My 99 park avenue has 167,000 miles and i have had the car for 4yrs. Need
help from you guys on what to do on my transmission. I am the 2nd owner and i bought the car when it had 100,000 miles on the motor. So my question is should i get my transmission flush or serviced. I don't know if the previous owner
ever had work done on the tyranny. I do have some slipping when accelerating
through traffic. I also checked my fluid an it smells burnt. The color of the fluid is like a dark reddish brown. What should i do. I like the car a lot and have recently did a tuneup, replaced the supercharger gasket, intake gasket and coolant changed.

I think others might agree, but don't flush that trans oil out. With what little clutch material you have left, is still in the the fluid keeping you going.

You might be looking at a complete rebuild.

what about a pan drop and filter change.

Sorry, I'll rephrase that. Don't change the oil or filter in it. The clutch material(whats left of it) is still floating around in your fluid. With it still in the fluid, the clutches and bands still have something to bite with. Otherwise, its all metal to metal contact, or no contact at all.

Unfortunately getting fresh fluid in there may be a bit late, if it smells burnt.
I just bought a 97 PA with 82 k miles & the first thing I did was do the tranny service!
I am picky with my transmissions, it dont matter what vehicles I own, I drop the pan & filter every 35k miles. Friction modifiers break down and things start to heat up then. I also use LubeGard Red additive. Fluids are cheap tranny'* rebuilds are not.
If it really is not slipping all that bad yet, and you feel that you could get by for a while yet, I would immediately drop the pan see how much clutch material is in there and do the filter. Shop may only charge $100 for it ? The other important factor is to ensure that when hot after driving a while, on level surface in Park you check tranny fluid level.
I ensure mine is never under the full line and often go just slightly above to gain a bit more pressure (sloppy slow into reverse) problem for instance on hill, problem be gone then.
Hope an immediate rebuild can be avoided for now...Drop the pan...

i have to agree with mike once you can feel it slipping and the fluid is burnt its only a matter of time. i do know there is quite a disparity in prices for rebuilds i looked around a found a place that did the complete job for 950 for my bonnie. i had to clean the guys boot prints off my rug after but thats worth saving $1000