Transmission Shifting Issues

Hey all, first post here since I'm experiencing an issue with my transmission. My motor and trans have 276k miles in my '03 Prerunner and I believe they're original.

I noticed my coolant temps were starting to be higher than normal, so I decided to go ahead and replace my radiator. When doing so, I lost about .5-1qt of transmission fluid since I didn't cap off the transmission cooler lines. After that, my transmission started not wanting to shift into 4th gear, and when driving and coming to a stop would not downshift into 1st gear. It felt like it was engaged in 2nd gear coming off a stop.

I then drained 4qts from the pan and filled 5qts to make up for what was lost during the radiator replacement. At first, the transmission seemed to shift fine, but then started not being able to downshift to 1st coming to a stop and now not wanting to shift into 4th, completely bypassing 4th and going straight into overdrive at about 4k RPM. I have now also intermittently lost reverse half the time it doesn't engage.

At this point I *think* I have the same amount of fluid before all of my problems. Checking the dipstick with the engine up to operating temp and running, the dipstick is about 1 inch above the highest hot line.

Do y'all think it's most likely a fluid level issue or does it sound like I screwed up some components in my transmission?

 

Yes… drain it out until it is at the proper level. Did you damage the trans, wont know until the level is correct.

 

As weird as it sounds, overfilling can cause similar problems to underfilling ime

 

I would get a bottle of Lubguard and pray....

Lubegard Automatic Transmission Fluid Protectant with LXE, Size 10 oz. - Walmart.com

 

Update: It was definitely overfilled, so I got it back to the correct level.

After driving at the correct level: sometimes it shifts totally fine, sometimes it won’t go back down to 1st gear. When it doesn’t go back down to 1st gear, it feels like I’m in 2nd all the way to 4k RPM when it slams into overdrive. I don’t seem to have any trouble codes related to the transmission, but I’m using a Bluetooth Innova scanner so I’m not sure.

 

Depending on if you have cruise control… you should have 2 cables on the throttle body, one goes to the throttle pedal in the cab they other goes to the transmission. The one that goes to the transmission controls the pressure that the transmission uses based on throttle pressure. This is the sheathed cable that runs on the outside of the intake down to the transmission. Follow it up to the throttle bellcrank. There is a black rubber boot over the end of the cable, push this boot off the cable end and look at the cable where it goes into the hole, there is what looks like a BB crimped on the cable. The end of that BB should be just inside the hole in the tube end. If it is outside the tube end, loosen the 2 lock nuts and adjust it, if it is too far inside adjust it also. There isn't much else you can do in the driveway meaning that it might be time for a transmission.

When you drained some fluid did you drop the pan and inspect the filter and pan for debris? Is the pan damaged in anyway?

 

@Glamisman I'll definitely check the throttle cable after work.

I did end up dropping the pan to inspect the filter. The filter looked immaculate and there was no heavy metal shavings in the pan, just an expected silver dust on the magnets.

 

Are you on the original shift solenoids?

 

As far as I know, I am on the original solenoids. Hard to tell since I've only owned it since 250,000 miles. I'll try to snag a pic if I drop the pan again.

Another tidbit of information from my driving yesterday: When I'm driving in overdrive and come to a stop, specifically when my coolant temp is showing very high (close to red), I experience what I think is torque converter lockup not disengaging and my engine shaking and dying. I restart it and am totally fine in park or neutral, but it'll die when putting the truck back in drive. I wait for the engine to cool off a little bit, then I can put it in drive again and be on my way.

 

So #1, 300k miles is a lot to ask of those solenoids - they're cheap and easy to replace so I'd put that on my mind if this doesn't get worked out soon. One of them specifically controls the lockup clutch.

#2, you should not be exceeding the mid point of the temp gauge, there's something very wrong if you're even approaching red. Your thermostat may need to be replaced.

 

I also just noticed this. You have 3 gears + Overdrive. Overdrive is your 4th.

 

That's strange, I guess I thought I had 4 gears and then overdrive. All I know is that I start in 1st and then shift 4 times to my final gear. I have more reading to do about the A340E.

 

You may be feeling/seeing RPMs dip slightly at the end due to the lockup triggering (usually drops my RPM a couple hundred)

 

I'll order the solenoids right after I finish the timing belt/water pump job.

The kit just arrived in the mail and I think I'll have time this weekend to knock it out. I'll see if it's overheating after the thermostat replacement.

 

Was the transmission shifting fine/normally before the fluid change? If so, the issue is likely not related to any solenoid issues or failures. It also looks like you're still chasing a major engine overheating problem. Does/did the transmission shift normally when it's cold/just started and begin to act up when the temp gauge is approaching the overheating/red area? Transmission fluid expands quite a bit as it heats up. This could push it into an over-filled level: An over-filled transmission will cause/trigger as many problems as an under-filled transmission. The transmission should be at the "full hot" level on the stick when the engine is warmed up to the normal spot on the gauge: not over the mark.

Chase and correct the engine over-heating issue before you start throwing any parts at the transmission, especially if the fluid change triggered this issue and it was shifting normally prior. The pristine condition of the oil pan and screen tells you a lot. At least you have a transmission dip-stick to work with: you're lucky.

 

Yeah that's some good perspective.

Yes so far it does seem to shift somewhat normally when cold and then have the problems I was mentioning while hot.

 

Agree totally with the second point above: Something is definitely wrong if a Tacoma of any flavor is approaching the full-hot range on the gauge. You're going to have worse problems than a limping transmission if the overheating problem isn't put to bed soon. Don't keep test-driving it into the "H" range to troubleshoot the transmission issue. You might lose both.

 

Update: I just changed out the timing belt/water pump/thermostat today. After a drive, the issue seems to persist about the truck not shifting down to 1st when slowing down. The fluid level is within spec. Should I be looking at solenoids next?

 

Another update: I changed out the shift solenoids and lockup solenoid. Buttoned it up and made sure fluid level was proper. Same symptoms as above. When car won’t shift back down to 1st, I lose reverse as well.

 

The issue I was experiencing turned out to not be mechanical, but electrical. I did my valve cover gaskets before I posted this initially. When I did that, I guess I didn’t snug the wire from the PCM that grounds to the intake plenum. My PCM had intermittent communication with the trans and therefore didn’t shift right sometimes.

I found this out by taking my truck to a shop and the tech let me know those details. It shifts good now!