case310350

My uplander tack show the engine rpms moving up and then down 250 rpms about every 4 seconds at 55 or more, happens in third as well. second is ok.

error code c0700. Is the the tcc valve? Can the dealer dignoise this problem with accuracy? I don't want to replace a part and "see if its fixed" then replace anther part and so on.

Chillz1

I asked this question months ago, as my '06 does the same thing. I never received a difinitive answer.

niceguy88

I don't know much about trannies but that rpm variance is consistent with a tq converter locking and not locking. So yeah it sounds torque converter related and can cause heat buildup and a loss of mpg.

The challenge might be to find a rebutable shop that can diagnose the precise cause.

rick444

Same for my 06 4t65e 120k:
I had cut the brown tx wire to prevent the hunting.
On theory of lazy lip seals and rubber orings, I added Lucas transfix, then a month later I decided to reconnect the cut brown wire to see if it helped.
Hey, its all better now. The additives attack the rubbers and swell em up for a few years when it may eventually harm the rubber. I suspect the 4th clutch rubber band was lazy and had a fatigue in its fitment. Like a loose bra.
Seems that blowby type leakage past rubber robs the pressure to the clutch friction discs causing havoc in the slip detection system. The machine is attempting to protect itself from friction material burnout.
Lucas had told me that I should use conditioner instead of fix after 2005 because fix is not compatible with dex6 so I used dex 3 upon refill figuring upon 50-50 result might work. I took a risk. And too I drink value beer and ten dollar bourbon in the same sitting
The story works for me, trans works like new.
Since dex 3 was ok in 2005, what the heck. I drive fairly easily. Uplanders have large cooling volume compared to its siblings. Good for trans.
This is a used van that does not need the best care; just good enough.
Really, trans fluid is only oil whose purpose is to apply clutch pressure and to operate a slush fan box, and give decent lube to the planetary system. It does not need to work as hard as engine oil unless you get it too hot. Do not let that happen.
Shucks, back in the 50s and 60s they used whale oil mix with sae 10 for trans fluid. It worked just fine. Todays boxs are not much different than the 52-55 oldsmobile cast iron hydramatic that is revered in history as the first great automatic. That 4 speed was the pattern for all for 60 years.
If an oil guru wants to blast my theory, id like the education.
I was ok not having tcc, compared to ripping it apart for repair i was willing to accept 3 mpg loss. But now i have it all. Good enough and works good as new. Rick