Tranny overfill good bad, ok? Ugly?

[drifter420]

There's been a debate @ another forum I frequent and thought I would ask you gurus here on what you think. These are for GM's if that helps any ( specifically 4t6x series )

when do you check the fluid.. with car runnin when cold, or after it reached operating temp?

IS it bad to overfill the transmission? How much overfill can you have before it becomes danderous if any?

They have a very small margin on the dipstick for wats acceptable for the transmission fluid... so just want to know.

 

[Bret Chase]

I have been told by a reputable local trans shop (who, from experience stand by their warranties 150%) that it won't hurt anything.. the worse that'll happen is that the excess will puke out the case vent. this was in reference to a TH700R4 (4L60).

 

[ARB1977]

quote:

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Originally posted by drifter420:
There's been a debate @ another forum I frequent and thought I would ask you gurus here on what you think. These are for GM's if that helps any ( specifically 4t6x series )

when do you check the fluid.. with car runnin when cold, or after it reached operating temp?

IS it bad to overfill the transmission? How much overfill can you have before it becomes danderous if any?

They have a very small margin on the dipstick for wats acceptable for the transmission fluid... so just want to know.

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Check it when its good and hot. Your better off checking it during the summer months since ambient temps play a factor when it comes to transmission temps. When i flushed out my 2002 Tacoma with redline D4 i over filled it by a pretty good margin but not enough to cause any to puke out. Just the other day i did a pan drain but i made sure this time not to over fill it. Right now its slightly over to top hot mark. How much fluid you need to add is based on how big of a pan you have. 1 qrt on a small pan can fill it way too much or on a bigger pan i may not budge at all.

 

[TR3-2001SE]

I think overfilling my Toyota transmission damaged an electric seloid. The transmission did have lots of miles at this point 190,000 so it may not have been the overfill but it happened a short time latter and the part that failed is in the transmission above the pan and should not get transmission fluid on it. The owners manual specfically warned against overfilling and as soon as I got it from the service station and checked it I pumped it out.
I now do all my service if possible to eliminate problems like this one.

 

[drifter420]

I"m hearing that it's as bad as overfillin your motor oil.. cause it will foam and cause issue with the pump and other devices that normally shouldn't get lubricated? like what happened to TR3-2001SE. Then there's other sayin it's ok since the full mark on transmission isn't really full.. and there's room for overfill..

 

[unDummy]

Bad and ugly! More than a pint can cause problems.

I've seen one underhood fire caused by ATF overfilling. The puked ATF has to go somewhere and just happend to locate some hot exhaust pipes.
And we wonder why ATF dipsticks are disappearing?

But, overfilling room is engineered into most automatics(to prevent lawsuits). This is because the level changes wih temp. If the dipstick is calibrated for 160-180f degrees, what happens when you're going uphill passing someone with a vehicle full of luggage/people and the ATF hits 240 degrees? Well, you don't usually puke ATF every time you stress the transmission!

I doubt that it can damage an electronic solenoid. One word for ya, COINCIDENCE.

 

[ARB1977]

quote:

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Originally posted by TR3-2001SE:
I think overfilling my Toyota transmission damaged an electric seloid. The transmission did have lots of miles at this point 190,000 so it may not have been the overfill but it happened a short time latter and the part that failed is in the transmission above the pan and should not get transmission fluid on it. The owners manual specfically warned against overfilling and as soon as I got it from the service station and checked it I pumped it out.
I now do all my service if possible to eliminate problems like this one.

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What i did notice was that it seemed to slip alittle bit but when i filled it this time it does not slip as much.

 

[Bryanccfshr]

I have heard of transmissions puking fluid when they get hot and have too much fluid... That in itself is not harmfull.. its just that hot transmission fluid is let lose on your undercarriage. Most vehicles can tolerate very well, it is actually a common practice among offroaders to prevent cavitation of autos at high angles.

 

[terminaldegree]

On a GM 4t-whatever:
Drive the car for 5-10 miles, and get it up to highway speed if possible. Car should be fully warm and fluid should at least be warm.
Stop the car on a flat surface, cycling it through each possible gear on the transmission for a few seconds.
Put car in park, shut off air conditioner, and wait a minute.
With the car running, pull the dipstick, wipe it off, and pull it again.
What you see then should be the accurate level.

Overfilling can lead to leaks. Overfilling a lot can cause more serious problems.

 

[drifter420]

questin is how can overfillin lead to leaks.. and overfillin a lot lead to something major? The transmission is vented correct? ( So access pressure can be relieved ) and if it's overfilled that much.. it would puke it out there and all over the undercarriage right?