4L80E Fluid Change ??

[WILLYD-MAX]

I did a search but could not find what I needed. My brother in law has a 98 2500hd 454 with 4L80E and I needed to know the fluid capacity when changing fluid and if I could flush it like the allison, as in pulling the from cooler line off and flushing it out? I was going to try and talk him into letting me put Amsoil synthetic fluid into it. Do these trans tend to run pretty hot when towing?

[JohnC]

Yes, they throw some heat when towing. I personally think this is the reason so many 6.5's have overheating issues. My 5 speed never got hot...

Here's a procedure I've used in the past. It seems to work pretty well.

Remove the top cooling line from the radiator and put a piece of rubber hose on it and run that into a bucket. Start the engine and idle in park until it stops pumping fluid into the bucket. Shut down, drop the pan and change the filter. Put the pan up and add about 7 qts of fluid. Run it again until it pumps dry. Repeat if you're a fanatic. Reconnect the cooling line and add another 7 quarts. Run it to temp and then check the level according to the manual.

You'll need 14 -16 qts (21-23 if you're a fanatic)

[DmaxMaverick]

About 7 1/2 qts. for just a pan removal. About 14 qts. total capacity. Different applications will vary slightly.

Yes. You can use the method described here for the Allison flush. With the 4L80E, you can also use any flushing machine method without worry, unlike the Allison.

The 4L80E does tend to run at a higher temp range with loads. Towing/hauling with the TC unlocked (lower speeds/high pedal input) will cause even higher temps. The tranny does tollerate it well, though. The key to longevity is fluid health.

Amsoil synthetic is an excellent choice for fluid, IMO. I use it exclusively.

[WILLYD-MAX]

Thanks JohnC and Dmaxmaverick! Very much appreciate the info, it was just what I was needing.

[DA BIG ONE]

I've spent lots of $$$$ for my 4L80e setup only to find trans cooler lines way too close to the exhaust, so, I installed AeroQuip fire sleeves over lines as heat barrier. I then installed B&M's super cooler which has a thermostatically controlled SPAL s-blade fan.

Note: Fire sleeves must be sealed at ends from the elements w/good quality hi-temp silicone sealer, then stainless wire ties to finish job at each end.