[lowrydr310]

I was about to do a drain and fill of the transmission fluid on my 06 325 with the ZF 6HP19 transmission, but an injury is keeping me from doing much work on my own so I took my car and the fluid I bought to a reputable independent BMW mechanic to have it changed.

The owner asked me why I wanted it changed and I told him because I have 220K miles on my car and don't know when (if ever) it was changed before, and because my 1-2 shift is a bit harsh. He told me don't bother changing it because it will likely cause more problems, making the shifting even more harsh.

Is that correct? That goes against everything I've heard regarding these transmissions. I was hoping to get this car to 300K miles or more.

[AlisoBob]

On neglected transmissions like yours, sometimes after you service it it will start to slip, act funky, or flat out quit.

Why? It needs the metal and other contaminates in the fluid to help the clutches and bands apply.

With clean, slick fluid.... the whole mess can no longer function. With the harsh 1-2 shift your describing, the trans might already be toast.

You can service it, and hope for the best, or leave it alone and see how much farther it will go. Your in "No Mans Land"..... and your mechanic does not want to take the blame if it craps the bed, soon after the service....

[whyzee125]

I personally would change it. In the rare case that issues were to arise as a result of the change, your trans was already on borrowed time, not to mention that this isn't a full flush. In the 4runner world, people drain and fill fluid for the first time with 250k plus all the time with no issues. Having clean fluid is better for your transmission than burned, old fluid.

[robthewrench]

I would change it, but not flush the transmission. Flushing can loosen gunk that will then get caught in the solenoids, but just changing the fluid rarely does this. New fluid should help extend whatever life is left in that tranny.

[Wolf 335]

Originally Posted by lowrydr310

I was about to do a drain and fill of the transmission fluid on my 06 325 with the ZF 6HP19 transmission, but an injury is keeping me from doing much work on my own so I took my car and the fluid I bought to a reputable independent BMW mechanic to have it changed.

The owner asked me why I wanted it changed and I told him because I have 220K miles on my car and don't know when (if ever) it was changed before, and because my 1-2 shift is a bit harsh. He told me don't bother changing it because it will likely cause more problems, making the shifting even more harsh.

Is that correct? That goes against everything I've heard regarding these transmissions. I was hoping to get this car to 300K miles or more.

Additionally to your fluid change you should seriously consider changing the following seals as well as they can be the contributing to the hard shifts.




If this doesn't solve your hard shifts then solenoids will need replacement.

[lowrydr310]

Originally Posted by Wolf 335

Additionally to your fluid change you should seriously consider changing the following seals as well as they can be the contributing to the hard shifts.

Attachment 1900862

If this doesn't solve your hard shifts then solenoids will need replacement.

My plan was to do a drain and fill now, then next year (10K miles or so) replace the pan/gasket, mechatronic sleeve, and other seals. I considered the solenoids too ($300 for the set) but decided that's overkill considering the mileage and unknown history.

I should clarify a bit. "Harsh" is a pretty relative term, difficult to describe in writing. In normal drive mode it feels just fine, in fact it's smoother than any of of the four 200K+ mile Honda/Acura I've owned. In DS, that's where the 1-2 shift is noticeably harsher, but only when not accelerating hard. When accelerating normally in DS, that's where I feel the harsh 1-2 shift. Under hard acceleration it feels just fine.

Also, so far, I don't have that aggressive 2-1 downshift that I frequently read about.

[nsjames]

Originally Posted by AlisoBob

On neglected transmissions like yours, sometimes after you service it it will start to slip, act funky, or flat out quit.

Why? It needs the metal and other contaminates in the fluid to help the clutches and bands apply.

With clean, slick fluid.... the whole mess can no longer function. With the harsh 1-2 shift your describing, the trans might already be toast.

You can service it, and hope for the best, or leave it alone and see how much farther it will go. Your in "No Mans Land"..... and your mechanic does not want to take the blame if it craps the bed, soon after the service....

BS.

people believe this because most ofthe time changing the fluid is a response to a trans that's already mechanically damaged by neglect.

new fluid is always better than old fluid, and new friction modifiers are better for the clutches locking up than a bunch of metal floating in the fluid, which is doesn't, because filter...

[jericho_17]

When you do the change go and check the magnets in the transmission pan if you see lot of metal residues in there there is a good possibility you're screw. But the new fluid is always better.

[lowrydr310]

Posting an update - I did a drain and fill with Mercon SP, and my transmission shifts noticeably smoother in all gears. It also resolved a screeching/squawking issue that I had on hard downshifts, which is apparently another symptom of old fluid. Shifting is much smoother and firmer, driving the car is significantly better now.

Also, I take back what I said about the 2-1 downshift. I do get a very slight jolt when I'm slowing to a stop, on the 2-1 shift. Not as bad as some of the cases I've heard about, but enough that I want to fix it. This is far too common on these transmissions. In 10K miles I'm going to replace the pan/filter, mechatronic sleeve/gaskets, and solenoids. ZF sells two solenoid kits, and apparently it's possible to use the cheaper set ($260) which doesn't have the two park solenoids.

Update: About a month after the fluid change, the 2-1 downshift jolt is gone!