To transmission flush or not to transmission flush? That is the question.

September 1, 2006 6:17 AM

To transmission flush or not to transmission flush? That is the question.

A few months ago, I took my (automatic) car to my local mechanic for a routine oil change. They told me that my transmission fluid was dirty, and that I needed a "transmission fluid flush". Since I'd never heard of such a thing and it wasn't part of my car's routine maintenance, I opted to put it off to a later date. I did a little Google research when I got home and came across a lot of conflicting opinions - some say transmission flushes are vital, others say it will permanently screw up your transmission.

Fast forward to this week. Three times this week I've started my car as usual, but when I shift it into drive the car accelerates sluggishly, as if the parking brake is engaged (it's not). Shifting gears does not alleviate the problem, nor does driving the car for a short period of time. However, turning the car off and re-starting results in a blinking O/D off light and normal acceleration. I checked the transmission fluid last night - the fluid level is fine, but the color is definitely off.

Regardless of the actual cause of the problem, I'm sure the mechanic is going to see this as an opportune time to recommend a transmission flush again. Since I'm a girl, and I look young and vulnerable to boot, I'd like to go in prepared. So, 1) Is a transmission flush a good idea? 2) How much should I expect to pay for it?

And a bonus question: Does my problem sound like something a transmission flush would fix? Personally, I'm thinking it's a computer problem (though I know very little about cars), and I want to make sure this problem isn't just chalked up to dirty transmission fluid so that the mechanic can make a few hundred bucks.

posted by geeky to travel & transportation (16 comments total)

I don't know whether you should get it done or not, but if you do decide to, don't get it done at jiffy lube...
jiffy lube scam video
posted by o0dano0o at 6:34 AM on September 1, 2006

Hmn, could be a mix problem. How old's your car? Have you checked or replace the spark plugs recently?
posted by SpecialK at 6:43 AM on September 1, 2006

The car is a 2001, with about 52,000 miles if that helps. I've kept up with regular oil changes, and the only thing that has been replaced since I've owned the car (bought it used 2.5 years ago) is the brakes.
posted by geeky at 6:49 AM on September 1, 2006

(Oh, yeah -- a jiffy-lube type place locally caused this problem in my car by breaking my air filter cover, which allowed a lot of unfiltered air into my engine and ruined the mix at start because intake pressure was a lot lower, albiet more volume, and it took the intake o2 sensor to fix it. This kind of problem is potentially indicitive of an o2 sensor going bad. o2 sensors are cheap, and you'll know it's bad when your car's computer codes out.)
posted by SpecialK at 6:50 AM on September 1, 2006

* took the intake o2 sensor a minute or two to adjust the mixture and fix it.
posted by SpecialK at 6:50 AM on September 1, 2006

I don't see how your transmission fluid could affect the acceleration of your car. It's more likely to be a fuel filter or something like that.

As far as transmission fluid flush, I don't think a flush would hurt, but don't let them charge you more than $100 - $150. know if you need a flush. Typically, they're not recommended until you hit ~100K miles - check your owner's manual. And make sure they put a new filter in when they do it.
posted by CRS at 6:56 AM on September 1, 2006

First off, this sounds exactly like a slipping transmission. Everytime the trans slips, you are doing severe, expensive damage. If your fluid is burnt, you may already have trans problems (all of which require a $2000 rebuild). I think you should have have the fluid and filter changed as soon as possible and hope that it is slipping because of a clogged filter. It probably won't help, but the alternative is a rebuild.
posted by 445supermag at 7:29 AM on September 1, 2006

Manufacturers recommend a ATF flush every 100K miles because their maintenance schedule is calibrated for a 100K lifetime for the car.

To get your car to last 200K or more, you need to do the routine fluid changes far more often than the dealer recommends. The standard for a tranny flush is 2yrs / 30K miles.
However, before you do it - pull your tranny dipstick and inhale deeply. If it smells burnt you are probably already screwed, and a tranny flush could finish off your transmission by loosing up the sludge that is holding it all together. If that is the case, you might just want to drive it until it dies, and deal with the $2000 rebuild then. If the fluid smells ok - and still shows sign of its original pink color, then a flush is in order ASAP.
posted by COD at 7:50 AM on September 1, 2006

geeky writes "The car is a 2001, with about 52,000 miles if that helps."

Make and model?

Transmission fluid and filter should be changed every two years on both the three and four speed Chrysler FWD transmissions (assuming regular driving patterns). On the three speed the bands should be adjusted at the same time. The four speed AOD transmission takes an expensive special fluid (Mopar 7176).

If the AOD is topped up with Dextron poor driving performance can result and eventually the transmission will be damaged.
posted by Mitheral at 8:26 AM on September 1, 2006

I don't see how your transmission fluid could affect the acceleration of your car.

It's the transmission fluid that transmits rotational motion from the engine side of the torque converter to the wheel side. (Specifically, transmission fluid isn't just transmission lubricant.) When it breaks down, either it doesn't transmit enough rotational motion and you lose power, or it does too much and it bogs.
posted by mendel at 8:31 AM on September 1, 2006

Make and model?

Infiniti G20.

I should also note that 1) the transmission fluid does not have any burnt odors, and 2) I have not noticed any other problems (transmission or otherwise) until this week. This problem had a very sudden onset. If this were a slipping transmission, wouldn't I have noticed some decline in performance or something before this week? And why would re-starting the car fix the problem?
posted by geeky at 9:10 AM on September 1, 2006

I'm always heard that you should change your transmission fluid every 100,000 miles. I've never heard of a case where a simple fluid change destroying the engine, but I would still take the advice relating to that above to heart.
posted by triolus at 9:57 AM on September 1, 2006

"Manufacturers recommend a ATF flush every 100K miles"

Uh...not all of them. It's actually recommended against flushing the tranny fluid in my Honda. You're supposed to change it, yes, every 90,000 miles. But Honda says never flush.

For what it's worth, your car's owner's manual says to Inspect the fluid every 15,000 miles, and replace "if necessary". (Unless you use a car-top carrier, or drive on rough or muddy roads, in which case it says to replace, not just inspect, the fluid every 30k miles.)

If the O/D light is blinking, the car's probably trying to tell you something. Take it somewhere like AutoZone that'll hook it up to an OBDII scanner for free, and tell you what the diagnostic code means.
posted by CrayDrygu at 4:39 PM on September 1, 2006

A little update for anyone else that may find this question useful: After perusing my owner's manual some more, I figured out that the problem is actually my car going into "fail-safe" mode. The sluggish acceleration is because in fail-safe mode the car locks into 3rd gear, and the blinking O/D off light on restart indicates that the car was previously in fail-safe mode. RTFM really works!

I took the car to a Midas shop (only shop open at the time) to have the computer checked, and was told they couldn't find anything wrong with it (it wasn't in fail-safe mode at the time). The following week, I noticed the car was also taking longer to start than normal. A little Googling lead me to believe that a dying battery may be the problem. I had the battery tested (needed replacing) and replaced, and I'm hoping that will be the end of this issue. *crosses fingers*
posted by geeky at 12:09 PM on September 12, 2006

A flush should be part of your regularly scheduled maintenance plan, check your car's manual. If you don't have one, check Parks, Advanced, etc. If they are out, order a book online from your car maker, or better yet, Amazon or B&N. G/L.
posted by BillyG at 9:47 AM on September 15, 2006

Another update: Around 60,000 miles I finally got my transmission fluid flushed because it was decidedly dirty. My transmission has not exploded and the car is still running fine, but I have not noticed any marked increase in performance either.

The transmission flush was unrelated to my O/D light problem, which was fixed by replacing the battery (as noted earlier).
posted by geeky at 11:23 AM on April 27, 2007