Automatic Transmission Won't Shift Right

I have a 92 four runner and the automatic transmission wont shift the gears right. I can not get it into overdrive?? It has a hard time shifting up to any speed and then I read about the speed sensor on the back of the transmission. WOuld this be bad and cause the shifting not to work?? I have replaced the transmission twice but used the speed sensor off the old one as I did not have on on the used transmission. Help as I am getting fed up and the Toyota shop just says to replace another transmission but I have and same result. I just caught on by reading postings that it may be the speed sensor.

I will take any suggestions

Thanks

Nipp :shakehead

It could be your engine thermostat is staying open and your engine is not getting completely to operating temperature. The shifting of the transmission is engine-temperature related.

This answer comes from personal experience with exactly the same problem. It had the Toyota mechanics stumped for a couple years.

A water passage is probably blocked. There is a cross-over water passage, that has the coolant temp sensors mounted in it. This passage is in a reomvable casting, mounted on top of the engine, next to the firewall. It is not easy to get to. You will see it in the repair manual, when you look for the coolant temp sensors.

This passage gets plugged with crystalized coolant deposits, and sharply restricts coolant flow. It also traps air, the cause of the crystalized coolant. Note - The red Toyota coolant is what crystalizes, the green stuff does not have this problem.

You may want to purchase a new casting and gaskets, as the original may be eroded to badly to repair. If you dont get e new casting, at least get new gaskets. Remove the casting, and scrape out the deposits. Replace the casting and gasket.

Check the sensors for proper function before re-installing, or replace them with new ones.

Bleed as much air as possible, any way you can, from the coolant system. Air gets trapped in the casting, and does not conduct heat to the sensors. Design error on Toyota's part.

I have a 92 four runner and the automatic transmission wont shift the gears right. I can not get it into overdrive?? It has ...


****DID YOU EVER FIND OUT WHAT THE PROBLEM WAS... I have similar problems

If your engine is heating up, the gage on your dash shows proper temperature, and your heater seems to be working fine, then you probably do not have a thermostat problem.

One of the ways I found to get the over drive (OD) to engage, was to pull over and turn off the engine, after it was all warmed up. Let the sensors soak up the heat, for a minute, then continue on my way. The OD would then work properly. After about 5 or 10 miles, the OD would start acting up again. This was the BIG clue that suggested the temp sensor was not staying hot.

I checked the function of the sensors, and they were working properly; but I still replaced them. This did NOT solve the problem. While I had the sensors out, I could see that the passage through the casting was blocked. I pulled off the casting, and found it was plugged with crystallized (red) coolant. After cleaning out the junk, I found that the casting had been eroded by 300,000 miles of water going through it; so I replaced the casting too.

With the new casting, and the air bled from the system, the OD works great.!

Extra info: The temp sensor for the Electronic Controlled Transmission (ECT), controls the OD and the lock-up torque converter. Your transmission will operate like a standard 3 speed tranny, until that temp sensor (switch) tells the ECT the engine is hot. Then both the OD and lock-up converter will work properly. This is normal, and helps the engine reach operating temp more quickly.

The casting traps air in it because it is the highest point in the engine block, the air will migrate to that point. With air in the casting, the sensors do not have good contact with the coolant, and therefore thinks the engine is not up to optimum temp for OD. If the coolant is moving properly through the casting, it will push the air out. If the passage is plugged with junk, the coolant will not flow well enough to push the air out, and the sensor will not switch over. The sensor for your dash gage is not a switch, and it may show the engine temp is OK, even if the ECT temp sensor (switch) is not up to proper temp.

The red coolant that Toyota (and Chevy) use, will create crystals where there is trapped air, for long periods of time. This is a problem for the DexCool types of coolant. The green coolant does not do this. The crud starts to build up in the casting, because it tends to trap air. This slows the flow, causing more air to get trapped, and more crud to build up. Eventually there is a shield of air and crud around the sensors. When this happens, the temp sensor (switch) does not tell the ECT that the engine is warm.

Recommendation: Remove and clean out the casting that houses the sensors (or replace it). Switch to the green coolant, and bleed all air out of the coolant system. This is something to check on the 3.0 V6 (3VZE), even if you don't have trouble yet.

If you have air "trapped" in those it will be at the top not at the manifold. The flow through the lines will force the air out, the real problem if there is air at the sensos is the flow.

The highest point is actually the heater hose that traverses the firewall. This is a great spot to bleed the air out of the coolant system. I installed a “flush kit” fitting in this location for air bleeding purposes.

You are correct about the air rising to the highest point, and the coolant flow keeping the bubbles out of the manifold passages, AS LONG AS THE ENGINE IS RUNNING.

The problem starts when the engine is shut off, and the suspended bubbles in the coolant flowing through the block, rise to the highest point in the block. That high point is the sensor casting attached to the top/back of the manifold. You now have a situation where there is air, and hot coolant. As the engine cools down the crystallization begins at the edge of the fluid meniscus, where it meets the trapped air. Every time the engine is shut down and cools off, the crud grows deeper. Eventually, it blocks the passage enough to prevent the high flow volumes from clearing out the air bubbles. This bubble will stay in place with the engine running. As the restriction gets worse, the bubble gets bigger, and it takes longer and longer for the sensor (switch) to engage the OD of the tranny. At some point the system just does not work properly, and OD becomes a memory.

What? I have to start calling myself Chemist Brian or Mod Brian now?

:)

In a "farm boys" word no geek speak, check your cooling system for proper operation. There are many post in this forum describing success stories of replacing the thermostat to cure transmission shifting calamities.
However it mainly concerns shifting points and overdrive engagement.
What you described could be purely a transmission issue. :crying:

Engineer Brian,
Quite sesquipedalian, but you might want to take a closer look at the 1992 V6 system.

Check out the "Water By-Pass Outlet"
first page or pg 9 of the pdf (FSM pg: EG2-FSM) Figure PO8444 second to last on this page
ie 1993 FSM:
http://personal.utulsa.edu/~nathan-buchanan/93fsm/engine/68cylinder.pdf

I tried burping my hoses but found that, even though it looks like air SHOULD be trapped there it was not.

231489 miles and I have never had a "crystal" problem. :lol2:
In fact I just rebuilt the motor a year ago with 221K and there was no blockage at all.
Good day

From 4Wheel
"In a "farm boys" word no geek speak, check your cooling system for proper operation. There are many post in this forum describing success stories of replacing the thermostat to cure transmission shifting calamities.
However it mainly concerns shifting points and overdrive engagement.
What you described could be purely a transmission issue."

The original post clearly states that he has replaced the transmission, twice; so I ruled out that option. Another post suggested replacing the thermostat, and the dealer probably skinned him for that before replacing the transmission also. That ruled out that option also.

As for "geek speak", the only word past 5th grade was "meniscus". I hope I was not writing at to high a level for anyone.

From 4Wheel
"Engineer Brian,
Quite sesquipedalian, but you might want to take a closer look at the 1992 V6 system. Check out the "Water By-Pass Outlet"
first page or pg 9 of the pdf (FSM pg: EG2-FSM) Figure PO8444 second to last on this page ie 1993 FSM: http://personal.utulsa.edu/~nathan-b...68cylinder.pdf";

The pdf listed shows the "Water By-Pass Outlet". That is the part I was referring to as the "sensor block". The Water By-Pass Outlet shown in the pdf seems to show a water outlet in the middle, between the sensors. This is different than my '88 3VZE, and is a great idea, as it would prevent air from being trapped in there.

From 4Wheel
"I tried burping my hoses but found that, even though it looks like air SHOULD be trapped there it was not.

231489 miles and I have never had a "crystal" problem.
In fact I just rebuilt the motor a year ago with 221K and there was no blockage at all.
Good day"

I am glad to hear Toyota made some improvements on the later 3VZE engine and systems. This is one of the big reasons I own Toyotas; they are always making improvements.

I believe the '88 4Runner was the first to have the 3VZE, and it definitely needed to have the Water By-Pass Outlet redesigned. If Toyota was able to make changes to the system, to prevent air traps, there would be no crystal growth and buildup. It has been well documented that the "Red" coolant has a problem with growing crystals along the edge of the fluid, where it meets any trapped air.

No Worries.

It could be that the OD solenoid in the tranny is bad.
Or it could be the trannies ECM.

If I remember correctly the OD solenoid is external, so you could apply +12V to it manually, and you should be able to hear/feel it click.

If I don't remember correctly, please disregard. :icon16:

Check your shift solenoids.