01M transmission differential fluid level too high, leaking from transmission?

alex_tdi

Veteran Member
Joined
May 15, 2001
Location
Los Angeles, CA
TDI
TDI GLS, 2001, Blue
Hi Everyone,

I recently changed the transmission fluid and filter on my 01M transmission on my 2001 Golf TDI. So to complete the job, I figured I would change the differential oil since the differential blew up and was rebuild/repaired around 50k ago.

When I took out the speedometer VSS to check the fluid level, it was really high. The fluid was half-way up between the tip and the bottom of the gear (similar to this http://s162.photobucket.com/user/Matilda-VW/media/IMG_6284.jpg.html).

The fluid didn't smell bad and it was a light brown color, which makes me think it's transmission fluid and not 75W90 gear oil, which I think would be thicker.

This makes me think perhaps transmission fluid is leaking onto the differential, but I also read on a post that early 01M transmission had the differential filled with transmission oil as well. The guy who repaired my differential might have just refilled it transmission fluid and filled it up too much.

So do you guys think if I should suck out the oil inside and fill it with gear oil? My concern is that gear oil would leak back into the transmission and gunk up the gears and kill the transmission.

What do you think I should do?

Thanks.

Alex
 

dober

Veteran Member
Joined
Jun 8, 2008
Location
Aurora, ON
TDI
00 Silver Jetta TDI, 2006 Jetta Wagon
You could try draining it down to the proper level and check it again in a few weeks to see if your right about the fluid leaking. When I changed mine this summer it was a bit low but was for sure gear oil inside.
 

hughesjasonk

Veteran Member
Joined
Nov 8, 2013
Location
New York
TDI
2002 Jetta MK4;
Too much diff fluid isn't a bad thing. Worst case scenario you'll have diff fluid leaked out of the vent. With how the transmission is diff fluid will not leak into the main transmission. It will be fine.

You asked what you think you should do and the answer to that is nothing

Sent from my SCH-I545 using Tapatalk
 

alex_tdi

Veteran Member
Joined
May 15, 2001
Location
Los Angeles, CA
TDI
TDI GLS, 2001, Blue
Too much diff fluid isn't a bad thing. Worst case scenario you'll have diff fluid leaked out of the vent. With how the transmission is diff fluid will not leak into the main transmission. It will be fine.

You asked what you think you should do and the answer to that is nothing

Sent from my SCH-I545 using Tapatalk
I like the do nothing idea. I basically just put everything back today and did nothing.

However, does anyone know if the transmission fluid wouldn't be up to the task of protecting the differential in some way? VW must have decided to use gear oil in the differential instead of their super expensive transmission fluid for a reason, right?

Thanks.

Alex
 

alex_tdi

Veteran Member
Joined
May 15, 2001
Location
Los Angeles, CA
TDI
TDI GLS, 2001, Blue
A little update....

So I read up on the difference between transmission fluid and gear oil and decided it was probably a good idea to change out the fluid since it's been in there at least 50K; a good time either way. With a bit more reading on the open differential design, I am also not too worried about the differential fluid going back into the transmission.

Man, was I glad.

When I took out the oil in the differential, it was much darker than I expected. It had the color of dark dark chocolate and the consistency of motor oil. There was no burnt smell, so I'm hoping I was able to make the flush before the old oil got too bad. I was able to suck out about 1.2 liters and put back in around 900 mL of the Mobil 1 75W90.

I haven't noticed any difference in how the car drives, since it has always shifted and ran very smoothly since the differential was repaired 50K ago. Fingers crossed that it will last another 50K.

Cheers,

Alex
 
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