Hi all. After a recent battery failure I am getting a delay them a clunk into reverse when cold. TL 4 speed, well serviced. Any thoughts?

Have you done the auto re-learning procedure?

Not sure how to do it. Any ideas? Would it only need doing on reverse?

The auto will re-learn how to shift smoothly itself in time with normal driving, generally only takes a few days I think. There is a procedure, this is the closest I found with a quick search but I'd recommend checking this with your own Googling:

"Bring engine up to operating temperature
ensure idle is below 1000 rpm

Manually move gear lever neutral to reverse and hold for 3 secs then back to neutral
repeat 5 times

Manually move lever neutral to drive and hold for 3 secs then back to neutral
repeat 5 times

Now without switching ignition off

Proceed to drive at light throttle for about 5 minutes on a flat road
max 15 percent throttle

then

Proceed to drive at medium 25% throttle for about 5 minutes on a flat road"

What transmission fluid are you using? Many years ago, I had a Range Rover with a horrible 3 speed Torqueflite transmission. It required Dexron 3 fluid, but I couldn't get any, so I used Dexron 4. Gear changes were much more positive, but in reverse, it was a case of grip/slip/grip/slip until it warmed up. This is probably not directly relevant to your problem, but the fluid type and condition can have a marked effect on performance.

I know you didnt mean that the OP should use Dexron erad, but its worth repeating dont use Dexron, of course, should be using only Mitsu SP 3 ATF.
The relearn sticky is here http://www.aussiemagna.com/forums/showthread.php?t=86194&highlight=transmission+relearn+procedure