4l80e. Transmission failure 1st trip for 2015

Hi Burbman,
Yes it was a wiring issue. The wiring harness and inside of the PCU were corroded. That caused the super high temps last season, and the transmission failure in 2015. I also had strange engine codes all last year that could not be isolated. I camped this weekend at my favorite park, up and down 15% grades and the beast was roaring. Lockout was working, engine max temp was 210 after a serious 5 mile climb. I kept the trans in 4th and tow haul on, and it performed flawlessly. I was talking to a local mechanic over the weekend and the same scenario just happened with a duramax/allison combo in the shop. Computer destroyed the innards of the allison.

Was it a wiring issue?

Trans was rebuilt with stage 3 shift kit. New issue discovered, no codes, or warnings. The PCU was not communicating with the transmission. It was never locking up the torque convertor. WTH, had the truck in 4 shops last year for the trans!

Thanks Burbman

Glad you have a good trans guy, probably a lot cheaper than a Jasper unit. Here's the tech bulletin that Jasper publishes on the 4L80E with the list of their mods as a point of reference:

The truck is being serviced by a Dodge dealership that rebuilds all of our hd truck's trans issues we encounter on auction bought trucks. Many cummins autos, gm 3/4 4l80 and 6l80 trucks. We bought a plow truck last week 6.0 4l80 combo. It only had 68k on motor and we need to replace the engine.
Oh the daily ins and outs of small used car dealership.

The dodge dealership even works on our medium duty 26,000lb Bering 5.9 cummins, 6spd rollback.

The work is being done by there gray haired transmission master mechanic. Transmission guts, clutches, and innards are all over his bench.

Ok the transmission is out of the truck right now and apart. The bad news was it had been rebuilt by previous owners and last rebuild forgot or f'd up an O-ring. Burned clutches for 3rd and Reverse. Seriously mangled pump piston area where the o-ring screw up occurred. It had a maroon torque converter, cracked upper engine block bolt tab, and needed to be machined off the bell housing. Last season's bandaids : hot trans warnings, and wasting $700 in diagnostic attempts, flushes, and re-flushes. Going with a new GM torque converter, stage 3 shift kit, additional clutches, and additional new parts if needed.

Man that stinks! I really don't know much about transmissions, but from what I was able to find out, there is a part in the reverse drive that is prone to failure and is fairly easy to fix....the problem is that it's the last part you would remove when taking that trans apart, meaning that it requires complete disassembly to get to. So, if you're going to repair, you may as well rebuild since you're paying for the labor to R&R it.

My preference would have been to rebuild it, but I couldn't find a shop I felt I could trust in small town Western KY....the local shop recommended by a fellow forum member was a general repair shop and a Jasper dealer. I ended up going the Jasper route since they have a 3 year 100k warranty honored by any Jasper dealer in the the US, and there are thousands of them. My buddy who owns a 6-bay independent shop in NY has been dealing with Jasper for years and advised that their warranty support is good. I figured that being on the road with the RV at least I would have warranty access if I needed it.

FYI, if you go with Jasper, be advised that the fine print on the warranty requires you to change the filter and fluid at 5k miles. You can do yourself but save receipts.

You have the advantage of being home and not stuck on the road...if you have a good trans shop that you know will do the right job, you really shouldn't have to rely on a warranty...and it will likley be cheaper to have it rebuilt than go Jasper.

I would suspect that the fact it works in 4LO has something to do with the line pressure or whatever in the transmission rather than with the transfer case...if the transfer case was bad, it wouldn't go forward in 4HI either. I never tried 4LO when my I lost reverse, didn't think it would make a difference.

I would not jump out and condemn the transmission or transfer until I had it checked out. There is several electrical connections on some that could cause issues including the transfer case.
Is there an engine check light? Some later rigs set codes for shifting problems identifying what the problem could be.

On my 02, I had a local performance shop rebuild mine. Now that being said, when they took it apart at 180k there was not much wear on the clutches. This is with the truck being abused the majority or it's life. It had been worked since day one and worked hard, that's why I got it cheap. Anyway the problem that I had was the torque converter not staying locked up. My problem was with the valve body assembly that went bad. I did lose reverse sometimes which also was a symptom. It would have cost me about 1200.00 for the new valve body and TQ converter, and a full performance rebuild was 1700.00 so I chose to rebuild the unit. The TQ converter from that era truck had some issues of cracking, which leaked fluid inside the unit. This prevents the lockup and other issues. The valve body assembly was going bad which caused the reverse not to work at times. But the 4l80e internally as far as forward clutches were in really good shape despite the abuse. If u have the 4x4 def check the pump rub. Take this truck to a trusted shop, if you were in florida I would send u to the shop who worked on mine. Btw when I had it rebuilt, I had them install a minor shift performance kit which was really nice for a firmer shift and after rebuild I will say the truck pulled better as far as tranny goes. The gears shifted quicker up the hills then before. Hope this helps, if u don't already know , the 4l80e is one of the most strongest tranny that was ever built. They use them in all differnt applications including racing. They are one of the best that I have used and very durable. Hope this helps,
Kris