Auto Transmission confusion

[europa88]

Hi
I was concerned that although my transmission fluid was showing a healthy level on the dipstick when cool, I never made it into the hot running marks !
So gave it a good run so as nice and hot and filled it untill it was a good way up the hot operating marks!(shifting the trans lever and leaving it running as per toyotas ins)

The box is ok ie. everything works ok (it was a little jerky when cold before i topped it up) but my dilemma now is when its cold and been left overnight it is way up on the hot mark!(almost full)

Have I overfilled it????
Some one please help!! I dont want to knacker the box, although it has been driven for a couple of days like this before I realised!

Cheers
Neil

[europa88]

I pretty sure Iv'e overfilled it! When I said i got the atf fluid nice and hot, I dont think It was hot enough! Toyota reckon a run of 15 km to get it to 70-80 degrees, on reflection i dont think it was anything like hot enough! So dodgy reading when warm!

Iv'e now drained off enough fluid to read halfway between the hot ,upper and lower marks when stinking hot!!!

The acid test is tommorrow morning when i do a cold test, though in theory if It's ok when hot!! You aint got a problem!!

I never liked auto transmissions! Iv'e rebuilt race engines and some manual transaxles restored classic sportscars etc etc! But auto boxes are the devil's work as far as my brain is concerned.

Cheers
Neil

[TonyN]

I wouldn't worry about the cold level to much, it does all its work when hot, and the dipstick only says cool anyway, and it'll be heating up as you dip it, wipe it, dip again, etc, etc......

[Guest]

I wouldn't worry about the cold level to much, it does all its work when hot, and the dipstick only says cool anyway, and it'll be heating up as you dip it, wipe it, dip again, etc, etc......

Plus if when you check it again you didn't have the engine running then the pumps won't be full so the level will be showing a false high anyway.

I disagree that slush boxes are the devils work, they are a piece of p**s to fix when they go wrong as large amounts of the internals are very large and come out as a unit. Once did a complete rebuild on a TH350 Chevy Autobox including a new high stall converter and a high pressure valve body. Whole job took 5 hous from start to finish including taking the box out and putting it back in.

Take you twice as long to do it on a manual. Problem is too many Auto transmission specialists have a vested interest in making you think they are complicated. Much less fiddly than manuals and a lot more reliable generally.

Cheers

[europa88]

Plus if when you check it again you didn't have the engine running then the pumps won't be full so the level will be showing a false high anyway.

I disagree that slush boxes are the devils work, they are a piece of p**s to fix when they go wrong as large amounts of the internals are very large and come out as a unit. Once did a complete rebuild on a TH350 Chevy Autobox including a new high stall converter and a high pressure valve body. Whole job took 5 hous from start to finish including taking the box out and putting it back in.

Take you twice as long to do it on a manual. Problem is too many Auto transmission specialists have a vested interest in making you think they are complicated. Much less fiddly than manuals and a lot more reliable generally.

Cheers

It me, not the slush box Andy!!

you might know this . If i check the fluid when cold do you still need the engine running to obtain the reading between COLD marks? Reading the above post i guess you do but being an Auto virgin I would appreciate some
knowledgeable input cos the reading is off the scale when cold and not running! But fine when hot an running!

[Guest]

It me, not the slush box Andy!!

you might know this . If i check the fluid when cold do you still need the engine running to obtain the reading between COLD marks? Reading the above post i guess you do but being an Auto virgin I would appreciate some
knowledgeable input cos the reading is off the scale when cold and not running! But fine when hot an running!

Yep.

To get an accurate reading you need the engine running. In fact although they say you do, on most auto boxes you don't need to warm up the fluid just have the engin erunning, the fluid expansion is not that great when hot that it would affect the reading, just runs a little thinner so it should settle to the right level easier.

It is basically because when you don't have the engine running, the pumps that control most of the internal functions in the box, empty out their fluid (which is what runs the box, it basically being a large and relatively complex, and electronically controlled set of hydraulic pumps). Also the Torque converter will drain out some fluid (although not very much - which is why it doesn't get flushed out just by dropping the sump plug on the box). Both these things will mean that you get a flase high reading.

The reason for cycling through the gears before checking is to make sure that all the pumps are full - there are a number of pumps in most boxes which control the different parts of the gear set and also control other functions like lockup etc.

Cheers

[europa88]

Yep.

To get an accurate reading you need the engine running. In fact although they say you do, on most auto boxes you don't need to warm up the fluid just have the engin erunning, the fluid expansion is not that great when hot that it would affect the reading, just runs a little thinner so it should settle to the right level easier.

It is basically because when you don't have the engine running, the pumps that control most of the internal functions in the box, empty out their fluid (which is what runs the box, it basically being a large and relatively complex, and electronically controlled set of hydraulic pumps). Also the Torque converter will drain out some fluid (although not very much - which is why it doesn't get flushed out just by dropping the sump plug on the box). Both these things will mean that you get a flase high reading.

The reason for cycling through the gears before checking is to make sure that all the pumps are full - there are a number of pumps in most boxes which control the different parts of the gear set and also control other functions like lockup etc.

Cheers

Brilliant!!
Well done mate, I now feel a whole lot better about checking the fluid levels!
It all makes sense now!
Just as well you gave me this info before i installed my additional atf fluid rad??

[Guest]

Just found this doing a simple search on Yahoo.

Might help anyone who feels scared by the Auto box.

http://www.familycar.com/transmissio...0transmission?

Cheers