ETOD of my tranny?

[jdwhitlo]

I need help "estimating time of death" for my Transmission. 72 GMC C20 350/TH400.

I am assuming It's the TH400 but I do not know that for sure. The guy I bought it from said that the tranny had been replaced about 30K miles ago but he didn't think it was the same as original. I wasn't very concerned about it because I have plans to do a 700R4 conversion this summer. But I recently moved to Colorado and in this cold weather it has gotten worse and I'm not sure it will survive till summer.

Symptoms:

1.) When cold it will not want to engage into gear. Reverse is the worst.
2.) When cold but having gone into gear and moving it will shift but will take a very long time to engage into the next gear. Acts as if it were a manual that you were burning the clutch in.
3.) Still cold, and I come to a stop it will shift in and out of drive and neutral causing the truck to jerk. You can hear the idle of the engine start to gradually rise then it jumps hard into gear. It will do this until it gets wormed up.
4.) Once wormed up all symptoms go away and the tranny works perfectly.

I would assume it's either the torque converter or the clutches but I haven't dealt with many transmission issues so I'm not sure.
I have checked fluid levels and all is well. It does not leak fluid either.
I would like to know if anyone has experienced this and if there is a low cost fix? If not, how long do you think it might last?