02J 5th Gear Lubrication Modification

[Scott_DeWitt]

Here's an invaluable how to to modify the 02J case in improving lubrication to the 5th gear area.

This photo is the case as it is before modification.

In the area marked, take a 1/4 inch drill bit and drill holes, pushing to the side to make a large oval for the port in the middle. The final product should look like this:

The reason for 5th gear failure is when the oil level gets the least bit low, the 5th gear is starved for lubrication. This image shows the lowest oil port from the top fill hole in the transmission. As you can see even at stock oil levels, the stock fifth gear port is marginal.

We perform this same modification on all our 5 speeds. It's possible to do this modification with the transmission in the car, however due to the amount of shavings that are produced I wouldn't recommend it.

 

[Ol'Rattler]

So what year cars does this apply to?

To drain all the oil in my A5 I have to remove the sector shaft. Could this be related to what your procedure corrects?

Best time to do something like that would be at clutch change time although I suppose that any aluminum shavings that got inside would be eventually ground up by the steel gears.

Also, something that the A5s sorely need is some sort of J tube at the fill port so that the correct fill level could be verified by just removing the fill plug.

 

[Scott_DeWitt]

So what year cars does this apply to?

To drain all the oil in my A5 I have to remove the sector shaft. Could this be related to what your procedure corrects?

Best time to do something like that would be at clutch change time although I suppose that any aluminum shavings that got inside would be eventually ground up by the steel gears.

Also, something that the A5s sorely need is some sort of J tube at the fill port so that the correct fill level could be verified by just removing the fill plug.

Pretty much every 5 speed made from the early 90's until present.

With the gearbox on the bench, you can make the modification and then flush the shavings, you should be fine.

 

[TDIkev]

From looking at this pic it looks like the oil fill hole and the oil supply hole are about level with each other, does that mean if the oil gets even a hair below the bottom of the filler hole you would consider the 5th gear not being adequately lubed?

 

[Scott_DeWitt]

From looking at this pic it looks like the oil fill hole and the oil supply hole are about level with each other, does that mean if the oil gets even a hair below the bottom of the filler hole you would consider the 5th gear not being adequately lubed?

Your correct, the lower the oil level is the less oil is available to the 5th gear area. Splash lubrication quickly becomes inadequate when the oil level is low.

 

[TDIkev]

If this is the only oil supply hole to the 5th gear and it's up level with the oil fill plug, when you do an oil change how does the oil drain out of that space that the 5th gear assy occupies. I can see how that area would drain after you do you mod, but how does it drain without those holes?

 

[Sbeghan]

Is there a reason to -not- overfill the oil by a few oz then? I don't have the time or ability at the moment to drill holes in my trans, but I can add a few oz to the fill hole just in case.

 

[TDIkev]

(Image borrowed from web, Sorry it's small, don't know how to resize)

It looks like there are two oil supply holes and they are both level with the oil fill hole. So if the oil level is a hair below the oil fill hole the only way the 5th gear gets lubed is by going up or down a hill so the oil goes in either of the holes. It seems like overfilling the tranny is the only way to ensure the gear gets lubed. Since the tranny is oiled by splash lubrication and there is no pressure in the transmission I will be checking my oil soon and 'overfilling' the tranny by about 500ml to ensure the 5 gear is lubed. Scott, any downside to overfilling?

 

[Scott_DeWitt]

It looks like there are two oil supply holes and they are both level with the oil fill hole. So if the oil level is a hair below the oil fill hole the only way the 5th gear gets lubed is by going up or down a hill so the oil goes in either of the holes. It seems like overfilling the tranny is the only way to ensure the gear gets lubed. Since the tranny is oiled by splash lubrication and there is no pressure in the transmission I will be checking my oil soon and 'overfilling' the tranny by about 500ml to ensure the 5 gear is lubed. Scott, any downside to overfilling?

The only issue is the trans might puke oil out the vent and make a mess. Also it's going to be very difficult to get an extra half liter in the box without making a mess, you will have to remove the shift tower and pour the oil in there as the fill hole is horizontal, meaning any excess oil will pour out.

 

[Powder Hound]

You can get a few extra ounces in by filling with the front up on jack stands.

 

[TDIkev]

That's what I was planning to do. My driveway is on an incline and I can run the car up on the ramps, should do the job nicely.

 

[Scott_DeWitt]

I can see how that area would drain after you do you mod, but how does it drain without those holes?

It does not drain.

 

[MCR]

We perform this same modification on all our 5 speeds. It's possible to do this modification with the transmission in the car, however due to the amount of shavings that are produced I wouldn't recommend it.

Let's say I really want to do this mod, but I have to do it installed. What would be the best way to do that?

I was thinking drill one hole, maybe 2. Do it without draining the fluid, so when it breaks through the draining fluid flushes out the shavings?

Or should I drain it first, drill it and use a deburr tool to get what I can on the inside edge, then refill with the used oil to flush? And then fill with new fluid?

How about just one easy hole now, and the whole mod if I ever have to take the transmission apart? I was thinking a straight hole might have less particles, but elongating it might minimize any burrs on the inside edge.

Say I want to drill that one hole: Which one should it be considering that 5th gear will be in place?

Thanks for this write-up. I've been driving forever with the fluid a little bit low.

{edit: Does that cover require a new gasket when it is removed?}

 

[TDIkev]

I’m not sure I would do this mod with the transmission in the car. You could potentially ruin and good transmission by not get all the cuttings out. There are thousands of these transmissions out there used by people not as anal about their cars as the people that frequent this site and they are running fine. Some people never check or change the fluid and don’t have any problems. We know about this engineering oversight and we are becoming paranoid about blowing up our transmission. Personally, I’m going to put my car on ramps and add a little more fluid to the transaxle and drive more – worry less.

 

[Scott_DeWitt]

Let's say I really want to do this mod, but I have to do it installed. What would be the best way to do that?

I was thinking drill one hole, maybe 2. Do it without draining the fluid, so when it breaks through the draining fluid flushes out the shavings?

Or should I drain it first, drill it and use a deburr tool to get what I can on the inside edge, then refill with the used oil to flush? And then fill with new fluid?

How about just one easy hole now, and the whole mod if I ever have to take the transmission apart? I was thinking a straight hole might have less particles, but elongating it might minimize any burrs on the inside edge.

Say I want to drill that one hole: Which one should it be considering that 5th gear will be in place?

Thanks for this write-up. I've been driving forever with the fluid a little bit low.

{edit: Does that cover require a new gasket when it is removed?}

I'd be a bit apprehensive about doing the mod with the gearbox in the car. However only aluminium shavings will be produced, and if circulated in the gearbox for a temporary amount of time, I doubt any harm would come of it. You would however have to flush the gearbox oil a few times.


Put grease on the drill bit that should collect most of the shavings, and take small bites using the drill bit blowing out the shavings produced.

You might be able to save the gasket, if it doesn't stick to the case you are fine.

 

[LNXGUY]

Jack the car up in the front a wee bit higher then you would usually do and add in a few extra ounces of oil via the normal fill hole.

 

[Dieselgeek]

I always fill the tranny with 2 quarts using a long automatic tranny funnel put into the speedo sender hole.

 

[turbocharged798]

Maybe I am missing something here, but when we drain our tranny fluid, whatever fluid is still laying in the 5th gear area will remain there unless you pull the cover off?

 

[TDIkev]

Read post # 6 then 12..

it does not drain.

 

[turbocharged798]

That's ridiculous. What was the engineer thinking when he designed the transmission? Must have been the same guy who designed the MKIV mirror heater switch and cruise light.

I wonder how hard it would be to drill and tap a drain plug for the 5th gear area? Then how much more fluid would it actually take if you drain the area? VW says 2L, but is that with the 5th area dry or with fluid?

I am getting ready to do a clutch on my 99.5, and when I pull the tranny, I plan on taking the 5th cover off and seeing how this really works.

 

[TDIkev]

I agree....just two 10 mm holes would do the trick...drain all the oil and solve the oil starvation issue.

 

[turbocharged798]

You know, I was thinking about this all day. This is what I am thinking.

The car is not a stationery object. It is constantly moving about and experiencing G-force. The oil reacts to the G-force and it causes it to slosh up the side of the transmission case. Now, I wonder if they designed 5th gear area like it is to act as a baffle during hard right turns? It would also allow the 5th gear area to fill up during a hard left turn.

Just my current thoughts.

BTW, TDIkev: I tried to reply to your PM and the fourms won't allow me to send it to you.

 

[Scott_DeWitt]

The car is not a stationery object. It is constantly moving about and experiencing G-force. The oil reacts to the G-force and it causes it to slosh up the side of the transmission case. Now, I wonder if they designed 5th gear area like it is to act as a baffle during hard right turns? It would also allow the 5th gear area to fill up during a hard left turn.

You are correct, but flat level cruising you do not experience any g forces significant enough physically move oil around the gearbox.

The 5th gears will tend to pump oil out of the existing oil slots (due to the rotation of the gears and the design of the gearbox, however there is inadequate mechanisms to return that oil to the 5th gear area. The lower the level the worse the problem is.

 

[Scott_DeWitt]

The car is not a stationery object. It is constantly moving about and experiencing G-force. The oil reacts to the G-force and it causes it to slosh up the side of the transmission case. Now, I wonder if they designed 5th gear area like it is to act as a baffle during hard right turns? It would also allow the 5th gear area to fill up during a hard left turn.

You are correct, but flat level cruising you do not experience any g forces significant enough physically move oil around the gearbox.

The 5th gears will tend to pump oil out of the existing oil slots (due to the rotation of the gears and the design of the gearbox, however there is inadequate mechanisms to return that oil to the 5th gear area. The lower the level the worse the problem is.

 

[Powder Hound]

That's ridiculous. What was the engineer thinking when he designed the transmission? ...

He was/is german, so he was probably thinking something like, "it vil verk because I say so!"

Or the lack of needed holes on the bottom very well could be a bean counter's decision. Probably saved 50 cents per unit.

 

[MCR]

Now, I wonder if they designed 5th gear area like it is to act as a baffle during hard right turns? It would also allow the 5th gear area to fill up during a hard left turn.

I may be wrong, but I think that is backwards. The cover is on the driver's side, so the cavity would fill in a hard right turn, and would "drain" in a left turn.

Regarding an earlier recommendation for me to just fill the fluid, my situation is a little more complicated.

I had a persistent 1cm or half-inch low fluid level. Two weeks before Christmas, I changed the fluid and got it a tiny bit above the fill hole drain level.

Two weeks later, literally on Christmas day, I had a slipping clutch. The first I noticed it was at about 80 mph---I hit a big wind gust head on and my rpms went really high. I slowed down (wind gusts scare me at high speed), and started thinking about what to do.

I read everything I could find on tdiclub, then bought a C60/VR6 setup. Under the car looking at everything, I noticed that the passenger side transmission output shaft flange (got that?) is lined up perfectly to the clutch vent slots. I thought maybe the low fluid level was the drain level of a bad seal, and when I filled it, that seal started leaking. It it was that right-hand side output shaft seal, it can run out the shaft and get flung off the flange into the clutch vent slots. My two guesses are that right-hand side output shaft, or the input shaft seal near the clutch itself. I've bought all those.

In the meantime, I babied that clutch for 3 or 4 months with no slippage I could detect. I was planning to change it, and a guy at work asked what it means when I said the clutch slipped. So we went to lunch, and I did the second gear test (Do first to second shift at low rpm, then floor it)---surprise---no slippage. I've been driving it like I stole it since, and still no slippage.

But I know I'm losing fluid somewhere, and I've got a bad outer CV boot to fix. So I'm thinking I'll just take off the half-shafts, fix the one boot, drill that hole in my fifth gear cavity (and check that gasket on the cover), then pull the output shafts and change those seals (they were like 2 for $12).

I'm gonna get a drill bit and some aluminum and drill some at my vise to see how much debris goes to the inside of the hole. My plan is to drill it with the fluid in. To stop every few seconds before break through to clear the hole and the bit. To have some q-tips to pull debris out. To maybe have some sticky tape on the end of a wire to pick up stuff through the hole. (I'm considering breaking through a tiny bit with the 1/4 inch, switching to a 1/8 to get a flow of oil, then switching to the 1/4. I don't know.) If I can find some good filter paper, I might filter the drained fluid and run it through again. It's only got about 20,000 miles on it. (I've got 2L I bought to do the clutch).

I'm trying to find an o-ring or a little metal spring clamp to put on that right-hand output shaft so if the seal goes again, this little o-ring will fling off the oil before it runs out to the flange and is lined up with the clutch vents.

I'm a little worried about it, but I want to get at least another 100,000 miles out of my car. That's 2.5 years. I also notice I don't drive as hard in the winter, so I really want that flow of oil into my fifth gear cavity.

 

[MCR]

I'm gonna get a drill bit and some aluminum and drill some at my vise to see how much debris goes to the inside of the hole. My plan is to drill it with the fluid in. To stop every few seconds before break through to clear the hole and the bit. To have some q-tips to pull debris out. To maybe have some sticky tape on the end of a wire to pick up stuff through the hole. (I'm considering breaking through a tiny bit with the 1/4 inch, switching to a 1/8 to get a flow of oil, then switching to the 1/4. I don't know.)

I found a little sheet of 1/8 aluminum, put it in my vise and drilled about 4 holes through it. (And this is wrought aluminum, not cast, so the experiment is flawed. I'm looking for some cast aluminum.)

There is a lot of debris on the drill side. If you baby it, it makes lots of little flakes. If you push hard, you can get these long spiral chips. I tried drilling (hard) in 5 second bursts. It let me clear out the hole and sort of see the break through before it happened. There was so much debris, it would be absolutely necessary to tape up some shield to keep the chips from going through the window holes into the "inside" of the transmission.

I used a 1/4 inch bit first. When it passed through, it dropped two little ball chips, both about 2 or 3mm in diameter (say 3/32in), plus a few really small flakes.

Next I did a 3/32 or 1/8 inch pilot hole (can't remember which), and then followed that with a 1/4 inch bit. Not a good idea. The small bit also drops 2 small chip balls inside (proportionally smaller than the 1/4 bit), but enlarging the pilot hole lets a lot more small flake debris inside.

I tried a step drill. I can't find my good one, so I used one from Harbor Freight. The two have different tips, and the one I used was like a 1/8 inch twist drill, so it was very similar. I went in until the hole was 3/16 inch (the 2nd step), and except for the 2 small chip balls with the first breakthrough, the debris was small, but there was a quantity of it.

The last thing I tried was a 1/4 inch bit backed up with a little piece of foam. It's called "Ethafoam", and it's kinda hard to get. This was very promising because the bit broke through the metal and then just instantly pierced the foam, but (!), the two little chip balls were trapped in the foam! I really don't think this is going to work installed, though, because I don't see an easy way to hold the foam on the wrong side of the metal bulkhead.

I'm definitely going to retry this with cast aluminum. I'm guessing the results will be similar, but you never know.

My plan right now would be to either: Drill one hole at 1/4 inch and remove the 2 chip balls, or drill one hole at 1/8 inch and don't worry about the two tiny chips. (I'm almost certain a small hole will equalize the fluid levels *and* won't be blocked by debris in normal use.)

It would be nice to try a little experiment with some oil level on the wrong side, to see if the drainage will flush the 2 balls. It would have to be right against the floor of the casting, or they'll just drop down and be trapped inside. But too close and you'll cut more flakes off the inside.

Is it crazy to think about doing this?

 

[TDIkev]

I put the car on ramps, added 600 ml until it ran back out of the fill plug. I've done about 200 km and no oil has burped out the vent so far.

 

[kooyajerms]

bump for folks

 

[jackbombay]

How about this for drilling the holes with the tranny in the car, use pipe fittings to make an adapter so you could put compressed air into the fill hole and then fill the tranny with regulated air pressure (the vent would also need to be plugged) maybe say 10 PSI, then drill the holes, as soon as the drill bit broke through the air pressure would blow any chips out.

Anything wrong with this idea?