Hi,

I'm looking for some advice. I picked up a 2500hd from an auction, knowing that there would be some issues. I have fixed most of them but stuck with a decision. I have contacted the local transmission places and I do not trust their assessment. I honestly believe they want to take me for a spin.

Transmission is a 6L90.

Initially I had a transmission code P0777 (Pressure control solenoid B - stuck on), and P0796 (Solenoid C - Performance or stuck off). Transmission has issues getting into and out of 5th gear from either 4th or 6th. It would whine for a couple seconds then settle. Transmission would overheat.

I changed transmission fluid and put a new filter. Fluid was dark brown. Metal filings found on magnet (see photo). The small little rocks in the photos are non-magnetic and I think they are stones/rocks. Shifting was better, but still had same issue with 5th. Transmission doesn't overheat.

Transmission will lock itself into 2nd or 3rd on long drives. I clear the codes and everything will be fine. New codes, P0700, and P0777. Provided I keep the transmission in 1-4 I don't have any issues. No sounds, whines, clunks, overheating.



Million dollar question.... Should I chance replacing the solenoid pack or should I replace the whole transmission?

FYI. Former aircraft mechanic. I am mechanically inclined, I just don't want to be taken advantage of from shady transmission shops.

 

How the hell do you get a rock inside the transmission? That alone would make me lean towards a rebuild.

 

Not quite sure how they would have gotten in there. They are small and could easily fit down the dipstick. Maybe 1/8" in diameter.

 

Those "rocks" look almost kind like oil-dry.

Looking at all that steel on the magnet, I'd say that solenoids are unlikely to repair the damage and fully restore the trans to proper function with longevity. That's gonna need a tear-down and rebuild. Some clutch looks like it has gone metal-to-metal for a LLLLLOOOOOOOONNNNNNNGGGGGGG time, or some hard part has destroyed itself against some other hard part. Not saying the solenoids are good, you shouldn't change the solenoids, or ANYTHING ELSE of the kind; only, that even if they're the root cause of all this, replacing them, by itself, isn't gonna fix it.

 

That’s what my th350 looks like after 4 pan drops. It still works hahaha.

But seriously, that trans is toast.

 

Thanks. That was my worst fear. I really was hoping to get a bit more out of it. Time to bite the bullet.

 

There's a 1% chance a solenoid pack fixes your issues long term
and a 99% chance this trans needs rebuilt.

the 6l80e is a problem child that I could go into detail on its shortcomings but the condensed version is that they are not cheap to repair the right way...and the right way very often does not include a complete solenoid pack replacement because their failure rate is surprisingly low.

 

Thats one of those “rock crusher” transmissions

 

I agree. That transmission is done for.
All of the 6L80 and 6L90's ive worked on had torque converters that were trashed.. all that metal gets into the transmission and destroys everything.

 

torque converter failure is often a result of other shortcomings, but it is the one thing that shoves metal through everything else and gets alot of attention

pressure regulator wear
valve body wear
both of these lead to a multitude of downstream issues

cracked pistons/drums are also fairly common...sometimes caused by the pressure regulator wear

the tune is a joke and GM should be publicly shamed for their lockup programming.
there are other ways to go about a smooth apply to keep the ride comfortable for the driver...but the way GM did it was to program in 20-60 rpm (sometimes more) of slip at all times when the torque converter is "locked"
That clutch is always slipping...and it is programmed to slip...and it just burns it up over time. Leading to the friction lining being worn away and plugging filters and sending material through the trans...and if it goes long enough you will wear away all of the friction lining and end up with metal to metal contact inside the converter that just send HEAPS of trash through the trans, cooler, pump, etc. It's horrible.

and despite all of these issues...the techm really has a pretty darn low failure rate. They can be partially disassembled and cleaned/rebuilt for very little cost and it works great