5hp19 torque convertor shudder?

[antonmnster]

My 02 BMW 325Ci has always had a very annoying habit and either I'm becoming more sensitive to it or it's getting worse. Car has 178,000 miles.

When rolling along at 50-60 mph in 5th gear, under light throttle load, the TC seems to be endlessly locking and unlocking. Every second and a half it will slowly lock, then release, slowly lock, then release. RPMs vary by about 200 through the cycle. Greater throttle input seems to cause it to lock harder or just downshift. It's super annoying.

Fluid has been changed several times since I bought the car a few years ago. Twice has been at a local transmission shop that claims to have lots of experience with ZF units. Last spring I did the filter and fluid myself, using MaxLife since it's 71141 approved. I do have to say that it seemed to hold the TC harder with that fluid.

Sadly, I had to take it in and have the shop redo it because I couldn't get the pan to seal for the life of me. (Thanks [censored] [censored] NAPA gaskets.)

Is my clutch going to blow up? Should I swap the fluid (sans filter since it's very fresh) and see what happens? I'd like to sell the car but I'm not going to do that if I have a reasonable suspicion that the trans is about to poop itself.

 

[threeputtpar]

I was having the same issue with the 5HP19FLA in my Audi on the Pentosin ATF1 fluid. I switched to Maxlife and did a couple of D&Fs and on the last fill I added a 10oz bottle of Lubegard Red. Problem solved.

Roughly 75k miles later, I'm noticing that at highway speeds when I give it a little gas it will downshift to 4th, but the converter will not unlock right away so it feels like two downshifts. Time for another fluid change and maybe another dose of LG Red.

Are you sure that the fluid level is correct first? Laying on your back in the garage is not the easist way of refilling these from underneath.

 

[Jim Allen]

That is called hysteresis. A "shudder" is something different.

Hysteresis is often an adjustment. I don't know your car at all but I have experienced it on vehicles where the TV (throttle valve) cable is misadjusted on cars so equipped. It could also happen if the PCM programming is off for some reason or mismatched to tire size or gear ratio. If you are running taller tires than stock or have changed the gearing without changing the EFI programming. Or you have installed a chip or a programmer. Basically, the trans is programmed to unlock (or lock) the converter at certain loads or rpm ranges. They are usually programmed not to have hysteresis at the common cruising speeds but some cars can have an annoying not-so-sweet-spot where it's more prone to it and that place could coincide with one of your common cruising speeds. Again, if the tire size is different than stock it can move the anpoing point to a different place. This might be something to take up with your friendly BMW tech.

Shudder is completely different and can be more fluid based. It's like a manual car with a warped pressure plate and as you are slipping the clutch you get a chatter, bucking or shudder. This can happen to the converter clutches when the lubricant is incorrect (wrong amount or type of friction modifiers) or if the fluid is just plain work out. In that case, a fluid change to the correct oil will cure the problem. Sometimes shudder is a mechanical issue as well.

 

[antonmnster]

Tires are all stock.

This T/C likes to lock in gears 2 through 5. Fairly regularly, it will make a "burrrrrp" noise and vibration as the t/c locks for a second. Again, under light loads, like a slow acceleration up to 35 mph.

For giggles I might clean the throttle body. I noticed the other day when I was trying to hold a high idle (1500 rpm) with the throttle, I was getting some surging, like the throttle plate was sticky.