Hi Craig - seems a shame to get rid of the old crate after putting in SO
much work! gasp!
Anyway, further to the fluid question, Dexron/Mercon transmission fluid of the type our cars need is no longer available, so folks use a substitute. One important spec to pay attention to when shopping for new fluid is the viscosity at a given temperature.
The stuff I use is for old cars like mine and called Motomaster ATF(DEXRON type), a brand from a Canadian big-box store so not available in the UK - however the specs on this stuff are better than the old Dexron/Mercon.
from the discussion on another site:
The viscosity of MotoMaster ATF is specified at 40 mm2/s at 40 degrees Centigrade, which is actually higher than original ACDelco Dexron III
Correct fluid is critical of course, but other issues could be at play. Smooth gear shifts are orchestrated between the ECM and TCM based on several sensor inputs, among them engine load (MAF sensor), engine speed (CPS), road speed (ABS Control Module), and throttle position (TPS). If any of the important signals are a little out of range, shifts can be affected. You might try cleaning the electrical connector at the transmission, drilling drain holes in your TPS housing and flushing it, cleaning the electrical connectors for all important EMS sensors, and cleaning the ground points referenced by the ECM (two at the intake manifold runners and the one on the firewall behind the cylinder head), the ones referenced by the TCM (there are three, at least one is on the firewall behind a blower motor), and the engine ground strap.
94 XJ40 VDP
Oyster Metallic/Doeskin on Aero Alloys
230,000 Kilometers 143,000 MilesDaily Driver
94 XJ40 SOVEREIGN
Diamond Blue Metallic/Barley
111,000 Kilometers/69,000 MilesParts Car