Transmission Fluid - Replace or add?

4eat or 5mt? Depends on the condition of the oil that's in there, is it brown and smells burnt? Imo the tranny fluid is cheap enough to just replace, seeing as you bought the car a few months ago I would just go ahead and do it for peace of mind that its properly oiled with new fluids.

Oh, it's a 4eat. I think I'm just going to take it to my mechanic and have all the fluids replaced. I've already done the coolant (had to replace the radiator) so I should probably do the brakes and AT.

ATF is more of a hydraulic fluid than a plain lubricant.

and as such it benefits from adding new fluid to the old.

and since subarus have a drain plug on the trans oil pan,

it is easy to do a ''drain and fill''.

the trans holds about 10 qts. of fluid.

but when you drain the pan you will only get about 3.5 qts.

so if you do 3 D&F, with driving around the block after each fill, you will replace about 75% of the old fluid.

(you could do a 4th drain and fill now, but 75% of what you drain will be new fluid.)

then do a d&f once every year while doing an engine oil change.

this will keep the fluid fresh.

each year you will replace about 35% of the fluid.

so 100% (sort of) in over 3 years, or ~50k miles, if you drive 12k per year.

a gallon of fluid cost about $15.00.

so 3 D&Fs will cost about $45 as opposed to the $100 plus most shops charge.

FYI: the difference between the low mark and the high is about a pint or 1/2 qt.

if you measure how much drains out each time and add back the same amount, you do not need to read the dip stick.

reading the dip stick can be a challenge.

good luck.

ATF is more of a hydraulic fluid than a plain lubricant.

 

and as such it benefits from adding new fluid to the old.

and since subarus have a drain plug on the trans oil pan,

it is easy to do a ''drain and fill''.

 

the trans holds about 10 qts. of fluid.

but when you drain the pan you will only get about 3.5 qts.

so if you do 3 D&F, with driving around the block after each fill, you will replace about 75% of the old fluid.

(you could do a 4th drain and fill now, but 75% of what you drain will be new fluid.)

 

Thanks! I think I'm going to have the mechanic change it along with the brake fluid. May as well do all of the fluids and have a known starting point.

 

then do a d&f once every year while doing an engine oil change.

this will keep the fluid fresh.

each year you will replace about 35% of the fluid.

so 100% (sort of) in over 3 years, or ~50k miles, if you drive 12k per year.

 

a gallon of fluid cost about $15.00.

so 3 D&Fs will cost about $45 as opposed to the $100 plus most shops charge.

 

FYI: the difference between the low mark and the high is about a pint or 1/2 qt.

if you measure how much drains out each time and add back the same amount, you do not need to read the dip stick.

 

reading the dip stick can be a challenge.

 

good luck.

Thanks. I think it's best to just have the mechanic replace it along with the other fluids I haven't done (think I just have the brake fluid left). That way I have a known starting point.

I never trust mechanics with my auto transmissions... I do the multiple drain and fills (every oil change if dealing with a bad one) replacing the filter (if its paper) every time. If there are not magnets in the pan I put some in to collect ferrous particulates. Half a can of seafoam trans tune on the first couple flushes isn't a bad idea.

Why? I have seen too many "flushes" do more harm than good. Google it and know what type of machine the mechanic is going to use. Some are safe.... Some are not.

I never trust mechanics with my auto transmissions... I do the multiple drain and fills (every oil change if dealing with a bad one) replacing the filter (if its paper) every time. If there are not magnets in the pan I put some in to collect ferrous particulates. Half a can of seafoam trans tune on the first couple flushes isn't a bad idea.

 

Why? I have seen too many "flushes" do more harm than good. Google it and know what type of machine the mechanic is going to use. Some are safe.... Some are not.

I've had many, many discussions about this with my BMW's. BMW advertises (or did...not sure about now) their transmission fluid as lifetime and the same argument is made by many BMW enthusiasts against changing the fluid.

I've had my mechanic change the transmission fluid in two of my BMW's and I've never had a problem afterwards. However he is a certified BMW mechanic and knows what he's doing. The only concern I have is he specializes in German cars so he may not be as familiar with other makes. But I do trust him...he's treated me extremely well...never had a complaint. Given this I'm going to just have him do it.

I have an updated question on this. When I originally posted this question I had checked the fluid level when the vehicle was cold and therefore used the cold level markings. A review of the owners manual stated it is better to check the fluid when hot. So I followed the hot check procedure and I'm confused with the results. The cold test indicates there level is right where it should be. The fluid even looks good (looks like it may have been recently replaced). However the hot check doesn't reveal any fluid on the dip stick. None at all. This has me concerned. I don't want to operate the vehicle with low fluid but the cold test indicates the fluid level is correct? Anyone have any thoughts on this?

I'm planning to have all the fluids replaced at the end of next week but would like to use the car in the meantime. But if it means risking damage to the transmission I'll hold off on driving it (I have another vehicle).

I have an updated question on this. When I originally posted this question I had checked the fluid level when the vehicle was cold and therefore used the cold level markings. A review of the owners manual stated it is better to check the fluid when hot. So I followed the hot check procedure and I'm confused with the results. The cold test indicates there level is right where it should be. The fluid even looks good (looks like it may have been recently replaced). However the hot check doesn't reveal any fluid on the dip stick. None at all. This has me concerned. I don't want to operate the vehicle with low fluid but the cold test indicates the fluid level is correct? Anyone have any thoughts on this?

 

I'm planning to have all the fluids replaced at the end of next week but would like to use the car in the meantime. But if it means risking damage to the transmission I'll hold off on driving it (I have another vehicle).

When you checked the level when the engine was hot did you have the engine on and in park, because it's not like checking the engine oil with the motor off. The engine has to be going when checking the trans hot.

When you checked the level when the engine was hot did you have the engine on and in park, because it's not like checking the engine oil with the motor off. The engine has to be going when checking the trans hot.

Yes, I did perform the test with the engine idling and the transmission in park. I followed the procedure outlined in the owners manual and that's what it called for. The exact steps I performed:

• Drove the car to bring it up to normal operatin temperature.
  
• Parked the vehicle on a level surface.
  
• While the engine was running I cycled the transmission from park through all of the lever positions to 1st gear and then back to park.
  
• While the engine was idling I checked the fluid level.
  

It's curious to me there is absolutely no fluid on the dipstick when I perform the hot level check given the cold level check shows there is adequate fluid. I would think there would be some fluid on the dipstick.

I'm going to call the service facility to see if they'll have time to perform fluid flush today. If not I'll drive my other vehicle. I'll keep the forum updated.

did you perform the cold test with the engine running?

I did not. The manual didn't specify the engine should be running when performing the check cold. But that may explain the difference. It's at the shop now so I'll know soon enough if it was low or not.

Yes, I did perform the test with the engine idling and the transmission in park. I followed the procedure outlined in the owners manual and that's what it called for. The exact steps I performed:

 

• Drove the car to bring it up to normal operatin temperature.
  
• Parked the vehicle on a level surface.
  
• While the engine was running I cycled the transmission from park through all of the lever positions to 1st gear and then back to park.
  
• While the engine was idling I checked the fluid level.
  

It's curious to me there is absolutely no fluid on the dipstick when I perform the hot level check given the cold level check shows there is adequate fluid. I would think there would be some fluid on the dipstick.

 

I'm going to call the service facility to see if they'll have time to perform fluid flush today. If not I'll drive my other vehicle. I'll keep the forum updated.

I would be going off the hot reading. I don't really go for these cold readings, the reason being is that I am older and for years used to drive a Pontiac Parisienne. These days we cry if we so much as see a single drip under our cars, but back in the 70s and 80s these big Impala type cars used to leak big time. Engines, trans and diff, it pissed out. There was no such thing as a cold check in those days, always hot. I would suggest that you only go off the hot reading and if it looks low then add to just under the full mark.

I would be going off the hot reading. I don't really go for these cold readings, the reason being is that I am older and for years used to drive a Pontiac Parisienne. These days we cry if we so much as see a single drip under our cars, but back in the 70s and 80s these big Impala type cars used to leak big time. Engines, trans and diff, it pissed out. There was no such thing as a cold check in those days, always hot. I would suggest that you only go off the hot reading and if it looks low then add to just under the full mark.

Thanks for the recommendation. I just returned from picking up the car from the mechanic. He said he was barely able to read the level even when cold. I suspect the location I was reading the fluid level is not completely level thus leading to the discrepancy. In the end he said it was about half a quart low. I had him flush it along with all the other fluids. Felt it was better to work from a known starting point.

now that you know it is right, i suggest you check the fluid level early in the AM before you start or drive the car.

this will give you a reference point for future comparison.

and just so you know, the difference between low and high on the dip stick is less than a qt., more like a pint.

so if you ever feel the need to add ATF because it is low, do it slowly.

now that you know it is right, i suggest you check the fluid level early in the AM before you start or drive the car.

this will give you a reference point for future comparison.

 

and just so you know, the difference between low and high on the dip stick is less than a qt., more like a pint.

so if you ever feel the need to add ATF because it is low, do it slowly.

Thanks John...I will do that...always good to know what it should be for future reference. And thanks for the information on the difference. They did say it was about 1/2 quart low so that would explain why it didn't read at all.