Low trans fluid fix = better fuel mileage?

I had the dealer check trans fluid while I was getting my first 10k oil change. Turns out it was a full quart low, which unfortunately seems to be very common. Has anyone experienced BETTER fuel mileage after this? For whatever reason I appear to be getting a full MPG better than I was previously.

 

You're a few hours south west of me, but we usually share the same weather patterns, up until today, I'm assuming you have been enjoying the same record setting warmth. If so, that's probably why. If your transmission was so low, it was shifting erratically (doubtful since they're electronically controlled) I suppose there's a chance, but I highly doubt it.

 

I would guess it’s placebo. These transmissions don’t operate differently based on such a minor difference in fluid level. That’s why they aren’t all that accurate when they fill them, because it mostly doesn’t matter.

 

That's what I hear but why is their checking protocol so stringent on temperature?

 

Fluid expansion.

#savethedipsticks #dipsticksmatter

 

Exactly, of they're will to compensate for fluid expansion, why wouldn't being low a quart be detrimental?

 

^ This. The thing holds ~11 quarts total. Even 1 qt low won't make any difference in how it operates.

Also, the dealer's estimate on how low it was may be inaccurate. The fluid temp has to be in a sweet spot and truck has to be perfectly level. Given that these techs seem to have a difficult time properly installing a skid plate, I wouldn't place too much faith in them precisely measuring ATF levels.

 

Personally, I think it is, because it should be filled to the engineered specification to provide cooling, additives and volume for proper pressures.

That said, it's likely over engineered to prevent damage from poor maintenance. Because the average bear can't/won't check themselves anymore, and the dealers don't want to go to the effort, calling it a 'lifetime' fill.

 

Fair enough. It just always puzzled me.

 

The only thing being a quart low will do is shorten the life of the fluid a bit. It won't affect cooling performance.

 

@gearcruncher any input?

 

The engineered specification has a range, just like motor oil.

 

I don't know who gearcruncher is, but in the meantime, while we're waiting for him to reply, think about it this way...

Let's say you have a two hour long drive ahead of you. As you're driving, it takes 10 quarts of ATF 15 minutes (making these numbers up) to heat up to operating temp, and 11 quarts 18 minutes... in both scenarios, the cooling system is what's regulating the ATF temps, keeping them stable for the remainder of the drive, not the amount of fluid in the system. There's a limit to this obviously... if you are extremely low on fluid and certain parts of the transmission are running dry, then yes, you can overheat it, but that ain't happening with 1 quart low on an ~11 quart tranny.

 

Yes , Any transmission needs to be filled properly period .
I believe we already know about multiple issues ? Aisn Seiki transmissions are incredibly sensitive . Below are just 2 examples

https://www.tacomaworld.com/threads...be-low-on-fluid-directly-from-factory.405642/


https://www.tacomaworld.com/threads...be-low-on-fluid-directly-from-factory.312718/

 

It was shifting erratically, that was the complaint (normal) and why I complained in the first place. I cant imagine 1 quart low would make that big of a difference but 10% low on fluid is still quite a bit. My drive's are also relatively short trips of 8-10 minutes with long cool downs between them. Warm weather might make sense but it is getting better mileage than I did when it was warm out.

 

Just wondering if the dealership reset your transmission computer back to factory specs when they added the quart of fluid . It,s not common to see a decrease in fuel mileage on the AC60 series transmission when they are low on fluid . 1 quart low usually has symptoms of delayed engagements on initial start up when cold as well as some shift busyness in and out of 6th gear .
If i had to guess , the dealership reset your adaptive learning back to factory . When these parameters are reset , the programming is designed for the best fuel efficiency. As you put on the miles , the transmission learns how you prefer the transmission to upshift and adapts to your driving making the transmission shifting feel better to you but less efficient on fuel

 

Wouldn't you need to be really low on ATF to cause delayed engagement though? The pan alone holds about 4 quarts. It it were nearly empty, and the fluid level in the pan fell below where the pump was picking it up, then yeah, I can see a low pressure situation where there may not be enough fluid pressure to to shift gears properly.

But is that really occurring with just 1 quart low? I have a hard time believing that.

 

In a lot of domestic vehicles over the years , you could drive forever being low a quart of fluid and never know it .
I have seen this same issue in older Ford trucks however where a tsb was released for a deeper fluid capacity pan . Unfortunately , these Aisn transmissions are very sensitive to fluid levels being perfect . I cant tell you why as I havnt taken the time out to do a pan level study on this transmission ? There is a test you can perform to identify low fluid issues where you measure the depth of the pan and compare it to the filter suction level . perhaps the engineer sitting at his computer designing the transmission pan for fluid capacity at the time thought the world was flat ,and the truck never turns corners or drives uphill . This is my best guess

 

In general,

Automatic transmissions push fluid via vanes through a stator. This creates a fluid coupling that allows you to brake the transmission/rear end without stalling the engine. This fluid coupling needs some volume to operate efficiently. There is almost always excess volume of fluid for cooling, lubrication, controls, etc. If you drop below the needed volume, you will lose efficiency. The total capacity of the transmission system is kinda big and usually, a quart low won't really make much difference. I think the capacity is around 10 quarts, so if you are a quart low, you still have 90% of the fluid.... even then, it'll take way less to lose the efficiency.