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Old 07-22-2013, 02:35 PM
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TCC comes and goes

My turn to ask a question!

Background:
- My daily driver/shop truck is a 1989 GMC S15 with a 1995 Franken Mouse 350in it ahead of a 4L40E transmission. Built 12 years ago has 250,000 miles on the current engine/transmission and driveline; 350,000 on the chassis.

- The 4L60E is original to a 1995 half ton pickup with Tow Package. It is unmolested except for a B&M Shift Plus.

History:
- The transmission shifted normally even with the Shift Plus including TCC function for several years.

- About two years ago the TCC got so it wouldn't lock up unless the engine was warmed to 160 degrees while not exceeding 40mph till that temp was reached. If 40 mph was exceeded before 160 gauge degrees the TCC would not lock untill a complete cool down and a restart following the 40 MPH/160 degree F rule was followed.

I suspected the tranny temp sensor was failing bought a gasket and filter to open it up and just jumper the switch, haven't gotten to it though.

As this period progresses the shifter (B&M Mega) to where adjusting the transmission side mount control arm has to be modified, curently you can have Drive 4th and no engine start in Park; or engine start in Park but the adjustment has to be to Drive 3rd, then upshift to Drive 4th. Originally and for years this function was normal Start in Park with Drive 4th available when selecting down.

- About a year ago TCC simply became not functional at all.

- During this time I replaced the started last winter and last week the alternator. Both times I noticed that when the battery is disconnected for this work that when it is reconnected the TCC functions normally for a few days then resumes its failure mode.

- The Brake Indicator on the panel was dimly on and is now off.

- The CEL light in the past came on after the engine was warmed above 180 degrees ane road speed exceeded 50 MPH, this showed code 32 EGR with headers and duals, this would cycle with every shut down and restart. This moved to on constantly when the TCC started not engaging. It might be setting another code, I havent checked. Like the brake indicator which is now off, the CEL has returned to its original format.

My guess that it the lack of TCC lock up due to a failure of the tranny oil temp sensor is out. My current guess leans toward the brake light switch, a missmatch between the front and rear systems, and or the engine coolant temp sensor being faulty. I looking for other opinions you guys may have that expain why typical operation is restored after the computer has sat long enough to loose stored codes.

I'll see if any new codes get set and the problem reappears as it gets more run time on it.

Bogie

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Old 07-22-2013, 03:34 PM
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Did you check all the ground wires?
Just a WAG but....
Could be the trans is getting worn and as it is driven, the shift adaption limits are reaching the max value and defaulting .
Not sure if you have scanned the trans as it is running. Just sayin.
Could also have a long standing issue with the 4th gear switch as well as the new problem.
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Old 07-22-2013, 04:17 PM
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Did you check all the ground wires?
Just a WAG but....
Could be the trans is getting worn and as it is driven, the shift adaption limits are reaching the max value and defaulting .
Not sure if you have scanned the trans as it is running. Just sayin.
Could also have a long standing issue with the 4th gear switch as well as the new problem.
Now that you mention grounding, while I was beating on the alternator I decided to change the way GM grounds things all over the place. I picked the right front intake mounting bolt that has a stud projecting from it where the battery/chassis grounds to the block as a common ground for all the various ground wires. So I pulled the stud cleaned the threads of it and its mounting hole, brought all the various grounds to that one point to connect with the battery/chassis ground cable. I also added a ground from the block to the stud along with a seperate #10 wire that connects the face of each head to that ground stud. So grounding the engine block and heads as well as the transmission is no longer dependant upon moving electrons through anti-leak coated bolts nor through gaskets.

Funny you should mention that as I'm pounding through my FAA bonding and grounding A&P re-cert right now.

Bogie
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Old 07-22-2013, 05:35 PM
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Reason I mention it, I have seen the ground from the rear of the passenger side of the engine to the frame completely disintegrated and it makes things go crazy. I had one a while back where that was the problem causing the fuel pump to lose power when the lights were on.
Seems the rear lights and the fuel pump ground off the frame...which is why GM put that wire from the back of the engine to the frame.
Had me scratchin my head for a while, stumbled onto it after thinking about it for a bit.
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Old 07-22-2013, 06:10 PM
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There are a couple of things that could be happening.The brake switch could be bad or goin bad.Usually when this starts,vehicle will not wanna shift outta park,cruise control won't set.With your shifter arrangement,IDK how that would effect things tho.Once this signal is lost,convertor won't lockup until it's reset by disconnecting battery.It will then resume until signal gets lost again.Watch your brakelites as someone mashes brakes.Sometimes they will come on during onset of pedal travel & then may go off the farther pedal travels.SOMETIMES.Another possibility is a bad or inconsistant TPS.Lockup will not work w/o the signal,or'an inconsistant signal.Ck voltage on I think the blue & balck wire.Voltage should be near 0 with throttle closed.Watch meter as someone opens throttle.Voltage should steadily,smoothly increase to near 5 volts @ WOT.No spikes or flat spots.The TPS controls TC lockup & line pressure to trans.Again,it will reset if battery is disconnected & work until it gets a bad or no signal.I would say 1 of these is your most likely culprit.Brakelite Switch or TPS,or,the wires connections associated with em.Also the 95 is a standalone year for the 4L60E.It was the 1st year for PMW lockup solenoid & has different electronis,switches,& solenoids.93 & 94 will interchange.95 is standalone.96,97,& I think 98 will interchange.Not sure either on your shifter setup & how it's wired in.TC lockup,park/neutral switch,cruise, all depend on a signal from brakelite switch.A bad. Or inconsistent TPS will also cause hard shifts.Make you appear to have no 3rd/4th.Gear seeking.you can be cruisin @ 60 in OD when trans may suddenly jump into 3rd or 2nd,or,seem to just go into neutral.

Last edited by jokerZ71; 07-22-2013 at 06:15 PM.
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Old 07-24-2013, 01:56 PM
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There are a couple of things that could be happening.The brake switch could be bad or goin bad.Usually when this starts,vehicle will not wanna shift outta park,cruise control won't set.With your shifter arrangement,IDK how that would effect things tho.Once this signal is lost,convertor won't lockup until it's reset by disconnecting battery.It will then resume until signal gets lost again.Watch your brakelites as someone mashes brakes.Sometimes they will come on during onset of pedal travel & then may go off the farther pedal travels.SOMETIMES.Another possibility is a bad or inconsistant TPS.Lockup will not work w/o the signal,or'an inconsistant signal.Ck voltage on I think the blue & balck wire.Voltage should be near 0 with throttle closed.Watch meter as someone opens throttle.Voltage should steadily,smoothly increase to near 5 volts @ WOT.No spikes or flat spots.The TPS controls TC lockup & line pressure to trans.Again,it will reset if battery is disconnected & work until it gets a bad or no signal.I would say 1 of these is your most likely culprit.Brakelite Switch or TPS,or,the wires connections associated with em.Also the 95 is a standalone year for the 4L60E.It was the 1st year for PMW lockup solenoid & has different electronis,switches,& solenoids.93 & 94 will interchange.95 is standalone.96,97,& I think 98 will interchange.Not sure either on your shifter setup & how it's wired in.TC lockup,park/neutral switch,cruise, all depend on a signal from brakelite switch.A bad. Or inconsistent TPS will also cause hard shifts.Make you appear to have no 3rd/4th.Gear seeking.you can be cruisin @ 60 in OD when trans may suddenly jump into 3rd or 2nd,or,seem to just go into neutral.
I'm a few days into this and the tranny is acting like its old self hitting all the gears in order, and the TCC is locking up. The brake light warning has cleared so has the EGR code. So for the moment we're back to good to go. Apparently the tranny temp switch was not the contributor I originally thought it to be. Certainly the brakelight warning has something to do with it, I think that big switch box on the side of the tranny is worn out, thus the issue of getting the Park interlock to work at the cost of D4 or D4 to work at the cost of the Park interlock. Other than this issue the tranny doesn't do anything unusual nor make strange noises or motions, runs by the book.

Bogie
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Old 07-24-2013, 04:55 PM
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I hadn't thought about the gear selector switch on the tranny.Some year models have an adjustable switch.I can't recall offhand if 95 was or not.even it still has ties to the brakelite switch,so,with the brakeswitch seeming to be the common denominator & most likely the cheapest,easiest to replace,that would be a good place to start if the problem returns.After maybe ckn the wiring for loose connections,etc.
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