Automatic Transmission fluid, add/check

jerry_njApril 6, 2007

The last previous automatic transmission I owned was a 1977 Pontiac which was sold in about 1984.

I now have a Subaru Forester 2004 with an automatic transmission and about 22K miles on it. On checking the transmission fluid level today (after the car was driven about 10 miles and was put in each gear) engine running and transmission in Park I found the dip stick to indicate the fluid level was a bit low, well above the cold marks, but below the hot marks. I added about 4 oz of Dexron III (as specified in the owner manual). This I added with some difficulty through the rather small opening for the dip stick which is low and hard to reach. Is there another/better place to add transmission fluid?

Then after driving the car again I check the level and it was up near the "hot" full mark, but there were some small bubbles in the fluid on the dip stick, is this normal?


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Why did you even bother to add fluid. It was between the
low and high. Was the vehicle parked on a level surface ?
It does make a difference. you add fluid through the dip
stick. there is no other place. Check the level about 3 times. This will get rid of the bubbles. NORMAL

    Bookmark   April 6, 2007 at 11:08PM
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Thanks, yes it was on the level, in my garage which has a good solid floor.

The level was between the "low" and "high" marks, i.e., below the hot level fill mark, albeit it may not have been as at full hot temperature, not sure. The car had been driven for a few miles before checking. I will check again this morning to see where the level is on a cold check.

The dip stick location on the Subaru Forester is particularly difficult to reach, even to pull the dip stick. To add I used a funnel with a tube of small diameter to add the fluid, perhaps that's what that funnel is intended for. I don't recall why I purchased it, just had it on hand. As stated, this is my first car with an automatic transmission in 25 years.

Do you have a view on the preventive maintenance recommendations to flush both automatic and manual transmissions at some interval, say 30,000 miles? I have never done that and have had cars with 100,000 plus miles on them before I junked them.

    Bookmark   April 7, 2007 at 9:54AM
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There are a number funnels available with a long flexible snout. There are also gizmos you can buy that just screw on the container you're pooring from and have a long clear tube and an on/off valve of sorts. Just look around, there's all kinds of things that may work for you.

As to the service interval, just do what the owners manual says. Recomendations are all over the place. Auto transmissions quite possibly self destruct at about the same rate no matter what.

The two ways to look at it goes like this. As the transmission operates, material sluffs off the clutch packs and bands into the fluid. This increases the space between the friction discs and spacers in the clutch packs, also the bands and the surfaces they rub against. This sluffed off material also makes the fluid thicker over time. That thicker fluid may actually make up for the added space created by the material that has worn off. So, change it all the time and keep the fluid looking nice and clean but resulting in added clearance between those friction some point to much to function. Or leave the thicker old fluid in it so it can make up for the increased clearance of the worn parts. Pick one.

Having clean fluids always FEELS like the right way to go. I can't say if changing it all the time @ 30k miles will get you down the road further or not as far as if you left it alone though. For that reason, I say break out the owners manual and see what it says. If it says do it every 30k, do it. If it says 100k, do it. If it says service is not recommended, don't. jmo

    Bookmark   April 7, 2007 at 1:11PM
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Thanks for the inputs. I did look at Walmart for a long funnel, and saw only what I have, may have purchased at Walmart a few years back. That funnel was long enough, but too big around to fit in the dip stick hole. It would surely have helped if the dip stick tube was 4" or so longer. I suppose the longer the tube the more error it introduces in the dip stick reading which is only the lower couple of inches of the stick. That said, another funnel, that I have had even longer, worked fine, albeit it is hard to decide how much to put in. I tried a little and figured if it wasn't enough I'd put more in. The dip stick, unlike the one for engine oil, doesn't caution against overfilling.

I am mixing transmissions here, the 30K mile question came up because I have a Clinton shop manual on another car (I quit buying shop manuals in 1999 when the price got to be a couple hundred) and decided to read it to see what it said about adding automatic transmission fluid. This is where I got the change the manual transmission grease (the older car to which the manual applies) at 30K miles. I was surprised and hadn't read that in the owner's manual as far as I could recall. I'll go to the car and get out that recommendation before giving this any more consideration.

    Bookmark   April 7, 2007 at 1:27PM
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Correction, the "Repair Manual" I have is a Haynes, for 323 and Protege 1990 thru 2000, I'm working a 1999. The owner's manual does not call for draining and replacing either manual or automatic transmission oil/fluid. Also, neither the owner's manual, better look again, nor the Haynes says anything about replacing the timing belt. My older Japanese engines required the timing belt to be replaced every 60K miles. Must be making the belts out of a much stronger material these days.

    Bookmark   April 7, 2007 at 6:02PM
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