Stuck in 3rd gear? (over shifted)
These pics show an AGB 16V trans that was stuck in 3rd gear. Sometimes you find an 020 stuck in 3rd, and it is due to over shifting. Unfortunately, I'm not sure what part or parts fail to cause this to happen.
To repair the trans, it must be opened. To open the trans, you have to remove the selector. To remove the selector it has to be out of gear. When it is stuck in gear, you cannot split the trans apart.
The VW procedure calls for the selector assembly to be driven out of the trans. The Bentley has a diagram and brief instructions... and I completely don't understand what they mean :)
Here is the diagram which I stole from Bentley...
They call for a nut to be placed at the arrow for support... and I have no clue how they intend for you to get a nut in there for support. Possibly if the trans has the big multi-terminal switch you could get something stuck in there, but it would only support one side of the sheet metal housing, so I'm not sure what they mean there.... if you do, lemme know!
Right, so I had this 16V trans stuck in 3rd. Often I can aggressively work the selector while moving the flanges or input shaft and can get them to pop out of 3rd. Not always though, and this was one of those times.
Start by removing the detent bolts on top of the selector, the reverse switch, and then the 27mm selector cover, which is shown on the far left in this pic with the large spring behind it. Remove the snap ring and the top cover (it has the 2 holes in it... when you remove the snap ring, the top cover will want to fly off at you so watch it!), then the smaller spring, then the spring cup (shown in order in the pic).
After the spring cup is removed you'll find one more snap ring, remove it and you should be looking at something like this...
I hammered on that shaft, but it just sprang against the shift forks and ate up any force I tried to put into it... so I grabbed a tool I bought probably 6 years ago now, and this is the first time I ever got any real use from it. It is a cheap chinese puller kit, with a hand operated hydraulic ram.
I tried fitting the trans into the shop press so I could drive the selector shaft out, but there was no way to balance the trans and support it while I pressed the shaft. As a last ditch effort, I tried the cheap puller set....
I attached it as shown, which I wasn't sure would work. I figured the force would be great enough to break the aluminum casing where the hooks are, as they are just barely snagged on the lip of the casing around the selector, and aluminum is fairly weak. Surprisingly, the force needed wasn't as much as I expected, and the case was just fine....
This is the shaft that was pressed out, and the parts I managed to dig out of the hole. The finger that actually moves the shift forks has been broken in half.
The roll pin that secures that finger on the shaft was sheared on both ends...
Inside will be the "sheet metal" cage, as VW calls it. When I think of sheet metal, I think of something easy to bend or flex. Apparently the Germans do not, because that cage is quite tough.
I couldn't get it to come out of the trans, it was stuck right there as shown in the pic. It was very loose, and ALMOST would come out, but not quite. I decided to split the trans and as I split the case, I worked that cage around out of the way of the shift fork tabs as the case came apart.
The other half of the broken finger was found on the magnet of the trans, it dropped into the box when the shaft finally let go under the ram pressure.
With the selector out, I could carry on splitting the trans. This pic is a reminder to go light on the sealant if you use it... the machined sealing surfaces of the casing will mash together very tightly, squeezing 90%+ of the sealant out of the joint, and it'll leave a bead like this inside the trans, and one outside the trans as well. You only need a very thin coat to fill in any micro imperfections in the sealing surface, so it doesn't take much at all!
And here is why the trans was stuck in 3rd gear.... the sync hub sleeve moved too far over 3rd gear, allowing the keys to pop out behind the sleeve, preventing it from coming out of 3rd gear again. All 3 keys were popped out and tilted, getting in the way of the sleeve.
As I mentioned, I don't know what is allowing this to happen. The gear stack assembly will do this normally... if you have the input shaft assembled on the bench and select 3rd by hand, you'll likely over-select it and the keys will pop out on you... so it isn't a problem with the shaft, sync hub assembly, gear, or the sync sleeve.
The shift forks may be one cause, but the selector should limit how much travel the forks have... so it is something with the selector or the forks as far as I know at this point, but I'm not positive what exactly causes it. Sometimes it is a hard shift into 3rd that does it, sometimes people shift gently and it gets stuck.
3rd and 4th gears are the only 2 gears in the trans physically smaller in diameter than the sync sleeve... so the sleeve can actually fit over the gear, allowing it to move too far, but this rarely happens with 4th, so I don't think it is the actual size of the gear that causes it... it is either worn forks, a worn selector (or selector detent bolt), or a combo of both.
Selector position in each gear