At what transmission temperature should I be concerned when towing

[terrapin]

Can someone explain to me how the fluid temp at the torque converter can fluctuate so rapidly? Mine will sometimes rise or fall 10-20 degrees in a matter of seconds. I can't imaging that the trans oil can cool so quickly. As previously mentioned, the pan temp is more stable.

Edit: I guess I see how it would drop so quickly if it was refreshed with oil from the pan but by the same token how can it rise so fast if fluid from the pan is flowing through it?

 

[skrypj]

Can someone explain to me how the fluid temp at the torque converter can fluctuate so rapidly? Mine will sometimes rise or fall 10-20 degrees in a matter of seconds. I can't imaging that the trans oil can cool so quickly. As previously mentioned, the pan temp is more stable.

Edit: I guess I see how it would drop so quickly if it was refreshed with oil from the pan but by the same token how can it rise so fast if fluid from the pan is flowing through it?

Because you’re driving potentially 10’s of hp worth of heat energy into the fluid during convert slip. Imagine how fast you could boil some water with 20kw of power. Your average electric kitchen stove is like 9kw total combined power across all the burners and oven, with one burner maybe being 3kw.

 

[weaponoffreedom]

I can't imaging that the trans oil can cool so quickly

Sure it could, but what you are reading is the temp change due to its replacement with new fluid. The old hot fluid which you were just reading is no longer there, it is on its way to the cooler.

 

[terrapin]

Sure it could, but what you are reading is the temp change due to its replacement with new fluid.

Thanks, I realized that shortly after I had posted my question. I still wonder about how it heats up so quickly but #skrypj provided an answer to that that I am still wrapping my head around.

 

[weaponoffreedom]

Thanks, I realized that shortly after I had posted my question. I still wonder about how it heats up so quickly but #skrypj provided an answer to that that I am still wrapping my head around.

He is correct. All the power from the engine has to be either change into propulsion, or heat. Worry not of the temps, they are intermittent, at that location. If the pan is 250, you better stop and let things cool.

 

[linuxgod]

Looking for some guidance on a new to me 2013 LX with 93k miles. The LX has a great maintenance history with all fluids being changed regularly against the standard schedule. Since I'll be doing some towing (3,500lb boat or 2,500lb UTV w/ trailer), I want to get the differential fluids changed and the AT fluid flushed.

Overall, shifting is fine but it can be a bit slow to shift while cold and at lower speeds. Occasionally when up to temp, it does hit a bit harder between shifts but nothing alarming, just not as smooth as my 100 with the 5 speed. I'm currently seeing AT temps in the 180 to 195 range around town without towing. After looking through multiple threads on here, I see that that temp range is normal for 200's. My 100 with 230k miles on the original AT fluid would run in that range or a bit lower until I hit a deer last year. They put in a new OEM transmission cooler and did a full fluid exchange and then I was seeing temps in the 135 range. It would only go above 150 if I was towing the boat, and then it would still stay below 180.

The local Toyota dealership doesn't want to do it as it's a Lexus and the closest Lexus dealership (2 hours away) recommends not doing it as they think it might cause more issues. The Lexus dealership said they only recommend it if there's an issue and then they want to diagnose it.

Other than doing a drain and fill myself, what's the general consensus on full fluid changes when under 100k miles? I'm thinking that if my 230k mile LC can handle a fluid flush, why can't a 93k mile LX? Would there be any significant benefit by doing, or not doing, the full fluid change?

Cold shifts can take longer. That’s part of the tuning to get the vehicle warmed up faster for emissions reasons. Once the transmission warms up shifts should be pretty smooth, though I’ve always found the 1-2 or 2-1 shifts to be a little firmer.

If your shifts are very firm/harsh it could be some driveline slop. Make sure all the driveshaft and u-joint zerks are greased, to start with

At 230k you could either swap all the transmission fluid or just do the pan. Toyota recommends just doing a pan drain and fill, which only exchanges maybe 25% of the fluid. The benefit is that if your transmission has some wear totally new fluid might be too slippery and cause some slippage. However I’m generally a believer in swapping it all and if you somehow are the unlucky guy to have that issue there are additives which resolve this (taken from experience on an old ford transmission).

 

[jlm43]

Cold shifts can take longer. That’s part of the tuning to get the vehicle warmed up faster for emissions reasons. Once the transmission warms up shifts should be pretty smooth, though I’ve always found the 1-2 or 2-1 shifts to be a little firmer.

If your shifts are very firm/harsh it could be some driveline slop. Make sure all the driveshaft and u-joint zerks are greased, to start with

At 230k you could either swap all the transmission fluid or just do the pan. Toyota recommends just doing a pan drain and fill, which only exchanges maybe 25% of the fluid. The benefit is that if your transmission has some wear totally new fluid might be too slippery and cause some slippage. However I’m generally a believer in swapping it all and if you somehow are the unlucky guy to have that issue there are additives which resolve this (taken from experience on an old ford transmission).

Thanks! The 2005 I sold last month had 230k on it, my new (to me) one is a 2013 LX with 93k miles.

Shifts are not harsh, just a bit firmer than I'm used to when it's cold. Mostly with the 1-2 or 2-1 shifts so that lines up with what you're seeing. I'm new to the 200 realm so I'm not quite sure what normal should feel like. I'd also like to start my ownership with new fluids throughout the vehicle, having multiple dealers recommend against it just seems odd to me. I also feel that I'd rather swap it all and hope I'm not one of the unlucky ones. If I am, I'll deal with it now rather than kicking it down the road and getting blindsiding when I don't expect it.