I have a 1989 D150 318 with 4-speed auto tranny. In the last couple of weeks it's developed an issue where it won't upshift when cold. I have to travel about a 1/4 mile before it shifts into 2nd, a mile before it will shift into 3rd and another few miles before it shifts to OD. After that the shifting is fine, so it seems to be a temperature issue and my Haynes book doesn't say anything about it. Any suggestions?

 

Low fluid level, misadjusted throttle rod linkage, misadjusted kick down band, and several malfunctioning inner parts can cause that.

 

I recently replaced the TPS, is there a possible connection there?

 

I don't see how the TPS could be the problem. The only connection for shifting thru regular gears between the engine and the trans is the throttle rod linkage. The first three things I mentioned can be easily checked and eliminated as the problem. Once they are eliminated as the problem I can take you further into diagnosis. When was the last fluid/filter change?

 

the TPS does control the trans,but a faulty TPS should only prevent it from shifting into OD. just my $ .02

 

That is correct to a point. That is why I said the regular gears and not OD. The SMEC actually limits the ability for the trans to engage OD until after certain parameters are met. The TPS and engine temp sensor must met certain required limits before the SMEC allows engagement of OD.

 

The last service, including band adjustments, was about 1.5 yrs ago. After my first post I remembered a Caravan we had with a similar problem and fluid/filter change cured it, but that oil was near black, while the oil in the truck is quite clean. When the weather warms up some I'll check the other two.

 

Put a drop of fluid on your finger and taste it. Then tell us what it tastes like.

 

Seriously? What should it taste like?

 

Yes,seriously. It will tell you if the bands are burnt,if there's grit in the fluid,or other troubles.