Is Transmission Temp Check Mode Necessary?

Did a drain/fill on my 2020 OR a few weeks ago and, for some reason (user error probably) I had a lot of trouble getting the truck into temp check. I finally was able to do it and the whole process went well afterwards.

I had planned to do another drain/fill again just to get more fresh fluid in the transmission this weekend. My question is: Is temp check mode necessary or can I just use my scan tool and wait until the transmission pan sensor reads 95-100 degrees and pop the check plug? Is temp check mode some mystical thing that's doing something else in the background or is it just simply telling me when the temp is ready?

 

Nope; all temp trans check mode does is give a visual indicator for those without a scantool. If you have Techstream or something that can read pan ATF temp, you are good to go.

 

All you need is a source for a reliable and accurate temp reading. I use my scanguage when servicing the trans in my GX.

 

How many quarts did you use on drain and fill? Sorry I am off topic just would like to know.

 

Thanks for the replies guys! I figured it just had to serve as an indicator but I ran across a couple of comments that made me think otherwise. That'll make it much easier to check.

@23YOTA I drained 2.5 quarts. I've seen anywhere from 2.5 to 3.5 but I think it just depends how much ends up in the pan when you shut the engine off. I added half a quart more during fill and ended up draining about 1/2 quart so I was back a 2.5 quarts.

 

Thank you!

 

I've always wondered why you have to measure at all if it's new and you're the one doing the first drain/fill. Drain a specific amount, put precisely that much back in. I'm guessing the only reason you'd measure the temp is to verify the factory actually had the level correct.

 

Unferfilled trans fluid from the factory has been documented countless times.

 

You can also use a laser/infrared thermometer and check the temp at the pan.

$35 Klein Tools IR1 Infrared Thermometer, Digital Laser Gun is Non-Contact Thermometer with a Temperature Range -4 to 752-Degree Fahrenheit

https://www.amazon.com/Klein-Tools-...utomotive+infrared+thermometer,aps,117&sr=8-3

 

@Pungo1 It’s interesting because the service manual says you can fill to the fill hole and then drain the excess…so the fear of overfilling is technically non-existent…but I’m sure we all don’t want to spend hundred of dollars on excessive fluid so measuring and overfilling is just a way to avoid waste.

@Captain Dirty Beard The gun I have was really inaccurate. It was off a good 10 degrees. I have a scan tool app but wanted to see how accurate my gun reading was.

 

Is 95-100 degrees F correct?

 

Or if you have a leak. It's not common, but you never know. With no dipstick it's the only chance to check the level.

 

if you have a scan tool, you’re good to go. That’s all you need for the level check.

 

95-113F to be precise.

 

Does temp really matter? I mean how much does liquid expand?

 

@SilverTRD Sport The service manual says between 95-113. My truck entered temp check mode when the oil pan transmission temp on my scanner app was about 98-100 degrees.

 

@tastethepoison Liquid expands quite a bit. Coolant levels can fall/rise in your reservoir if the ambient temps swing even 10-15 degrees. Of course this liquid is suspended in a column (coolant hoses, etc.) so the level you see is more sensitive. But temps matter. I have a Mazda I did a drain/fill and the temp needed to be 120 degrees to get a proper reading. All of this is in the service manuals for these cars.

 

OP, does your tranny have the traditional black thin gauge pan at the bottom of the transmission? If yes, an IR gun will be within four degrees of the internal ATF pan sensor reading, based on my readings comparing my IR to my UltraGauge reading in my 2nd gen. If you don't have the thin gauge pan, the IR reading will not be accurate.

 

What about expansion of the parts of the transmission when heated? My thinking is the small pathways will be affected when heating up and change the fluid level. Maybe a tranny expert can comment.

 

@Chuy Yeah, it seems thin. It's definitely black. I have a cheap IR gun so I don't necessarily trust it but comparing its reading to the scan tool they were off almost 10 degrees. Glad to know I can just use the scan tool app and be done with the temp check mode. Frustrating experience for me.