THD 400 whining

[chev80]

I have 1980 Chev 4x4 350 CDI with a THD 400. When its cold on start it will whine and be sluggish to go into gear. This whine occurs in park and then goes away after 20 sec. to 1 minute depending on how cold it is. When I shift it into gear and this occurs again with a 5 to 10 sec delay before it kicks in. Once it is warm this stops. Could some one help as to where I should start in the diagnose process.

[Gandalf]

I assume it's an automatic? When was the last time the transmission fluid was changed?

[apavlov13]

Yeah the 400 is an auto. Honestly I don't know how much more can be done to an auto other than changing the fluid.

[chev80]

The tranny fluid is newer and nice red not smelling burnt. I thought it might be the torque converter or the pressure pump. Any ideas

[apavlov13]

Hmmm....Are you comfortable enough pulling the valve body out and cleaning it out?