Hello first time posting here but I've been lurking for a while. Here is something I could not find although there are several threads about the 4l80e tranny are for older ones and the symptoms not exactly like mine.

Tranny was shifting fine but it would delay to get to drive or reverse, was overheated so I put new fluid in it (dx6) and a cooler with a thermo switch, then I also replaced the input and output shaft sensors. Tranny would shift a little better (was banging gears before) but still delay to get on drive or reverse a lot and would not downshift very well. Now it does not go forward or reverse, tranny would delay before but at least it would shift through all gears, I'm hoping this is some electronic failure (van is not molested) and I don't need a rebuild.

Someone please help.

 

filter ever changed? how many miles/km on tranny?

 

Tranny has 116k miles, when I changed the fluid it would take a little time to start flowing but once it started I could get a hole gallon out then refill start the engine and get another gallon out. Is it possible the pump is out? If so how hard is to get it out? Anything else I could check?

Thank You for Your help, much appreciated.

 

Here is an update, I pulled the harness going to the tranny and plugged it back in after a few minutes check to see the wires were all connect where they should and then started the engine, put it in drive and it went forward, put it in reverse and it went backward. I took it for a ride in stop and go traffic then on the highway at 70mph and it feels like when it is on a flat it wants to engage the TC (just guessing) and it vibrates, I release the go pedal and press it again and it will clear, some times it will do this a few times and will clear the same way.It doesn't bang gears anymore.
It still delays to go on drive and reverse as well.

I could use some help , Thank You.

 

I'm really lost here, is there anywhere I can find some information to guide Me troubleshoot this behavior?

Thank You.

 

I had similar problems with a G30 i recently purchased. Had the transmission "flushed" to clean fluid trapped in torque converter.The flush is more than just a drain and fill. Replaced tranny filter, fluid, and added Slick 50. Problem cleared up. Flushes can be a little pricey as fluid replacements go, but there are instructions online if you wanna' try it yourself. You could always drain a little fluid and add the Slick 50 and see if that helps if ya' don't wanna' spend the money.

 

You put the wrong fluid in it. DX6 isnt for your car. You should have used DX3 or DX4.

4L80E is a heavy duty transmission so frequently the "banging" was never banging, just the transmission case pitching against the motor mounts. That trans is meant for high torque applications so it performs differently than others do because of the wide variety of large displacement and powerful engines it is used with.