How to measure transmission temp when changing fluid/filter?
 

I'm planning on replacing the transmission fluid and filter on my 2009 XKR this weekend. How do I accurately measure the temp of the fluid to make sure it's between 30 and 50C during the level check?

I see some are using a non-contact thermometer on the pan, but how accurate is that with a plastic pan?
On my Lexus, I was able to hook up my code scanner and read the trans temps. I tried it last night on my Jaguar and it wouldn't show trans temp. Is there a specific scanner that's recommended?

Does anyone have a been-there-done-that solution?

The criteria was created using a plastic pan with the laser thermometers (or equivalent) so there is no problem there.
The thermometers are fairly cheap, and even the dumpy ones are accurate enough for this procedure.

Theres a 1* difference as read by trans temp sensor in the trans and shooting the pan with a temp gun. And once i checked this out years ago thats all i use since its so much easier

Some odb scanners will give you a reading of the temps I'll check mine tonight and let you know which brand

50`C is 122`F so let it run until the transmission case is warm to the touch.

Go to Amazon. But an ELM 327 bluetooth OBD thingy. They are about $10.

Download an app called Torque to your Android phone. (I don't think it works with iPhones). The Torque app will tell you your transmission fluid temp.

I'd go with Brutal's answer...

Between 30C (sort of warm) to 50C (starting to get hot) is a pretty big gap, and not critical in the overall scheme of things. The difference in fluid level will be several drops, if that.
Just make sure the transmission is warmed up for a bit.

Its more than a few drops. Think about a car with a trans dip stick and the cool reading and hot reading. The difference is the volume of fluid in the pan.between cool/cold and hot.

Yeah, not much. Maybe a 1/10th of an inch? And that's from Dead-Cold to Full-Hot.

I'm glad you brought that up though.....
What's the range on a dipstick transmission between ADD and FULL??? About an inch??? I really don't think even an ounce more or less in a ZF is going to do anything. If the fluid level was THAT super-critical, the change would have to be done at a laboratory, in a hyperbaric chamber, air filtered, at sea level, humidity-controlled, float-leveled, and at midnight on a new moon.

There you go pouring ice water on hot righteous rationale.

Yes, and that's after so much of the fluid gets coated around parts and pipes.

So about that, for those who are willing to do the fluid change themselves, I wrapped the pipe in aluminum foil. That keeps the fluid off the pipe, though I suspect it would burn off quickly anyway.

I cut a small piece of hex head wrench off (3/4"?) using a hacksaw and stuck it in the cap using some thick grease, which held it in place allowing me to screw the plug in enough with my gloved fingers.

It's the little things that make this job easier and 95+% of the guys on this forum will outsource the work, which is understandable. I have a lift so not that big of a deal but I admire the ones who tackle it on Jack Stands.

The potential is about 4 fl ozs from 35 C to 50 C depending on the precise coefficient of expansion.

If I know that I performed the transmission fluid flush and fill correctly I would have 100% confidence with my work. The ideal temp being 40 C according to ZF.

Coefficient of thermal expansion for oils and transmission fluids is around 0.0007 per degree C (0.07%/C).

Me adding Trans Fluid to every Dipstick vehicle I own for my entire life----- "Meh, about half a quart should do fine.... 'glub-glub-glub'..... There we go..."

Four ounces (+/-, which could also be had by the vehicle being off-level by 1 degree either way) when the entire transmission and Torque Converter holds like fifteen quarts is less than 1 percent.

Now, can we get off this ridiculous subject and press on?

Capacity of 6hp26 = 10.53 quarts = 337.5 fl ozs

337.5 x .07% = 0.2362 fl ozs x 15 C = 3.5437 fl ozs.

Is the above math incorrect Cee Jay?

I would gladly move on if I am wrong.

There is a simpler math; every manufacturer in the world, for decades, makes a big fuss about the difference between hot and cold ATF measurement. i.e. a non-negligible amount. You can believe them or....
There is a much more simpler math, they know nothing!

Did I SAY it was wrong??? No. I said it was Insignificant. An eighth of a quart. I sneeze out that much snot on a bad day.

Engineering toolbox comes up with @2oz difference between warm and warmer. I don't think there's anything to worry about and am pretty sure there's enough difference between the cooler, lines and what's in the converter.

I've changed my mind on this. I've been using the Torque app and it appears as if the transmission temp it shows is really just the engine coolant temp.

If you have the 2010 onward you can set up the Torque app to read the Transmission temp. See here from Cambo:

https://www.jaguarforums.com/forum/g...p-more-213503/