transmission problem

[92128 4Runner]

Hi, I have a '94 4Runner with an automatic transmission. The problem is that it will not change into the high gear on the freeway until the engine reaches a certain temp. This usually takes around 20 minutes or so of driving at 60mph in the slow lane. Once it shifts, its fine. But until it does, the RPMs are around 3500 at 60 mph and it sounds as if the engine is over-revving. I even took it in to a transmission shop about four yrs ago. B&M TRANSMISSIONS IN NW AUSTIN, TEXAS (HWY 183 LOCATION). They told me it needed to be rebuilt. So I dropped $1800 on a rebuild only to have the problem continue. WTF!? The guy at the shop explained this by saying that it was "supposed to do that". Apparently it won't shift until the engine temp reaches a certain point (his explanantion) So why didn't he tell me that before I paid him nearly two grand for a rebuild? I figure the answer to that is obvious. Like many car mechanics, he is dishonest and/or underqualified. Either way, I was out $1800 and still have a truck that doesn't shift correctly. And since I don't have a legal team and have yet to find a mechanic I can trust, I've pretty much given up and just dealt with the problem. So if anybody on here has any insight to this problem I'd love to hear it.

 

[ALLEGRO]

If it makes you feel any better, I have had several suv's that acted that way in cold weather. In fact, I think that my 07 Limited may too be that way in the coldest of weather.

Good Luck

 

[92128 4Runner]

Yep

Thanks for the reply. Unfortunately, it acts this way even in the insanely hot Texas weather.

 

[ALLEGRO]

Surely someone can chime in and help you to solve this situation.

Good Luck

 

[fourwd1]

It doesn't matter what the climate is, the engine must be up to operating temp before the OD will kick in. I think 20 min would be a bit long even when if it was 20* outside.
It may be that the temp sensor used by the ECM is bad (not the same one the temp gauge uses). If it consistantly kicks in at the same temp as observed on the gauge (whatever it is), it may be that the trans is doing it's job, it's just not being told to do it at the right time (temp).

 

[hix]

It is an EPA thing. A cold engine runs rich thereby polluting more when cold,the EPA mandated the manufacturers engines warm up quicker so one way to do that is lock overdrive out to keep the rpms up thereby warming the engine up faster. Toyota is not the only ones that do that. Another thing they did was make the coolant ports in the cylinder head smaller to warm the engine up quicker. The old style heads are popular with rock crawlers/racers because they run cooler as the cylinder head is is the hottest part of the engine and the weakest link. A stuck open thermostat or one that is opening too soon will also cause delayed overdrive shift.

 

[4x4runrfan]

I had the same problem. I changed the thermostat to a 90o one and it solved the problem. I wanted to say thanks HIX for the help. I'm new with my 95 V6 runner, now it runs great and it cost me $8.00. Thanks again.

 

[80truckluv]

Hi, im new to this site and new to toyota as well. Im having similar trouble with my transmission. when my 91 4runner is cold and i go above 50 it hovers around 3000 to 3500rpm and consistently stays there. also when driving at these speeds the overdrive lite starts flashing. i also noticed that my overdrive button does not work anymore. but once the tranny is hot it will engage into overdrive but all the while flashing the overdrive lite on and off. im on my way to get a new T-stat for it now so i hope that helps but i was wondering if anyone has similar problems or can explain mine. thanks!

 

[4runnerkucool]

I had exactly same problem but as soon I replaced the thermostat, the od/ gear shift normal. Like 4x4runrfan said too.

 

[90toytruck.]

Hi, im new to this site and new to toyota as well. Im having similar trouble with my transmission. when my 91 4runner is cold and i go above 50 it hovers around 3000 to 3500rpm and consistently stays there. also when driving at these speeds the overdrive lite starts flashing. i also noticed that my overdrive button does not work anymore. but once the tranny is hot it will engage into overdrive but all the while flashing the overdrive lite on and off. im on my way to get a new T-stat for it now so i hope that helps but i was wondering if anyone has similar problems or can explain mine. thanks!

welcome to the forums:cheers:

 

[80truckluv]

Thank you all for the warm welcome to the site! ok, so i went down yesterday and bought a new thermostat and pulled Nancy (my truck) into my garage to swap it out. im used to small block chevys so finding the T-stat location took me a few seconds to find it. so i pulled the top and bottom bolts out just fine but when i went to start on the middle bolt i found that the previous owner had stripped it out completely! in the proses of putting the other 2 bolts back in i discovered that the radiator had a pinhole in the top tank that looks like it has been j.b. welded... needless to say it still leaks. so thats what i get to do today... try to pull out the rad and get that darn bolt out. this is going to be way more work than i expected but hopefully once i get the t-stat in it will fix my problem... thanks again everyone!

 

[dakine]

Hi, I have a '94 4Runner with an automatic transmission. The problem is that it will not change into the high gear on the freeway until the engine reaches a certain temp. This usually takes around 20 minutes or so of driving at 60mph in the slow lane. Once it shifts, its fine. But until it does, the RPMs are around 3500 at 60 mph and it sounds as if the engine is over-revving.

I'm having this same problem, going in to pick up a Temperature Sensor and thermostat tommorow. Hopefully that will fix it right up. Also going to check my Shift Linkage just to ensure everything is as it should be.

 

[red90]

Its doing whats its supposed to do. It has to reach thermostat opening temp before overdrive will engage. If a new thermostat doesn't fix the time problem then it has a bad splice in the main wiring harness located behind the power steering pump. Toyota had a recall out concerning high resistance in this splice.

 

[dakine]

Its doing whats its supposed to do. It has to reach thermostat opening temp before overdrive will engage. If a new thermostat doesn't fix the time problem then it has a bad splice in the main wiring harness located behind the power steering pump. Toyota had a recall out concerning high resistance in this splice.

Yea, no-go on fixing this issue with the temp sensors or switch. Just won't go into 4th gear. It shifted very few times into 4th over this past week, but always for a very short time, and almost immediately went back into 3rd.

Gonna try disconnecting the harness from the tranny next to do the manual shift test to isolate the ECM. Anyone ever try flashing the ECM to reset the factory settings?

Update: Resistances and voltages are all correct according to the manuals. Going to try a new ECM as soon as it arrives, after that it's on to a solenoid replacement.

 

[dakine]

So, after replacement of the temperature switch, temperature sender, testing all the resistance and voltage readings, replacing the ECM, it all came down to a $12.99 thermostat valve. I found that the PO had modified the thermostat to allow unrestricted flow, which never allowed the engine to reach the temperature required for the ECM to tell the transmission it could shift to OD. New Thermostat, shifted right into OD. Thanks PO. :gun5:

 

[Classic Style]

Thermostat range

So what is the range thermostat you guys are swapping out to? I've got this same "problem" going on in my '95, and hate it cause I coast down a long grade every night and the engine cools off by the time I get to the bottom, causing it to downshift yet again!

I saw 4x4runrfan said a "90o", meaning 190F?

Thanks much, and great forum!

**Edit** I think I found my answer. It looks like Autozone has a 195F alternate tstat. Cheers!

 

[dwride]

I have had similar issues with my 93 V6 SR5 since last fall -- wouldn't shift into O/D until I had driven it about 10 minutes. I had a tranny flush with no improvement. Then I had a tranny shop do a quick scan and they said it didn't bring up any fault codes so there was no obvious problem. That was at the end of September -- and I only bought the thing in August!

Lately (January), it hasn't been shifting into O/D on my usual 10-15 commute, but I remember driving for 30 minutes last month (which is rare) and I noticed it had finally shifted. I was reading this forum about temperature impact and it seems like the onset of winter temperatures could be the explanation for the issue worsening. I am considering replacing the thermostat; however, I have also read that replacement on the V6 models is a bit more hassle, because the thermostat is on the bottom hose.

So I decided to call the tranny shop back and ask them about this as a possible solution. They said that it is definitely a common problem on all sorts of vehicles (not just 4Runners), but unlikely in my case because my car does start blowing hot air out the vents like it should and the temp gauge does appear to be registering temperature changes, so the thermostat seems to be working. He said not to waste my time with the thermostat replacement, and that the next step to diagnosing the problem would be to start testing the wiring harness.

I am tempted to just replace the thermostat anyways, but I don't have a garage to tinker around in and it's -30 degrees outside, so I would be taking it to a shop for the job (rather than freezing my fingers off on my driveway). I don't want to drop another $100 in vain, so please give me your opinion whether the thermostat could be the culprit.

Much appreciated.

 

[run4yota]

i had the same problem.. the thermo was replaced, and no dice.. i tried the sensor.. checked out fine.. no dice

i turned my heater on in my truck one day, and i dont know what happened but now it works fine.. ever since then. i think it has something to do with the valve going to the heater core bypassing the thermo and putting hot coolant thru the section where all the temp guages are.

jus my 2cents, good luck! hope you get it solved

 

[dwride]

I took it to the garage and asked them to replace the thermostat. They misunderstood the instructions and tried testing it instead with an infrared sensor. They said that it reached operating temperature, and they didn't change the thermostat because they didn't see a problem. They later realized that they'd done the wrong thing and didn't charge me, but I still don't know if changing the thermostat would fix the problem.

I have been watching the temp gauge and it seems like shifting starts when the needle is just about to touch the temperature symbol in the middle of the gauge. I swear this is a temperature issue, but it seems so weird that the temp has to reach so high before it will shift.

I tried covering the grill with a 16-inch piece of cardboard to see if I could push the temperature up faster when driving, and it still takes 10 minutes on a day that is near freezing. Something must be wrong, because I can't imagine that the truck was designed to behave this way. Perhaps I really do need to get the wiring harness tested.

Does anyone know what the min temperature reading has to be before the truck is supposed to start shifting into O/D?

 

[jdemetrician]

Where did you guys happen to buy your new t-stats? I've been looking to do a similar upgrade to my 92' and want to put a 90 degree t-stat in.