Transmission service

I own a 2009 Cadillac DTS, which has 80,000 miles on it. The question is , Should you follow the manual which says transmission service at 100,000 miles or listen to the dealer who does my oil change. They suggest I should get it at 60,000 miles, plus they also suggest a tune up, engine flush, and something else, which the manual does not, estimated at $1100.00. I do not think i need to do all that. My driving is very normal. No stop and go rush hours.

The reason I am asking about the transmission in particular,is because I use to own a Buick Rendezvous, whose manual suggested transmission service at 100,000 miles and the mechanic i used suggested at 50,000 miles. i ignored him. And lo and behold my transmission went out.

any advice.

I would probably listen to the dealer they have real world experience with that particular car.
I think the manufactures tend to be a bit optimistic with their mileage recommendations.

If I was buying a car and the recommended service for one car said 60,000 miles and the other said 100,000 miles I would probably buy the one that said 100,000, which is why I think the manufacturers tend to recommend the higher mileage, to keep up with or beat the competition.

The dealer knows better, they have done them at 100,000 miles and at 60,000 miles and they have probably discovered that 60,000 miles makes the transmission last longer with fewer repairs.

The transmission should be serviced more often and if the truth be known, should be done at about 30k miles intervals.

An engine flush I would skip; whatever that is or however it is defined.

Tune-up is pretty much an obsolescent word in the modern automotive world. A “maintenance service” might be a better term.
In a case like this changing the spark plugs and servicing the filters and PCV system should be part of it. While not often done, an inspection of the battery and charging system would be a good idea; especially if the battery is the original.

The trans service is a good idea, as stated above the factory service intervals are more of sales tools than realistic.

I agree with most posters here that doing the service sooner than 100,000 miles can’t hurt and will probably help. On the other hand I disagree with ok4450 (please don’t hurt me) and others that still recommend a 30,000 mile service interval. Most extended service intervals are due to advanced synthetic fluids that hold up for incredibly long times. I know that it is also important to clean out particulate matter as well but most transmissions have sufficient filtration to deal with extended service intervals.

As far as trusting dealers to know your car better than the manufacturer? HA! Dealers know how to make money on extra service that you often don’t need. Not that manufacturers are infallible or don’t occasionally make mistakes (i.e. Toyota engine sludging due to extended oil change intervals) but the manufacturer typically has designed and tested all systems in the car to the extreme and does not design the maintenance schedule to destroy your car. We, as car owners, are our own worst enemy when we apply old standards to new technology. Remember when we replaced spark plugs every 10,000 miles? And antifreeze at 30,000? Sometimes we need to put our buggy whips away and move forward with the times. FYI, I am a bit of a retro-grouch myself so don’t lump me in with all those people who embrace anything new just because it is new.

I’m a mechanic, and I also hate “wallet flushing”, what many people refer to when talking about changing or flushing fluids before the recommended interval. I tend to stick with manufacturer recommendations.

Having said that, for cars or trucks that are used for towing, hauling, or heavy duty service I recommend transmission service every 30,000 miles. For regular driving every 60,000 miles. Why? Transmission fluid is cheap, transmissions are expensive. Say servicing your transmission and filter using the synthetic Dexron 6 fluid your car requires costs $180. By the time you hit 120,000 miles you will have spent $360. If you never service it and need a transmission, that will cost you $3500 or more. Pretty cheap insurance. Servicing your trans won’t guarantee it will last forever but it increases the odds.

+1 for @asemaster because that’s basically what I was going to write. Thanks for saving me the time and effort.

A long time friend who has worked in and now runs a very reputable transmission shop that was established by his dad way back in the 50s is the sharpest transmission guy I’ve ever known. He should be after 40 years of transmissions only.

He has told me that almost every transmission failure he sees has been caused by a fluid issue.

  1. Low on fluid due to a leak and continued operation.
  2. Failure to change the fluid regularly.

As asemaster mentioned; cheap insurance.

I agree with doing a transmission service as long as they drop the pan, replace the filter and refill. I would not allow them to just hook up a flush machine to the transmission.

Now if they drop the pan, replace the filter, then reinstall the pan and refill AND THEN hook up a fluid exchange machine, they will get all the old fluid out that was trapped in the torque converter and upper valve body. I don’t think this last step is necessary if you do the drain, filter and refill every 30-40k, but it wont hurt.

Just using a flush or fluid exchange machine with out first dropping the pan and replacing the filter will result in a dirty filter and not all the ATF will be exchanged in spite of their claims. The fluid exchange machine puts fluid in one side of the pan and take fluid from the cooling lines that is getting fluid from the other side of the pan. Its just a continuous dilution process, not a true exchange. But if all the fluid in the pan is fresh, then is does become a true fluid exchange.

BTW, the rest is bogus until the 100k mile mark. Just follow the maintenance schedule in your owners manual.

"I agree with doing a transmission service as long as they drop the pan, replace the filter and refill. I would not allow them to just hook up a flush machine to the transmission."

You are right on the money with that statement @keith .

I know no one can see me but I’m holding up my fingers in an X pattern right now. That’s what I think of transmission flushes.

I have a 2009 Toyota with the “sealed” transmission and “lifetime WS” fluid.

Two Toyota dealerships and an independent transmission shop (in business 30 yrs, same owner) all told me no need to change the fluid until 100,000 miles.

I did read somewhere that the operating temps for some later model transmissions are running a few degrees cooler than in the past. If that’s true, then that would enable longer intervals between changes.


My brother’s 2008 Toyota also has a “sealed” transmission and “lifetime WS” fluid

The owner’s manual makes no mention of a dipstick

Yet, if you pop the hood, there is a dipstick. A sticker on the dipstick says the fluid is lifetime fill

And it gets better . . . there’s a drain plug on the pan

It takes brass balls for a manufacturer to claim their transmission is sealed, yet it has a dipstick and a drain plug

I’ve already changed the fluid and the filter. I take Toyota’s “lifetime WS fluid” claim with a large grain of salt

what is WS fluid?

WS means “world standard”

I believe it is Toyota’s latest, and most expensive, full synthetic atf

I’ve worked on a lot of cars and I can say I’ve never seen one with a “sealed” transmission. What on earth is it that makes all these people say that they have a sealed transmission.

If it’s hydraulically operated there’s fluid in it and there’s a way to get the fluid out and a way to get it in.

“sealed” is a term often used by Toyota for their recent transmissions. It may be a marketing term, but their TSB does caution that the WS fluid must be stored in sealed containers that aren’t exposed to the atmosphere where they can absorb moisture.

Toyota 5-speed transmissions up through 2010 had a dipstick and drainplug. Their 6-speed transmissions do not.

Here’s a google doc of a Toyota TSB (T-SB-0006-11) describing some of it:

I can’t find a link for the procedure involved to change the fluid.

I wonder if the new CVT on the Corolla will be “sealed” with “lifetime” fluid?

The cvt on the Corolla is “sealed” and the fill procedure is rather complex. Worst part is the cost of fluid $80 a gallon if my memory is correct, replaced one under warrany about a month ago.

@SteveC76‌ I had a Jaguar in once, car bottomed out and tore open a transmission cooling line. Repaired the line easily enough, but gave the customer a choice between aftermarket synthetic transmission fluid and Genuine Jaguar Esso part#XYZ123whatever. Customer wanted to stick with the factory fluid at $59/quart.