Looking for straight answers for transmission issues

JCL · #1 12-11-2010, 01:56 AM

A shudder is due to the friction characteristics of the clutches on engagement not being what the transmission expects. Off the top of my head, that can be due to worn clutches, the friction properties of the fluid being out of spec, low pressure, a problem with the actuators that apply pressure to engage the clutches, or a control issue. This is all very general, but since worn clutches and worn fluid are not typical or common, to me it points to either an actuator, or a control issue (either valve body or software). It could also be something unrelated to these themes, like the torque converter.

There are many reported issues with these transmissions, but it can't be narrowed down to just one cause, and trying to diagnose one transmission by comparing symptoms to others, is near to impossible. You will see many posts from people (on a variety of topics) saying "it is xxx, that sounds just like my vehicle's problem". Unfortunately, far too often, those are dead ends. Mechanical problems on the X5 such as driveshaft splines, or CV boots, are common and reproducable, and the symptoms can be readily identified. Problems inside a transmission are nothing like that, with the rare exception of a manufacturing defect, and so it requires hands-on diagnosis. That starts with reading the codes, and then following a troubleshooting guide specific to your transmission.

You can drive it until it fails, or have it overhauled. An overhaul can be done by a shop familiar with the transmission. It cannot be done by the dealer; they are not trained to repair them and for their own reasons BMWNA uses a program of centralized remanufacturing and only does full transmission replacement at the dealer. That is expensive.

I don't agree that it never hurts to change the transmission fluid and filter. In fact, changing transmission fluid can cause a failure in some cases. That is because the new fluid has lots of detergents, and cleans out the transmission. There is nowhere for all that cleaned out residue to go, if there is any. That said, if you want to change the fluid on the off chance that it gives you a little more time, go ahead. If your problem is a clogged filter, it would help, but it wouldn't address the issue of why your filter is clogged. If you do it, use factory spec fluid, and a new OE filter. You have to consider that your transmission is not healthy, though, so changing the fluid may make it worse or better. It shouldn't be considered a cure, rather a bandaid.

m5james · #2 12-11-2010, 02:14 AM

Quote:

Originally Posted by JCL

I don't agree that it never hurts to change the transmission fluid and filter. In fact, changing transmission fluid can cause a failure in some cases. That is because the new fluid has lots of detergents, and cleans out the transmission. There is nowhere for all that cleaned out residue to go, if there is any. That said, if you want to change the fluid on the off chance that it gives you a little more time, go ahead. If your problem is a clogged filter, it would help, but it wouldn't address the issue of why your filter is clogged. If you do it, use factory spec fluid, and a new OE filter. You have to consider that your transmission is not healthy, though, so changing the fluid may make it worse or better. It shouldn't be considered a cure, rather a bandaid.

I can agree that sometimes chaning the fluid can be a way to speed up the means to an end. I remember when I was on Toyota Tacoma forums, and just like here, people had mixed reviews of changing fluid when their transmissions started giving them issues. Either way, if he calls/emails me, I'd be interested to take a look at it since my X doesn't exhibit any symptoms like this.

At this point it won't happen till after the new year, but I'm looking forward to doing a complete rebuild on a 5HP24 so I can see first hand what failed clutches, 1st/Reverse drums, etc look like when they break/fail.

Critical Drew · #3 12-11-2010, 04:37 PM

Thanks for the great input everyone. I will definately take m5James up on his offer. and I really appreciate JCL's knowledge. One Question, Does the computer record/store any information regarding pressures or performance? I have used scanning tools to diagnose and clear issues with my X5 before, but I have never looked deeper into stored data for detective work. I don't think I am looking at a fluid replacement, but I was going to get under there and see if I might be low on fluid.