Any GM 4L60E experts?

[Falcon_LS]

To make along story short, the 4L60E in my Envoy only has 66,000 miles on it, but will be rebuilt and upgraded by the end of the year. The previous (original) owner never dumped the factory Dexron-III fill until I got the car at 56,000 miles, at which point I just did a pan drop and refilled with 5 quarts of Dexron-VI along with a new filter. When I finally installed a ScanGauge-II, I realized the unit has been seeing some very extreme temperatures, so I got a Derale cooling pan with a drain plug and have been draining and refilling 7 quarts of Dexron-VI with LG Red every 3,000 miles. Temperatures up to 225°F are a common occurrence with this unit and the transmission cooler through the radiator isn't as effective as the air-to-oil unit it will be getting. Other than extreme temperatures, there are no problems with the unit. It shifts smooth through all four gears and runs smooth.

Nevertheless, although the unit will be rebuilt voluntarily, I need to be able to use the truck until December and I have a slight concern, leading me to believe this may be the TCC solenoid.

Driving along at any speed, upon releasing the gas, one would expect the engine speed to drop, even slightly. If you drop it in neutral, you would expect the engine to return to idle speed, even when moving. That does not happen. If I'm doing 75 MPH at ~2,250 rpm, even if I drop it in neutral at that speed, the engine speed remains ~2,250 rpm and comes down gradually with vehicle speed. It basically drags, behaving just like a manual when the clutch is not depressed.

The other thing worth mentioning is torque converter shudder, enough to vibrate the rearview, at 2,000-~2,500 rpm.

We have Trailblazers at work, and a friend of mine has a MY2005 Envoy that's identical to mine. All five trucks do not have this issue. So I'm trying to pinpoint what this may be, and reckon it probably has a role to play in increasing ATF temperature, even if it's slight. Thanks!

 

[SteveSRT8]

We have raised and killed a lot of those in Silverados, and I even had one in my old Impala SS.

Sounds to me like a TC issue, odds are the clutch for lockup is malfunctioning. Could also be a simple throttle issue. But the symptoms are not familiar to me, as most of the units we had ran great for a minimum of 100k miles and some went much more...

 

[Falcon_LS]

I've had experiences with the 4L60E in V8 applications, not that it matters, and they ran for a long time. I think the problems I'm experiencing are the result of a poor ATF cooling setup more than anything else.

If it's the TC, so long as it lasts another four months, I'm not all concerned. Just need it to run until December, and a TC is part of the rebuild anyway.

 

[The_Jeff]

I wonder if it's an emissions thing specific to that model and year, a dashpot like function to get the engine to rev match the transmission. That said I wonder if you have "overseas emissions" that aren't as strict. Maybe you have that on the Trailblazers (only).

Does the TC unlock happily when you tap the brakes just enough to get the brake lights on?

 

[SwampSurvivor]

I think staying at high RPMs is normal in neutral. It is so you don't end up putting it in drive, at 70MPH with the engine idling. My taurus would do that if I put it in neutral while it was moving - it would idle right up to 2500RPM.

My focus (manual trans) will idle at 2500RPM-3000RPM if I put it in neutral while rolling at highway speeds.

 

[UNC017]

The hanging high RPMs in neutral is certainly normal for my 90s- and later Mopars. Its a PCM thing that holds the idle high so that if you re-engage "D" it doesn't clang your eyeballs. Even if the TCC were sticking, in neutral it doesn't matter because the TC isn't connected to the driveshaft anymore.

225F isn't really all that hot for the fluid and parts- yes, I wouldn't expect to see it quite that high when not towing, but its not damaging. I don't personally think you're looking at a problem that will kill it in 4 months. The TCC shudder is the most worrisome thing of all to me.