Solved - Torque Converter Clutch Flutter

[Trail X]

I was getting a fluttering torque converter clutch. So I did some reading, and the bore on the PWM valve can open up after a lot of use, which allows pressure flow across the valve, which induces slip, which the computer notices, so it increases pressure to the clutch, which causes the flutter. Feels like a misfire, but only when the TCC is demanded on. The TCC is only demanded on when in 4th gear, or when in manual D3 3rd gear.

Anyways - I decided to tear into the transmission valve body and install a transgo SK 4L60E kit, which is supposed to fix this issue along with making shifts firmer and making other changes that should prolong the life of the transmission.

I actually found the instructional video on the transgo site (http://transgoonline.com/4L60E_HD2Video.html) to be very helpful, so if you're doing this same kit, watch that first. It really does help.

On to the pictures.

Pan dropped:



Filter removed:



Wiring, TCC solenoid, TCC TWM solenoid, and TFP Valve Pos. Switch removed:



Valve body removed:



Separator plate and 1-2 accumulator removed (visible at top right is the 3-4 accumulator):



Swapping springs on the 1-2 accumulator:



The Isolator/Converter valve that was causing all my troubles, and it's one-piece replacement (lower):



Adding internal spring to the actuator feed limiting valve, inside the same bore as the pressure control solenoid:



Wear in the check-ball holes in the separator plate (replaced the plate):



The hardest part of this kit was getting the retaining ring (221 below) back into the hole in the transmission (still on the vehicle) after changing out the pressure regulator spring. You can see the hole at the bottom left of the pictures of the transmission.



Change out the the low overrun valve spring in the forward accumulator, also visible is the new separator plate (plated and heat treated):



Valve body back in, wiring back in place (be aware, if you do this, there are very specific places these bolts go, and how/where you install them is critical):



Drain plug installed on the clean pan:



Note: trailblazer transmissions have a special filter with a beveled edge on the front left... I'll know for next time!



My transmission now allows 0 rpms of slip when the TCC is demanded on. It used to allow ~100 by design. Also no more TCC flutter, and I'm a happy camper. Shifts are a tad sharper, but not much.

Also included in the kit are a few other things that I didn't show or I didn't change out (mainly because overall, I feel my transmission shifts pretty well).

I hope this may help someone down the road.

[bartonmd]

Good to hear it worked out well! You can DEFINITELY tell that there's no PWM on the TCC clutch now, can't you?!

Mike

[Trail X]

Yeah, it engages much more sharply now, and my cruising rpms are 100 rpm less than they were before.

But, I think as a result of having no slippage, I may be noticing better mileage... for instance, on a recent out-and-back 2 hour trip, I got an average of 18.5 mpg. I haven't seen that in a while.

[bartonmd]

I totally believe the slightly more mileage thing! I bet the trans runs a couple degrees cooler in the summer, as well...

Funny the things we trade for smooth, "slick" driveability...

Mike

[Trail X]

Good point, I forgot to mention that. I've already noticed that it stays cooler longer. Seems to stay at ~180 F now when I keep it locked up, vs 200 F where it used to sit.

[DirtyBacon04]

I know I talked to you, James, about doing this... but the pictures are even more intimidating than I thought.
you should move here so you can "supervise" this task.

[Trail X]

You can handle it. Just take it slow, follow the steps, be methodical.

[fishsticks]

I'm interested in the symptoms. I have what feels like a misfire at 45ish mph that comes and goes. I chalked it up to another U joint but this seems like it fits the symptom list I'm having. I need to go see if mines happens outside of 3rd/4th gear.

[bartonmd]

I'm interested in the symptoms. I have what feels like a misfire at 45ish mph that comes and goes. I chalked it up to another U joint but this seems like it fits the symptom list I'm having. I need to go see if mines happens outside of 3rd/4th gear.

It comes and goes because it only happens when it's PWMing the TCC clutch for 5% slip. After you've been on the highway, at constant speed, for ~2-3 miles, it goes 100% locked up, and you don't feel it any more.

Mike

[Trail X]

45 seems too low of a speed, but maybe yours can lock at 45 due to the gearing you have - or you're in D3 maybe?

One of the easiest ways to test it is to get into a steady state throttle & speed where you're regularly feeling the bump/flutter. Then lightly tap the brake (just enough to turn on your lights) to signal the PCM to disengage the TCC. If your flutter goes away after the tap on the brakes, it could be the same TCC flutter I had.

[HARDTRAILZ]

Well done

[fishsticks]

My TCC locks up at low speeds, but I get "into" my torque converter a lot on the highway due to very little flat land out here plus my driving style.

I will try the brake thing.

Hell, the transgo kit may be worth it just to take that damn 100 rpm slop out. I've ALWAYS hated that... like driving a boat.

[Opeth]

I was waiting to see what the outcome of this was, I don't think I am having any weird TCC lock up issues but rather a random 1-2 gear bump or double bump when it shifts. It isn't all the time so I've never had the shop look at it since I know they'd tell me they weren't able to duplicate symptom. I cant watch the video either, yet another stupid iPad fail...

[plaen]

My transmission now allows 0 rpms of slip when the TCC is demanded on. It used to allow ~100 by design. Also no more TCC flutter, and I'm a happy camper. Shifts are a tad sharper, but not much.

Also included in the kit are a few other things that I didn't show or I didn't change out (mainly because overall, I feel my transmission shifts pretty well).

I hope this may help someone down the road.

I just picked up one of these to put into my 07, just curious as to what parts you left out? And where you picked up your separator plate, I haven't torn into mine, but i figure might as well have it on hand incase. I can't seem to find one for the 07 4l60e.

[Trail X]

I left out the 2-4 servo changes, I read a suggestion somewhere online to not touch it.

Also if I recall, I didn't change the 1-2 accumulator valve spring because you are supposed to get a number from inside the 2-4 servo in order to determine the proper replacement spring. Since I didn't touch the 2-4 servo, I decided not to touch this spring for fear of messing up a delicate balance.

I got my separator plate from transmission parts USA - this page:
http://www.transmissionpartsusa.com/4L6 ... s/5564.htm

Seems this would be the appropriate plate for an 07: http://www.transmissionpartsusa.com/4L6 ... 35098d.htm

Also, be sure to get the separator plate gaskets too. I was glad I got replacements because my stock one ripped on one side.

As for filters - it would APPEAR that we use a deep pan filter: http://www.transmissionpartsusa.com/4L6 ... 35921a.htm


ETA: For a little more assistance, the overhaul document, found here: http://www.offroadtb.com/articles/tech- ... documents/ is somewhat helpful.

I was waiting to see what the outcome of this was, I don't think I am having any weird TCC lock up issues but rather a random 1-2 gear bump or double bump when it shifts. It isn't all the time so I've never had the shop look at it since I know they'd tell me they weren't able to duplicate symptom. I cant watch the video either, yet another stupid iPad fail...

I think this kit advertises to fix a bump or double bump. I didn't have that symptom, so I wasn't really paying attention to it.

The video does take a long time to load, even on my computer at home. Big file apparently.

[HARDTRAILZ]

You can look at pan and see if you need deep filter or not. There is a step down if you do.

[Trail X]

Ah, so some trailblazers actually have a flat pan? I had no idea I had a deep pan, I figured it was just a normal pan.

[HARDTRAILZ]

My research indicated both were used on our platform. Mine was deep as well.

[bartonmd]

My research indicated both were used on our platform. Mine was deep as well.

Yeah, all the parts stores said they had a shallow and a deep pan for this vehicle... Mine was the deep.

Mike

[dvanbramer88]

I am really considering this as a summer project. Also, my 97 4L60E has the deep pan, Maybe 2wd trucks get the shallow pan? Gearing also has an effect on trans temp. Did they anticipate higher temps with certain drive train configurations?