About two weeks ago, my car periodically started to lose the ability to shift from second to third and third to fourth regardless of manual shifting or not. I had the transmission built about 6 months ago because of this problem and also changed to TC. So, about three days ago, I completely lost third and fourth gears. As far as DTC's, here they are:

P0751, P0752, and P0756.

Can somebody please tell me if this is an easy fix or if I'm going to have to rebuild/replace the tranny?! Thanks for any help!

 

DTC P0751
1-2 Shift Solenoid Valve Performance

DTC P0752
1-2 Shift Solenoid (SS) Valve Performance - No Second Or Third Gear

DTC P0756
2-3 Shift Solenoid Valve Performance

 

Anybody know if this is just a connection problem, electrical, or bad transmission? I've had a few people on another forum tell me it might be a connection.

 

Please post if you determine what the issue is.

I have an identical problem. I parked the car for storage, it sat for 6 months, took it out of storage and now won't shift to 3 - 4. Car drove ok when I put it in storage. Car has only 8500 miles on the rebuilt - put a $1000 in the rebuild.

I can get it to shift with EFI live but just one time - then won't shift again until I use EFI live to reset again. I replaced both shift solenoids which is easy and cheap - about $40 - but not the problem.

 

I will if you will do the same!

 

Did you get the trans tuned? If not, there's your problem.

 

It's tuned for a 4000 stall, but I have a 4400 in it now. Would it make that big of a difference? I never had this problem with my old stall before it was tuned.

 

When I parked the car for storage we disconnected the battery. Thinking maybe the PCM lost power for such a long time I reflashed the pcm with the original tune before the installation of the ATI charger and then tune after the install of the ATI charger. Neither tune made a difference. I used LSEdit.

So in my case I don't think it's the tune. It will blow the tires in first and second so it's not the convertor either.

 

So if it isn't the tune, the next thing to do is to attack what the codes spit out, the solenoids.

 

What is the best way to check them without having to open up the trans?

 

Some transmission shops have the tools and software to manually reset the codes and manually turn the solenoids on and off (same as I did with EFI live).

I am told you can hear the solenoids click as the operator switches them on and off.

Since you recently changed to a higher stall, there is a thread you might search for. It explains what happens when the computer senses there is too much slippage (your higher stall) and the program logic built into the pcm programs to account for the slippage (your higher stall).

So if you don't have a tuner program (LSEdit, HPTuners,EFILive) then you need to find a tuner as suggested above and one who really knows how to retune the PCM to account for your higher stall, possible knock retard, shift points, and other parameters that need changed as a result of the higher stall etc.

Good A4 tuners IMO are hard to find - at least in my area.

Good luck and hope you find the cause and someone honest to fix what is incorrect and no more.

If you've never had the car tuned as a result of the convertor change it's likely the car will be like night and day difference for driveability once you get it tuned.

For example after my TQ swap the tuner gave me the car and said it was good. Problem is that at 75 mph the convertor wasn't locking up - it was still slipping at 75. I made him fix it. Same goes for lockup at 40-45 mph in the city.

 

If I took it to the Chevy dealership would they be able to check it out for me or would I have any luck with a tranny shop? The closest tuner is two and a half hours away.

 

A good reputable transmission shop should have the tools to scan for the error codes and turn on and off the solenoid switches.

If they reset the code and you can drive the car and it shifts ok into 3 and 4 and does so without slipping - that tells you 3 and 4 are still ok.

If after driving the car the error codes occur again - then something else is wrong - 1) the TQ is setting the pcm to throw the code or something else.

Do a search - enter - po757 - the search will return many possible causes. Personally I think the code is set as a result of your new TQ setting the code.
Getting the tuner to come and tune you car will be much cheaper than tearing into the transmission replacing parts etc that aren't needed. Work with your tuner.

Here's some interesting info:

DTC P0757 Set, SES Lamp Illuminated, Poor Performance of Transmission, Transmission Slipping (Clean Transmission Valve Body and Case Oil Passages of Debris) #01-07-30-038B - (Jan 26, 2004)
DTC P0757 Set, SES Lamp Illuminated, Poor Performance of Transmission, Transmission Slipping (Clean Transmission Valve Body and Case Oil Passages of Debris)

with 4L60-E/4L65-E Automatic Transmission (RPOs M30/M32)

Condition
Some customers may comment on any of the following conditions:

The SES lamp is illuminated.
No 3rd and 4th gear.
The transmission does not shift correctly.
The transmission feels like it shifts to Neutral or a loss of drive occurs.
The vehicle free wheels above 48 km/h (30 mph). High RPM needed to overcome the free wheeling.

Cause
The most likely cause is chips or debris plugging the bleed orifice of the 2-3 shift solenoid. This will cause the transmission to stay in 2nd gear when 3rd gear is commanded and return to 1st gear when 4th gear is commanded.

DTC P0757 may also be set if the 2-3 shift valve or 2-3 shuttle valve were stuck, restricted and/or hung-up in its bore.

Correction
Inspect / Clean the 2-3 shift valve, the 2-3 shuttle valve and the valve bore of debris / metal chips.
Inspect / Clean the 2-3 shift solenoid opening of debris / metal chips. While inspecting the 2-3 shift solenoid, look for a screen over the solenoid opening. If the solenoid DOES NOT have a screen, replace the solenoid with P/N 10478131 that does have a screen over the solenoid opening.
Refer to the appropriate Service Manual for additional diagnostic information and service procedures.

Parts Information
Part Number
Description
Qty

10478131
Valve, 2-3 Shift Solenoid
1

 

Ok, the car even after having the battery disconnected overnight and clearing the codes with a Predator Programmer, 3rd and 4th don't work. Also, P0757 has come up in the history as well as p1870. If there are no other opinions, it's going to have the solenoids tested next week.

 

question does the trans just stay in second or does it neutral on the 2-3 shift

 

It's an odd feeling. It doesn't FEEL like it leaves gear. After second gear, it will go along like normal until the time to shift at which point the motor continues to accelerate in RPM's but the car doesn't. The reason I say it doesn't feel like it leaves the gear is because when I let off the accelerator, I can accelerate again with feeling anything like a shift. Occassionally, the 1 - 2 shift is very hard as well. I will have to rev the motor around 4500+, let off, and then it will shift into second.

 

It sounds like it's in limp mode, but I don't get any gears back after I turn the car off or disconnect the battery.

 

Bump.

 

Have you gotten the solenoids tested yet? That P1870 code bothers me. When I would go into limp mode, the only codes I would get would be the P0757 and P0751 codes. Once those was taken care of in the tune, I haven't had that problem again unless I stall up the car to 4000rpms, which I don't do anymore.

 

Haven't gotten them tested yet. Unlike in limp mode though, my car doesn't regain the gears.