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4L60E slipping out of overdrive


bbullsj
03-01-2016, 04:19 PM
I have a 97 k1500 cheyenne with a 5.7 vortec and a 4L60E transmission. I initially had an issue with the central port injection system so I replaced with an upgraded Delphi unit. I then developed an issue with the transmission. It will shift into overdrive and then with low load it will stutter. It feels like the transmission is slipping and then slams back into gear. I have watched for misfire data on a tech2 and there is none. I read that dexron3 is terrible fluid and can gel up. I ran some Gunk trans medic fluid through it for a couple hundred miles and then did a drain and fill with a new filter and Mobil1 ATF synthetic fluid. I was told it could also be the TCC lock up solenoid so I replaced that with a GM solenoid. After about 15 miles it started to do that same thing again. it only happens on low load in overdrive and is worse once the fluid has warmed up. Am i going to damage the transmission if I continue to drive it like that? What are my next steps to check or parts that I may need to replace?

maxwedge
03-01-2016, 04:33 PM
This didn't happen til the work was done? Can we assume any more load in lock up causes it to down shift and shudder stops?

bbullsj
03-01-2016, 05:31 PM
Correct, everything was fine before the injection system was replaced. Yes if I push the pedal down more the transmission will downshift and accelerate properly and the shift back into overdrive.

j cAT
03-01-2016, 06:41 PM
Correct, everything was fine before the injection system was replaced. Yes if I push the pedal down more the transmission will downshift and accelerate properly and the shift back into overdrive.

this does sound like the dexron III acid fluid eat out the a b shift valve bodies. those valves if worn will cause a drop in system pressure . low pressure will kill the transmission . possible much more is in need of replacing. shift solenoids are just electrical these do fail over time . The valve bodies with dexron III do take a beating . This is usually how these gradually die. very common Dexron III damage. pressure testing by a tranny shop should know if its just those valves need replacing.

maxwedge
03-01-2016, 07:15 PM
I would drive this moderately til a code is set, which will happen, this will give you an accurate diagnostic path.

bbullsj
03-03-2016, 06:23 PM
At this point am I going to damage anything that I wouldn't have to replace anyways? I've done some more reading and I've found it could be the brake switch messing up, The steel ball for the TCC solenoid hammering on the aluminum valve body and causing a drop in line pressure due to losing pressure around the deformed aluminum and TPS sensor (since it only happens around the same throttle position). ANy way to clean the TPS or check it's values? I do have access to a Tech2.

Schurkey
03-04-2016, 10:07 AM
The title of this thread involves "Slipping out of overdrive".

Have you determined that this is a gear-ratio problem (actually losing overdrive, dropping to a lower gear) or is this a TCC problem (stays in overdrive, but the converter clutch disengages).

First step in diagnosis is describing the problem properly.

bbullsj
03-04-2016, 01:17 PM
It is not downshifting. It feels like you cut spark for half a second. It is a distinctive stutter/hesitation.

Schurkey
03-04-2016, 01:34 PM
It is not downshifting. It feels like you cut spark for half a second. It is a distinctive stutter/hesitation.
It's possible for that to be a symptom of transmission problems. I would not rule out that it may just be plain ol' misfire. I'd hope that the computer would spit out accurate misfire data...but I'd want to see the O2, MAP, TPS, and RPM data just before, when, and just after it's stuttering/hesitating.

I'm not familiar with the '97 transmission. Can you install a pressure gauge on the case? Are there temperature and pressure sensors in the trans that can report to the computer--and thus to the scan tool?

What info does the scan tool show for transmission operation? I assume there's more available than just TCC and shift-solenoid operation.

j cAT
03-04-2016, 01:51 PM
It is not downshifting. It feels like you cut spark for half a second. It is a distinctive stutter/hesitation.

with what you say here as was mentioned this can be the tranny or engine miss fires. using a scan tool see if the engine is good. also check for proper fuel pressure 60-65 PSI key on eng OFF......... all that good then good chance tranny has worn valve bodies / possible electrical connector at tranny or even the ignition switch.

bbullsj
03-04-2016, 02:35 PM
I will check on Monday about transmission data available. I'm pretty sure it can be pressure tested, not sure I have the tools to do it though. I'll check fuel pressure as well. New fuel pump and injection system was installed immediately prior to this issue. The spider poppet valve system failed and was filling the crankcase.

I have replaced the ignition due to a code.... P2780 I think? It's been a couple years. CEL would come on and I wouldn't not have overdrive at all. Has been fine since that was replaced.

bbullsj
03-11-2016, 03:21 PM
Ok, so I was sick this past week and just had a chance to put a tech2 on it. It is definitely a misfire. As soon as it happens I can watch random misfires happen. It's usually at least 2 cylinders at once, sometimes more. I have a bunch of snapshots I can post but it won't let me do it from my phone. The CEL is not on but I have 3 history codes. P0300, P0141, and P0157.

j cAT
03-11-2016, 03:37 PM
Ok, so I was sick this past week and just had a chance to put a tech2 on it. It is definitely a misfire. As soon as it happens I can watch random misfires happen. It's usually at least 2 cylinders at once, sometimes more. I have a bunch of snapshots I can post but it won't let me do it from my phone. The CEL is not on but I have 3 history codes. P0300, P0141, and P0157.

all those codes I would guess is 2 bad cat converters.

miss fires from restricted exhaust. both downstream O2 sensors reporting low voltage output to the PCM.

check for restricted exhaust . fix all exhaust leaks check fuel pressures and do the fuel pressure test. check the fuel trims should be close to zero +/- 10 ..
If the O2 sensors are old replace . if the converters are bad find out why they are damaged. injector leaking or other fuel ratio issues.

bbullsj
03-11-2016, 04:29 PM
About 2 months before the fuel issue I did have to cut open a converter and pull out a piece of metal that was rattling around :/ Plugged cats could be a good possibility. They are at least 10 years old at a minimum. 02 sensors were all replaced in 08.

j cAT
03-11-2016, 05:38 PM
About 2 months before the fuel issue I did have to cut open a converter and pull out a piece of metal that was rattling around :/ Plugged cats could be a good possibility. They are at least 10 years old at a minimum. 02 sensors were all replaced in 08.

excessive back pressure will cause 300 code. the other codes would indicate the converters are dead. or the O2 sensors are. with fuel delivery failures not properly controlling the fuel mixtures this will damage the converters. remove the upstream O2 sensors leave the holes open see if the engine has much more power if so then the converters may have melted down also converter internals may be in the muffler restricting flow.

bbullsj
03-11-2016, 07:47 PM
I forgot, when I replaced the injection system I also installed a new distributor, cap, and rotor. Is it possibly that the new dist is acting up? What about the new fuel system? I can't reemember which but it was a Delphi or Delco fuel system. The dist was Duralast. I just don't understand get how all of a sudden from sitting for 4 days it developed this problem.
It seems like it has plenty of power. No less than it had before. Should I be able to tell and feel a big difference? Won't that throw a bunch of codes from taking the sensors out?

j cAT
03-12-2016, 06:21 AM
I forgot, when I replaced the injection system I also installed a new distributor, cap, and rotor. Is it possibly that the new dist is acting up? What about the new fuel system? I can't reemember which but it was a Delphi or Delco fuel system. The dist was Duralast. I just don't understand get how all of a sudden from sitting for 4 days it developed this problem.
It seems like it has plenty of power. No less than it had before. Should I be able to tell and feel a big difference? Won't that throw a bunch of codes from taking the sensors out?

do some study on "how to determine cat converter failures" troubleshooting methods / back pressure testing .

like I said removal of the upstream O2 sensors holes open , see how it runs. fast method I explained those codes not an ignition problem.
down stream O2 sensors are not operating properly voltage should be .4-.8volts steady. your PCM is seeing low volts .1-.3 volts or less...........

Schurkey
03-12-2016, 03:52 PM
Plugged cat converters don't cause sudden, abrupt misfire symptoms that come and go. They cause unending no-power problems.

If the converters are faulty, it's a symptom, not a cause.

bbullsj
03-13-2016, 11:05 AM
So my pictures are all too large to attach and I even tried compressing them but no luck.

bbullsj
03-17-2016, 04:32 PM
So I took out the 2 upstream O2 sensors and it didn't run or drive any differently. Sounded like it had a nasty exhaust leak but that was it. What do I check next?

j cAT
03-17-2016, 06:17 PM
So I took out the 2 upstream O2 sensors and it didn't run or drive any differently. Sounded like it had a nasty exhaust leak but that was it. What do I check next?

so the exhaust is not the problem . now what are the fuel trims long and short ? what are the fuel pressures ?

Schurkey
03-17-2016, 08:29 PM
What do I check next?

I'd want to see the O2, MAP, TPS, and RPM data just before, when, and just after it's stuttering/hesitating.
At least we know KNOW that there's misfire.

what are the fuel trims long and short ? what are the fuel pressures ?
Thanks, I forgot to list those previously.

bbullsj
03-27-2016, 09:02 PM
Long term fuel trim is -7 for B1 and -17 for B2. Short terms are 1 and 0. These readings are at idle which is around 640-680 rpm.
I can't check for vacuum nor does much of any of this matter anymore. I was driving home and heard a rattling noise, figured it was a heat shield or something in the cat came loose, nope. I got off the expressway at an exit and as soon as i got below 50 mph my oil pressure went to 0 psi and then it was apparent I have a rod knock. Was that or anything else going on the cause of my misfire...... who knows but before I can go further on any misfire diagnosis I will be rebuilding the engine first. It'll probably take me a month or 2 to get it done but if I will update you as to if the problem still exists or not. I can't see to post any pictures on here because they are all too large. Very frustrating but oh well. I should be able to do all the bottom end and heads for around $600ish.

j cAT
03-28-2016, 09:09 AM
the negative trims though not that bad would indicate a rich condition un-burned fuel . s it could be the valves where not working properly low compression .

see if you can get another engine from the scrap yard that has low mileage on it .. should be cheap faster fix to get you running again. if you can find one .

Schurkey
03-28-2016, 02:35 PM
I should be able to do all the bottom end and heads for around $600ish.

see if you can get another engine from the scrap yard that has low mileage on it .. should be cheap faster fix to get you running again. if you can find one .
$600 is used-engine territory. I don't know how you'd get the heads and short-block PARTS for $600, never mind the machining.

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