Torque Converter lock/unlock?

[WhoaTed]

'01 5.4 4x4...

I've noticed the tach cycling up then back down a few hundred rpm's while cruising anywhere from 40mph-70mph (my usual trip to work speeds). It does it with no load (steady cruising), OD off doesn't affect it other than the much higher rpm of no OD. Common sense is telling me it's the torque converter locking/unlocking for some reason, it doesn't do it every day but about every fourth trip to work or so it'll do it consistently for the entire 30 mile trip. Don't know much about this particular trans since I've had zero issues with this truck but figured I'd post it here in case someone has had the same issue and can point me in the right direction. BTW I have super mechanical skills and an awesome set of tools (joke, there) so I can fix whatever's wrong...thanks in advance for any thoughts aside from take it to a trans shop.

 

[01yellerCobra]

When was the last time the transmission was serviced?

 

[rburch]

Im having the same problem with the Expy i have now and the 97 i had. Dont know alot but what i do know is that there is a TCC (Torque Converter Clutch) solenoid on the valve body that could be going out.

But what i have learned is that this is often misdiagnosed as the TCC going out but it is actually a low grade miss fire that is causing it.

 

[1997SCEBFEX]

Gents, don't discount the throttle position sensor. Mine did very similar quirks/symptoms for quite sometime before it threw a code. pulled it down, repalced the sensor, problem solved. not saying this is your particular situation, but after so much time at certain rpms, that's what happens.

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