HELP!! TH400 tranny cooler lines...

[Dirtball]

It actually looks like the 4L60 is more like the TH400 so far as where the high and low lines go into the trans... lots to think about...

 

[Dirtball]

I pulled the high pressure line and inspected it closely. It has no visible signs of damage. What is the next best place to look?

I guess I can fill it back up with fluid, drive it, then see where it's leaking... maybe I should have done that to begin with, but I was just relieved to have truck and boat in the driveway!!

 

[Schurkey]

I pulled the high pressure line

There's no "high pressure" in the cooler circuit. If there was, the crankshaft thrust bearing is in trouble. Cooler pressure is moderate-to-low.

and inspected it closely. It has no visible signs of damage. What is the next best place to look?

I guess I can fill it back up with fluid, drive it, then see where it's leaking... maybe I should have done that to begin with

First I'm hearing about leaks.

Cracked flares are a problem, as are cracked trans cases where the adapters screw in. I've seen cracks on the tubes themselves--generally from not being supported, vibrating, and then work-hardening (Metal fatigue.) Sometimes the tubes are worn-through by rubbing on something. An acceptable fix is to cut-out the cracked/worn section, add some tube nuts before double-flaring the ends, and install an inverted-flare union. Most folks don't bother with the flares, they use compression unions. It's simple, less-expensive...but not as secure.

The 4L80E cooler tubes had a major change sometime in the '97 model year. Early '97 and older was set up like the 400. Late '97 and newer has the return tube plugged into the trans farther to the rear, by the planetaries.

 

[Dirtball]

There's no "high pressure" in the cooler circuit. If there was, the crankshaft thrust bearing is in trouble. Cooler pressure is moderate-to-low.


First I'm hearing about leaks.

Cracked flares are a problem, as are cracked trans cases where the adapters screw in. I've seen cracks on the tubes themselves--generally from not being supported, vibrating, and then work-hardening (Metal fatigue.) Sometimes the tubes are worn-through by rubbing on something. An acceptable fix is to cut-out the cracked/worn section, add some tube nuts before double-flaring the ends, and install an inverted-flare union. Most folks don't bother with the flares, they use compression unions. It's simple, less-expensive...but not as secure.

The 4L80E cooler tubes had a major change sometime in the '97 model year. Early '97 and older was set up like the 400. Late '97 and newer has the return tube plugged into the trans farther to the rear, by the planetaries.

It blew out coming up a very long, steep incline pulling my pontoon boat... spraying fluid all out behind the truck... when I got to the driveway it poured out into a big puddle on the driveway. So not just a leak, LOL...

 

[Schurkey]

Have you verified that this is a cooler-tube problem? Maybe you cracked the trans case or blew-out the torque converter seal. Dipstick tubes are known to crack, especially the older ones with an O-ring seal instead of the newer "top hat" seal.

ATF is surprisingly flammable. You're lucky you didn't burn the truck down.

 

[Dirtball]

Have you verified that this is a cooler-tube problem? Maybe you cracked the trans case or blew-out the torque converter seal. Dipstick tubes are known to crack, especially the older ones with an O-ring seal instead of the newer "top hat" seal.

ATF is surprisingly flammable. You're lucky you didn't burn the truck down.

No... it was so late when I got in on Sunday, then it was too rainy that week to even think of crawling around on the ground under it. Sunday was my first chance. I guess I'll splurge on enough fluid to fire it up and see where it's leaking... Thanks so much for the info!

 

[Dirtball]

Anyone have thoughts on this?

Look... I'm really ignorant when it comes to trannies... after I put the high line back on (after pulling it and checking it) I filled it up with fluid and drove it several miles down the road and back. It pulled and shifted just like it always did. When I got home, I crawled under it and no leaks of any kind were to be found. The next day, no puddle.

Is this crazy/unusual/rare/common... anything? I don't know enough about them to know where it might have puked all the fluid out but now not puking at all... unless it was leaking from the fitting that I removed and put back nice and properly tight. I didn't notice being overly loose when I removed it, but then, I wasn't looking for it to be loose either...

Can anyone shed light on to what is a mystery to me?

 

[Schurkey]

Got overheated pulling the pontoon boat up the long, steep incline; expanded, got whipped-up into foam by the rotating assembly, blew out the vent? As it cooled after the steep incline, it contracted. The level was low, so the pump sucked air, which continued the foaming, and release out the vent?

I dunno...but hitch the boat and go climb that incline again.

 

[Dirtball]

Got overheated pulling the pontoon boat up the long, steep incline; expanded, got whipped-up into foam by the rotating assembly, blew out the vent? As it cooled after the steep incline, it contracted. The level was low, so the pump sucked air, which continued the foaming, and release out the vent?

I dunno...but hitch the boat and go climb that incline again.

It puked at least half a quart after I pulled into the driveway... it took it a day to a day and a half... all in one big puddle. Does that fit into the narrative above?

 

[stutaeng]

It seems unlikely that it would leak from the cooler lines sitting on your driveway. What's the story with the truck? Have you owned it for a long time? Have you towed the same boat with it before? If you just bought it perhaps it was overfilled? Did you check where the level of fluid was? What does the dipstick say?

Generally, where did the puddle appear? Near the engine, near the driveshaft, passenger side or driver side?