'84 Pioneer XJ Reverse Problem

Hi All. I'm new to but it looks like a good place to ask questions.
My '84 XJ is an unmodified 2.8L with automatic tranny. The transmission has had no problems since I got it 6 months ago and the only maintenance I've had done to date is changing the tranny fluid and filter and changing out the fluid in the NP-207 when I got it.

Once the weather turned cold the reverse takes about a half minute or so to engage. It goes into 2-HI right away no matter what the temperature but not reverse. Once the transmission is warmed up it shifts into reverse promptly with no hesitation.

Any idea what is going on? Thanks!
OBXXJ

You have a sticky valve in your tranny, I advise a tranny flush.

Hi All.

Cherokee Briarwood. Just over 100,000 mi.

I'm having a similar problem. No reverse after start up. Transmission was very clean when I dropped the pan and changed fluid last time. Don't believe it could be a stuck valve (solenoid) because I think it would act up in first gear too. After it engages reverse works fine (no slip) and all other gears ok too.

Any tips.

Patrick