lock up in and out

[bp042665]

Make

Chevy

Model

1500

Year

2000

Miles

212000

Engine

5.3 L

hi all just putting this out there 4 L 60 E transmission at crusing speeds of 55 to 60 mph lock up kicks in and out does not set codes i have checked all the sensors all ok i can engage it with scanner manualy does not do it watch lock up data and computer is comanding it to do this havent seen why

 

[billr]

Oops, I meant to connect a scanner to my 4L60E yesterday and check some things before posting, but I forgot.

How can you tell the TCC is going on/off, are you looking at "turbine speed" or "converter slip" in live-data?

Have you checked what the TCC command being given is; and, is this TCC PWM at times or just "on-off"?

I would put an ammeter in series with the + lead to the TCC solenoid (is there just one on this version of the trans?) and see for sure when it is being energized.

I'm thinking a short in the wiring from the solenoid or a bad solenoid. Do you know if this solenoid is energized to set the TCC on, or is it de-energized to turn the TCC on?

 

[bp042665]

well bill i read live data and yes it is a pwm style so i can see the % comanded by computer and it is turning it off and back on i also checked the TPS sensor for a glitch and nothing there all good readings

 

[billr]

So, the trans (TC) is responding correctly to the commands; the question is why the PCM is playing with the TC lock so much. Yeah, I would be looking at the TPS, MAP/MAF, and VSS. Those (and rpm) are what I expect the PCM is looking at to determine if TC lock is appropriate. Oh, and CLT and trans fluid temp... No codes set? If not, then probably no freeze-frame either. You need to be able to log everything, there is too much to be watching as this problem flits in-and-out. I think those ELM327 things can log. Speak up, nickb2!

 

[nickb2]

Yeah on the elm, they can log Bill. The torque pro app has a function for that, but it does not log alot of pids. I think OBD doctor has some pretty useful trans pid data, but that depends on the manufacturer.

But I think BP already has a high end scanner that can do that. He can tell me which scanner he has and I will tell him how to log/record data so when he test drives it, it will capture the event when it aggravates, however, I am assuming he probably knows how to do all that.

I think it would be important, as Bill mentioned, to read input and output sensors, monitor slippage. A 2000 chevy should have sent a code if there was slippage/ I will check direct hit for this particular problem and post back in a few minutes whilst sipping my first beer after a hard days work. Whew, what a doozy today.

Back in a few.

 

[nickb2]

Ok, I am seeing something interesting that may apply. Many techs are getting a slight shudder @ 48-50mph, lock up, no lock up, no codes. Many have had success by cleaning the MAF sensor.

That would be nice to check as it is free and easy to do.

Give it a try.

Also, many others got this fixed with a reflash/upgrade of PCM software. I don't know if BP has the J2534 capability, but that also would be worth a try before tearing into it.

Test summary as follows.

Tests/Procedures: 1. Watch Torque Converter Clutch (TCC) slip RPM in scan data while the condition is present.

2. Disconnect the Mass Air Flow (MAF) sensor, road test, check for shudder.

3. Engage the tow/haul function, road test, check for shudder.

4. Watch a line pressure gauge, compare actual line pressure to desired line pressure based on Pressure Control Solenoid (PCS) command in scan data.

5. Determine if the shudder is at the point of TCC release, 4th gear release or if it occurs while the TCC and 4th gear is applied.

6. Watch short term fuel trim and long term fuel trim while the shudder is present.

7. If above checks are OK, reflash the PCM with the latest software, road test.

 

[nickb2]

Would be nice to monitor line pressure before and after MAF cleaning. A dirty MAF element may cause line pressure to be lower than normal and cause a TCC premature lock up and disengagement as the PCM wants to increase line pressure. However, I would assume a code such as a P1870 (trans slippage) would appear, but in BP's case, no codes. But yeah, still worth a try in my book.

More from direct hit.

Customer Concern: The transmission has a surge/shudder feel at highway speeds. No Powertrain Control Module (PCM) codes. Noted that TCC slip RPM is ranging from 0 to 200 RPM as the surge is felt. The transmission fluid appears OK. Average Reported Mileage: 203559

Tests/Procedures:

1. Clean the Mass Air Flow (MAF) sensor elements, road test, evaluate.

2. If same, monitor line pressure with a gauge vs PCS command, (amps), in scan data.

3. Verify that line pressure corresponds to the amp value given, using line pressure chart.

4. An example, line pressure should be 53-85 PSI with 1.0 amp PCS command and 198-227 PSI with 0.0 amp PCS command.

5. If above OK, check torque converter appearance, look for signs of overheating, blue/brown appearance.

6. GM has a PI related to a 2/4 band or 3/4 clutch slip that may be the cause of this surge/shudder. Tech Tips: NOTE: TCC slip RPM does not necessarily mean that the slip is coming from the torque converter.

 

[bp042665]

ok guys sorry havent checked in but was busy building a few transmission busy week yes i have 3 top notch scanners i also have ease diagonstic system with the reprogramer i have to do alot of reprogramming with the new transmissions with the TCM on valve bodys i should have vehicle back monday so ill check more stuff and get back to you

 

[bp042665]

ok problem fixed come to find out there was a cross leak in the pump causing it to drop out put new pump and problem solved