vegascoug

1990 4Runner 3.0 V6 Auto Trans

I started to notice an issue with my O/D a while back when my speedo cable snapped, my O/D light was blinking all the time, and once or twice I lost O/D. I fixed the cable a while ago and now all is back and working again and has been for a long time, but every once in a while I will lose overdrive randomly.

I have read a lot about thermostat problems, so I am wondering if that is my problem. Thinking about it I cannot remember exactly but I think most of my issues have been in the cold (or late at night when it's cooler).

This weekend for example I had issue going up in the mountains in the snow. When the weather got cooler as I was driving down the highway, my O/D suddenly turned off without any reason. Cruising at 70 MPH it randomly downshifted and wouldn't come back. If I click the O/D on/off button, nothing happens, shift into N and back, nothing. After a few minutes it goes back in to O/D all on it's own. I noticed this happening mostly when I was "cruising" or going downhill...basically when the truck wasn't working hard at all.

The reason I am posting is to find out if the experts on here think this could be related to the thermostat or something more serious? I am curious about the thermostat issue because it doesn't happen starting up, only after it's been running for a while and while I have driven several miles. If my thermo was bad, could I be running too cold for it? I have absolutely no other shifting problems. Shifts in and out of gear, reverse, between gears, etc. all fine. The ECT button or whatever it's called that changes the shift point works great, and when O/D is working I can turn it on and off with the button on the shift.

Any thoughts? If so I'd love to hear them.

Mike

mt_goat

Sounds kind of like the t-stat could be stuck/broken open, but that would also make it take longer to warm up and the heater wouldn't work as good. Do you notice the temp gauge dropping at all? Not sure if it would or not, the dang temp gauges on these trucks are basicly an idiot light with a needle instead of a light bulb.

Is the OD light still blinking?

vegascoug

No, the OD light stopped blinking when I replaced the speedo cable about a year ago.

I have noticed that it's tough to start in the cold, almost like it's flooding. Turns over and over some mornings, and when I let it sit in the snow covered parking lot for a day, it took me forever to get it started. When it finally did start, you could smell and hear it was running rich, really rough, and when it eventually burns off that extra fuel it runs fine. Could a t-stat be causing this issue too? I am wondering how that works, but if the t-stat is telling the system it's too cold, it might be supplying too much fuel, but I am not a mechanic, nor do I play one on TV

mt_goat

You and this guy seem to share the same starting problem: https://www.yotatech.com/forums/f116/cold-start-injector-103220/

I kind of doubt the tranny problem is related to the starting problem but stranger things have happened.

Back to the tranny problem, any other signs of the coolant temps being too low? Heater working good? Temp gauge needle slightly down? Try feeling the radiator hoses for a while after a cold start. The upper hose should warm up much faster and get much hotter than the lower until the t-stat opens. If your t-stat is not working and open all the time they would be closer to the same temp. If your t-stat is working the lower hose will have a more sudden warming when the t-stat starts to open.

DCS

I'm having exactly the same OD problem on exactly the same vehicle: 1990 4runner 3.0 auto.

I'm not having any engine starting problems.

My tranny works fine in all gears, except when it shifts into OD it's a little "rough". The other gears shift smooth. ODkind of clunks into gear. It will jump right out of OD when I get to a hill, but usually seems kind of reluctant to clunk back into OD once I've passed over the hill.

Then, after 30 minutes or so of driving, it doesn't want to go into OD at all, even if I let-off the accelerator on a downslope at 60mph.

I've tried clicking in and out of OD with the button on the shifter. Every once in a while, that will work, but usually not.

ECT button has no effect on this OD problem, but seems to work fine otherwise.

I just replaced my WP and flushed my cooling system by detaching the lower hose and putting a water stream into the radiator. I could actually see the thermostat woking, It would open and dump hot water into my big catchpan, then close after taking a drink of cold water from the radiator. I watched it cycle for 10 minutes while running the heater, to totally flush my system.

My heater works fine; will roast you out of the car if you leave it on hot.

So I logged on today to ask about this, and found this thread with search.

vegascoug - did you ever get to the bottom of it?

mtn goat: any other ideas?

I know that OD is unavailable until the engine warms up, but I don't think temperature is my problem.

I just checked my tranny fluid level (20 minute warm-up, then park on level surface, shift through gears a few times, then put in park and check fluid with engine running). I drained a half pint out, then checked it again. Drove some more, checked it again. My fluid level is just above the lower hot mark when properly checked. I drove some more: it shifts fine but is still just a bit rough when clunking into OD. Same as before. No help from draining the little bit of fluid.

Is OD governed in any way by vacuum? Or is engine temp the only factor other than speed and perceived load?

Is my tranny dying? Lord, I hope not. I am definitely not in the "get a new tranny" mode with this vehicle!

Any and all help appreciated!!

DS

mt_goat

Might also check the kick down cable for proper adjustment. Its that cable that goes from the tranny to the throttle body.

http://personal.utulsa.edu/~nathan-b...autotrans.html