4.6 HSE 97 128K Auto box or Engine Faulty??

Guys...

How do I know if I need to either;

Rebuild engine
Rebuild Autobox
Or just do the Tourque converter

I have a 4.6SHE Auto 97 with 128K on the clock. I have slight tapping when warm (yes there is oil in her) and she seams very slugish (less powerful than my onld 2.9 classic). If you dump your right foot - she'll kick down but will just rev at 3 to 4K rpm without anything hapening.

I'm looking at either a replacmenet engine or a rebuild top end (assume I'm lokoing at the corerct things here) - but am woried about the auto box etc. How do you test these things without spending out??

last one i saw with a fault like that had a cracked gearbox case (apparently a common fault)

any particular point on the box... and is there a test I can do to find out?

Torque converter... how do you change it?

Assuming the vehicle has been well serviced, ie, plugs, filters etc. If it is a tapping noise from the engine, it could well be the hydraulic tappets, if the engine has not had regular oil changes, they can become carboned up and stick so they do not open fully hence a larger valve clearence, resulting in lack of performance, at the milage you state, it is a possibility. worst case new camshaft and followers (tappets).

They gearbox ecu takes readings from the engines output, if power is down it affects the gearchanging.

These cars need to be tip top for everything to run right, some view them as a step forward from the classic, others a step back.

Any suggestions about using a good additive / fuel system cleaner to flush out the carbon then?