Discovery Sluggish When Cold

2001 Land Rover Discovery V8

I let it warm up for a minute or so in the morning, I put it in reverse and it backs up ok. I then put it into drive and I hear a clunking noise for about 30 seconds and after that, all seems good for the day.

Are we talking a Tranny Filter and Fluid change ... a Torque Converter or Regulator.
I've heard that changing fluid can dislodge debris inside the Tranny which will build up in the regulator requiring that it be cleaned.

Can the requlator be removed and cleaned without removing the tranny from the vehicle?
How serious is this?

Discover Series II - 4.0 Bosh Engine.
Did some more checking, it starts and runs for about 2 seconds then dies, usually stays running on the 2nd try. Was looking to change PCV valves, the WEB alleges that it has 2, (one in the top of each valve cover). Some WEB sites mistakingly identify the EGR system as the PCV system ... Anyways,

There is an Oil Separator http://www.roverparts.com/Parts/LLJ000010.cfm in the passenger side valve cover with a hose running up to the intake manifold, but the Oil Separator is missing on the drivers side Valve Cover? Can't find that it fell down into the engine or was sucked up into the intake manifold. WOW massive vacuum leak aye! The reason for crappy gas milage and maybe even the reason for all the missfire codes on the even cylinders? Are there supposto be two Oil Separators - one in each valve cover??

http://www.roverparts.com/Parts/9205B.cfm

Nope, there is only one Oil Seperator - in the Right - Passenger Side Valve Cover.

Bad MAF's on a D2 normally cause 3 codes, one for 4th gear out of ratio and two for lean codes on banks A and B.

For Bank 1 & 2 System Lean Codes when the truck sounds like it's backfiring from the front of the truck upon acceleration and accelerates sluggishly and goes away after heating up. Your probably getting the following codes.

P0734 A - Gear 4 ratio
P0174 B - Bank 2 system lean
P0171 B - Bank 1 system lean
P1174 - MFR controlled fuel and air
P1171 - MFR controlled fuel metering

Also, to try and narrow it down, other than the MAFs, it could be your spark plugs, oyxgen sensors, or engine coolant temperature sensor...

Swapping the MAF fixed the code for 4th gear out of ratio and the two for lean codes on banks A and B.

I've only seen spark plugs go bad on two vehicles ... one was a Jeep Grand Cherokee and the other on this Discovery. The ignition system fires such a hot spark on these two vehicles that they eat the electrodes leaving the gap on the plugs double what it should have been due to the "missing metal" and causing mis-fires.