Vehicle: 296k miles 06 Chevy Tahoe 2wd 5.3L / 4L60E stock drivetrain for the most part (heavily molested otherwise; has 37's on 22's, 6suspension+2body lift, full denali interior swap, denali front end and cowled hood, some ridiculous gauge cluster thats metallic blue that i cant really even read in the day time, LCD stereo, subs, light bars front and back, etc) Its hard to tell what's stock and not on this truck is my point.

Bought it with known intermittent trans issue(screamin deal)

Issue: After driving 20 minutes or so and coming to a stop for a few minutes(heavy traffic, drive through, heat sink period(stopping at a light for a minute wont trigger it)) the trans will get stuck in 1st. It will not shift up going to high rpm and letting off, romping on it doesn't seem to help, but eventually if i just drive around 2-3k in 1st it will snap out of it and go back to normal. It will continue to drive normally unless it gets a long park idling or traffic heat sink again. Then rinse and repeat, though sometimes if I'm romping on it trying to get it to shift, it will trigger the same issue but stuck in 2nd though this is rare. Seems to be heat related. If I'm just driving to the gas station or fast food, its a non issue doesn't even malfunction. If I'm freeway driving, unless i hit traffic its a non-issue doesn't trigger. Its only if i get stuck in a drive through for 10 minutes or in heavy traffic it triggers - then once i get some airflow and chill around 2-4k rpm it will snap out of it and drive normally again. When it is having its fit, if i shift manually down into 1st the TC will stay locked, when in D or 2/3 it will coast and rpm can drop. Does the same when it gets stuck in 2nd(more rare case, usually when very hot it seems) it will lock the TC when in 2 and free coast in 3/D. Really no luck trying to manually shift it in these cases, usually just chilling on RPM around 2-3k for a minute in D or 3 will break it free and it wont happen again the rest of the drive unless i get another heat soak or long period parked or in 1st at idle. Usually when I'm pushing it frustrated when its stuck, trying to manually 1-2 it with the column or doing 45 in 1st it will trigger the 2nd gear stuck issue. Typically, its just a 1st stuck and then chill for a minute and it all opens back up. Sorry if I'm repeating myself, just trying to give all diagnostic info i can. To test my attempts at fixing it, i have a solid 20 minute route that i take to get everything heated up, and then i still usually have to park in a gas station idling in park to get it to trigger, puling out it doesn't shift up to 2nd and i know I've failed yet again.

I added a trans cooler first trying to buy some time before rebuild - this seemed to prolong the good operation, only a real heat sink gets it to malfunction(Texas heat + stopped). But didnt make it go away.

Rebuilt trans - took it to a local small mom and pop shop for 2k cheaper than the big names(3500 vs 5500). The guy did a good job from what i can tell, he had many trannys in progress and we had a good chat about cars and more technical engine/trans stuff, he didn't set off any red flags, pretty honest guy. He was even telling me about the little GM plastic ***** getting stuck in the separator plate, etc. He seems like he does know his ****. I get the truck back, drive home was 10 minutes it was fine shifting great - second day took it on a longer drive in town, same issue stuck in 1st. Nothing changed. Climbing under, it is cleaned up and has a fresh trans mount and new rear shaft boot, initially i thought i got full scammed but it does look rebuilt and does shift a lot more firm now 1-2. I took it back to him, a week or so in his shop he said he pulled the the valve body and made sure it was done correctly, but in the end he couldn't figure it out, said driving it to get parts and lunch etc he never reproduced it and it drove fine. After the week or two of messing with it he said maybe PCM is going out but didn't put much effort into figuring it out beyond that. I took it back as i can still drive it for the most part and didn't want it sitting at his shop. It definitely shifts better now, more firm 1-2 etc, it operates great when its not throwing a fit.

I replaced the speed sensor on the trans - didn't change anything.
I replaced the position sensor/NSS - didn't change anything.
I replaced the PCM - didn't change anything. I haven't done the cam position calibration yet, but the truck threw 2 knock codes and an evap code after i test drove it to check the trans issue(didnt fix it), but not the code for the cam position calibration. Im assuming maybe the previous PCM tune had the knocks disabled - its a pretty heavily modified truck and essentially everything has been touched except the drive train, i wouldn't be surprised if the tune was messed with. The tranny guy did say the tranny had a marking and had been rebuilt before.

I confirmed with the mechanic, he did not replace the manifold pressure sensor on the valve body. He said it looked fine and reused it, no visual damage and its not throwing a code, and mentioned when the MPS is going out its usually really hard shifts not what's happening to mine. Which is another interesting factor in all of this - it has never had codes except for the new ones after the PCM replacement(2 knock and an evap).

The combination of no codes and drives completely fine(drives and shifts amazing to be honest) until it gets heat sink has me stumped - maybe mechanical swelling in a valve during heat sink and something sticking, and then freeing up and being fine until the next heat sink event?

At this point my only idea is to swap the entire valve body out with the MPS, wiring, and solenoids - they are relatively cheap and i can slap it in pretty easily. Maybe the MPS is failing when it gets hot, but I'm also thinking mechanical swelling due to no codes.

Also, i replaced the ground from the back of the head to the upper firewall area and piggy backed a second ground from that connection on the firewall to another ground on the firewall just incase that ground wasn't grounding, and have inspect most wires i can track - no obvious wiring issues(and no previous codes either).

Thanks for reading. Looking forward to figuring this one out finally and knowing what gremlin ive been chasing. Shes a looker, definitely my highschool dream truck. PS if you are in Texas and know who built this monstrosity i would love the back story, someone put a lot of money and miles into it.

 

Did your trans rebuilder vacuum test or replace the AFL valve in the valve body? A valve body with that many miles on it the ALF valve bore in the valve body is most likely worn.

 

Me before i started throwing parts I would make a simple togggle switch box to operate the 1-2 a 2-3 solenoids along with lockup
THE THEN SOME SORT OF BOX AND 4 TOOGLES.
12V PIN E
SOL TO SWITCH TO GROUND ON SOL A AND B 1 SWITCH PER SOLENOID
TCC TO SWITCH AND GOUND
PWM TO SWITCH AND GROUND


PIN E RED OR ORANGE

1-2 SOL LIGHT GREEN
2-3 SOLENOID YELLOW BLACK STRIPE
TCC- TAN W BLACK STRIPE
PWM (I THINK PURPLE BUT DOUBLE CHECK )

1 ST IS 1-2 0N AND 2-3 ON
2ND IS 1-2 OFF AND 2-3 ON
4TH IS 1-2 ON AND 2-3 OFF

LOCKUP REQUIRES PWM AND TCC ON , BEWARE PWM NOT INTENDED FOR CONTINUOUS USE SO JUST FOR QUICK LOCKUP TEST .


Then if you cannot duplicate the situation with the box. You have a pcm issue. Suprised trans shop didnt do this.

As for codes if a performance truck hard to say what codes may have been turned off . in tune.

 

ill have to ask him. AFL is definitely suspect though, that bore especially would have a lot of wear at 300k. i see a pretty nice sonnex sleeve design AFL that looks pretty trick.

looking into that thing, the trick sonnex AFL alone was 50, i dont even want to say what the sonnex reamer kit is lol i found a complete sonnex VB for 275 i think im just gunna go all the way to hopefully only open that thing once, just incase that MPS is having a stroke too or it is the 1-2 solenoid coil failing at temp or something. The fact that it only fails after a heat sink and does return to crisp normal operating makes me think most of that stuff would test out with a voltmeter or vac test on the bench or installed unless i tested it during failure. The way it behaves, i do think a binding valve due to the aged bores and swelling makes the most sense(and no codes). That AFL in particular does a lot of work, a lot of bouncing, etc. Also a bit worried that if this valve did bind open at idle when it heat sinks, it would be sending a lot of pressure downstream and might have damaged other things in the VB. Although you would think high pressure at the MPS would signal a shift... maybe it gets stuck when it strokes the spring and causes low psi in the VB? I feel like im thinking in circles as i add more of the trans components to the equation lol Complete VB it is, ill dissect the one that comes out.

Ive been fantasizing about a 3 on the tree swap in this thing so that i would never have to worry about an automatic transmission again, and keep my center console too - i had a 69 chevy with it long ago and it was an absolute blast to drive. Ill have to search and see if anyone has attempted that feat yet.

 

Yes the AFL is suspect at 300k . but was curious to the NO CODES as a failure to shift should have set codes for shift solenoids. The MPS only tells the PCM what manual position the shifter is in.

 

You are correct but I have seen some FPS/MPS codes cause 1st and 2nd gears only. Although I have never seen it to cause it to be intermittent like he is describing. They also always set codes. One that comes to mind. Only set a P1810 after 45 minutes of highway driving. New FPS/MPS fixed it.
I have also seen Big tires like that cause issues with gear ratios...
Personally I would like toe see the shift commands and the FPS/MPS states when it is acting up.
I would also go drive it with HPtuners while controlling the unit through that and see if you can mimic the complaint. Sounds like the owner knows exactly how to make it act up...

 

Updates;

I installed the valve body yesterday, kind of convenient being able to fit a plastic storage bin underneath without jacking it up.

Install was pretty straight forward, no crazy metal in there or anything. Attached are a few pictures.

I just slapped in the VB, no plate or gasket. I did not do the harness/lock up solenoid though i wish i would have(damn laziness).

Truck shifts great now, ran it on the 30 minute test loop and it does not get stuck in 1st/2nd anymore in D. BUT; when i use the manual gears 3/2/1, 3rd acts weird kind - kind of searches, doesn't know what to do. 2nd is fine but doesn't lock the TC in 2nd as it did before, 1st same deal doesn't lock the TC as it did before in 1st. When i learned this issue, it also seemed to be stuck in 2nd once i went back into D but i also realized my linkage was funky when i parked at home after the drive - wouldn't go into park, had to fiddle with that bracket location on the trans before i got enough hose clamps on it to keep it from flopping around. I pulled codes this morning and it had a P1810, I'm assuming this was from low fluid before i topped it off last night? Maybe it threw it when it was being weird though. I didn't clear codes before the test drive last night. This morning, went to get coffee and its totally normal running in D, but when i used 1/2/3 manually it was not locking the TC again. When i went into D it did go back to normal driving, no stuck in 2nd deal like last night. I cleared the codes before the coffee trip and it had none when i got home(20 minutesish). I will give it another longer test drive today to see if it comes back. Ive read about the brake switch causing open loop no TC lock, but not sure why it would pop up now. What else can stop the TC from locking in 1st/2nd manual?

Before i replaced the VB, when it would get warm and get stuck in 1st, if i put it into 1st manually it would lock the TC and use the engine braking etc no coast, same with second - was that part of the issue or is that normal operation in 1st/2nd? I did like it to be honest, being able to use 2nd for braking and getting some snorting and popping was nice - just not sure if that's normal operation or part of the previous issue. With this new VB, 1st and 2nd will coast. Dosnt seem like i could use it for engine braking with a trailer or something, or in the mountains. The amazing performance of the lock up solenoid previously is why i did not replace it - surely it was not having an issue with the last VB.

Really wish i would have replaced the lock up solenoid/harness, seems that may be next? Though it does seem like its locking fine in D at speed. Will test more today. Is there a free software to monitor during a trip with a laptop? My scan tool is insufficient, doesn't have that listed in the live data.

Also i didn't torque wrench anything, couldn't find mine and was not in the mood to run down to autozone covered in trans oil - i did a few rounds on the VB snugging them down and one pass with a little more torque but didn't smoke anything down too hard. Made sure to get the right bolts in the right spots, though. I suppose if i end up going back in there, ill make sure i get one beforehand.


old vb

old vb

reused plate

 

Damn - i think i missed a ball thing - i only put 6 back in that i found in the old VB locations(i remember thinking i should google this when i was moving them from the old VB), just a quick google now says i should have 7 - i think i lost one in the oil tub, i think i left out the double ball one on the top right of the picture(i dont recall any double ball locations and did notice the weird longer channel). Guess i am opening it up again. Does this align with my symptoms?

 

OK so it was definitely the double ball location, this is the overrun clutch ball and does exactly what im experiencing. Well ill be damned. Im so excited to pull it again, have a torque wrench this time, and wrap this thing up to have a reliable truck.



edit: just adding some references for people troubleshooting later

 

Yes if you missed the bathtub ball I call it , you would have all sorts of issues with the overun / manual gears.
You speak of lockup? You mean converter. Generally it only locks at part throttle 3rd and 4th year.

 

yea just TC lockup, when i try manual 1st/2nd it coasts and dosnt engine brake. makes sense if that ball is missing.

when i tear it back apart, im also going to disassemble the old VB and see how muffed up the AFL bore is - it must have been seizing in there when it got hot. Will get some pics of that. At least thats my guess. Something in that old VB was toast, interested to see what it is once i get this thing back in running order and do a post-analysis.

Im also debating putting the old PCM back in - would the crank position learn still be in it or would it have to relearn if it was uninstalled/reinstalled? I noticed also with the new PCM my speedo is way off from the tires, though i think my crap scanned can put that calibration in.

 

The old PCM does not require power top retain memory so should be fine . The speedo isue may be your lockup issues also with new PCM

 

The TC does not lock up in 1st or 2nd gear. What gives you engine braking in 1st and 2nd gear is the overrun clutch. The no engine braking in these gears is most likely cause by omitting the bathtub check ball.

 

I pulled the valve body today, indeed there was 1 missing ball causing those symptoms.

However, i drove my standard test route and when i got to the spot, it was still all gucci - shifting like butter. I had tested the 1st/2nd manual already, both upshifted perfect and had lock on decel, the ball fixed that. I kept driving and maybe 15 minutes later(in town/city, lights etc) the shift up to second from first started to lag, then got to where i had to let off gas to help the shift, and within 10 minutes or so wouldn't shift above second. If i stayed in D it would not go to 1st at lights, but if i did manual 1st it would go to it instantly and upshift when i went to manual 2nd perfectly, crisp shift to 2nd. But then thats it, no shift moving to 3 or D - from a light 2nd only in D. In this truck, thats 0-50 in one gear pretty impressive honestly. But a depressing outcome yet again, though a different one.

Anywho;

No dash lights - its still throwing a knock a/b and evap but those started with the new PCM. I also noticed less backfire and poppy in the 2nd manual decels, i think im going to put the old PCM back in - pretty sure its tuned and it didn't have any change on the tranny behavior either way. Interesting today though, i cleared codes before i drove today and when i got home and cycled the power/restarted it, i put the scanner back on and the codes were there but still in pending - usually after a drive(since i installed the PCM), it would throw them back after a power cycle. Also, i never got the code for crank position calibration. It came with the VIN programmed in, just had to do the power cycle to train security, but the instructions it came with also said it would throw P0315 for crank calibration and that never happened. It does throw the knocks and evap, those are new to this PCM. Also, maybe a fluke but when i got home today after the test drive i hooked my scanner up after the power cycle and it flashed blue and said its files were corrupted plug into PC to fix, i unplugged it from the OBD2 and plugged it back in and it was fine back to normal and i scanned it. Now that i think of it, when i got checked the dude said his **** didnt read and failed me. I pulled out into the parking lot and hooked up mine and looked at the monitors, and pulled back in and it hooked up to his machine and passed. Im going to inspect that under dash tomorrow. idk why it would cause trans issues but maybe its related. but why no codes. fml.

List of replaced parts so far chasing this;

Added large trans cooler (its like 9"x22" ish, decent size)
Trans Rebuild (supposedly, im questioning everything now)
Output speed sensor on trans
Shift lever position sensor(some people call it NSS?)
PCM
Reman Sonnex valve body w/ all solenoids and MPS (no wiring harness or the TCC solenoid on it though)

Im not sure what else to even throw at it. I suppose i could buy a whole complete trans to swap in.

There was a bit of shine to the oil, had to look pretty hard though imo ive seen worse. The magnet in the pan had a bit of black dust, not even gritty and not much. Assumed it was from all the new stuff breaking in(bands/clutches?) Are there any mechanical components like bands/clutches that could produce these same symptoms?

I removed the AFL valve from the old valve body to see if it looked scarred - neither the valve or the bore looked particularly scuffed, not like it was seizing at least. The inner spring was coated in something white - it looked like maybe heat damage? There was some material at the very bottom of the bore, looked like either metal dust or whiteish material from the spring. Picture attached of that spring(could see it through the VB, forgot to take the pic of it removed, but ide say the middle half of the spring had that white stuff.

Ran out of time but will continue taking apart the old VB tomorrow, as well as swap in the old PCM.

Are there any other electronics in the loop for the trans? There's no actual TCM right, its part of the PCM? Checked most fuses long ago. I guess i could pull the pan again and replace the wiring harness inside too?

The main factor that continues to baffle me is no codes, and it operates perfectly for so long until it throws the fit. Today it made it so far i thought it was gucci. The new VB and same delayed fail time makes me think its unrelated to the VB now.

I lean towards electrical more, but no codes ever seems odd. If i get HPtuners will i be able to see the trans temp or would i need to add a bung maybe in the cooler line? Not even sure if its getting hot at this point, would be odd with the large cooler i think.

Another easter egg maybe, when it is in first either in D from a stop or in manual, it does have a whine - almost like a supercharger/straight cut whine but quite faint - and when it shifts up to second its gone. Always done that, but also has always had the trans issue since ive owned it. I always imagined the load of the 37s on first gear contributed to that. Maybe the actual pump is going out and having a fit when it gets hot? Maybe the PR valve in the pump?

I was much faster doing the VB today, shaved like 2 hours off from yesterday mostly by knowing i was going to be covered in trans fluid by the end no matter what. Exactly 5 quarts to refill both times.



first pan drop fluid

missing ball

white on spring

 

new info today - nice cool morning, went on a test run at grandma speeds, super chill driving. no issues. i drive in 3 manual often to keep it out of OD in the city. i tested out 2nd manual a few times, np shifting up back up to 3rd and D. I came to a stop at a light and used 2nd manual to decel, and then 1st manual around 15mph. When i took off shifted into 2nd manual perfect, but when i went into 3rd manual it stayed in 2nd. Drove a bit trying to get into 3rd, nothing. I stopped, cycled power and pulled codes - had a P1810 pointing to illegal MPS reading. I cleared, cycled power, code was present again. I cleared it again and took off - right back to normal operation. Cycling power seems to reset it back to functional. I tested the 2nd manual to 3rd shift, worked perfectly. Tested the decel at another stop sign shifting into 1st around 15mph rolling into a stop, and it again triggered the issue - no 3rd shift. BUT it also added a new symptom - when i would attempt to shift into 1st again during the behavior to decel, it would not manual shift into 1st until it was below 10mph - and, when i took off in 1st manual, it would auto shift into 2nd at 10mph while in manual 1st!! But still no 3rd. Tried it a few times, would not operate in 1st manual in 1st gear unless under 10mph during decel or accel. Fascinating transmission. The P1810 is new to this installed VB, the old did not throw these codes and had stuck in first symptom triggered by unknown(maybe heatsink). New symptoms with new VB are good 1/2 operation, no shift to third. Power cycle resets to normal operation.

My scanner also gave me failure to connect twice when i got home, even after i had already connected to the OBD2 and scanned, when i pulled codes it failed to connect. Power cycle didnt fix it while plugged in, i had to unplug and reconnect and it worked.

Going to swap the old PCM in today and see how it behaves.

Found an interesting thread about the PWM set points causing weird surge at highway speeds, which mine does also - i dont drive it on the highway often because it has its issues, but when i do i stay in 3rd manual to avoid the super low rpm OD at 80(feels bogged), and surges anytime i try to accel in OD even slightly, though if i push it down itll shift down and try to make speed. The truck also struggles to do 80 - i can make 70 pretty well solid accel, but i hit a wall and struggle to make that last 10mph to 80 and then thats pretty much it - feels like i hit a HP wall - can maybe get 90 down a hill. I read a thread today about PWM set points indicating this condition also, sluggish at high speed but not elsewhere and also a related P1810 - not sure what his solution was, looks like changed the PWM setpoints but im unsure if that made the other issues go away or not. Not sure how this relates to the no 3rd issue though.

https://ls1tech.com/forums/automatic...problem-3.html

https://forum.hptuners.com/showthrea...ybe-I-can-help

I feel like i need buy HPTuners to get more detailed info and possibly make adjustments.


P1810

after F1 press to read codes, no communication.

1st screen of status read, press F1 to open codes

 

You may have messed up one of the o-rings on the Manifold Pressure Switch the last time you pulled the valve body. Did you unbolt the switch when you installed the missing check ball?

 

The MPS was preinstalled on the new VB assembly, and when i pulled it to put the ball in i didnt remove it, only the long bolts that go through the VB to the housing. I would say maybe one of the seals shifted with those long bolts out, but the code did happen on the first run too on top of the no check ball symptoms. This new MPS even has a little tag on it like it was tested out during the reman.

At this point im wondering if the pump is going out/bad, the whine sound has persisted through the rebuild, new VBs, etc. If pressure is inconsistent as the manual position valve changes there could be odd readings to those diaphragms.

Im also still considering heavily a wiring issue causing all of these issues - those illegal read configurations that throw the p1810 can be result of open or shorted circuits on those same loops, not necessarily from bad readings at the diaphragm. I was also able to trigger the no shift to 3rd yesterday without using 1st manual, and it wouldnt reset when i cycled power, so the variables continue to pile up.

I swapped in the old PCM yesterday and went on a drive and still have the same no 3rd issues. The old PCM seems to have traction control disabled(i get the dash light TC turned off when i start it), and all of the knock codes and the evap code went away, and only the p1810 continues to come back. I tried to cycle power 2 times during the drive and neither reset the issue back to normal operation.

Other than pulling that VB again to make sure its correct, adding a new wiring harness inside with the lock up solenoid, idk what to do. If the issue is the pump, i cant fix that in my driveway. I would add too when it was still in the shop and the guy who rebuilt it was trying to figure it out, he did pull the VB again to make sure he did the entire VB right - so the VB has been dropped twice during the rebuild, and now replaced and dropped again. I dont think the issue is the VB at this point, its just where the symptoms are being triggered.

Ive found some rebuilt 2wd trans on FB for like 750$, debating a full swap at this point but i cant do the full tranny install in my driveway(at least im not motivated enough to). Financially this rebuild, and the list of parts and my time fighting this thing is beginning to wear on me. Closing in on $5k now with the same/similar issue i started with.

 

I may be remembering wrong, but I believe that a knock sensor code will prevent the torque converter from locking up.

 

Went on a freeway test drive today to determine if me shifting around so much testing it is part of the issue, about 15 minutes in it dropped out of 3rd into second and would only run 1 and 2 in any lever position, took the side streets home np in 1st and 2nd. It would also do 2nd from a stop unless manual 1st. Continues to throw the p1810.

Im going to replace the wiring harness inside the pan and lock up solenoid, reinstall VB, and pull the MPS and inspect/reset the O rings before i torque it all - its possible an O ring wiggled during the first install getting that VB into place before everything was torqued down - the p1810 is very much new to this VB and the symptoms are different now(old VB was stuck in 1st, no codes), its either a short on that harness or an O ring or both.

Thinking more, im not sure the pump going out makes sense - i still have plenty of pressure to lock clutches and bands even when it has its fit, 1 and 2 still run great no slipping or anything.

PCM swap had no affect, i have the old one back in now and have no more of the knock codes that would possibly mess with lockup - ide read that also somewhere in here.

 

Solved !

Today i replaced the wiring harness w/ lockup solenoid and inspected the MPS - all of the O rings looked fine, but i swapped it with the old MPS from the old valve body that had never thrown a code. The wiring harness did have a tiny bit of trans fluid at the bottom of the plug, ive read thats a symptom of these failing, it wasnt much though and very well could have been from my glove fighting that thing out. One of these was the issue. I think the new MPS was fine, kind of swapped it on a whim while i was comparing both of them - it looks like the old MPS got new O rings in the rebuild at least - both were near identical in condition. I think in the end it was probably the harness all along - thankful to be done for now.

Took it on a long test drive, went through all manual positions, did 2 pretty long freeway runs and a bunch of city street stop and go, probably 45 minute in total - no issue at all, smooth as butter. Seems surreal.

Will stretch its legs a bit more in the coming week, will update if it resurfaces!