..   it is a generic scan tool.. it does not do all the functions that a $5,000 dollar and up scan tool does..  but it will let you get most things solved..

toyota factory service manuals are available in print from Toyota parts departments...

used on line...

in electronic versions from alldatadiy.com or eautorepair.net    

these last two sources are the same that professional mechanics have on their work benches..

CODES first.,..  do not erase the code yet...

then into the manuals proper section for that code...

diagnose.. and that might also take a 25 buck digital volt meter..

if you want a car or truck that does not have any electronics on it..  or minimal.. you will have to get something older than 1980..

and no matter how easy it looks to fix cars..    its only easy watching me fix cars.. as i am fairly good at it..  but then i have been doing it for 30 years..  

For the tcc problem since you have it hooked up with a toggle switch then you can check the wiring without running the vehicle. Activate the solinoid and put a volt meter down by the connector and wiggle all the connections to see if you lose power.If that checks out then you need to drop the pan and check it all the way at the solinoid. If the electrical checks out ok then you know your dealing with a hydraulic issue. The most likely place for a pressure loss would be at the solenoid itself.A lot of times they just get loose.  

Ambrose75:  Since it was fine until the body work was done then it could very possibly be electrical. You need to scan the computer system for codes .If there is an electrical problem there should be a code. That is a very good transmission so an internal mechanical problem is not likely especially with that mileage. Bad shift solenoids are a common failure on those transmissions that would also create a code in the computer.