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Having problems with a 2008 Colorado 4L60e 175K miles. Transmission history is unknown but it shifts perfectly firm, quick, no slipping or delays but the converter is giving me problems. I think the torque converter is having trouble staying locked (shuddering). When the converter locks the rpms drop to 1500, moving about 45-50 mph. For a brief period, 5-10 mph range, there will be a rumble / grinding sound heard and felt mildly to medium from the floorboard. Don't feel like it is slipping/grabbing. If it is going faster say 55 mph it will not happen. Only when the rpms are very low (as low as they can be for the trans to lock up the converter) and the gas is pushed lightly causing the engine to be in a lugging situation for acceleration. If the trans downshifts or unlocks it will not happen. It also, goes away after the truck accelerates about 5 to 10 mph faster. Hooked up a scanner and there are no codes or misfires. Checked the fluid level and it is full. If anyone can help me diagnose this or get me in the right direction what to do first, it is greatly appreciated.
Thank you
What do you have for rear differential gearing? My 70 El Camino with a 4L60E and 2.73 diff gears does not like moderate and slower speeds unless I manually shift into D3 around town. It tends to hunt between D3 and OD if I select OD. Highway speeds are no problem.
Could this be similar to your problem? Try a manually shifted D3 and see what happens.
Rear is stock Gt4/G80 3.73 Eaton Locker. If I leave the truck in D3 it will not happen. If I am on the highway traveling from anywhere between 45-50 mph cruising and push the gas light enough to accelerate the truck but not enough to unlock the converter it will make the noise but it goes away when about 55-60 mph is reached. I have not been able to duplicate the noise at any other time.
History is of the truck is not known. It is a stock truck, nothing visual has been modified body, wiring tires/wheels. So, my guess would be a stock program as well. As for the converter my guess it is stock maybe a re-manufacturer if the transmission has been rebuilt. With 175K miles I would think the trans has been rebuilt because it shifts very well but I don't have any documentation.
History is of the truck is not known. It is a stock truck, nothing visual has been modified body, wiring tires/wheels. So, my guess would be a stock program as well. As for the converter my guess it is stock maybe a re-manufacturer if the transmission has been rebuilt. With 175K miles I would think the trans has been rebuilt because it shifts very well but I don't have any documentation.
I noticed on the scan tool the transmission fluid temperature is stuck at 32 degrees Fahrenheit, never changes. Does not throw a code? Is there a temperature fluid sensor? Where would it be and could that be my problem?
Last edited by turbo1002; Dec 3, 2019 at 09:15 AM.
The trans temp sensor is located in the manifold pressure switch. You can access manifold pressure switch by dropping the trans pan and filter. Then just 5 bolts hold it on, 3 short and 2 long. Most GM vehicles won't engage lock up until a preset temperature is reached, I'm not sure if it is based on engine or transmission temp. You will have to do some research on that to be sure or hopefully someone here can confirm. But there does seem to be something wrong with the trans temp circuit that needs checking out. My diagnostic theory when dealing with something like this is to repair what you know is wrong and it may fix the main problem that you are dealing with.
After rereading your 1st post, I don't think your problem is related to the temp sensor. It could be that the converter regulator valve bore in the valve body is worn and losing pressure. It could also be the lock up clutch in the torque converter. Fitzall.com makes a converter regulator valve that will work in a worn valve body, I think this is the part # for your year trans SKU# A74741CB.
Good news and most likely bad news. Two codes just set today. P0700 and P0741. I thank everyone here so much for the help and support. Will this help? Where to start? If this was you and only wanted to drop the pan once what parts would you change out?
Last edited by turbo1002; Dec 4, 2019 at 01:29 PM.
Bbond. I think you hit the nail on the head. The tcc bore is worn. Code p1870 sets under the same criteria as p0741. I read that here. https://www.sonnax.com/tech_resource...p0742-and-1887
Sonnax has a repair part as well but a reamer is needed which is about $100. I will be purchasing the fitzall part, manifold pressure switch. Should I change the solenoid as well? Any other parts should be replaced while in there? Also, what type/ brand filter and gasket should I use? Acdelco brand ok? Crossin my fingers the torque conveter frictions are still good. Thank you so much for the help. Extremely appreciated!
DTCs (P0700: Generic Trans code, P0741: TCC stuck off) would usually indicate that there is torque converter slippage while commanding lock-up.
While this can occur in a PWM style TCC 4L60E transmission for multiple reasons... The most common cause is excessive TCC regulator/ isolator valve-train/ bore wear of the valve-body.
In my shop; when this is found to be the cause of improper operation/ inoperation:
-The original TCC valve-train (valve-body and pump) are discarded.
-Internal wiring harness and components are tested and replaced as needed.
-The valve-body is completely disassembled.
-The valve-body is lightly blocked and squared.
-The TCC valve-train bore in the valve-body is machined in my mill with a Sonnax tool set including reamers, guides/ jigs, and guides/ pins to recondition the bore.
-The valve-body and any other removed components are completely cleaned.
-Install new Sonnax improved design TCC regulator/ isolator valve-train, and change TCC lock-up function to "ON/ OFF" from PWM.
-Install new Sonnax valve-body end plugs and seals to correct leaks.
-Give the customer the option for any other valve-body and separator plate changes/ modifications/ shift improvement parts.
-Replace separator plate if needed; otherwise clean-up/ sand/ repair and final clean.
-Install new Sonnax design TCC apply valve-train.
-Install new TCC apply solenoid.
-install new valve-body gaskets and screens, filter, and pan gasket.
Thank you vorteciroc for a detailed explanation. I just purchased the fitzall repair, manifold pressure switch, filter, gasket and oil. The sonnax is a quality product but the fitzall is a much easier install for a backyard job. Do you think the tcc pwm solenoid should be replaced as well? If someone could please answer me soon. I ordered all the other parts and would like to have this done before further damage occurs.
Bad news today. Installed the Fitzall A74741CB, Tcc pwm, manifold pressure switch and the problem is still there. I did notice while driving it after the parts were installed, I am getting a few misfire counts on all the cylinders. Each cylinder is giving me any where between 1- 4 counts all at different times. Would that anything to do with a code p0741(which has gone off)? Am I looking at two different issues? Is my next step a torque converter? If so, what is a good company to get a stock rebuild. Need this fixed and it is driving me insane.
Thank you for the help.
Last edited by turbo1002; Dec 8, 2019 at 08:27 PM.
But I am not an advocate of just throwing parts at a problem.
Did you inspect the TCC regulator/ isolator valve-train and bore for wear or proper operation?
Or did you just stick the Fitzall part in (and other new parts) without confirming a problem with parts removed?
While the torque converter clutch could be the problem... So could a leak in the circuit, such as the turbine-shaft TCC O-ring or bushing in the Stator support tube.
I don't recommend that you continue on this path of purchasing more and more parts.
What are you going to do if you replace the torque converter and still have the problem?
Now about the misfiring... Do you only see those really low counts?
Or have you had a P0300 or 301, 302 Etc... DTC post?
Depending on the tool/ method you are reading those low counts... they could be erroneous or could be the start of a problem.
Having only 3 misfires per cycle is too low normally to determine.
Thank you for the response. I don't like throwing parts at a job either but an educated guess is sometimes much cheaper than sending it out to a repair shop. Especially, if the shop is not good at thier job. You know as well as I do many transmission shops will just say "rebuild" 2k plus.
I am very grateful for all the help everyone is offering. As of right now it looks like a new torque converter is needed. What other parts should be looked at or changed to make sure the fluid paths are sealed other than turbine shaft o-ring and stator tube bushing for wear?
fix the misfires. if you're seeing them often enough on the scanner that you mentioned them...there's an issue.
Fix it.
Misfires cause a huge headache with gm TCC strategy
Looks pretty normal.
Fix the misfires. You can add a superior TCC valve in the pump if you want to and have the pan off...but I certainly don't think you NEED to.
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4L60E Converter help please 
