Steve, this gearbox / diff noise / clunk is intermittent, have done over 200 miles since I picked her up on Thursday and it has happened around 75% of that time when coming to a stop only! Driving she is perfect and goes through the gears nicely and kickdown is very good aswell, not ever having had a classic car before and never an automatic new or old, am I just being paranoid? Diff oil was fine and transmission fliud too but wasn't as red as it maybe should be, would it be wise to drop fluid and install correct AQF for peace of mind? thanks Rich..
Was intermittent on mine too, it'd predictably do it at some junctions on my regular routes. I tried investigating and the gearbox/diff idea was the only thing that seemed plausible - everything else was perfect. I replaced all the rear suspension and bushings (was doing that anyway) and it still happened. Granted I can only speak for my car, maybe a few other people can chime in?
As for the fluid, given how much of a pig the auto-boxes are to work on it may be worth new fluid anyway. It's not uncommon for people to just put in whatever ATF they can find, but there are many guides online saying how important it is to use Comma AQF.
Sadly I'm not really able to do more diagnosing on mine as the engine/box is being changed for an MX-5 1.8 litre engine... Big project!
1978 Triumph Dolomite MX-5 Build (Project) viewtopic.php?f=19&t=29239
1959 Morris Oxford IV Traveller in Red/Cream (Daily)