Slow TH400 Transmission??

[rdurh]

After four years I have my 1979 Jimmy converted over to diesel. The engine, TH400 transmission and transfer case came out of a 1984 CUCV Blazer with 15,247 on the drive train according to the National Guard service records. The original truck sat for several years in a National Guard depot before I got the drive train. Then the drive train sat in the Jimmy for roughly four years.

The issue that I'm having is that first thing in the morning, especially when it's cold, the truck will barely move with the throttle floored. After the transmission warms up, after about a quarter of a mile driving, it then acts fairly normal. I have no idea how well this was treated while it was with the National Guard. I pulled the transmission pan and everything looked OK with no metal fragments or band material. However, the NP208 transfer case went out the first week when a bearing failed between the input and output shafts. I've added some Lucas automatic transmission additive but no improvement when cold though the shifts became better once it warmed up. I've never worked on a TH400 and could use some guidance.

[HammerWerf]

Sounds like the seals inside the tranny have hardened. My wife's 63 Comet had that in the Merc-O-Matic tranny. Unit was about 20 years old when this was happening. She would start to drive, and it would not shift out of low until the fluid got nice and hot to soften the necessary seals to hold pressure and shift into Hi.

A rebuild fixed the problem.

HammerWerf

[rdurh]

Darn, I was afraid that a rebuild might be the resolution. Thanks.

[zijmer]

you did'nt mention reverse? how is it?