I changed the transmission oil in both my vehicles. Used Royal Purple 75W-90, exactly the amount that the book says. Now the 1-2 shift in both vehicles is rough -- the '01 more so than the '97. In fact, the '01 is so bad that I'm worried about damaging the thing -- feels like I'm beating the synchros.

All other shifts are fine (including 2-1), and the 1-2 shift gets smoother as the oil heats up. But this really pisses me off. The 1-2 shift was smooth before the oil change in both cars.

Thoughts? Not enough / too much oil? I measured it very carefully and I'm sure I put exactly the right amount in...

 

I assume the vehicles were both level when the gearboxes were serviced. Did you notice any metal in the old lubricant? When refilling the gearboxes, did you add fluid until it began to come back out the opening?

 

No. The driver's side was jacked in both cases. I lifted the car enough to get the wheel off, and to provide enough clearance for my breaker bar, then lowered it until it was nearly -- but not completely -- level.

No chunks, but there were (what seemed to be) very fine metal flakes. I haven't tossed it yet, so I could have another look at it if necessary.

No. I just added exactly the amount recommended by the service manual: 2.75 L.

 

Some metal particles in the gear oil is typical when draining after a long interval. If the particles are 'gold', that may be an indication of worn blocker or synchroniser rings. If the particles appear more 'silver', that can be worn bearings or gear face surfaces.

How was shift quality prior to the service and how many kilometres/miles are on your vehicle?

 

Did you drain 2.75 L? As I recall, you're supposed to have the car level, and fill until the fluid starts to drain out the fill port. I wonder if you have too much/too little fluid in there.

 

With the fill plug removed and the vehicle level, a small amount of lubricant should drain out of the fill hole when the gearbox is full. If the vehicle is not level, the gearbox can be either overfilled, which can lead to leaks from the seals, or under filled.

Even with a suction-type pump, it can be difficult to get the correct amount of fluid into the gearbox if the vehicle is not on a hoist. It can sometimes be easier for someone working on jack-stands to use a long, clear plastic hose so the gearbox can be filled from the engine compartment.

 

Okay. I'd guess that I didn't fill it quite that full. I'll try adding more with the car level.

Yup. Did that.

 

What colour are the particles you found in the drained lubricant?

 

It is also important to mention that upon refilling the transmission with the correct fluid, you are supposed to have the vehicle jacked up evenly so its straight, fire the car up, accelerate slowly till about 40-45mph. If its an auto, the transmission will go into the appropriate gears by itself. If a manual, well you know you gotta switch those gears. In any case, it is important to accelerate a little bit because when you accelerate and shift, the transmission draws the fresh fluid in. Secondly, after you do that, your supposed to take the plug back out and top off the transmission. Let the fluid flow out till it stops. Operation complete.

And in regards to what HBAudi said, he is also spot on. Sometimes you have to filter out the metal particles out of the old fluid and inject them back into the transmission.

 

In my experience, I have never seen, nor recommended adding metal particle debris back into a gearbox with the clean lubricant.

When a driver is having difficulty shifting and metal debris is present, it is common to see what the debris looks like so a further diagnosis can be made. The two most common failures in manual gearboxes are blocker/synchroniser wear or bearing wear. Other failures such as chipped gears or broken selector forks are often the result of a catastrophic bearing failure.

Of course driver error can also cause catastrophic gearbox failure...