4L80e P0894 code

[mikez71]

150k miles, Suburban 2500 6.0, seemed to run and shift fine when I bought it 100 miles ago..
Last night decided to pop a P0894 code. Looks like slip in 4th gear TCC locked code.

For approximately 1 mile afterwards, the 1-2 and 2-3 shifts were extremely harsh.
After about a mile, the shifts returned to normal?
Drove this morning, still normal, but no TCC activation with the code I have not cleared yet.
I'm hoping worn transmission/engine mounts exacerbated the harsh shifts.

What sounds like the issue? @NickTransmissions?
Leaning towards taking it in to a transmission shop.

I am not ready to dump big $$$ into it currently, maybe after I fix a bunch of other smaller issues..
Would driving in 3rd gear avoid the issue? Or disabling TCC in the tune?
I do not want to experience those harsh shifts again. Felt like it might break something..

I did lockup the TCC through a scantool at idle in park.(oops)
That stalled the motor completely in 5 seconds.. (Took effect in ~2s, but fully stalled in 5s)
Logged shift time errors for 1-2 and 2-3, frequently 0 or 0.1s, but also frequently 6.4seconds.
I do not notice any delay or other issues shifting, wiring harness appears intact on the transmission.

 

[strutaeng]

You think the torque converter clutch (TCC) clutch is slipping?

Here's what ATSG says could be the issue:

https://atoc.ru/uploads/manual/5fad1cea696b1.pdf

That's an older manual, not sure if their current manual shows diagnostics for the PXXXX codes or not?

Any time I remove a transmission (like for a RMS), I always replace the turbine shaft seal since they are only like $7 or something (also called torque converter lockup o-ring), and they always seem kinda flattened out but I have never had this issue yet on these transmission units...

Maybe @NickTransmissions can offer some advice for you.

Edit: it's this one here shown in green-ish. https://www.ebay.com/itm/3245970741...bAh0BkbFpXaIoMrs0phN8HvOkDtx3-6se59ACF07PLLlk

They are kinda hard to find at the local parts stores. Last time I ordered from WIT, I ordered like 6 of them to have in my transmission parts bin.

 

[mikez71]

Thanks for those links!

You think the torque converter clutch (TCC) clutch is slipping?

The diagnostic parameters (posted above, copied from 'auroragirl' at silveradosierra.com btw) seem to say it could be 4th gear clutch and/or TCC clutch.

I don't need to drive in 4th for now, and would prefer to smog this thing and re-visit the issue later if possible. If I can get the rest of the truck satisfactory, I would feel much better about spending some $$$ on the transmission.

Also noticed my transmission appears overfilled, and plan to correct that, but it doesn't sound directly related to my issue..

One interesting thing I found online regarding 4L80E's, is the US Army ordnance mechanical maintenance school manual for the Humvee's, that apparently also use this transmission..

 

[mikez71]

Confirmed at least my TCC is slipping. (bottom graph)
TCC duty cycle at max for 1.5 seconds at 18% throttle, and slip only drops from 350 to 315.
(TCC was max duty cycle for 3 seconds, but I'm not counting end throttle lift portion.)
Peak during 6 second ramp in was 390rpm slip, but the ramp started at 6% throttle and basically 0 slip, hitting 20% max throttle input around middle of ramp in period.

Hoping I can just disable TCC to prevent code and harsh shifts...
This chevy surprises me with something new everyday, it seems..

 

[strutaeng]

Confirmed at least my TCC is slipping. (bottom graph)
TCC duty cycle at max for 1.5 seconds at 18% throttle, and slip only drops from 350 to 315.
(TCC was max duty cycle for 3 seconds, but I'm not counting end throttle lift portion.)
Peak during 6 second ramp in was 390rpm slip, but the ramp started at 6% throttle and basically 0 slip, hitting 20% max throttle input around middle of ramp in period.

View attachment 484116

Hoping I can just disable TCC to prevent code and harsh shifts...
I dunno, this chevy surprises me with something new ,everyday it seems..

Would you mind posting the HP Tuners log file? I need to diagnose our 2013 T&C that's got a TCC code, and could use your file for comparison. I can also log my Suburban similar to yours for added data comparison. Hopefully this weekend I can do that. TIA

I'm not too savvy with HP Tuners actually. I've only used it to do basic gear ratio change, delete VATS, and such. But I would like to learn about about tuning and stuff soon. This seems like a great exercise for me...

 

[randeez]

One interesting thing I found online regarding 4L80E's, is the US Army ordnance mechanical maintenance school manual for the Humvee's, that apparently also use this transmission..

i always get a laugh when i hear about rolls royce/bentley using them from 90s- early 2000s

 

[mikez71]

Would you mind posting the HP Tuners log file?

Sure thing, just rename file.
There isn't much TCC activation in my suburban logs..

I'm going to write a TCC disabled tune and see how much driving I can do,
and hope no more codes pop up...
(before either throwing a used trans in, or if I can find a good priced rebuilder..)

 

[strutaeng]

i always get a laugh when i hear about rolls royce/bentley using them from 90s- early 2000s

"My world-class ultra luxury Bentley has a trannie from a Chebby box van!" LOL

I've never seen those versions of those transmissions, but the Jaguar 4L80e are kinda cool. The bellhousing has some ribs and the case connector is on the back, and some other minor differences. https://www.mez.co.uk/4l80e-new.html

I think back in their day, that transmission was pretty good. I mean, good enough for Rolls Royce, Bentleys, Jaguars and a few other luxury or exotic cars.

 

[mikez71]

So Bentley's might get a P0894 code too?
That makes me feel better, I only had to pay a fraction of the price!
(Still, a bigger fraction than I should have paid...)

 

[strutaeng]

Sure thing, just rename file.
There isn't much TCC activation in my suburban logs..

I'm going to write a TCC disabled tune and see how much driving I can do,
and hope no more codes pop up...
(before either throwing a used trans in, or if I can find a good priced rebuilder..)

Is that file supposed to be a text file?

I opened a sample file on Hp Tuners and it's this file extension:

[thinking emoji]

Edit: I just deleted the ".txt" portion and I got it! Thank you sir!

 

[mikez71]

Is that file supposed to be a text file?

I opened a sample file on Hp Tuners and it's this file extension:
View attachment 484157

[thinking emoji]

I assumed the message board wouldn't accept unknown file extensions. You need to rename the file minus ".txt"
Yet just tried it, only txt zip pdf png jpg's gif and doc extensions allowed.

 

[strutaeng]

I can see what you are talking about. But I do see sometimes the TCC slip go down to almost zero like here:

Would TCC excessive slip mean your torque converter clutch is starting to slip? That's a lot easier (relatively speaking: you still have to remove the transmission) and cheaper than a transmission overhaul. I'm just thinking out loud here...

Although Google says this:

 

[strutaeng]

Another option is to simply turn off that code from being triggered...

 

[mikez71]

Well the times the slip is low, I'm completely off the throttle I think..

Possible it's just the TCC and I won't need a full rebuild..
But, by the time I get a new converter and valve body serviced.. I'm probably halfway to a full rebuild. (maybe not quite.. )
Also, I just don't want to get my hopes up.. There is some whirring noises when cold start..
I thought/hoped it was power steering noise, but the way things have gone been going.. I better plan for the worst!

Good point about just disabling the code..
The TCC hardly/never engages in most of my logs.. possibly because I rarely get the trans upto temp, so far..
I'll try the TCC disabled tune first, and if it heats up too much, I will try disabling just the code..
(I'm curious if the code history is clearable. If not, I may have to wait for a new trans and enough TCC cycles to clear it..)

 

[mikez71]

First test with power enrichment activated.. Maybe more responsive..
Unfortunately I got 5 degrees of knock retard a couple times around 4000rpm+.
(KR degrees actual degrees, not 2:1 like someone was mentioning...)
And that's only with the front knock sensor wired up.. *sigh*

With TCC disabled, my trans temp went from 80degF to 180degF in 20mins around town. (at 80deg ambient..)
Right, temps did seem lower with it engaged, so maybe it's doing SOMETHING... Will test a little more before I disable just the code..

 

[strutaeng]

I rebuilt my 3rd 4L80e a few months ago. I was going to swap (along with Ls or 8.1 swap)into my old beater K3500, but decided to scrap that truck and focus on the GMT800 generation: https://www.gmt800.com/threads/any-tips-on-parting-out-a-truck.9287/page-3

I just realized that transmission is actually a 2005 model, lol.

I'll try logging my 06 in the next few days.

Regarding those Google AI potential issues, I'm pretty sure that Sonnax valve is not the culprit. That beater truck had a stall when shifting into gear, and that's the valve that supposedly fixed that. But you don't have those symptoms...

Doesn't seems like you need an overhaul because none of the clutchpacks seem to be slipping. That leaves the solenoid or maybe another valve body part? What else?

 

[mikez71]

Are you saying you have a rebuilt transmission to get rid of?
(i couldn't load your link, maybe if I join that forum..)

It would be great if I only need a valvebody! Maybe converter too?
First gear seems slacky at low speed, converter feels kind of on-and-off when crawling around the yard at 5mph..
Sometimes (usually when cold I think) there is a whirring sound, so I worry about the pump too.

Then sometimes there is a pinging or tinkling sound, maybe not transmssion as it happens at low load, and seems to go away when I get into the throttle more..

I'll log a couple more drives, then re-enable TCC lockup with P0894 disabled and compare temps..
Will it not run the P0894, or only not report it?
There are these settings for P1870 in hptuners, that sounds like the older version of P0894. Looks like the same criteria for shown for P0894..I will tweak that as well..

I know, I'll have to drop the pan someday...

 

[strutaeng]

Ok, I figured out my HP Tuners Scanner issue. I simply wasn't hitting the "record" button after hitting the "connect" button. I just logged my morning commute on my 99 Silverado, same transmission tho. This is the older P01 operating system, not sure if that differs any over the P59.

I haven't looked at it, so will have to do that later. I've never really logged anything so hopefully I did it correctly. If not, PM and maybe I can email it to you.

Edit: that file may be of no use, because I didn't add the TCC channel before logging it. Doh! I'm assuming I can't add one now?

 

[strutaeng]

Ok, let's try this again...

Drove around my office, just to make sure I got the correct parameters added to the channel. Try this one:

 

[mikez71]

Yea, I can see it. You log has a nice flat spot as you cruise.. Mine NEVER does that.
In fact it heats up a bit with converter engaged as well.. so I think my converter is probably toast.. (plus who knows what else..)
BUT it does seem to shift alright..

Trying to smog this pile of doo doo, then will take it to a trans shop and see what else they can test (pressures?)
Hoping I don't need a full rebuild.. If I do, I might gamble on a used one..