Does the 4L60 transmission have lockup solenoids? Or just shift solenoids?

[Steevo]

I have a 2003 Envoy XL with the L6 engine. Automatic transmission, I understand it should be a 4L60.
I have noticed a problem the last week or two of stopping at a signal and the drivetrain is obviously dragging the engine down, sometimes it quits, and sometimes when I noticed it I took it out of gear and then it's all OK.
I haven't checked yet but originally there were no codes. I'll be checking that again today.
I see a parts listing for shift solenoids on that transmission, but no listing for lockup solenoids.

Normally when I have had this problem on other vehicles I just had all the lockup solenoids changed to resolve it. But I don't find a parts listing for this vehicle. Does that transmission have lockup solenoids or just shift solenoids?

 

[Mooseman]

Yes it does, called a Torque Converter Clutch Solenoid.

2003 GMC ENVOY 4.2L L6 Torque Converter Clutch Solenoid | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

 

[Steevo]

Is there just one? I see there is a solenoid only, and there is also a Torque Converter Clutch Valve.
What is involved in changing that?

 

[Steevo]

The last one on that list is completely different from the others. The others appear interchangeable, but the last one is not. The funny thing is oreilly lists both of those. Which is which, or are there two different ones?

 

[Mooseman]

Because the PCM uses PWM to modulate the TCC valve to allow it to slip into engagement, it wears the bore in the valve body where this valve resides. That last kit by Transgo fixes that problem. We usually turn PWM off either with a tune, a modification of the solenoid or another kit by Transgo. Failure of this valve will cause TCC slippage, so not your problem.

Checking the FAQ, we have a list of symptoms and causes. It gives this:

14. TCC always locked: TCC apply solenoid circuit shorted to ground, TCC solenoid blockage (easy fix in pan), or TC broken (must remove trans and replace TC).

It could be the solenoid itself that's shorted to ground or a wiring issue. Might as well replace it while in there.

Here's the link to the Drivetrain FAQ which has a whole section on the transmission.

 

[Mooseman]

And there are two solenoids. One is for the TCC and the other is for the TCC PWM. As the TCC solenoid opens, the PWM solenoid controls the slip of the TCC. You can modify the PWM solenoid so that it sends full pressure all the time when the TCC solenoid opens so that it won't slip and just engages completely.

 

[59840Surfer]

The PWN never really achieves 100% lockup nor disconnection. It always has some slip factor going on ... all the time ... and that generates heat and horsepower losses.

After changing to Gil Younger's PWM-DELETE, you will get a nice firm, detectable lockup and lower transmission operating temps, provided that the TCC isn't totally destructo'd already.

I went with an S10/4.3 700R4 converter. It SERIOUSLY locks up when it goes into action!

I don't care IF there's "diagnostic clinical proof" that a stock PWM & TCC get to 100% lockup .... if it did, then why does the fluid run 15-20°F cooler afterwards on high speed @75MPH+ for miles and miles (no shuttle shifting at that speed) on CC after just a PWM-Delete?

Gears and clutches don't make heat .... only the converter does that.

 

[59840Surfer]

PS .... 'tuning-out' of the TCC operation will seriously drop fuel economy and create a lot of fluid destroying heat because the convertor is always "in conversion".... a very wasteful and loss-y condition.

The factory built it in --- originally to satisfy the Fed EPA and CAFE Standards, but it has carried over as a necessity to let brands of vehicles get better fuel mileage over the competition.

TCC L/U is a very good, if not misunderstood process. If you dink with it, be prepared for the consequences either good or bad.

If you are building a unit ... of course add the whole Gil Younger Shift-Kit!

Then add the 3" 2/4 band and new drum, a 5 pinion OD, a Corvette Servo, full teflon/bronze bushings, every Torrington available, a vulcanized Direct piston and that S10 small diameter torque convertor w/TCC LU clutch.

Shifts will no longer be vague and the TCC will feel like another firm gear shift.

Now if I'm accelerating more than 1/2 throttle, the 1-2 shift can chirp the tires. I was gonna change back to a stock 2-4 servo, but I've kinda grown to like it the way it is.

4th gear (OD) has the same feel as the 1-2 shift now too. EVERY GEAR will announce itself .... this is not for soccer moms!

That 3 inch band makes a WAY HUGE difference, especially on a new drum.

I know Mooseman doesn't agree with me about the stock TCC qualities ... but I can overlook his opinion .... (xxx`s & ooo`s, Mooseguy! Love ya anyway!)

 

[Steevo]

Because the PCM uses PWM to modulate the TCC valve to allow it to slip into engagement, it wears the bore in the valve body where this valve resides. That last kit by Transgo fixes that problem. We usually turn PWM off either with a tune, a modification of the solenoid or another kit by Transgo. Failure of this valve will cause TCC slippage, so not your problem.

Checking the FAQ, we have a list of symptoms and causes. It gives this:



It could be the solenoid itself that's shorted to ground or a wiring issue. Might as well replace it while in there.

Here's the link to the Drivetrain FAQ which has a whole section on the transmission.

I agree, not my problem. So what do I do about my problem? The TCC solenoid after dropping the pan? About $20?

 

[59840Surfer]

---> Most times when the TCC Solenoid (the PWM, really) is bad --- it has eaten out the bore of the valve body too and you need a special reamer to resize the valve body at that spot.

Not a job for a newb.

 

[Mooseman]

PS .... 'tuning-out' of the TCC operation will seriously drop fuel economy and create a lot of fluid destroying heat because the convertor is always "in conversion".... a very wasteful and loss-y condition.

I didn't say tune out the lock up, I said tune out the PWM so it locks up to 100% instead of slipping the clutch into engagement.

---> Most times when the TCC Solenoid (the PWM, really) is bad --- it has eaten out the bore of the valve body too and you need a special reamer to resize the valve body at that spot.

Not a job for a newb.

Which is not the OP's problem.

I say replace the TCC solenoid and mod the PWM solenoid as per the video for a 100% positive TCC engagement to reduce wear and heat. Verify wiring to ensure there are no shorts to ground. Use the schematics (check the link to manuals in my signature) to trace the wiring.

 

[59840Surfer]

I didn't say tune out the lock up, I said tune out the PWM so it locks up to 100% instead of slipping the clutch into engagement.

That wasn't clear.

Which is not the OP's problem.

I say replace the TCC solenoid and mod the PWM solenoid as per the video for a 100% positive TCC engagement to reduce wear and heat. Verify wiring to ensure there are no shorts to ground. Use the schematics (check the link to manuals in my signature) to trace the wiring.

Yeah --- but when someone recommends "tuning out" the PWM and we know that's a bad idea, I just wanted to snap that one off early in the bud.