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4L80e Replaced solenoids A + B, now missing 2nd? [Video + Picture]

Question: 
8K views 11 replies 6 participants last post by  grancito 
#1 · (Edited by Moderator)
Hi all, I've been lurking a while but this is my first post.

First off, a link to a video illustrating my issue:



I have a 1997 K2500 Silverado 6.5TD. I bought it with some issues, but got a good deal so now I'm finding myself crawling around this thing getting greasy every spare moment I get!

Anyway, when I bought it, it had codes P0751 & P0380 (I believe p0380 was due to a fuel leak... partially remedied, still chasing other leak points.. different topic though..). As you probably know, P0751 is shift solenoid A Performance/Stuck Off. Also had no OD, but it shifted smoothly 1-3.

Replaced the solenoids, fluid, filter, and pan gasket. The fluid was in good shape, no burnt smell and definitely red. The inside of the pan was pretty clean, magnet had minimal build up.

After putting it back together, I cleared the codes and took her for a quick spin. Good news is I have OD again! Bad news was I noticed late, hard shifting from first gear to what I believe is third. I can minimize it if I feather the throttle near the shift point, but it's still kinda rough. If there's moderate-significant throttle in first it just won't shift up, it will sit at high RPMS until let up of the throttle.

It's worth mentioning that I'm having a hard time reading the fluid level in the trans (probably just my lack of experience). I poured ~4.5 quarts in after putting the pan back on - started seeing it on the dipstick. Went for a short slow drive to warm it up, checked it again and slowly added another 1.5 quarts. After that, I was getting confusing readings. It seemed the fluid was dripping from the dipstick tube onto the dipstick. I let it sit overnight to let everything drain into the pan from the dipstick tube, and checked it again this morning. I "warmed" it up by driving around the block for about 5 minutes, never over 30mph. Attached is a photo. The mass of fluid is below the cold mark, but I see traces of it all the way up in the hot marking. Which is the one to follow?

Thanks in advance guys!
 

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#2 ·
Figured I should read the sticky after all!



1. State model, year of vehicle and mileage:
1997 K2500 Silverado, 167K


2. How long did you own the truck? Recent purchase?
Three Weeks


3. Any service engine light: yes/no. Intermittant check engine light?
This is called CEL or MIL
Yes, described above. None have come on after replacing the solenoids and clearing the codes though.


4. Fluid level okay with the engine and transmission warm? Check on
a level surface?
I might be reading it wrong.. I don't know. Engine and trans are warm, level surface, and checked with the engine running and trans in Park.


5. Have you retrieved Codes? AKA DTCs Diagnostic Trouble codes.
These are the OBD2 Codes yeah? If so, I did and mentioned above.


6. Fluid color and smell? Red or Brown does the fluid smell burnt?
Red, no burn.


7. Speedometer reading correctly at the appropriate speed? Are the tires the within OEM specifications and size? Use your GPS and verify speed. electronic transmissions remember?
Very close. Might be slightly off due to tire size


8. Is the transmission shifting normal? Is it shifting hard? Do recall the shifting symptoms or any shifting changes before or after the check engine light or after you retrieved codes.
Hard 1 to 3, no check engine light since this has happened.


9. Did you or anyone else conduct any kind of maintenance to the vehicle recently?
I replaced shift solenoids A + B, trans filter, trans pan gasket, and of course the trans fluid.


10. Can you explain the type of driving? Heavy towing? Snowplowing?
Light cruising. As seen in my video


11. Typical weather. Arizona hot mild winters? Minnessota cold. Please explain.
Western WA state. Moderate climate


10. Any problems with driver commanded/selected shifting into any gear?
ie.. 1st, 2nd, 3rd, 4th, Rev?
Doesn't seem to go into second.


8. Describe symptoms: Does the transmission refuse to shift in first? Will it shift into second and just stay in second gear?
Seems to skip second gear regardless of position of the gear selector


8a. TCC Locking? Is the transmission slipping in any gear?
TCC seems to lock, trans is not slipping.


8b. Is the transmission shifting into all FWD gears? At the
normal RPMs while the shift selector is in drive? Is it shifting later
than usual?
Not second. Stays in first late, then seems to jump to third.


Can your vehicle shift into all gears?
No, not second.
 
#3 ·
Small update...

Took it out again, I am pretty sure it will shift to second now. I may have just been too light on the throttle earlier, which made me think it was going to third.

On one of those hard shifts, my P0751 code came back. So I'm wondering now if I have something killing my "A" solenoid, or if I got a faulty one..
 
#5 ·
Yes, I did wipe then re-insert and check. By laying it on a paper towel, that would mean that the part that's not as heavily coated (by the hot area of the dipstick) would be the part to read, yeah? Since there would be fluid left on the towel by the little bit of fluid on the dipstick.
 
#6 ·
You might want to get the transmission warmer. I know for my '04 Sierra 3500, which has a 4l80e, the owners manual says to check the fluid when it's between 180 and 200F, then it lists a fairly specific procedure for shifting into all the gears, waiting, then checking the fluid level.


As for fluid level on the dipstick after adding some fluid, I find I can tell between where it's actually dipped in fluid and where fluid is just along one edge of the dipstick from touching the dipstick tube.
 
#7 ·
Thanks guys, I can read the fluid level correctly now. I've overfilled the trans by a bit.

This means I've had hard shifts in all 3 conditions:
- low trans fluid level
- correct trans fluid level
- over full trans fluid level

I was doing some more reading. I saw some people have success with pulling fuses ECM-1 and ECM-B in the Relay Center under the hood, then reinserting them. Gave it a shot.

When I started the truck I noticed the CEL went away (cleared the memory so that makes sense). Went around the block one time, and my shifts were smooth! What a relief! I didn't want to drive it with hard shifts, I'm scared of damaging it. Since my trans fluid is over full I put it back in the garage, so it only did the shift 1-2 twice over 1/5 of a mile. Not 100% confident yet, but I'll get to draining some fluid out later this week and give it some more testing. It still shifts a little late, but not nearly as late as prior.

(Disclaimer: I am NOT a mechanic, these are just my sleep deprived theories)
It seems that somehow the ECM learned to put much gusto into the 1-2 shift. Pulling the fuses reset it's memory. My guesses are it learned to shift hard because the old Solenoid "A" was bad (so it had to try really hard to move it). Or the PO beat on the truck, which is also entirely possible.

Will report back after getting the fluid to the proper level and some more testing.
 
#8 ·
I wonder if the shift adapts got messed up somehow.
 
#9 ·
Well guys, got home tonight and got the fluid level straightened out.

Took it on a test drive, shifted super smooth, all was great! Until I got on the highway. No overdrive again. All my reading to this point shows I've now entered the "start throwing parts at it" stage. TPS, VSS, TCC... IF I'm lucky.

Will keep this posted if anything of interest happens
 
#10 ·
#11 ·
You need to go through and do a complete diagnosis before you go through the frustration and cost of throwing parts at it.

Has the fluid been changed? always a good place to start. it doesn't sound like anything was previously slipping because you said the fluid was pretty clear.

Now when you say no OD, does it shift to 4th? does it lock the converter clutch? Or neither?

I would start by getting a scan tool that can read live data. Absolutely invaluable. I have this little bluetooth reader and it works great with the torque pro app (it's like 5 bucks to get the PID list for your truck)

Use the tool to monitor commanded gear and TCC lockup. This will help narrow it down to something internal or a computer/electrical issue.

Just because you had those codes doesn't mean that a solenoid was at fault. As I found with my tranny, it could be something broken inside that tricks the computer into thinking it's a shift solenoid code. In my case, I had p0752- shift solenoid B stuck on. Well, After months of frustration and diagnosing, I pulled the tranny and found the lip seal for the 2nd apply piston had a big chunk missing on it so it couldn't build enough pressure to apply 2nd. Not saying thats what happened here, just trying to show the importance of a proper and thorough diagnosis.
 
#12 ·
It can be an electrical problem, I would find no gear changes and had from one to three solenoid codes on start up. It would come right after unplugging the ECM, then some time later, same problem. One occasion on the long drive the volt meter started reading low, it was OK the next day but no gears, un plugging the ECM didn't fix it. I flew with the ECM to the other side of the world, because I was parked at the airport but no one could check it, a call to an expert transmission consultant in Australia, said it was electrical fault, check grounds and connections. When I returned it had gears so got home, and changed the ignition switch, they are useless after the 1994 model. It was fine for six months then failed again, changing the ECM cured it. I have been told that an electrical fault can damage the ECM.
 
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