Transmission flushing at home: Really easy, really effective

[volvoshad]

You're not the first person to have difficulty finding the tranny dipstick, which is not even mentioned in the owner's manual. It is on the very front of the transmission, near the lower radiator hose. It's yellow, and you have to push a little clip on the stick to remove it. I think it is easiest to see when you are standing on the driver's side of the vehicle. The distance between the two marks on the stick are only 0.2L apart. Overfilling will cause foaming of the ATF, and can apparently be as harmful as underfilling. It is best to measure the level with the tranny hot (as in after a brisk drive on the highway) and with the engine running, so wear gloves and long sleeves to protect from burns. At least there's no moving parts nearby.

[ricnordgren]

I'll give it another go tonight. Thanks.

[zildjianl]

Hello,
I have a 2001 VolvoXC...Did the Gibbons flush...BUT I'm not to sure of the AMOUNT of trans. fluid after the power flush. How many ltrs. to fill a flushed trans? How many ltrs. stay in trans. after flush? I need more Info. please

[ltoolio]

Did the flush tonight and for the most part things went pretty well (except for that damn green plug!).

The dipstick reads perfectly in the cold section right after I did the flush (I let it sit for a while before I did my reading).

How long do I need to drive before I can get an accurate reading at Hot? I did about a mile loop 2 times and didn't notice any sort of appreciable increase in the reading.

So after posting this I noticed the post above from VolvoShad about running it on the HW and then measure.

However - measure with the engine running? Does this apply on the cold reading as well? I was measuring with the engine off...

[BillAileo]

Engine running.

Bill

[ltoolio]

Engine running.

Bill

Thanks Bill. I did a few reads with the engine running and discovered that I was a bit low.

One more question, if I may - I was finding that I didn't get a terribly good reading if the stick wasn't put in with the measuring lines facing a certain way (i.e. if measuring lines were towards the front, I really couldn't get a solid reading)

To ensure a reading that I could actually deduce from, I rotated the dipstick while in the hole. Is this consistent with anyone else's experience?

[gibbons]

I found that the temperature makes a surprising difference in the reading on the dipstick. I measure mine at about 80C, which takes quite a bit of higher speed driving in warm weather to reach. I have a laser aimed infra-red thermometer I use to check the temp by shooting the transmission case.

There is graph in my Vadis software that shows the proper reading vs temperature. It shows that at one temperature temperature, you may be just right, and at another, off the chart. I will try to capture the image and post it.

The vadis documentation says to never use a towel to clean the dipstick because of fibers that might contaminate the tranmission. Now that's finnicky! I just wipe the stick with a paper towel, then a bunch of times with my fingers to remove any lint.

Getting the level right is the worst part of the job.

[ltoolio]

Getting the level right is the worst part of the job.

I still will go with removing the green clip

I found that the temperature makes a surprising difference in the reading on the dipstick. I measure mine at about 80C, which takes quite a bit of higher speed driving in warm weather to reach. I have a laser aimed infra-red thermometer I use to check the temp by shooting the transmission case.

There is graph in my Vadis software that shows the proper reading vs temperature. It shows that at one temperature temperature, you may be just right, and at another, off the chart. I will try to capture the image and post it.

So with the variability in the reading, what is the liklihood that the flush at the dealer will get it accurate? I'm thinking that I/we are spending far more time on it than any tech.

The vadis documentation says to never use a towel to clean the dipstick because of fibers that might contaminate the tranmission. Now that's finnicky! I just wipe the stick with a paper towel, then a bunch of times with my fingers to remove any lint.

Ditto.

I'm still not sure that I'm getting any sort of "real" reading with the cold fluid. I think I'm going to take it to the dealer to get their read on it. It just doesn't feel right as it currently is (what I'm seeing...not how it's driving).

I know that there is .2L of play inbetween then top and bottom lines, but when I think of how much was left in the tubes, on the sides of my transfer containers...there may have been a total of .2L right there after doing the flush/refill 5 times.

[gibbons]

Here is the temp vs level chart, as you can see, the temperature makes a dramatic difference in what the reading should be, you gotta have a way to check the temp....

[Pennhaven]

Here is the temp vs level chart, as you can see, the temperature makes a dramatic difference in what the reading should be, you gotta have a way to check the temp....

[Edit]Since there were two incorrect assumptions in the original post, I have rewritten it to avoid confusing anyone else.[/edit]

I found the temperature/level chart to be confusing, but now, after a few more hours straightening out a mistake I made, it makes more sense. I had a difficult time correlating the markings on my dipstick to the diagram on the chart, as the relative spacing on the dipstick is significantly different than on the chart. Especially the distance between the HOT and COLD areas.

But, leaving the relative scale of the chart aside, I am sure that the chart is indicating that at 40°C the level should be somewhere in the COLD area and at 80°C it should be somewhere in the HOT area. You can also use the chart to interpolate the correct level range for in-between temperatures, but that is a lot more difficult given the differences in proportions between the chart and the actual dipstick.

I checked my "cold" level before I flushed, when the transmission was truly cold (20°C), and found that it was slightly below the COLD area on the stick. After flushing the new cold level was about 1/3 of the way between the COLD and HOT areas, so at first I thought that I needed to pump out about 3 oz. But this was assuming that the 0.2L (6.6 oz) range was between the COLD min and the HOT max. My first bad assumption. The 0.2L range actually refers the difference between min and max levels at a given temperature. I finally figured this out after several attempts to pump out 3 oz. at a time were barely moving the level.

At first I thought the problem was that the temperature was changing while I was measuring, so to nail that down I came up with a process to minimize the temperature variation. I used an indoor / outdoor thermometer from Radio Shack. I could not get an accurate reading by placing the outdoor probe on the case of the transmission, so I resorted to inserting it in the dipstick tube, with a knot in the lead so it would go in no further than the length of the dipstick. This worked fine. I found with the engine running that the fluid temperature would rise about 0.1° C every 15 or 20 seconds. And since I could not measure the temperature while I was using the dipstick, I decided to shut off the motor and let the temperature fall slightly below 40°C then start the motor, and take two measurements with the dipstick before the temperature could climb above 40.5°.

Now I knew I had a valid temperature and accurate level, but my level was to still too high. It would not drop as much as I expected. It was then that I figured out my assumption about the 0.2L was wrong.

But why was my level so high? (It eventually turned out to be 25 - 31 oz. too high!!) That was caused by my second bad assumption. I assumed the 16 oz. graduated cup I was using to measure the discharged ATF was accurate. It was not! After checking I found it was over-reading by about 8%! This would not have mattered if I had used the same cup to measure the new ATF going in, but instead for refilling I relied on the assumption that each bottle of ATF contained exactly 32 oz. and used the graduations on the bottles to measure ounces when needed.

So lesson learned. If you do not use the same device to measure both output and input, be sure that all devices agree.

BTW, my flush went very well otherwise. My only issue, other than overfilling, was that some fluid apparently dripped out of the return line while it was disconnected. I didn't notice the spill in the drip tray behind the radiator until I was cleaning up. Good thing I didn't see it while I was flushing or I probably would have added another oz. or two to compensate and overfilled even more!

I also changed my coolant while I had the belly pan off, and I found that to be very easy too. Probably the easiest coolant change I have ever done, due to the handy petcocks on the rear of the block and under the radiator.

Thanks again Gibbons for posting your transmission flush instructions and now the chart from VADIS.