Notchy gears problem

[46lukasz]

Hi Guys,

I have a problem with my gearbox when the car is cold.

Changing gears from 1st to 2nd feels notchy when it does go into 2nd, but sometimes its hard to put it into 2nd at all.
When that happens I have to put the lever back a bit and try to engage 2nd again, and then it goes in.

Sometimes when 2nd goes in, there is a single clunk sound.

There is NO synchro grinding sounds at any point.

This doesn't happen all the time, and sometimes it shifts smoothly into 2nd when cold, but the problem happens often enough to annoy me and think something is wrong.

When the car warms up, everything works perfectly and its a joy to drive.

I recently had the clutch and DMF replaced, because the DMF was gone bad.
Since the gearbox was out of the car, I had 1st and 2nd gear synchros replaced too, because I had trouble putting it into 1st.
(the mechanic said 2nd gear synchro is worn too, so it was also replaced)

Given that the synchros are new, and everything works perfectly when warm, I think the issue is somewhere else.

I did some research and came across this thread: https://www.audi-sport.net/xf/threa...gear-changes-when-cold-2-0-tdi-s-line.201592/

People are saying that notchy changes from 1st to 2nd are a common thing and some Audi cars have that problem from new.

I read there that a thinner oil with specification G 052 171 A2 solved this problem for many people.

The standard oil apparently is spec G 052 532 A2

However, that thread is quite old, and the car in question was a different year than mine.
So I wanted to ask to confirm if changing the oil would be worth a try in my case as well.

My car is a 2016 A5 B8.5 2.0 TDI Sportback, CNHA engine, 140kW, 165,000 km on it, with the 6-speed Manual 0B1 (front-wheel drive) PJD code gearbox

 

[Gazwould]

Yes G 052 532 is a 75W80 , to make the gear change better when cold you want a thinner oil when cold as from cold to hot there is a huge viscosity change .

G 052 171 is 70W75 ( 75W ) so the Fuchs Titan Sintofluid FE SAE 75W and the Millers TRX SYNTH 75W , according to the data sheets the Millers is thinner when cold than the Fuchs so I'd be inclined to go for the Millers .

 

[46lukasz]

Thanks for confirming, I'm glad to hear that a simple oil change can cure the problem. I will call up the local Audi and see how much they charge for OEM oil of that type. If its expensive I'll go for one of the 2 you mentioned.

Few general questions about oil viscosity:
I am confused by the G 052 171 oil being 70W75(75W) like you said. So is the viscosity when cold 70W or 75W? How does that grading system work?

So the standard (bad) oil is 75W80 and the good oil 70W75.
This means its thinner when cold to fix the issue, but when it warms up, the viscosity changes to the one at which the problem occurs.
Doesn't that mean if i use this oil the problem will occur when the car is warm instead of when cold?

 

[Gazwould]

No not at all , it's confusing , grading is such a rough guide I wish everything was in units like centiStokes , with engine oil there are about 4 units in a grade and the line has to be drawn somewhere but this can mean a particular oil might be 0.5 centiStoke between a 30 and a 40 grade .

I wouldn't bother with the genuine 052 171 oil , bound to be dearer and no data sheets on it either so can't tell how thick or thin it exactly is .

 

[46lukasz]

Thanks, and what do you think about FEBI Bilstein SAE 75W (GL-4) - Manufacturer number 21829

This one is most accessible to me - easiest way for me to get Fuchs or Millers would be eBay UK which means import charges from UK.

 

[Gazwould]

It's on par with the Fuchs for 40° C @ around 40- 41 centiStokes but the Millers is 28.9 !!

 

[46lukasz]

Seeing that this is a big difference in viscosity, I decided to splash out on Millers and just ordered a bottle today.
I will update the thread once i get it changed.

Thanks for the help so far!

 

[46lukasz]

OK so I had the oil changed for the Millers TRX SYNTH 75W and drove it from cold a few times now.
The coldest morning we had here since the change was about 8 deg C, which is pretty warm in my book, so I'm still curious how it behaves when the temps drop to about 0-3 deg C.

So far the change is really noticeable for the better.

When driving normally and changing gears gently, 2nd gear goes in very smoothly without any sounds and I am really happy about that.
When driving "aggressively" and trying to shift quickly, there still is a clunk sound but the gear goes in.

Before the oil change, 2nd gear sometimes didn't want to go in at all, and I had to put it back into neutral and try again, and then it would go in.
This problem also didnt happen to me again since the oil change.

When I undid the drain plug, I saw some grit on the top of the bolt. I think it was the friction material broken off from the synchro ring, which would mean it is worn.
This puzzles me because this synchro was replaced 10k km ago, when the box was out to get the DMF replaced.
But it would also explain why changing gears gently works better - the synchro that is left, has more time to do its job and synchronise the rotating parts fully, so the gear goes in smoothly.

Anyway, I am happy with the difference it made, and I can live with having to change gears gently as long as it doesn't get worse - beats paying for synchro replacement again.

I only wish I used this oil right from the point when the synchros were replaced.
It has made a big difference, and maybe the 2nd gear synchro wouldn't wear out if this oil was used from the start, crazy how big of a difference oil viscosity can make.

 

[Gazwould]

 

[46lukasz]

Quick update on the oil relating to temperature.
We had some frosty days like -4 deg C over Christmas and the box is working the like in temps like 8 deg C, so i'm really happy with the improvement.

2nd gear is still not perfect but ill have to live with that, the bottom line is, the oil change to Millers TRX SYNTH 75W made a big difference for the better and that effect is still there in colder temperatures.

Thanks again Gazwould