Transmission issue & P0741

TJBaker57

Well-Known Member
2005 5.3 (LM7) Yukon SLT 4WD

So I'm tooling along 3 hours into a 5 hour trip, doing about 50 mph and suddenly something feels wrong with transmission then I lose all drive and am coasting. Engine running fine just acts like it slipped into neutral. Coasted down to about 20 mph and we reconnect. Try to accelerate and we break loose again. Quick glance at Torque app already running and trans fluid temp is ~160 so we are good there. TFP switch shows Drive, as it should leading me to believe I still had fluid pressure. No place to get off the road so I limp along till I get to a stopping place to check fluid level and so forth. Any time I try to get over 20 to 25 mph it breaks loose. Tried 3rd instead of Drive, much the same. Called Triple A and got towed. Only code is P0741, TCC Clutch performance or stuck open. Fluid looks & smells OK. Just ran through Transmission Data with the Tech2, though admittedly I know next to squat about transmissions. No shorts or open circuits though there could be intermitents I guess.

Did a pan drop, filter screen change and partial fluid change back around March this year.

Thoughts?
 

Reprise

Lifetime VIP Supporter
Your TCC Solenoid may be bad. It's on the end of the valve body, and you should be able to replace it with the VB in place. It connects to the wire harness, and there's also a wire retaining clip that holds it in the VB (you should be able to get out with a pick, via a slot in the VB.

What this solenoid does is prevent PWM (slippage of the torque converter) when it's time to lock the converter (or shift to high gear). It can fail either electrically or due to breakage (it's mostly plastic); if it breaks, fluid leaks through and the correct pressure can't be applied to activate lockup. Sonnax does make an improved (metal) version of the part, if you find it broken. You can check the resistance of the part off-vehicle. I think the acceptable range is 0.4 - 0.6 ohm. If yours is fried, it'll be way outside of that range. Also check your wiring harness near where it attaches, to make sure it's intact.

If your TCC solenoid is OK, there's one more related solenoid that can go bad, but it's located near the pump (meaning the trans has to come out). Depending on odometer (and how attached you are to the vehicle), you may want to rebuild / replace the trans, since it's coming out.

Finally, I'm not a professional mech or trans expert; most of the above info I got from a little internet research. E.g.; it may be worth no more than what you paid for it. Good luck, and post back with what happens.
 
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TJBaker57

Well-Known Member
Would a failed or failing TCC solenoid cause the vehicle to completely decouple at 20 to 25 mph? When it breaks free there is absolutely no power to the wheels, just like being in neutral.
 

Reprise

Lifetime VIP Supporter
IOW, at that speed, you expect a shift, and instead, it flares (tach climbs higher, but speed doesn't go higher)? The info I saw suggested it could, yes. It could also be a failed 3rd clutch pack (one of the weak areas of the 4L60). Or something else, entirely. But that's a full rebuild.

Usually 3rd clutches fail due to heat -- but you say the fluid isn't burnt, and you did a drain / fill recently, *plus* you were monitoring the fluid temp when it happened (kudos for that), and you *also* got the code indicating a TCC solenoid issue.

It's worth a bit of time (and a relatively small amount of $) to investigate the solenoid issue, given the above info, and you're likely capable of being successful if you tackle it yourself (e.g.; you'll perform the work correctly, given what you've relayed to us so far.) The alternatives are pretty much $$$$, IMO.
 
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TJBaker57

Well-Known Member
The whole thing leaves me baffled. Automatic transmissions are a mystery to me. Unfortunately I am away from home and must be back to work at a jobsite Monday morning. So this will go to a transmission shop and I'll be renting a vehicle. Some years ago my Trailblazer had the classic slipping TCC but that continued to put power to the output shaft when it slipped. I would see the slip speed in Torque Pro. Had that trans rebuilt. With this vehicle right now I am fully coasting when the failure happens. Today will be spent calling trans shops and rental car agencies.
 

Mooseman

Moderator
If there was an issue with the TCC solenoid, the trans would still work normally, it would just not lockup while cruising and throw a code for it. That I'm pretty sure.

Could be something with the shift solenoids or the valve body. A ball might have punched through the separator plate. Oil pump issue is possible. If there was an oil pressure issue, it could explain the P0741 if it didn't have enough pressure to work right. Could be the tranny itself is shot. These are just guesses though.
 
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TJBaker57

Well-Known Member
Just dropped it off at the tranny shop. Drove 30 miles to get there. Called 3 places before finding one open. . While cold it behaved reasonably, I was very light on the throttle and monitored performance with the tech2. Started slipping out when trans heated to about 160 F. Shifted to 3rd and engaged tow/haul mode while keeping the TCC slip low and taking back roads. For sure the TCC is struggling trying to lockup. There may be other issues I guess. They look like a decent shop and fairly busy but they'll evaluate it after lunch and likely pull it this afternoon.
 
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TJBaker57

Well-Known Member
Heard from the repair shop....not really surprised. Had my 02 TrailBlazer 4l60e rebuilt in Knoxville, TN 5 years ago for $2000. This one is quoted at $2400 South Bend, IN.

"Your transmission has a 2-3 spin up and slips in 3rd and 4th gear and shows excess slip when tcc is applied. So the transmission will have to be rebuilt."
 

seanpooh

Well-Known Member
That's really expensive for a rebuild... It's cheaper to buy a ready built 4l60e and bolt it in. Actually, a GM SRTA trans is cheaper.
 

Mooseman

Moderator
How many miles did you get out of this one? Makes me lose faith in rebuilt anything unless done yourself.
 
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TJBaker57

Well-Known Member
181xxx miles on this Yukon. Have put 53xxx so far on the rebuilt TrailBlazer trans.

Edit: to be clear...I am speaking of 2 different vehicles here. I own both an 02 Trailblazer and an 05 Yukon. TrailBlazer got 225k miles on the original trans before rebuild. Yukon got 181k miles on the original trans.
 

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