Taking the car in tomorrow to get the transmission oil and filter changed. I will tell them to be careful when they unscrew the big nut on the filler tube that connects to the pan. On my other XJ6 that fitting where it goes into the pan had liquid steel on it where someone had put too much torque it.

I will also have them blow out the filler tube as I found some rust on the dipstick when I was checking it recently, that really surprised me, I had never seen that before.

The shop works on European cars only and had the Redline D4 fluid I was looking for. Am I correct in thinking that this transmission only has to have the level checked with the dipstick and not have to have any temperature measured like the XJ8?

Anything else I should tell them or look out for?

 

Redline D4 is the best fluid I've found for the ZF 4HP24, so I hope you'll be happy. The transmission may behave differently than it has up to this point, but that will be the torque converter actually locking up instead of slipping.

Will the do a complete flush via the cooler lines (best), or just a drain and refill? If the latter, it would be best to drain and refill three times to replace most of the fluid that is retained in the torque converter and passages in the transmission and can't be evacuated from the pan drain.

You're correct that there is no specific temperature specification for checking the fluid level, but in my experience checking the fluid when cold is meaningless. What is critical is to test the level after driving the car at least 15 or 20 minutes at speed to get the fluid up to full operating temperature. Then park on a level surface, and with the engine running, the hand brake set, and your foot on the brake pedal, move the gearshift lever through all the positions, pausing in each position at least 3 seconds. Now return the lever to Park and check the fluid. It should be right at the HOT mark on the dipstick. Being a little over is no better than being a little low. The transmission may not behave properly. If it's overfull, suction some fluid out through the dipstick tube. If it's a little low, add a few ounces at a time, rechecking after every addition until you get it exactly at the HOT line.

Cheers,

Don