4L80E Service Question

[DitchDr]

Greetings,

I will be droping the pan on the transmission this weekend. I have not had much experience with the 4L80E transmission. Is there any thing I should check, change, adjust, while I have the pan off.

The truck is a 96 GMC K2500 HD Ext cab F engine 3.73 gears. 216,000 miles.

Thanks. I enjoy the forum a great deal......

[93_Burrito]

Are you changing the fluid and filter for maintenance? Or are you dropping the pan for another reason? If the transmission is working properly, I would just replace the filter and the few quarts of ATF you drain to drop the pan.

If you want to firm up the shifts, this would present an opportunity to add a shift kit. Otherwise, if it ain't broke... don't fix it


Andy

[DitchDr]

The primary reason to drop the pan is to change the filter and fluid. I have read there are switches, sensors and soleniods that can cause problems. Just wanted to know if there was anything I should pay close attention to.

Thanks for the reply.

[john8662]

Usually, if it ain't broke don't break/fix it.

Solenoids can be renewed, but this is usually necessary after a performance ECM has been isntalled, because they all increase trans internal pressure for crisper shifts. Seems to cause issues with some transmissions that had been working fine before.

J

[Robyn]

To get a good fluid change you need to purge the system.
Unhook the cooler lines at the radiator and place a short piece of hose on the ends of the lines and run them into a bucket.
Run the engine with the trans in "N" and then shut off just as soon as the fluid clow starts to drop off. Refill the pan and do this again and again until the flow is bright red.

Now yank the pan and replace the filter and wash out the pan.
Take note of any large accumulations of crap.
A gray residue or goop in the bottom of the pan is normal.
If you find larger pieces or flakey stuff or metal chips then this is an indication of issues that need attending to.

With the good purge of the tranny you get the bulk of the dirty fluid from the converter.
This type of change is going to use up a case or more of tranny fluid.
Years ago the converters had a drain plug but not any more.

The large shops have the flushing machines to do this.

**NOTE** do not run the rig after the fluid flow drops off while purging.
Have a helper work with you.

This wont take a long time but is well worth the effort to get the old fluid from the tranny.

As has been said if the sucker is working ok leave it alone.
There are no adjustments inside that need to be messed with.
The days of adjusting the bands is long gone.
These boxes dont have any adjustments anyway.
The stuff that is adjustable can only be done with the box apart and on the bench and then its "select fit" parts that are used to achieve the correct settings.

Good luck

Robyn

[DitchDr]

Thanks everyone.....