Hi all,
It took us 9 months to figure out why my car would not shift into 4th gear anymore, and it was having a problem with it not shifting until 4000 rpm's which is high. Thought I'd share what my issue was as well as ask some TC lockup question as I don't think that part is fixed yet.
Long story short: the problem was my 700R4 throttle valve which you can get to by dropping the transmission pan, you can get to the outside part, the part the shows when its pushed out, but when you press gas pedal and your mechanism that pushes the throttle valve IN, you can't easily get to without removing the I dont want you call it, i'm calling it assembly at the moment, anyways we had a transmission shop rebuild the the stuck throttle valve with I think new spring and whatever else, anyways just happy yesterday it shifted early and normal and even into 4th gear.
TC LOCKUP: I don't think this part is working though, and unsure how much I will worry about it, but I don't think TC lockup is working anymore. So I wont be getting that last 10% of fuel economy, rpm drop. At the moment just happy to have 4th gear again. As part of our troubleshooting we replaced the TC Solonoid as well as a 4th gear pressure switch, but think we didn't do it correctly. We just replaced the TC solonoid and wired it like it was, and replaced what was a 1 prong 4th gear pressure switch with another 1 prong. I saw we probably didn't install it right cuz per some youtube video's I believe it was saying we needed to change the 4th pressure switch and/or solonoid to a 2 wire, 2 prong. But I dunno.

 

A one wire 4th gear applied pressure switch will work depending on how the rest of the circuit is wired.
Basically, it'll be: Ignition power to brake light switch (normally closed) to a vacuum switch (but not always) then to the transmission. Entering the transmission you pick up one leg of the TCC solenoid and the other leg lands on the 4th gear switch.
So, the TCC will be engaged when no brake is applied, the vacuum switch is satisfied (set at a point where that switch contacts breaks on vacuum drop) and your in 4th.
There are other ways as well.

 

Thanks for your reply @skinny z . I took it out for a test drive today. I honestly can't say for sure whether the TC lockup is working or not. Before I could tell rather easily when it went into Lockup in 4th gear. Being that I can't tell. I'm leaning towards its not working. Regardless if its working or not, i'm very happy overall for it to be shifting "normal" again and at a minimum have my 4th gear back.

 

I took a video to capture the speed & rpm's on the interstate. I don't recall what it should be, but now at 80mph it was right around 2500 rpm's. It has the 9bolt 3:27 rear gear ratio. I also noted around 64mph it was 1900 rpm's. I used to know what it should be, but don't remember now.

 

It sucked not having 4th gear, in 3rd gear on the interstate max speed i felt I could go crusing wise was about 65mph and it would be near 3000 rpms. And I didn't drive it alot like this. It pretty much sat until we finally got it figured out and fixed.

 

What all do you have for components in the TCC circuit?
4th gear applied switch in the valve body is noted.
​​​​​​OEM has the brake light switch. Later models used the ECM to control the clutch. Earlier models used a vacuum switch.
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Oh gosh I really don't know. My dad did the replacing of the TC Solonoid and 4th gear pressure switch. We noted I didn't have a 1st 2nd or 3rd gear pressure switches that some do. Just noted my 4th gear pressure switch was a 1 prong, so we decided to replace it with a 1 prong (although video we saw said something about we would want to replace it with a 2 prong) but we ignored that and also the last half of the video cuz the other half was how to wire it to your brake pedal, and we sorta felt we didn't need to do all of that. Sadly now after saying this, wish we had left the solonoid alone, although from looks of it, it looks roughly the same to me as the one we replaced it with. I only saw 2 wires coming out from the TC solonoid. Afraid that's about extent to what i know. I sorta trusted my dad with the wiring of it. He did wire it incorrectly we believe the first time and used a different ground which i noticed it made it feel like the TC was locked nearly all of the time which wasn't good, like it bogged down in 2nd gear instead of what i call "free revving" you know how when its in gear but you can still tap the gas pedal and it kinda lets it free rev a little bit before going back into gear?(anyways i hope so).. anyhow, so i had my dad rewire the TC solonoid w/the "extra" ground wire (which is the way it was wired from the factory) that was there before which we believed maybe ran to the brake pedal somehow or something like that. Sorry I have no good response in regards to ECM, vacuum etc.

 

@skinny z What you said in a earlier post sounded right on to me(on your 1st post here), like that was or is how mine should be wired. I used to be able to tell the TC lockup happening very clearly say a year ago when things ran right. You would feel the TC lockup happen around 40mph+ after it was in 4th gear and then you would feel it lock up and to me felt like a "5TH GEAR". If you can relate to that. However now, so far I can only tell 4 gears, and so far not noticing anything locking or unlocking up, so I'm having a hard time telling if it is locked up or not. I lean towards its not just cuz i can't tell, and before I could. Knock on wood if car continues to do well, i'll be testing with gas milage and seeing if I still get 15/19 city/hwy gas milage which is what I used to get. If I see a 10% drop 13.5/17 mpg then that will be a tell to me that it's not working.

 

I do want to also note when my GTA transmission started acting up 9 months ago, that the first thing that stopped worked was the TC lockup. It had a day or 2 of it not staying engaged or seemed to be confused or to me just seemed like it was having a hard time staying engaged, like it kept letting up. Then shortly after it started doing the weird thing of not shifting until 4000 rpms... and then it stopped shifting into 4th gear at all, so was running just first 3 gears for near 9 months now. First thing I tried was trans fluid additives to try to get something to unstick (the throttle valve), tried some type of pink fluid stuf didnt work, then tried lucas, that didnt work either, then tried another called TRANS-X per my transmission guy, but he said it probably wont work cuz of the other additives i already added, and the LUCAS stuff was think like MOLASSES purple fluid. Anyways so tried trans fluid additives.... then we checked governor, governor was fine, then replaced TC solonoid and 4th gear switch which all of this did nothing that we can tell. Then we had throttle valve rebuilt and now it seems fixed, but I don't think TC lockup is working.

 

A simple test for TCC operation involves cruising speeds and OD. If the TCC is engaged, slight application of the throttle should see the tach stay stable. If it rises 300 RPM or so without a downshift then it's a safe bet the clutch isn't working. If gently accelerating causes only a steady rise in revs, without that initial RPM increase, then the clutch is probably in play.
If you're clever enough with wiring, (or your Dad), you can cut a manual on/off switch into the TCC circuit. If can then easily observe any differences in operation with the switch on or off.
By the way, the brake light switch is an essential part of the circuit. Otherwise weird things happen not unlike slowing down in a stick shift car in high gear. It's better that the clutch disengages on brake apply.
One other thing, having the clutch working as it should will make for a cooler running transmission. You won't have that 5-10% slip action all the time. Heat is the transmissions worst enemy.

 

I think you can test for this with the brake pedal as well. As above, operating temp, steady highway speed on flat ground. Keep your right foot steady on the throttle, holding your cruising speed. Very lightly apply the brakes with your left foot, and watch the tach. You should see the rpm increase a few hundred rpm as the TCC disengages. This is a light brake application, enough to illuminate your brake lights is all that is needed. You don't have to fully apply or stab the brakes. Lift your left foot off of the brake, and TCC should engage again, and the rpms should drop slightly.

 

@DynoDave43 Thanks! I will try that next time! @skinny z Roger on the manual switch but hope that won't be needed. In some ways just giving it a little gas at 30,35,40ish mph it sorta feels correct to me in I see the rpms go up a little bit then kinda get locked down(I just sorta don't know if its just going to 4th, or if its the TC lockingup) . I saw rpm's as low as 1100 rpms which to me looked very low probably 30-35mph. I like Dave's idea, i'm thinking that test should work.

 

I thought I read that you had not considered the brake switch as part of the circuit?
Maybe I misread that.
Be sure to report back on your testing results.

 

For some reason this website does not want to let me copy & paste(today?), what is the deal w/that?!?! Anyways.. apparently... my TC LOCKUP WORKS!!! I got up to speed around 40mph where I felt my tc lockup might be engaged and each time i hit the brakes my rpm's would shoot up about 200-300 rpm's. Thanks @DynoDave43 & @skinny z !!

 

I do have alot more question's lol but perhaps a new thread for each subject. I'm very greatful for this website as it helped me 11 years ago figure out that the problem I was having was my fuel injectors. Replacing them resolved the issue(s) I was having. Thanks to @ASE doc .

 

I tried to do the brake test on the 2012 kia soul, and evidentally the TC lockup works differently on it cuz rpm's didn't rise when i applied the brake.

 

True. Newer vehicles have more complex methods of achieving the same thing.