Today I marked the dipstick at 704mm to make sure I fully inserted it. It did not seem to go all the way down until I jiggled it and pushed a bit harder. I started the car, shifted through the gears with the brake on, then checked the fluid level with the engine running and the dipstick now fully inserted. I considered the fluid to be “cold” at this point, so it should be between the two lower marks in the 25 degree range (see pic of the dipstick). It was much, much fuller than that, clear up in the 80 degree band. I am now prepared to believe that I had not been fully inserting the dipstick, unbeknownst to me, and that I’ve been overfilling the transmission ever since I first checked it. Yikes.

My question now: Here is a picture of the dipstick. How much capacity is represented by the gap between 25 degrees and 80 degrees? I’m trying to determine how much fluid to drain out. I mean, you gotta be kidding me if this has been the problem the entire time......

 

The only way is to drain some out (say, half a litre) and check the level again. Then, either drain more or put some back. Be prepared for a number of "iterations". As you will have a number of engine starts/stops, the ATF may warm-up a bit in the process so, perhaps, when you finally reach the level around the 25C range, make a judgement as to how much higher the ATF temp is (touch the sump by hand) and set the level a few mm above the upper 25C mark. You can then, the next day, have another go when the ATF is at your ambient temperature.

 

A progress report and follow up questions:

I drained out over 2 quarts of fluid this week, and added back about a half pint at a time as I checked and rechecked the fluid level from day to day. Today drove the car a little over 5 hours, including hills and start/stop driving which should have been more than enough time/miles to get everything HOT and cause the shifting problem to surface. It shifted fine. At no time did it do the Jake brake thing as I slowed the car for a stop light. At no time did it require 2,500-3,000 rpm to upshift.

I hesitate to say it’s fixed for a few reasons: 1) I’ve been disappointed before, 2) It was only about 75 degrees outside today, so I’m not sure if I got the fluid as hot as it might be if it was 95 degrees outside, and 3) see question 2 below.

A couple questions:
1. I checked the fluid again after my drive. It is right at the top of what I will call the operating range, but not in the upper 80C range. Am I safe to leave it at that level, or do I need to add a bit to get it up in that range? I hesitate because I do not know for sure what the fluid temp is, and I DO NOT want to overfill it again.
2. When I pull away from a stop sign and proceed down the street, it shift from second to third around 1500 rpm, but it doesn’t like to shift from 3rd to 4th until about 1900 RPM. If I lift my foot off the accelerator before it has made the shift, it does not upshift either. It just decelerates. That seems a bit wrong, and is reminiscent of the old shifting problem. Yet, if I let it get to 1900, it shifts fine, and at no time did it require me to hit 2500 or 3000 rpm in order to upshift like it had been.

So, give me your assessment, especially with Question #2. I plan to just drive it normally and see what happens. I do want to make sure I have adequate fluid in it, but I very much suspect that I’m onto something with the overfill, so I want to be careful.

 

As you do not know what the actual temperature of the fluid was after the drive, you should not try to correct the level to the 80C range as the fluid temp may not have been as high. If you got the level right at the ambient temp, leave it there. In any case, the conductor plate has a sensor to warn you of low level (unfortunately, the sensor does not tell you when the level is too high).

That may be normal (I think my transmission does about the same). The TCM may be programmed to shift 3-4 a bit later than 2-3. In any case, you can disconnect the battery for a few minutes to reset the TCM. Reconnect the battery and then drive the car gently for a while and see if the shift point 3-4 has changed to a bit earlier.

 

Thanks for the continued advice. I will monitor the fluid level, but for now I’m not going to add any. I think we’re finally making some progress. Almost hate to say it out loud.

One other question: I assume the fluid has gotten foamy a number of times. Did it damage the fluid?

 

Serious overheating will damage the fluid but the foaming will not. The foaming is created mechanically by the rotating shafts when the too high fluid level reaches them (milk shaker). The fluid will be back to normal when it settles down and the air bubbles are expelled. This will probably take place with the car sitting overnight.

 

More bad news. It was hot outside today, around 90F, so I did another long drive followed by stoplight to stoplight driving. Same shifting problem as before.

It is obviously heat related, but I have no idea where to go from here. There has never been an error message of any kind, and there still isn’t a trouble message.

I ordered a TCM today on eBay, so we’ll see if that makes any difference. Supposedly the TCM had been swapped out at the repair shop, then swapped back in after it was determined that it made no difference. As I’ve said, everything is on the table.

I’ll either figure it out, or never drive it when the temp is above 80-85 degrees. That literally seems to be the temperature line. Last week I drove it for 5 hours, and had zero issues, but the temp was only around 75. I drove it yesterday to a wedding 120 miles away, with zero issues. Temp was around 80F.

I don’t get it. What the heck am I missing...?

 

There should be DTCs logged in the TCM but you will need a diagnostic device that can communicate with the TCM.

bob

 

Are you saying that DTC’s can be logged in the TCM without a check engine light or any other dashboard message? Because I’ve never seen a message related to the transmission in the instrument cluster. The only check engine light the car has ever given me was due to a vacuum leak that ended up being the part load breather tube. Since then, zero visible messages.

 

There is no CHECK GEARBOX light. There is a CHECK ENGINE light because the gov't demands there be one for diagnosis (especially for EMISSIONS).

Sometimes a TCM fault will set the engine MIL but not always.

bob

 

Ok thank you. I know there’s no Check Gearbox light, but from other threads, I know that there can be visible warning lights that are related to the transmission, such as Gearbox Temp, Gearbox Fault, etc. My vehicle has never shown one of those warning lights. Good to know that there could be codes in the TCM without a visible indication of them.

When they did the ECM immobilization setup for me, I asked if there were any codes, and there were not. But I didn’t specifically ask about TCM codes I guess, and I don’t know if they read the TCM codes during the immobilization setup. I will revisit this.

Thanks again.