Trans “disengages” from engine on highway

MaverickT883 · Feb 2, 2021

Fun fact.... if you put a toyota trans in reverse on the highway, you will get the exact same effect. Sounds electronic to me, like the safety is engaging due to an electrical fault.,

Tacllama · Feb 2, 2021

I think the weird thing is that it started after the fan clutch went. Makes me wonder if maybe in that time or the cleanup afterward some gunk got swept into the transmission somewhere.[/QUOTE]

I’d second this opinion. Considering all the damage that occurred when the fan clutch went, and you mentioned transmission cooler lines being part of that, could be that some debris got passed along into the tranny and is stuck in a perfectly bad spot regardless of fluid changes. If so I’d say you have a bullseye for bad luck!

gmtech · Feb 2, 2021

so no "tech" has driven this to point of problem with scan tool? if so and you have to drive it on the highway for multiple hours? you should be looking to paying the tech multiple hours. for his time driving your truck

Xplosiv · Feb 2, 2021

Darty[OP] said: ↑

Quick Update:

The truck has been at the second dealership now for almost a month. They can't duplicate the issue after driving it a few times, so they ran some updates that were available and hoped that that would fix the issue. Needless to say, I had a guy pick it up for me last week, and it did the exact same thing to him on the way back. He was driving at the same speed I do on the interstate, but in a little more hilly country. He said there was a thud, almost like he hit something, check engine light came on, went into safety mode, and he coasted to a stop on the side of the road. The SW at the dealer said if it happened again, he or a tech would drive right out and hook up a scanner before we turned off the engine to pull the codes. Well... when he called the SW, he declined to come out and just left him hanging. He turned it off, back on, and finished the trip.

It's obviously time to move this issue up the chain. Truck has been at dealership almost 10 weeks now, and zero advancement in diagnosis. The common sense problem to me, is narrowed down to transmission. It seems that the issue occurs once the fluid is up to temp or potentially above (SW noted that when he drove it, trans fluid temp would increase slightly above normal on inclines) and there is a slight incline in the road causing a downshift. Maybe stuck piston or valve? Maybe valve body issue? Potentially a sensor or module issue? They did drain, refill, check and recheck fluid level. Transmission has never been apart up to this point.

I'll be getting in touch with Toyota regional to see what the next step needs to be. As a former tech, I'm struggling with the "no codes, no fix" mentality, as opposed to the common sense diagnostic approach. Maybe its just my lack of common sense assuming the dealer could fix their own product?

Any other constructive thoughts or input would be appreciated.
Click to expand...

Whats telling SW that the trans temp was increasing? Do you have some sort of scan gauge on it?

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Trans “disengages” from engine on highway

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Trans “disengages” from engine on highway

#41 MaverickT883 Paintless

#42 Tacllama Well-Known Member

#43 gmtech Well-Known Member

#44 Xplosiv Well-Known Member

Products Discussed in Entire Site Forum: 3rd Gen. Tacomas (2016-2023)

#41
MaverickT883 Paintless

#42
Tacllama Well-Known Member

#43
gmtech Well-Known Member

#44
Xplosiv Well-Known Member

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