I was checking fluids in my 1997 X300 and I discovered that the fluid on the trans dipstick is not red as I would expect. Instead it appears to be completely clear. I am really not certain about the previous owner's ability to do even basic maintenance on the car so I am wondering if there might be some sort of incorrect fluid in the transmission.

Was there ever any factory or otherwise transmission fluid that is clear instead of red?

 

Hi Steve,

The short answer is no, the fluid should not be clear.

Sorry in advance for the long answer, but this is something I've done a lot of research on.

The gearbox is the electroncially-controlled 4HP24 made by the German company ZF. The original fluid specification was Dexron III, which was always red. The last of the Dexron III licenses expired at the end of 2006, which GM had replaced with Dexron VI, which is also red.

GM claimed the new Dexron VI was backward-compatible in most Dexron III applications, so that's what I used for a few years in our '93 XJ40, which uses the same gearbox as your X300. On my next fluid change, at the recommendation of a friend on the Jag-Lovers forum, I tried Redline Oil D4 ATF. The difference in performance was absolutely staggering. I had not realized that with Dexron VI the torque converter had never been fully locking up. Now, with the Redline D4, the converter locks up great, providing better acceleration, true engine braking when descending hills, and in Sport mode it holds gears noticeably longer when accelerating out of corners.

I did some further research and discovered that the kinematic viscosity at 40C of the original Dexron III was 35, but at the same temperature the KV of Dexron VI was only 30, meaning that it is significantly "thinner" than Dexron III. This may be fine in many applications, but in our transmissions it doesn't seem to work optimally.

It is interesting to note that ZF recommends its Lifeguard 8 for its new 8-speed boxes, Lifeguard 6 for its 6-speed boxes, and Lifeguard 5 for its 5-speed boxes, but for its old 4-speed boxes like ours it still recommends Dexron III (and not Dexron VI). I think that is telling.

I don't know if Redline Oil D4 ATF is the only currently-manufactured fluid with the right viscosity, friction modifiers, etc., but it works great and I highly recommend it. Typical disclaimers, no affiliation, etc. It's not cheap, but the difference in performance is well worth it in my opinion.

I think I used 3 gallons with three repeated drain/refill cycles to get as much of the old fluid as possible out of the torque converter. In your case, it might be advisable to do a true flush via the cooler lines to remove all of the clear fluid.

Cheers,

Don

 

Thanks a bunch for the info Don!
Great answer

 

I have been using Mobil 1 ATF for five years with excellent results. Not sure, but I think Grant Francis from down under suggested using synthetic ATF.

 

Just to add a little more to Don's info on transmission fluids I have attached an article I compiled some yrs ago on Jaguar transmission fluids.
You might note I am in Australia & some brands are peculiar to here.
I have used Castrol Tranzmax Z in my XJR (GM 4L80E transmission) with good results. It is fully synthetic & suggested for vehicles under heavy loads or extreme conditions wherever Dexron 11 or 111 is recommended. It does not however satisfy the lower viscosity requirements of Dexron V1 fluids.
Viscosity requirements was a matter mentioned by Don.

John Herbert

 

Thanks for that tip, RJ.

The kinematic viscosity of Mobil 1 ATF at 40C of 36.3 cSt, so from that standpoint it looks like a good candidate for the ZF 4HP24. Here's the link to the Material Safety Data Sheet:

Mobil 1 ATF MSDS

I can't speak to the suitability of the friction modifiers, but I doubt anyone can at this point. In the first Dexron ATF introduced in 1968, the friction modifier was sperm whale oil!

Cheers,

Don

 

Great research, John, and a well-written article. Thanks for sharing!

Cheers,

Don