Rebuild th400 or 4l80e?

[txaggie]

Howdy all!

I have an 85 454/th400 suburban and my first travel trailer pull (6miles in) caused me to puke out new tranny fluid out the vent tubes. The fluid came out burnt and black so I’m guessing the clutches are shot. Should I rebuild this thing (much cheaper?) or swap to a 4l80e (new shaft, controller, etc?)?

The turbo 400 looked good on the inside but I wonder if being 40 years old made it take the cake when I towed with it?

 

[idahovette]

Got a trans cooler on it?

 

[txaggie]

Got a trans cooler on it?

Yes. External cooler

 

[Ricko1966]

Yes. External cooler

In series with the radiator transmission cooler?

 

[Vbb199]

This is all a matter of opinion... it should be obvious

OD or no OD, to break it down to its lowest common denominator

 

[txaggie]

I daily drive

In series with the radiator transmission cooler?

not run through the radiator. Exterior only.

 

[NickTransmissions]

I daily drive

not run through the radiator. Exterior only.

Run it through the radiator then to the ext cooler. You're giving up a lot of heat exchange by not including the internal cooler in the system.

Also, Id swap in a 4L80E if it's in your budget to do so.

 

[txaggie]

Run it through the radiator then to the ext cooler. You're giving up a lot of heat exchange by not including the internal cooler in the system.

Also, Id swap in a 4L80E if it's in your budget to do so.

My tech told me it would be cooler if it didn’t hit the warmer radiator. More cooling time does make since.

 

[Ricko1966]

My tech told me it would be cooler if it didn’t hit the warmer radiator. More cooling time does make since.

Your tech was wrong. A fluid to fluid cooler is more efficient than a fluid to air cooler.Burn your finger,then wave it in the air,or dunk it in water which one cools faster?And I don't actually 100 percent agree with Nick. I run through the external cooler to the radiator. The radiator regulates the transmssion fluid temperature so it is not too hot not too cold. Transmission fluid should be in the 175 to 225 range. Engineers discovered a long time ago,engines didn't wear as much if they maintained the proper oil temperature,not just as cold as they could keep them. Transmission fluid is oil.

 

[Bennyt]

I'd rebuild the 400 and add a Gear Vendor.