Transmission "releasing" out of gear

My 2009 Tacoma w/automatic transmission has about 150,000 miles on it (I've owned it for just about 10,000 of those miles). Recently, when stopped at a stop sign, it seems the transmission "releases". It acts as though it's in neutral, even though the indicator still says its in gear. (So far, I thin that's normal.) What is odd is that when I let off the brake and step lightly on the gas to go, then engine revs way up like it's in neutral, then grabs suddenly, slamming into gear and chirping the tires. On rare occasions, it does this when shifting form one gear to another (though not as bad as from a stop). I don't really notice any slipping once it gets into gear.

I had the transmission fluid changed a few hundred miles ago, but it made no difference.

Not sure if it's related or not, but occasionally when I shifted, it almost felt as though I was moving the lever through a tub of peanut butter. That seems to have cleared up (might have been related to the transmission fluid change, but it did happen once or twice after I got it back).

Any thoughts? Wondering if I'm looking at something major, or if there is something simple to check here. (I will be taking this to a mechanic - I don't mess with automatic transmissions, and most of my experience is on small equipment like antique UTVs.)

 

My first thought was low fluid, but you say that was recently addressed. It certainly sounds like a pressure issue if you're getting rpm flares.

 

For me, when the shift was hard to move, I sprayed the neutral safety switch, getting between it and the transmission and that cleared that up.
Who changed the fluid? This transmission doesn't have a dip stick, it has a port on the pan. The fluid is supposed to be within a temperature range for this check with the motor running.
Do you have a scan tool? Creating gauges with the torque or obd fusion apps for trans and torque converter temps make it an easy job to check the level yourself.

 

The guy who did the transmission fluid change is in experienced mechanic who is well respected in our area. Tacomas are very popular around here, and he's worked on tons of them. I trust he knows what he is doing when changing the transmissions fluid.

I'll ask him about the switch.

I do not have a scan tool. I can't imagine the transmission is overheating, since I'm not towing, and it's happening within a few miles of my home on rural roads (little traffic, 40 MPH speed limit, the first stop sign is about 3 miles away, which is often where I notice things not engaging as I pull away from that stop sign). What are the apps you mention, and what hardware do you need to interface with the truck?

 

Did you have the issues before getting your tranny fluid changed? My first guess would have been low fluid in the tranny as the symptoms would be what you described.

 

If the NSS is not reporting the gear that the shifter is in, the transmission will do strange things. Look at the shifter position dash indicator lights when you have a problem.

 

Yes. That is one of the things that prompted me to get the fluid changed (that and the fact I bought the truck with 140,000 miles on it, and didn't know what the previous owner had done for maintenance.) The "Shifting through peanut butter" feeling seems to have gone away (though it did happen once or twice right after the change). The transmission not engaging (or rather delaying engaging) occasionally when moving away from a stop does not seem to have changed.

 

Do you know exactly what fluid he used and are you sure it is filled properly? I would be suspicious of any "universal " type of fluid that may have been used. It may also be low on or leaking fluid now.

Have you seen any leaks? It may be that one of the transmission pressure increasing additives may help buy some time here, like Lucas brand or similar. It could be that the transmission is going or gone which is why it was sold. I hope not.

 

The valve body may need to replaced. Had a G37 act kinda like this, scan tools said ok, dnr the fluid and all that. Worked for a few miles then refused to shift or acted like a manual with a crapped clutch..... replacement of the valve body fixed it, something electronic was acting up.

Expensive, but not as bad as a full trans.

Something to look into.

 

I've had first hand experience with the transmission not shifting back down to low when coming to a stop, especially when I did a quick stop. After sitting for a sec it would clunk/lurch into low gear and then I could take off again. If I took off too fast, before it shifted down, it would do the exact same thing you described.

I had my mechanic top off the transmission fluid and this issue stopped. I knew it was low because I was aware of a leak at the transmission output shaft seal.

My recommendation is to take it back for a new top-off or flush (with WS) and if you STILL have this symptom you have real issues.

 

top it off yourself so you know its actually topped off. DIY trans fluid change with full fluid level check instructions here on the forums.

 

Valve body. I’ve heard of a lot of 2nd gen tacos doing similar to what you’re saying. Some guys just had to clean the valve body. Some had to replace. But every one of them had zero issues after.

 

check fluid level before undoing anything more than the fluid check and fill bolts.

 

I'm not usually one to use any additives but I did recently tried the Lucas Transmission Fix ($10 @ Walmart) just last weekend and added it a Chevy that occasionally kicked into gears. It didn't fix the kicking but I can say that it lessened the frequency and softened the kick to at least a third. Might be worth giving it a try but like others have said, check for proper fluid level. Even though you mechanic has a good reputation and lots of Tacoma's where you live, how many people do you actually know that gets their transmission serviced? The Tacoma is a bit tricky with it's fill procedure.