Naturally its been getting very cold here in NJ 30-40F. First thing in the morning my Disco fires right up but is extremely sluggish and will slightly buck if I try to force it to accelerate to quickly through 1st and 2nd. After a few minutes of gently driving she shifts fine. I have 105k, fluid looks red with some Lucas added. (I intend to do a drain and refill with new filter) . No codes, no clunks, no bumps etc new u joints, new rotoflex, 75-90 IIRC in TC and diffs. Just wondering if this is common for our D1s in colder weather until they warm up. I should probably clarify that I am referring to the transmission, and not necessarily the engine.

Doesn't sound unusual. The transmission takes a bit longer to warm up compared to the engine because the truck has to be moving, not just idling. Transmission flush will probably help a little bit if the fluid has a lot of miles on it.

Agreed on fluids change, the performance is by pressure, and the fluid has to come up to operating temp. There is the fluid in the pan, in the lines and radiator and cooler, the actual transmission, and the torque converter. Fresh fluid cures many ills. Now changing the filter takes much more work to get the parts off to get the pan off.

Just draining the pan leaves the material in the torque converter, so you have to plan on drain and refill and drive several times to effect change out of most of the old fluid.

Get that God damn Lucas out of that transmission now before you burn it up.
Lucas thickens the fluid, doing this in the winter makes it to thick to pump through the transmission and you will burn it up.
I have ruined 2 power steering pumps using that crap, get it out of there ASAP.

Belay that.

The Lucas transmission additive isn't the same heavyweight oil that you add to the crankcase, it's about the same weight as Dex III, if not slightly heavier. I have it in my DII (with the electronic version of the DI transmission), and it's been fine, even with the arrival of colder temps. I added it to a perfectly working transmission during a filter change, and I still have a perfectly working transmission 5000 miles later.

Additionally, the transmission takes a bit longer to warm up than many other cars and trucks, because the cooler isn't integral to the radiator like it is on so many others. Just go easy on it for the first 5 minutes, and you should be ok.

Now, all this said... is your bucking accompanied by any other behavior, like the truck feeling like it's in neutral and revving, or a backfire noise, or anything else that is out of the ordinary? Any Service Engine Soon lights?

I am aware that it does not turn your ATF into gear oil like it does with engine oil, it does make the ATF thicker, does the same thing with the power steering fluid, makes it thicker.
Warm weather no prob, cold weather prob.
30-40 is not cold enough to make much of a difference, but once winter hits and it gets down into the single digits...problems.

I have never used any additive in my trans and it is still working fine.
This is my experience, yours may vary.

Also, at least on my D1, the tranny cooler line runs thru the driver side of rad and the "towel bar" in front of the condenser. You may be able to improve things by idling until warmed up.

Yikes ill drain it tomorrow. It seems like the fluid is very thick until it warms up. This is my first winter with my Disco. Thanks guys

X2, idle it in neutral until it warms up.

Keep in mind that one simple drain does not get the large quantity in the torque converter. May take three times with a little driving inbetween to dilute things with the new fluid as it circulates thru the tranny. As for Lucas in the tranny, I started using it at 150,000 in a Mitsubishi Montero Sport, and sold the vehicle at 295,000 and slipping was just beginning to return. But, I must admit it never saw winter beyond Mt Mitchell and Asheville.

I'm a sucker for snake oil. The latest I want to try - ATP AT-205 Re-Seal Additive 135-AT205 - SummitRacing.com