Automatic transmission fluid change?
 

I recently purchased my first automatic, an imola red X5 4.6is! It has 135K miles and I plan to change the differential and transfer case oil immediately. I'm unsure about the transmission oil. I've heard that at this mileage if it has not been change it's better to leave it unchanged. Any thoughts or suggestions? Thanks!!!!

You will find a very large number of posts on this exact topic. Suggest you do a search, and a little reading.

New transmission fluid will have a high amount of detergents in it, by design. Those detergents can clean out the transmission, shifting small amounts of deposits that were throughout the transmission but not hurting anything. The deposits are not metallic, and do not cause wear.
They are primarily friction material from the clutch packs. The deposits can cause havoc in the valve body (which controls the shifts) and cause subsequent failures of the entire transmission.

Many owners (myself included) do not believe that automatic transmission fluid changes in these specific vehicles have any benefit, and that they in fact have a small but real risk of causing damage. If you are going to change transmission fluid, the safe way is to do it early and frequently, ie every 30,000 miles. Whether there is a benefit to that or not is debatable, but regardless, a lot of us do agree that that approach at least doesn't have much risk. Changing the fluid for the first time at higher miles does have a risk.

If it was me, I wouldn't touch the transmission fluid. I would check the level. When I did that, I would check to see if the fluid was burnt. If it isn't burnt (and colour doesn't matter, just smell) then I would leave it.

If you do change it, make sure you use OE fluid spec, and an OE filter, and fill it correctly by bringing the fluid to the correct temperature.

Thanks for the info! I've decided against changing the fluid.

I changed mine when I first bought my X5. It had 108K miles on it at the time. It's now a year and 10K miles later and not a single problem.

I'm confused. Didn't you have a failure of a valve body on a high mileage used X5, which cost several thousand dollars to repair? Different vehicle?

Different X5. The VB issue was on my 2000, the fluid flush was on my 2001 (which I currently still own).

I have 120K miles on my 03 4.6is and I am letting the trans fluid ride.

Same thing with my E38 740i, although that car has under 100K miles so I might consider doing a drain and refill on that one just to refresh the fluid a bit. Not sure it's worth it tho.

I did change the transfer case and front and rear diff fluids in my X5 at 100K miles just for yuks. Can't hurt to refresh those fluids - no such risk as in the case of an AT trans.