Overdrive issue. Tstat, shift solenoid, trans temp sensor???? - Page 2 - Toyota 4Runner Forum

Bad Luck · 01-15-2020, 12:49 PM

Quote:

Originally Posted by Tampa_T4R

Maybe I don't know what I'm looking for here, I've owned 24 cars and 22 of them have been manual, so I'm not too familiar with the TC.

What should I feel?

When the torque converter locks up you will see an rpm drop similar to the drop you would see during a shift. So if your torque converter is locking up you'll see an rpm drop from 1st to 2nd, 2nd to 3rd, and then 3rd to torque converter lockup with overdrive off and the gear selector in drive.

Tampa_T4R · 01-15-2020, 01:05 PM

Quote:

Originally Posted by Bad Luck

When the torque converter locks up you will see an rpm drop similar to the drop you would see during a shift. So if your torque converter is locking up you'll see an rpm drop from 1st to 2nd, 2nd to 3rd, and then 3rd to torque converter lockup with overdrive off and the gear selector in drive.

With OD off:

So after it goes into 3rd, I should see ANOTHER drop in RPM, almost like it goes into another gear? This will tell me my TC is working properly or not working properly?
If it's not working properly and I'm not throwing a code, would it be likely that the TC is screwed?

phattyduck · 01-15-2020, 01:37 PM

Quote:

Originally Posted by Tampa_T4R

With OD off:

So after it goes into 3rd, I should see ANOTHER drop in RPM, almost like it goes into another gear? This will tell me my TC is working properly or not working properly?
If it's not working properly and I'm not throwing a code, would it be likely that the TC is screwed?

When the torque converter is unlocked, RPMs will go up and down slightly with mild movements of the throttle. Kinda like a slightly slipping clutch.

When the torque converter is locked, RPMs will stay the same for changing throttle position (but will unlock if you apply too much throttle).

The torque converter will only lock in the highest available gear (3rd of OD is off starting around 45mph, 4th/OD if OD is on starting around 50 mph). And it does look/feel kinda like a shift to another gear if you watch the tach.

-Charlie

Tampa_T4R · 01-15-2020, 02:31 PM

Quote:

Originally Posted by phattyduck

When the torque converter is unlocked, RPMs will go up and down slightly with mild movements of the throttle. Kinda like a slightly slipping clutch.

When the torque converter is locked, RPMs will stay the same for changing throttle position (but will unlock if you apply too much throttle).

The torque converter will only lock in the highest available gear (3rd of OD is off starting around 45mph, 4th/OD if OD is on starting around 50 mph). And it does look/feel kinda like a shift to another gear if you watch the tach.

-Charlie

If the bold above is true, I think my TC is locking just fine. If I have OD off and in 3rd at ~60mph and i lightly increase throttle, RPMs will increase without any slipping to higher RPM. If i'm in '2' in 2nd gear, and I lightly increase throttle, I do see the slight slipping of RPM before it changes to 3rd.

I don't however, remember the "change of gears" feeling when the TC locks after getting to 3rd with OD off.

This guy had exactly the same issue as me and fixed it with a new ECU: Shifts in-n-out of OverDrive... Look at post #7 for solution
Can't there be more than just torque converter lockup that would cause my issue because of a bad ECU?

Thanks guys, I really appreciate you time.

Bad Luck · 01-15-2020, 03:30 PM

Quote:

Originally Posted by Tampa_T4R

With OD off:

So after it goes into 3rd, I should see ANOTHER drop in RPM, almost like it goes into another gear? This will tell me my TC is working properly or not working properly?
If it's not working properly and I'm not throwing a code, would it be likely that the TC is screwed?

You should see another drop in rpms when the torque converter locks up. If you don't see another drop, then the torque converter isn't locking which could be a failing torque converter or a weak solenoid.

phattyduck · 01-15-2020, 03:35 PM

I went back and watched the video again...

After you finish accelerating to 70 and start to cruise, the RPMs drop to ~2400 (4th, torque converter unlocked), then drop right after that to ~2100 (4th, torque converter locked).

It looks like your truck is hunting between 3rd and 4th/OD, but each time the RPMs drop (back into 4th/OD), you can see the torque converter lock.

It does sound like it could be a control issue (ECU)... Though I still like to think of those problems as rare. Any chance the truck sat unused for long periods of time? That can cause capacitors to go bad...

-Charlie

Tampa_T4R · 01-15-2020, 04:03 PM

Quote:

Originally Posted by phattyduck

I went back and watched the video again...

After you finish accelerating to 70 and start to cruise, the RPMs drop to ~2400 (4th, torque converter unlocked), then drop right after that to ~2100 (4th, torque converter locked).

It looks like your truck is hunting between 3rd and 4th/OD, but each time the RPMs drop (back into 4th/OD), you can see the torque converter lock.

It does sound like it could be a control issue (ECU)... Though I still like to think of those problems as rare. Any chance the truck sat unused for long periods of time? That can cause capacitors to go bad...

-Charlie

Regarding the bold above...Actually, yes. He has had it sitting for about 5 months. He would start it every once it a while to keep the battery charged, but he has only put 26k miles on it the last 6 years.

Well, at least that's good the TC is locking correctly.
It was mentioned that 96-98 models do not throw a code for by transmission temperature sensors, correct? Maybe that's my issue, the ECU thinks that the trans is too cold for OD engagement? Does it work like that?

Edit: You're right, I just watched the video again too and it does have the extra little drop once it goes into OD/4, good catch!

thegipper · 01-15-2020, 04:47 PM

ECU can certainly go bad but it is somewhat rare.

A couple years ago I was getting a random pending misfire code even though the engine was running perfectly fine. While I was trying to diagnose a different issue with my transmission, I swapped in a different ECU I got from a junk yard. While it didn't fix my transmission issue, the code has never came back.

Down by the Water · 01-15-2020, 07:11 PM

Hey,
I'm the guy in the post referenced above. The ECU was bad. Replacing it with a used one fixed the shifting issue. A used one should run you around $85. Swapping it out is easy (though I had a shop do it, long story.) It never threw any codes related to this problem.

Tampa_T4R · 01-15-2020, 07:59 PM

Well, looks like my trans fluid is actually fine after all. Blue shop towel had me thinking it was grey -_-

Took a 20 mile drive home today at 70 MPH... Overdrive worked perfectly the whole way. Has to be ECU acting up.

Tampa_T4R · 01-15-2020, 08:07 PM

Trans fluid, the dark parts are from the top of the stick

phattyduck · 01-16-2020, 01:19 PM

That fluid does need a change, but it probably isn't an emergency. It should look cherry red with no hints of brown when it is good shape.

I actually drove the 4Runner this morning and checks - those are the exact RPMs/speeds for what I described above (4th locked, 3rd, 4 unlocked, 4 locked).

I have a '97 4WD ecu in the garage, but I'm not sure if it is compatible with a '96...

-Charlie

Tampa_T4R · 01-16-2020, 02:55 PM

Quote:

Originally Posted by phattyduck

That fluid does need a change, but it probably isn't an emergency. It should look cherry red with no hints of brown when it is good shape.

I actually drove the 4Runner this morning and checks - those are the exact RPMs/speeds for what I described above (4th locked, 3rd, 4 unlocked, 4 locked).

I have a '97 4WD ecu in the garage, but I'm not sure if it is compatible with a '96...

-Charlie

NICE.

Yeah, I plan on doing a trans flush with new filter eventually. I'll probably just start with a drain and fill for now. The main thing is it looks like I don't have a huge issue there and no strawberry milkshake is a plus

I'll do some research on the ECU and see if it will work.

Thanks again Charlie

EDIT: oh, also it once again did not have the overdrive issue this morning driving 20 miles to work. I hit 80 at one point and it stayed in OD. I didn't know 3rd gens have magical healing powers?

Tampa_T4R · 02-05-2020, 08:11 PM

She’s fixed! Turns out it was in fact the ECU! No more p0505 code and no more overdrive issue! Thanks for all your help fellas! Hopefully this helps someone down the road!

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