07 Suburban C0379 , P0756 Trans in limp

[smokymtn65]

Yea debris on the bore obstructing the valve's movement can potentially cause a dtc to set for that solenoid though ive heard of builders blocking that valve inboard for quicker 2-3 upshifts but have never done it myself. If it happens again, Id drop the valve body and go through it (all valves out, clean it in a parts washer or hot tank) and install a Transgo shift kit and convert the pwm tcc apply to an on-off config using Fitzall's valve kit ($15.00 or so).

Thank you for your input!

 

[smokymtn65]

So update on this one, truck worked fine for two weeks started doing same thing again. I took back to shop that built transmission. They changed the vave body and separator plate told use good to go. 20 miles later same thing trys to pull from stop sign in 3r. Take it back, they change all electronics in transmission, solenoids, harness. Kept it a week works fine. I go to pick up start it up go to pull out it is in third. Shop ower say that was first time he witness the problem, grabs scanner no codes no falts everything read like it should. The TCM has been changed as well. Does anyone have any more ideas?
@NickTransmissions

 

[smokymtn65]

@NickTransmissions any input on above post?

 

[NickTransmissions]

@NickTransmissions any input on above post?

Take it back to the shop that built it...If there's truely no electrical problems that would be putting in limp mode then there may be a problem inside the case. If you pinch the green o-ring at the base of the forward drum, you'll have third gear starts. You should still upshift to 4th in such a situation so if you dont upshift at all from 3rd to 4th its not as likely.

Its all just a guess from here, of course but if a shop took that thing out, rebuilt it and put it back in, let them deal with it. Its either a short in the transmission's electricals, vehicle harness, tcm/pcm or some other sensors that are throwing off the tcm's command and contol of the trans (MAF and TPS are a couple examples) or a problem in the forward drum.

 

[smokymtn65]

Take it back to the shop that built it...If there's truely no electrical problems that would be putting in limp mode then there may be a problem inside the case. If you pinch the green o-ring at the base of the forward drum, you'll have third gear starts. You should still upshift to 4th in such a situation so if you dont upshift at all from 3rd to 4th its not as likely.

Its all just a guess from here, of course but if a shop took that thing out, rebuilt it and put it back in, let them deal with it. Its either a short in the transmission's electricals, vehicle harness, tcm/pcm or some other sensors that are throwing off the tcm's command and contol of the trans (MAF and TPS are a couple examples) or a problem in the forward drum.

Thank you, yes it has been at the shop that built it now over 2 weeks. I am looking for things they or i may have overlooked. His last answer was to build a new one and put in. Since i had found what looked like a piece of gasket material in the 2-3 valve i am guessing therei another piece in there somewhere that is the issue. We all want definitive answers fir peace of mind problems that come a go are frustrating.

 

[NickTransmissions]

Thank you, yes it has been at the shop that built it now over 2 weeks. I am looking for things they or i may have overlooked. His last answer was to build a new one and put in. Since i had found what looked like a piece of gasket material in the 2-3 valve i am guessing therei another piece in there somewhere that is the issue. We all want definitive answers fir peace of mind problems that come a go are frustrating.

I'll speak from the point of view as a transmission builder, we all have that occasional unit that gives us nothing but problems and heartburn...That no matter what we do, multiple iterations in and out, it doesn't work right...It's rare but does happen and sounds like yours (unfortunately) was one of those units...Sounds like the shop is trying to make it right, which is all that counts at this point as many will throw their hands up and customer either has to sue (rarely works out in the end) or eat the loss and find another shop.

Hopefully yours gets fixed and you can resume driving it around normally again without problems...

 

[smokymtn65]

I'll speak from the point of view as a transmission builder, we all have that occasional unit that gives us nothing but problems and heartburn...That no matter what we do, multiple iterations in and out, it doesn't work right...It's rare but does happen and sounds like yours (unfortunately) was one of those units...Sounds like the shop is trying to make it right, which is all that counts at this point as many will throw their hands up and customer either has to sue (rarely works out in the end) or eat the loss and find another shop.

Hopefully yours gets fixed and you can resume driving it around normally again without problems...

Understood, yes shop went way above from the offer point of view. Needless to say the important piece of information is it's my wife's daily driver and try to keep her from being upset is hard part. Lol i do appreciate your input and time spent to respond. If we find a definitive cause icwill post it.

 

[smokymtn65]

Fast forward 20k miles the shop never figured it out. Swapped to a different case and got it back on the road. During last 20k it has had the occasional slip in 1-2 shift and 2-3 shift mostly at light throttle. I has has very noticeable slip on hard acceleration in reverse. I have a U0073-00, and P0741-00 codes. My gut feeling is bad torque converter am I jumping to conclusions? I never had full confidence in the shop, the one I have used every other time was 12 week back log and I gambled. @NickTransmissions
Any input and thoughts are appreciated

 

[NickTransmissions]

Fast forward 20k miles the shop never figured it out. Swapped to a different case and got it back on the road. During last 20k it has had the occasional slip in 1-2 shift and 2-3 shift mostly at light throttle. I has has very noticeable slip on hard acceleration in reverse. I have a U0073-00, and P0741-00 codes. My gut feeling is bad torque converter am I jumping to conclusions? I never had full confidence in the shop, the one I have used every other time was 12 week back log and I gambled. @NickTransmissions
Any input and thoughts are appreciated

Take it out and completely go through it yourself or have a competent shop do it (obviously a diff one than last time).

Refer to my 4L60E information thread for guidance, parts selection and other tips/pointers...