Slipping 3rd to 4th when hot...

[lswing]

So if I'm at 66C in my driveway at idle on a warm day, without any driving, there doesn't seem to be much wiggle room before I get to 93C, which would be around the max desired operating temp of 200F.

Can someone else check temp at idle just so I have reference of trans fluid temp? Or temp after driving too, any numbers would be good.

Grabbed a temp reading when I got home from doing some errands and stretching of the legs. 90 degrees F out today in central, TX. Car read 91C for the trans fluid temp once I was in the driveway. Puts me at 196F. Temp code for intermittent G93 sensor is back right away.

Seems reasonably warm for how hot it was. I'm always amazed the carbon on the air box isn't completed cracked and fried. If I was really out doing some spirited driving I would assume the trans fluid temp would reach at least 220F, based of my moderate driving today.

My plan is to take it easy until I move later this summer and find a new mechanic. I guess we'll check all connections like last time; and then replace the G93 like last time; and maybe all will be good.

[Other_Erik]

Grabbed a temp reading when I got home from doing some errands and stretching of the legs. 90 degrees F out today in central, TX. Car read 91C for the trans fluid temp once I was in the driveway. Puts me at 196F. Temp code for intermittent G93 sensor is back right away.

Seems reasonably warm for how hot it was. I'm always amazed the carbon on the air box isn't completed cracked and fried. If I was really out doing some spirited driving I would assume the trans fluid temp would reach at least 220F, based of my moderate driving today.

My plan is to take it easy until I move later this summer and find a new mechanic. I guess we'll check all connections like last time; and then replace the G93 like last time; and maybe all will be good.

hmm... Moderate driving, even at 90F ambient should not put trans fluid at 196F, unless you've removed the warm weather package secondary radiator. I'm not saying that that _is_ the issue, but heat-soaking the trans would worry me a lot. Spirited driving would probably put you in the 250F region depending how long you keep your foot in it. I see in your sig you say Aux Radiator Delete - you mean the secondary oil coolers from the backs of the stock IC's, not the transmission cooler mounted on the main radiator, right? We may have found our culprit, even if you still have the trans cooler hooked up - assuming it's still there, have you flow-tested it? Enough gunk buildup from 12 years of spirited driving may have plugged the rad line, giving a plausible reason your trans runs so hot.

Regarding the G93 code you're getting - I love how word order can make a difference, especially when translated from Deutsche.
G93 Sensor temperature high warning intermittent
Is completely different from
G93 Sensor intermittent temperature high warning

The first means your temperature intermittently spikes high, while the second means your sensor intermittently fails signal at higher temperature.

I need to modify my sig to note that I'm not an expert, I'm basically doing guesswork based on second-hand knowledge of the integrated systems of this car. Take everything I say with a massive grain of salt and listen to the real Pro's here.

O_E

[lswing]

hmm... Moderate driving, even at 90F ambient should not put trans fluid at 196F, unless you've removed the warm weather package secondary radiator. I'm not saying that that _is_ the issue, but heat-soaking the trans would worry me a lot. Spirited driving would probably put you in the 250F region depending how long you keep your foot in it. I see in your sig you say Aux Radiator Delete - you mean the secondary oil coolers from the backs of the stock IC's, not the transmission cooler mounted on the main radiator, right? We may have found our culprit, even if you still have the trans cooler hooked up - assuming it's still there, have you flow-tested it? Enough gunk buildup from 12 years of spirited driving may have plugged the rad line, giving a plausible reason your trans runs so hot.

Regarding the G93 code you're getting - I love how word order can make a difference, especially when translated from Deutsche.
G93 Sensor temperature high warning intermittent
Is completely different from
G93 Sensor intermittent temperature high warning

The first means your temperature intermittently spikes high, while the second means your sensor intermittently fails signal at higher temperature.

I need to modify my sig to note that I'm not an expert, I'm basically doing guesswork based on second-hand knowledge of the integrated systems of this car. Take everything I say with a massive grain of salt and listen to the real Pro's here.

O_E

Good input, thanks.

We removed the Aux Radiators just after I got the car, they just flow engine coolant through them. Took about a year or two for the G93 sensor code to show after that. But I would agree that these have an effect on overall temp, cooling of the engine coolant would help keep other fluids a few degrees cooler.

You mentioned what I've been thinking, that my trans cooler up front is not flowing correctly. That would be a very reasonable explanation for this same code two times in a row now. I'm getting the G93 Sensor intermittent signal (don't think it says anything about high temp, but I will confirm), and this either gets activated at 90C+ or is faulty. Since I've now had the same code on two separate transmissions it makes me wonder. We did purge the whole trans cooling system a while back and fluid seemed to flow fine though.

The temps from this last log were basically a grocery getter run, on a warm day, with a few miles of highway. I could and would typically drive the car WAY harder, so I think that trans temp could really escalate.

I'm going to try a few start and idle sessions in the garage, 15 minutes each time, to see if the G93 code pops back up. It does not throw a CEL by the way, just sits there stored for some reason.

[Other_Erik]

Good input, thanks.

We removed the Aux Radiators just after I got the car, they just flow engine coolant through them. Took about a year or two for the G93 sensor code to show after that. But I would agree that these have an effect on overall temp, cooling of the engine coolant would help keep other fluids a few degrees cooler.

You mentioned what I've been thinking, that my trans cooler up front is not flowing correctly. That would be a very reasonable explanation for this same code two times in a row now. I'm getting the G93 Sensor intermittent signal (don't think it says anything about high temp, but I will confirm), and this either gets activated at 90C+ or is faulty. Since I've now had the same code on two separate transmissions it makes me wonder. We did purge the whole trans cooling system a while back and fluid seemed to flow fine though.

The temps from this last log were basically a grocery getter run, on a warm day, with a few miles of highway. I could and would typically drive the car WAY harder, so I think that trans temp could really escalate.

I'm going to try a few start and idle sessions in the garage, 15 minutes each time, to see if the G93 code pops back up. It does not throw a CEL by the way, just sits there stored for some reason.

NP. Do you have a block log with trans temp from a regular drive? Compare engine coolant temp gradient to trans temp gradient.

Engine coolant should show a steady uptick, followed by a valley after it peaks at/just over your thermostat temp (thermostat opens), then temperature gradients depending on engine speed. Should end up looking like a peak, a valley, then shortwave peaks and valleys as the radiator and water pumps do their jobs.

Trans temp should show steady uptick from cold to operating temp (170F or so), then short peaks and valleys as you drive. If all you see is a peak followed by steady temperature with no valleys when you're idle-cruising, chances are you've got a flow problem in the cooling loop of the trans fluid.

If the code for G93 Sensor Intermittent Signal happens to coincide with peaks in the actual trans temp, it may actually be heating to the point that the TCU rejects the sensor signal (not sure of the temp peak for this sensor) - let's say for sake of argument the maximum temperature signal the TCU accepts is 250F (121C) - if you hit 255F or higher, the sensor will be sending what the TCU sees as "Implausible Signal" - which could happen intermittently as the trans temperature fluxuates back under and over the 250F mark.

TL;DR version: Go for some moderate drives, log engine coolant temp and trans temp blocks, let's see what the pretty little graphs show. If you see peaks with flat caps, you may be overheating the trans to the point the TCU doesn't recognize the signal.

O_E

[lswing]

^^^Good call. I'll go out and log some data in the next week or so and report back. Thanks again for the good ideas and helping me think out a good troubleshooting process.