torque converter slipping

[99avenger2.5]

i have a 99 chevy blazer 4x4 with 54000 miles on it. the other day the rpms started to jump 300rpms at around 50mph. after doing that for a while it started to do it at almost any speed. it did not set any codes. reading other thread i found out that the vavle body could cause that problem. so i replaced the vavle body with a rebuilt one but it did not fix the problem. now i am lost does anyone know what else could cause this problem. there is still no codes.

[MT-2500]

Needs to be put on a good transmission/engine capable scanner and tested out.
A good scanner will show what is going on and if any codes post back code no.

[Blue Bowtie]

The torque converter is supposed to slip. The torque converter clutch should not, however. Since the vehicle speed is close to the point where the TCC is programmed to engage/disengage, you may be noticing the symptoms of a TCC that is randomly dropping out due to TPS or engine load. There may also be a problem with the TCC boost valve or sleeve, and those are NOT part of the valve body (they are stuck into the bottom of the pump body).

As advised, you may want to connect a scanner and either monitor the TCC and pressures during operation or command the TCC off and see if the symptoms persist. You can also used the Tow/Haul mode if your truck is so equipped to change the shift and lockup points, and see if the symptoms change.

[99avenger2.5]

i was able to connect a generic scanner that monitors tcc lockup and found that the tcc was engaging at the incorrect time. at around 30mph on slight acceleration the tcc would engage then disengage and almost stall the vehicle because the rpms dropped so much. however when it acted up at 50mphs the tcc stayed engaged but showed around 150rps of slippage

[blazes9395]

The transmission TCC lock-up strategy used in those years begins to lock up the TCC after it shifts into second gear. The lock up is a controlled slip lock up, so you'll see slippage until the TCC reaches lock-up. Now seeing 150 rpms of slippage sounds concerning. At that speed, and if your at steady speed(no pushing the pedal), you should see 0rpm slippage. When was the transmission last serviced? If its hasn't been serviced, that would be my first place to start. I'd also consider using some lubegaurd and see if that helps.

[99avenger2.5]

I did change the fluid and filter as soon as it started happening. It didn't change anything. The pulse width of the tcc changes when the slippage happens so something is telling the tcc to dissengauge but I don't know what that could be. The tcc should engauge in 2nd gear but not while accelerating and not for 1 to 2 sec at a time

[blazes9395]

Have you checked to see what your force motor voltage is? You did change the valve body, so thats hopefully still not the problem What is the temperature reading at the transmission? If everything checks out, than the last choice for me would be to get a pressure guage installed at the main pressure port and see what is happening as your driving it.

[merc Dod]

Did you resolve this issue? I have the surge now and was hoping you may have found the answer.

[MT-2500]

If you need help on yours
Just start a New Thread / Post and give all info.
Make and model and engine and transmission and mileage and codes.
Also what it is doing or not doing.

[merc Dod]

Duh....tranny fluid low. I may have a leak. Added fluid and all is well again.