Transmission/changing gears issue.

Hey guys, I have a second GEN Tacoma 2006. 4.0 pre-runner sport with auto transmission. I’m just starting to have issues with my taco not knowing which gear it should be in. Sometimes when going up the hill, it will not downshift and I’ll have to downshift for it. Sometimes going down a hill it won’t upshift so I throw it in four and then back to drive and it will up shift. I’m not even sure where I should start with this. Would this be a transmission issue or more of like a control board somewhere telling the transmission what gear it should be in?

 

Have you checked your fluid lately, and or when was it changed last?

 

Probably electrical, but I'd take it to a TRUSTED transmission shop for an evaluation. On a truck that old a lot of shops are going to just say replace/rebuild the transmission without doing a lot of diagnostics. And to be honest that may well be the best option. A rebuild by someone who knows what they are doing works pretty well and isn't as expensive as buying new.

 

How much does a rebuild cost? It is an older truck, and I do have about 160,000 miles on there now. Maybe it is time. My only issue is this is only intermittent and only happens every now and then on certain pills I would hate to get my transmission messed up worse than it is. I too feel like it is electrical or something computer related does the ECM control gearing at all?

 

I do a transmission flush every 60k to 70k miles. I just did the most recent one, 20 or so ago. Maybe I should check the levels again.

 

Can I ask a dumb question? How many miles on the spark plugs?

 

Should be about 20k or so, I did them with my last flush. My plugs are pretty easy, maybe I’ll give those a try and see if that helps out at all. It’s just so strange.

 

I’d start with new spark plugs. Sorry, I’m not much help but good luck

 

The computer has been programmed to shift at certain shift points. When going up a hil it takes into consideration the throttle angle that you are stepping on the gas.

There are basic input signals that your transmission's computer needs.
1. Vehicle speed
2. Engine speed
3. Transmission input and out put speed
4. Throtle angle
5. Transmission fluid temperature
6. Which gear the driver selects.
7. Which gear that the transmission is in.
8. Engine load

A wild guess as to why your transmission is not downshifting would be 1. Throttle angle, Engine load and Vehicle spurred.

I would also check for vacuum leaks.

I would also check any and all grounding within the engine compartment.

 

First step is to check the fluid level

 

Exactly. Check the fluid level and check for micro leaks in the trans cooling lines. Been there, done this.

 

I just did it because it was suggested in another post and maybe slight over charge cause when I took out the over fill screw a small trickle came out. But very minor.
The transmission is smooth and fine most of the time just ever now and then it won’t pick the right gear. When going down a hill it does up shift for a be and some time is just manually go from D to 4 and then back to D or going up a steep hill it try’s to up shift too soon. It really feels like what ever tells the transmission to shift is the issue

 

Did you have the smoke type of symptoms?

 

You might start by cleaning the throttle body & MAF sensor, and doing a battery disconnect, @gearcruncher my have some suggestions as well. Do you have a CEL on or any codes present?

 

No codes present I will get on that tomorrow and report back.

 

First try all the other above suggestions.
Did you do your own trans flush and only the pan type, if so that left most of the dirty fluid in the converter still.
I know many on TW do not like full dealer flushes but that would be my suggestion if you haven't yet.
Helped mine with quicker shifts and converter lock up.

 

I do the whole flush like outline on here. I disconnect the return line and I usually run line 15-18 quarts. I’m really excessive with the maintenance stuff. Still doing oil changes at 3k:/

 

The trans in my 06 PreRunner was having intermittent issues shifting last summer. Truck has 180,000 miles on it. It worked great most of the time, but on occasion would not shift up above 3rd gear. Trans shop diagnosed a bad selonoid. Had a new one installed and is now working normal again.

 

How much did the solenoid cost?

 

The total bill was about $500 at a local transmission shop. That included all new fluid, labor, ect.