Car Question: Transmission and Coolant Fluid Exchanges

[Philociraptor]

When I had a recall fix done on my car 10 days ago the dealership suggested both transmission and coolant fluid exchanges. Car is at 125k miles, I bought it about 10k miles ago last September. To my knowledge neither service has been performed before. I went through the maintenance schedule papers and it says to check both the transmission and coolant fluids but doesn't mention performing an exchange. Question: Should I have one or both of these services done during my next oil change?

[Jack]

I recommend changing the fluids, but I do not recommend having a dealership do it. Go to an independent mechanic (that you trust, or at least that somebody you trust recommended) instead.

[Greg]

A lot depends on the specific car...

Transmission fluid exchange (meaning change I think) is a good idea especially for automatics, and often should include a filter and pan gasket change, depending on your car.  A manual transmission can go longer, but if it were my car I'd change it just so that I knew what and how much was in there.

Same goes for coolant.  Some manufacturers use "long life" coolant or other special fluid so you need to verify what your car is supposed to have and try to figure out what it does have.  If it's green, it's likely plain old coolant and so if you change it (a flush is a good idea when you do, plus any cooling system repairs like hoses) be sure to use what your owner's manual specifies.

[Thegoblinchief]

You can buy a cheap coolant tester at an auto parts store. I usually just go by the color. If it's either bright green (standard) or red (either dexcool or Toyota's proprietary), it's fine. If it's getting dark, or murky, then change.

Transmission fluid is similar. Also worth feeling the texture between thumb and forefinger in case there's any grit.

I have occasionally read that transmission flushes (as opposed to simply drain and fill) are actually bad for the transmissions. No idea what the truth is.

[r3dt4rget]

When I had a recall fix done on my car 10 days ago the dealership suggested both transmission and coolant fluid exchanges. Car is at 125k miles, I bought it about 10k miles ago last September. To my knowledge neither service has been performed before. I went through the maintenance schedule papers and it says to check both the transmission and coolant fluids but doesn't mention performing an exchange. Question: Should I have one or both of these services done during my next oil change?

Asking a shop whether you need a fluid flushed is like asking a car salesman if you should buy the more expensive car... Most of the time the answer is biased because, after all, business is for profit and not to help people out. It's important to do your own research and make a decision based on facts, not trust a service salesman. You've looked at the owners manual. Great. It says the fluid doesn't need flushed, just inspected. That means that the fluid should be fine and not need flushed. It's asking you to look for anything out of the ordinary such as discoloration, low fluid levels, etc. At 125k those things indicate a bigger problem causing your fluids to need changed so early. Follow the advice above and from the service manual, and check the fluids yourself. Most modern auto transmissions are sealed up and not designed to need any service or flushes.

[Philociraptor]

When I had a recall fix done on my car 10 days ago the dealership suggested both transmission and coolant fluid exchanges. Car is at 125k miles, I bought it about 10k miles ago last September. To my knowledge neither service has been performed before. I went through the maintenance schedule papers and it says to check both the transmission and coolant fluids but doesn't mention performing an exchange. Question: Should I have one or both of these services done during my next oil change?

Asking a shop whether you need a fluid flushed is like asking a car salesman if you should buy the more expensive car... Most of the time the answer is biased because, after all, business is for profit and not to help people out. It's important to do your own research and make a decision based on facts, not trust a service salesman. You've looked at the owners manual. Great. It says the fluid doesn't need flushed, just inspected. That means that the fluid should be fine and not need flushed. It's asking you to look for anything out of the ordinary such as discoloration, low fluid levels, etc. At 125k those things indicate a bigger problem causing your fluids to need changed so early. Follow the advice above and from the service manual, and check the fluids yourself. Most modern auto transmissions are sealed up and not designed to need any service or flushes.

Coolant is yellow-ish in the hose, clear in the hand or on a napkin. Transmission fluid is black with a bit of very fine dust when I feel between my fingers (uniform, not different sizes). Car is a base, automatic 2008 Scion xD.

[kendallf]

Coolant is yellow-ish in the hose, clear in the hand or on a napkin. Transmission fluid is black with a bit of very fine dust when I feel between my fingers (uniform, not different sizes). Car is a base, automatic 2008 Scion xD.

Both of these jobs are DIY-able, with the coolant change being the easiest. 

You can probably find some detailed instructions or a Youtube video for your car.  For coolant, you basically need to loosen a drain near the bottom of the radiator, drain the old coolant, close this, and open the radiator and pour in new coolant and water.  There are some minor complications such as doing this with the vehicle cold, then checking and bleeding for air bubbles if necessary when the car warms up and the thermostat opens, that sort of thing, but it really is simple.

The trans fluid exchange may actually be worth paying for; some dealers have a machine that goes "inline" with your transmission (they disconnect a trans cooler line and loop the machine inline there).  This allows them to capture the old trans fluid while putting fresh fluid into the trans while the car runs.  This has the advantage of getting the fluid in the torque converter which is not changed in a static trans fluid change.  It has the disadvantage of not changing the trans filter, which requires dropping the trans pan.

There are separate arguments to be made over whether a transmission fluid change is advisable on a higher mileage car at all.  Some people believe that this leads to internal hydraulic leaks past worn seals that were previously kept sealed with grit, leading to problems after the fluid change such as line pressure drops and clutch pack wear.  I'm agnostic on this subject but don't bother to change the trans fluid on most of my cars.

[Jack]

There are separate arguments to be made over whether a transmission fluid change is advisable on a higher mileage car at all.  Some people believe that this leads to internal hydraulic leaks past worn seals that were previously kept sealed with grit, leading to problems after the fluid change such as line pressure drops and clutch pack wear.  I'm agnostic on this subject but don't bother to change the trans fluid on most of my cars.

Ideally, one should have a car that uses gear oil instead, rendering the issue moot.

[RyanAtTanagra]

I recommend changing the fluids, but I do not recommend having a dealership do it. Go to an independent mechanic (that you trust, or at least that somebody you trust recommended) instead.

+1

I did transmission, power steering, and brake fluid at about 125-150k.  I figured it would be a one-time thing, if the car made it to 300k I probably wouldn't care enough to bother doing it again (sold it at 280k before I had to make that decision).