1988 V6 auto having a hard time getting into OD! HELP!
 

Hi guys, Ive been away for a while! I finally got my fiberglass bed installed, no paint yet but it already looks freaking sweet compared to the rust holes. Anyway, my truck is having a hell of a hard time getting into over drive lately. Today I went at lunch to get it inspected 8 miles away from work at 60 mph on a 4 lane highway it never went into OD, I kept hitting the button and hitting the ECT button but nothing. On the way back from the inspection station it finally dropped in.. it happened again on my way home from work, this time it never did go in! I really don’t like running my engine hard, its on the original HG with 160,000 on the clock! Is the OD actuated at a certain speed or RPM or what? Is there a valve that could be sticking or needs to be replaced? The OD used to drop in with NO problem at all. Could the semi synthetic Mobile ATF be to blame? I did a full 16 quart flush, I cant imagine that would be to blame? Most of the miles on my truck are highway and back road so the OD goes in and out ALOT with the 3.0 as you can imagine. Any help would be much appreciated! Thanks again, Matt :treadmill I feel like I am always getting ahead with this damn truck then falling back to another issue, it may be time to part ways and buy a newer Taco.... :soap:

I had a thermostat stick open on mine and it would not warm up enough on the highway to go into overdrive. It worked fine in town when there was not as much airflow through the radiator. I have a 95 4Runner but I think its the same setup. Might want to check that.

Yup what ThomasJ said. exactly

it did it again this morning
 

It happened again today, it never did go in! What thermostat is it? Where is it located???!!! Do I have to drop the pan to get to it? Thanks a million, Matt

I've heard of this problem before too, and the recommended solution above.

To find the thermostat follow the lower radiator hose, it's in that housing (I think, someone smarter than me will have to verify).

The thermostat is relatively cheap to replace. I have a Toyota OEM one that I was going to replace this summer but never got around to it.

so the thermostat is
 

So the thermostat is in line on my trans cooler lines? Does it have an electronic sensor that tells the trans to shift into OD or what???? Does anyone have a picture of what we are talking about? Are you pretty sure this would correct it? Toyota PN? Ill call the stealership and order the part today if this is what I need!

The themostat is in the housing that runs from the lower radiator hose. It's on the engine. If you're good with tools you don't have to remove anything but the housing. How does you're engine temp gauge look when it's not shifting into OD? Is it in the middle?
Also I've heard of the clutch convertor going out after a tranny flush.

Well, usually the engine temp...
 

The engine temp usually goes right up to the middle mark.. I always thought OD was based on speed or RPM not temp! So the thermostat that I need is the transmission thermostat? I guess thats the place to start. I cant imagine that my trans is chewed up, the truck has never been used for towing and has always had the ATF changed and all... Once OD drops in the first time its OK its just that first time around its taking for ever, it does seem to be a temp thing, when it was 100 out it droped in OK but now that its cool out side.. Does any one know the part number or should I call the dealer and tell them I need a transmission fluid thermostat for an 88 V6 auto? Thanks again I really appreciate it, Matt

OK you need some help.

The computer reads the engine temp (radiator antifreeze) and does two things when it is cold. 1) won't let the engine rev too high (ie it will short shift, saving wear & tear from reving too high when cold) 2) will prevent the transmission from shifting into OD. allowing the engine to ward up quicker (from higher rpms)

The fix to your problem is that you radiator thermostat is stuck open (has nothing to do with the transmission) This is preventing the engine from warming up quickly, therefore preventing the transmission from shifting into overdrive when it is cold.

On the 3.0 I believe the thermostat is in the upper rad hose where it enters the timing belt cover. (someone can correct me on the location if I am wrong)

Matt

No the transmission doesn't have a thermostat, it is the rad thermostat, based on engine temp, not tranny temp.

That makes some sense
 

I really allways thoght that OD was based on RPM like a true 4th gear! So I need to try a new thermostat.. I am pretty sure that I had the stealership replace that when they did my H2O pump and timing belt job last year.. Its worth a shot! Thanks for the help, Matt

Thermostat is in the LOWER radiator hose hosing. You can change this yourself if you want to.
Drop the skidplate, Get you a 12mm long socket (or 14mm can't remmember). Drain radiator. Remove lower radiator hose from engine housing. Unbolt 3 bolts, off comes housing( You have to work around belts). Out comes thermostat. Put new one in + gasket, little notch valve thing facing 12 o'clock (north, up). Reverse order for installation, oh torque nuts to 11-15 ft pounds.
What Celica said about no OD shift with cold engine is correct. Engine must be warm enough to shift into OD.

Thanks for all the help!
 

Thanks again for the help, Ive changed many engine thermos.. I was confused! I thought the trans had its own in line on the trans cooler lines :laugh: .. Would you buy a Napa thermo or stick with Toyota, the stealership wants $24 for the therm where Napa wants $7 and they are both 180degree. CarQuest has them in stock for $9 as well, Ill never use another AutoZone part on anything I own as long as I live! :shocked: