ATF auto transmission fluid change

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littlepolo
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Posts: 705
Joined: Thu Jul 21, 2011 9:47 pm

ATF auto transmission fluid change

Post by littlepolo »

I've had the parts and fluid at hand for some time and the warm weather is encouraging me to do the job.

Just wanted to check in in case anyone has any tips or suggestions for the job.

I've been trying to pinpoint the problem that causes transmission snatch after slowing/stopping and then taking off again. It's worse in the warmer weather, for some reason. I did read some comments about the ECU cutting fuel but the engine picks up and revs freely from slow/standstill whereas the transmission does not - so not sure about that as a possible explanation.

While doing some other repairs recently, I did notice 'oil' around the transmission as per photos. I'll have a closer look to try and determine if the oil is indeed oil or if it could be ATF fluid. Unlikely that engine oil would be deposited on the outside (near side) of the transmission case? On the inboard side, maybe?
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littlepolo
Gold Member
Posts: 705
Joined: Thu Jul 21, 2011 9:47 pm

Re: ATF auto transmission fluid change

Post by littlepolo »

Started the job and found the ATF to be dark in colour with an odour that is not fresh.

I'm not sure there is a leak from the sump but the sealant around one of the bolt holes looks a little suspect. I was surprised to find sealant as I had purchased a rubber seal for the job and it's not correct. Does anyone have an idea what sealant/mastic is needed for this job?

I dropped the strainer and more fluid came out. The strainer itself looks OK, though I have a new one at hand.

Can the sump bolts be reused?

Presumably the strainer bolts (very long) can be re-used, at the right torque setting.

There is a deposit aft of the auto box and I wonder if there is anything leaking around there. Will clean it up and try to find out. Does anyone know what the big nut/plug seal is back there (see photo below)?

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littlepolo
Gold Member
Posts: 705
Joined: Thu Jul 21, 2011 9:47 pm

Re: ATF auto transmission fluid change

Post by littlepolo »

IN looking through my old Haynes manual, I noticed there are two speed sensors - road speed and transmission speed. Does anyone have any history of these sensors being problematic? I will connect my diagnostics laptop and look through for any issues/codes.
littlepolo
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Joined: Thu Jul 21, 2011 9:47 pm

Re: ATF auto transmission fluid change

Post by littlepolo »

I see the Haynes manual specifies torque for the sump to transmission shield of 45Nm/33 lb ft, yet nothing for the sump pan to transmission (18 x 10mm hex bolts) or strainer to transmission (11 long hex bolts). The strainer bolts 'felt' like they are around 33 lb ft grunt when I undid them but it would be helpful if anyone has the correct spec ;-). I read elsewhere that the sump pan bolts are 7 lb ft (on a 5 speed box) tighten diagonally then 11 lb ft final torque (so I guess these are similar).
littlepolo
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Joined: Thu Jul 21, 2011 9:47 pm

Re: ATF auto transmission fluid change

Post by littlepolo »

Posting this which might help anyone doing this job with torques!

Interestingly, the schematic shows the 'plug' I spotted from the underside. It looks like this might well be the final drive/differential drain plug? Since, like the auto box these are 'sealed for life' I can find no information at all on what it is, or how to drain and refill the final drive, or the gear oil specification.

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littlepolo
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Joined: Thu Jul 21, 2011 9:47 pm

Re: ATF auto transmission fluid change

Post by littlepolo »

For anyone doing this job, the hex plug is the lowest drain point for the ATF. Another 100ml or so of ATF dropped when I opened this.
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littlepolo
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Posts: 705
Joined: Thu Jul 21, 2011 9:47 pm

Re: ATF auto transmission fluid change

Post by littlepolo »

After purchasing an additional 2l of ATF to go with the 2l I had at hand I thought I'd be OK for the refill. I firstly poured in 3l. When the transmission temp reported 40C I ran through the gears, into park and then added ATF from the last litre bottle and with the drain plug removed expected to see an overflow. Nothing. I had poured all of the 4l in and it was below level. 3l was the volume I had taken out - possibly a little more than that allowing for absorption of spills into rags, etc

Ordered another 1l bottle from Amazon and waited until next day.

Set up funnel into the transmission sump filler again, brought the transmission up to temp, ran through the gears, back to park and poured from the 1l bottle. After about half the contents emptied I started to see some drips below! The ATF coming out was still dark in colour and there was still an odour (though not as bad as before). I put the remainder of the bottle in to force more out. Waited for the fluid to start dripping, checked the temp (41C) and replaced the drain plug.

In total I had purchased 5l of new ATF and poured it in. The total capacity is reported to be 5.7l (residual ATF would have been in the torque converter). My best estimate is that I firstly drained a max of 3.1-3.2l and when pouring in the fifth litre an additional 500ml came out. So, a total of 5l in and max 3.7l out, leaves a shortfall of at least 1.3l. Likely evaporative loss over a 20 year period, and possibly minor seepage (still investigating - I degreased the entire under engine area and will monitor).

Went for a test drive and all seems to be well. I think the low fluid and its poor condition might account for the difficulties I had experienced, namely slow take up on drive after changing gear (e.g. D to R and back to D), and in particular the clunk when resuming from slowing down to about 5-10mph and pulling away from standstill after a long run (particularly in hot weather). I had the 'clunk' problem since 50,000 miles. I've not had a chance to see if the clunk problem has cleared as I have not yet driven on a long run. Otherwise, the drive seems to take up very well.

My plan is to drive for a couple of hundred miles or so then drop whatever comes out cold from the transmission sump, measure it, and replace the same volume/weight with new fluid. I'll report back on the symptoms (hopefully a lack of them) in due course.

So much for sealed for life.
littlepolo
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Joined: Thu Jul 21, 2011 9:47 pm

Re: ATF auto transmission fluid change

Post by littlepolo »

Just in case anyone ever takes on this job, I used Dirko HT (red) to seal the transmission sump pan after cleaning and refitting. I had a tube of Dirko grey at hand from when I did the top end overhaul back in Dec 2018/Jan 2019 but did not want to risk it being up to spec. I think there is only 20C difference between regular Dirko and the HT version (so of no import here). It's not that difficult a job really, just a bit messy. Also, you don't need a computer since you can use an IR thermometer to check the transmission sump pan (which will likely read a degree or two low from outside). The temp range is 35C to 45C and I went for 40C. I would not measure out and refill fluid if it has not had a service before, especially when the overall volume could be low like mine was!
littlepolo
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Posts: 705
Joined: Thu Jul 21, 2011 9:47 pm

Re: ATF auto transmission fluid change

Post by littlepolo »

After several long journeys (including some in warmish weather) I am quite convinced the problem with the transmission snatch on restart after slowing down and stopping is solved. Reason - low ATF fluid.

If anyone is experiencing the symptoms it's worth checking your ATF fluid.
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