4L60E and TCC

up4x4 · November 22, 2005

I have a 95 GMC K1500 5.7, 4L60E tranny with TCC, and 3.73 gears. at approx. 40-45 MPH the TCC engages, and seems to be fine untill i try to accelerate slightly say under light load then the engine seems to load up slightly and almost like a slight miss untill i press the accelerator enough to kick out the TCC. Is this normal or do i have some issu

es? if so would it be tranny related or engine?

GM-Tech · November 22, 2005

Hard to say from here if it's a misfire or a TCC issue. Keep in mind that when the TCC is locked, you might notice even the slightest misfire that may be masked by a fluid coupling. This could cause you to think it's a TCC when it's not evident with the TCC disengaged.

A TCC is *usually* more of a rapid shudder, but it can be mistaken for a misfire and vice versa.

up4x4 · November 22, 2005

Hard to say from here if it's a misfire or a TCC issue. Keep in mind that when the TCC is locked, you might notice even the slightest misfire that may be masked by a fluid coupling. This could cause you to think it's a TCC when it's not evident with the TCC disengaged.

A TCC is *usually* more of a rapid shudder, but it can be mistaken for a misfire and vice versa.

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I'm sure its not a miss fire, since i noticed this problem i have had the truck on a diagnostic scanner and all sensors and ecm check out good, under advice from the garage i have replaced the fuel filter, cap and rotor, plugs and wires and still the same! now the garage is telling me that i should try replacing the distributor, they tell me that GM distributors have junky magnetic pickups in them and over time they crack or just become weak so as not to fire well? They also suggested that i may want to try MDS components to generate hotter spark? What are your thoughts on the distributor? The truck has 103,000 miles

GM-Tech · November 23, 2005

they tell me that GM distributors have junky magnetic pickups in them and over time they crack or just become weak so as not to fire well?

Not too far from the truth on some of the older trucks, maybe even those of your model year. However, the problem this caused was usually a stall at idle or a no start.

It's pretty unlikely the distributor would present a problem only under the conditions you described. I'd say that would probably be a waste of money.

up4x4 · November 23, 2005

they tell me that GM distributors have junky magnetic pickups in them and over time they crack or just become weak so as not to fire well?

Not too far from the truth on some of the older trucks, maybe even those of your model year. However, the problem this caused was usually a stall at idle or a no start.

It's pretty unlikely the distributor would present a problem only under the conditions you described. I'd say that would probably be a waste of money.

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thanks for the tip, i think i'll save my money or at least spend it on something else, just one last Q. i found a tsb on TCC, #97744L60E13A-chuggle/surge, reflash pcm. This is the only info available on-line, can you expand on this bulletin and could it be related to my problem, and what is "flashing the PCM" ? If it means disconnecting the neg. battery cable for 30 min. i've already done that too.

GM-Tech · November 23, 2005

found a tsb on TCC, #97744L60E13A-chuggle/surge, reflash pcm.

I don't know what kind of number that is. It's definitely not a GM TSB number. Reflashing means updating the programming in the ECM/PCM's memory. Usually with updated calibrations that fix some concern, improve the operation of something specific, etc.

Usually, if it does fix something, that problem has been there since 1995. It's not as if the programming suddenly needed updating last month. You can forget about this fixing anything.

Let me rephrase that. You can forget about a calibration update fixing your concern if the problem is something that has recently developed.

up4x4 · November 23, 2005

found a tsb on TCC, #97744L60E13A-chuggle/surge, reflash pcm.

I don't know what kind of number that is. It's definitely not a GM TSB number. Reflashing means updating the programming in the ECM/PCM's memory. Usually with updated calibrations that fix some concern, improve the operation of something specific, etc.

Usually, if it does fix something, that problem has been there since 1995. It's not as if the programming suddenly needed updating last month. You can forget about this fixing anything.

Let me rephrase that. You can forget about a calibration update fixing your concern if the problem is something that has recently developed.

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Ok let me explain further, I have true dual exhaust and since the duals ive noticed the problem, my local garages seem to think this could have been a problem that has existed and become more evident after the duals were installed. And for the tsb # i got that from NHTSA.

GM-Tech · November 23, 2005

I have no idea what the NHTSA numbering scheme is all about, but they are not GM TSB numbers. Plenty have given me stuff they've found on the NHTSA site and the numbers are meaningless to me and don't come up in any GM informational sites.