4L80E Help

[Jrgunn5150]

I bought a 1998 K2500 Sierra with a 5.7 Vortec and supposedly fresh 4L80E. The trans does show signs of having been R&R'd at least.

Since I bought it basically not running, the issue didn't show up right away.

It shifts HARD, I mean, stupidly, something is going to brake hard. The indicator works in Park, Reverse, and Neutral, but not in the forward gears. The one longish trip I took in it, it did sometimes shift properly, with the indicator lit in the neutral position.

Since I had no confidence in the PO, I took all the connections lose, sprayed them out with brake cleaner, and put them back together. The shift indicator still isn't reading properly, and now it's locked in 2 gear.

When i took the connectors apart, the big one that goes through the case fell inside and I'm certain it isn't hooked up properly now.

Does anyone have any other suggestion's of what to look at or why?

I am pulling NO trans codes, only a MAF code and a O2 sensor code.

[Valarius_Starchaser]

so the large connector thats in the side of the case fell into the trans?!?!?!?!?!

[Jrgunn5150]

Originally Posted by Valarius_Starchaser

so the large connector thats in the side of the case fell into the trans?!?!?!?!?!

It pushed in instead of letting me really push the outer connector into it. But i drove it about 5 miles today and still didn't get any trans related codes, so who knows.

[Valarius_Starchaser]

well the way the connector works is it has on O ring that seals it and tongs that hold it to the case side so either the tongs broke off or its not installed all the way which should be addressed which obviously requires a pan drop I have heard that the connectors can leak through the pins too causing goofy issues (is ATF conductive? )

As far as the hard shifting goes it could be a bad accumulator spring "ie broken" but the fact that the PRNDL signal doesn't operate properly makes me think more toward electrical as that is how that system operates I would be replacing that harness first and inspect for metal or excess debree in the pan to decide if it just needs torn down

I work at a GM dealership and if you get me the last 8 of the vin I can tell you the exact GM part number you need for that harness as from my experience looking them up there is something like 9 options which would prove difficult

member clinebarger is a pro with 4L80e's so hopefully he will stop by and may be more capable to know if theres a deeper internal failure to it

[Jrgunn5150]

Originally Posted by Valarius_Starchaser

well the way the connector works is it has on O ring that seals it and tongs that hold it to the case side so either the tongs broke off or its not installed all the way which should be addressed which obviously requires a pan drop I have heard that the connectors can leak through the pins too causing goofy issues (is ATF conductive? )

As far as the hard shifting goes it could be a bad accumulator spring "ie broken" but the fact that the PRNDL signal doesn't operate properly makes me think more toward electrical as that is how that system operates I would be replacing that harness first and inspect for metal or excess debree in the pan to decide if it just needs torn down

I work at a GM dealership and if you get me the last 8 of the vin I can tell you the exact GM part number you need for that harness as from my experience looking them up there is something like 9 options which would prove difficult

member clinebarger is a pro with 4L80e's so hopefully he will stop by and may be more capable to know if theres a deeper internal failure to it

That's what I was unsure of, it seemed to me I should have been able to press the other side of the connector on without dropping the pan, like, something should have been holding it. It's on there now, but I'm nearly certain it's not correct. The second gear only condition I have now confirms that.

With the shifter disconnected I moved the lever on the trans through the gears and it still didn't read them properly. I've been reading on the internet that it doesn't matter to shift, but that doesn't really seem right to me.

I'm pretty close to just buying a new harness and all the solenoids in one of those kits, if I have to drop the pan, I'd like to just do it once and be done, 25 bucks of fluid every time I drop it adds up lol.

I'll get the VIN tomorrow, I'm at work currently, but I'd like to be able to get this on the road this month, so I appreciate the help!

[Valarius_Starchaser]

the solenoids have an ohm rating that shows if they are good or not you can also send 12v to them to check but I have never done the 12v test I can get that information for you aswell

[Jrgunn5150]

Originally Posted by Valarius_Starchaser

the solenoids have an ohm rating that shows if they are good or not you can also send 12v to them to check but I have never done the 12v test I can get that information for you aswell

I got the manual off Dieselsite, and I have a Chinese Tech 2 clone, so I'll go at it in depth this weekend.

I may just order everything and replace it and be done with it lol. Since it looks like I have to drop the pan no matter what, I may as well make sure it's good for a couple years.