Is a transmission service necessary?

[ZDA3]

The car is a 2015 Mazda 3 isport. I don't see the transmission dipstick being easily accessible. The car isn't acting up or anything but I'm curious if the transmission needs some type of regular maintenance at some point? The car has over 250k miles.

 

[sm1ke]

Most people who service their transmissions regularly do it at 30k-50k mi intervals, and they'll typically drop the pan the first time so that they can replace the transmission fluid filter as well, since the filter would have caught any of the metal wear from the initial break-in of the car. After that, it would be just standard drain and fills at each interval.

At 10 years and 250k mi, if you've never serviced the transmission, it's probably best to leave it alone so that you don't make anything worse. Definitely don't do a transmission flush. The fluid has likely gunked up over time and there are deposits that will come loose during a flush. Those deposits can clog the valleys in the transmission and cause some serious shifting issues. Again, it's probably best to leave it alone and ride it out until the transmission dies, then replace the transmission or scrap the car at that point. There are cars out there that have never changed their fluid out and driven 350-400k mi, but I wouldn't rely on that.

 

[ZDA3]

My old car (2001 Toyota Celica GT) never had a transmission service and went over 300K miles. I'll take your advice.

If I remembered correctly, my old car had a transmission dipstick that was accessible but not this Mazda. I was thinking the transmission was "electric" that's why I couldn't find the transmission dipstick, turns out it was the power steering that was electric (since it requires no power steering fluid).

 

[ZDA3]

Anyway we have another mazda 3 (2016), with about 260k miles. It was recently taken to the dealership for a possible timing chain replacement but turns out it wasn't the issue. The diagnostics revealed all kinds of other issues one of which was the transmission pan was leaking. The suggestion was to remove and reseal the pan. Is this do able by a certified mechanic (meaning it's easily accessible), and not just "at the dealership only"?

 

[sm1ke]

Any competent mechanic should be able to do that for you. You can get the gasket/sealant and the new pan (if needed) from the dealership, along with the replacement ATF.

 

[Lazy2.5]

Anyway we have another mazda 3 (2016), with about 260k miles. It was recently taken to the dealership for a possible timing chain replacement but turns out it wasn't the issue. The diagnostics revealed all kinds of other issues one of which was the transmission pan was leaking. The suggestion was to remove and reseal the pan. Is this do able by a certified mechanic (meaning it's easily accessible),

Absolutely yes.

and not just "at the dealership only"?

Absolutely not.


Yes, definitely do it. Once the bottom of the pan is new and clean, clean magnet, new strainer, I would suggest doing 2-3 drain and fills on top of that to get the rest of the dirty fluid out of the torque converter.

 

[SparkYellow]

Once you remove the air intake box, the dipstick is easily accessible. It is secured by a 10mm bolt. I have completed three rounds of drain/fill in the last 3 weeks, and the fluid is still brown. Fresh fluid is blue FZ on Skyactiv, or red M5 on pre-Skyactiv. My oversight for doing this at 155K miles. I thought it was done at 60K miles along with the differential and transfer case. Last month I noticed hesitation and jerky movement in shifting and realized that it needs attention. Symptoms were relieved after the first round of drain/fill AND shifting pattern reset.

Waiting for the fluid sample analysis to determine if I should replace the filter and reseal the pan. The only aspect about this task that is unsettling to me is the cure time of the RTV. My reading indicates that OEM is RTV for a CX-3, and there's no confirmed fit of any aftermarket paper gaskets. If there's a paper gaskets for your Mazda, then it's a more straight forward job, owner-doable with proper access to the undercarriage.

 

[ZDA3]

Even at 267K miles?

We'll probably get the drain and fill done at a transmission shop since I can't get under the car.

 

[Lazy2.5]

Even at 267K miles?

We'll probably get the drain and fill done at a transmission shop since I can't get under the car.

Yes. The only time I would be careful about a full transmission service would be in the event of serious transmission issues. Not just some jerking/hesitation or whatever.

 

[Lazy2.5]

Even at 267K miles?

We'll probably get the drain and fill done at a transmission shop since I can't get under the car.

At your mileage assuming no prior transmission service, ensuring the bottom of your pan is clean is a critical, very overdue service. You're lucky that your pan needs to be replaced, otherwise I'm sure you wouldn't have bothered.

 

[ZDA3]

Yup, there's really no jerking or hesitation issue so far and the car has never had any transmission service before (no fluid flushes or drain/fill). Perhaps just leave it alone?

How does one actually reseal a pan when there's leaks, does one buy a new fluid pan or best to keep the original one?

 

[Lazy2.5]

Yup, there's really no jerking or hesitation issue so far and the car has never had any transmission service before (no fluid flushes or drain/fill).

Perhaps just leave it alone?

Absolutely not.

How does one actually reseal a pan when there's leaks, does one buy a new fluid pan or best to keep the original one?

Depends whether it is the gasket or the pan itself. I'd just get a new one.

 

[SparkYellow]

About the older Mazda3 with 267K miles, after the shop noticed that the transmission pan was leaking, did they check the fluid level at the dip stick with the engine running? If they didn't, was it because the leak was minor/mild? If they checked the level, was it low, and did they top off?

I come from a long-line of leaks on all sorts of cars. Some slow leaks are ok as long as the proper level is maintained.