Help me understand this transmission problem

[lendaddy]

My 2000 Tundra had a issue year or so back where the coolant mixed with the tranny fluid. Anyway I had it flushed several times and it began working normal again. In the interim I bought a rebuilt unit to swap in (I got it dirt cheap) when it eventually failed from the abuse.

Well the other day it started slipping badly at takeoff from a stop. The weird thing is I can manually shift from 1st to second to drive and it operates seemingly fine but in Drive it slips(from a stop or moving slowly). Does this indicate a valve body issue? Why would first operate correctly when the stalk is in first but slip badly when in auto (in first)?

As a side not the tranny I picked up cheap turned out to be a 2WD tranny so I'm searching for a replacement and/or deciding if this one can be fixed easily enough.

[Walter_Middie]

lendaddy,

Most automatics change the fluid pressure when shifted manually. By dropping it into low, you are applying more pressure to the low/reverse clutch packs. Nothing wrong with your valve body. You soaked the clutch plates with coolant when you had the leak. Once they start to slip, it's downhill fast.

Rex - or know locally as Tranny Source Rex

[lendaddy]

Great info, thanks. At least it makes sense to me now.

[Shawn 357]

When you had the coolant and the tranny fluid mixing you replaced the radiator right?

[lendaddy]

Originally Posted by Shawn 357

When you had the coolant and the tranny fluid mixing you replaced the radiator right?

Yes.