Transmission and Heat Exchanger Problem?
 

Hello everyone,

I purchased this car when it was 90K so I don’t have any records if the transmission has been replaced/rebuilt. I know I have the ZF 5HP24 tranny, no sign of any leaks.

My driving pattern within the last 12 months is about 10 miles per day.

When my 2002 X5 4.4 reached 124K, I replaced the spark plugs with NGK as recommended by the dealer and replaced the radiator because the top nose was cracked. This summer I went for a long trip and due to traffic I had to made a hard stop then quick acceleration and guess what I felt shuttering.

Now, every time after 30-40 min of driving I felt slipping/shuttering between 2 & 3 gear. I also noticed there is a small coolant leak between the bottom of radiator connection with the Heat Exchanger (see below picture). It could just the O-ring requires replacement.

For sure, I need to replace differential (both) and trans-case fluids.

Questions:

(1) Do you know if the slipping/shuttering cause of heat from transmission system, because the symptom only happened after 30-40 min of driving (S mode)?
(2) How do you determine if the Heat Exchanger is malfunction?
(3) Can it be the Heat Exchanger not working properly and make the transmission system overheat?
(4) I read almost of the transmission issues thru this forum but I still think my situation has to do with heat or electronic issue not mechanical, what do you think?
(5) At current stage, should I get the transmission fluids replace?
(6) Will the reprogramming the module unit help?

Heat Exchanger
http://www.pbase.com/renem24/image/92719199

Ahadi, I got your PM. I will try and provide some answers. Please understand that remote web-based diagnosis is no replacement for a mechanic actually driving the vehicle and determining the cause themselves.

I don't think it is due to heat. The heat is a factor, but not the cause. Think of the heat as modifying the underlying condition. The cause is due to the friction characteristics in the clutches on the planetaries. They are likely slipping, due to worn friction material, a control circuit (sensor) problem, or a problem in the piston that applies pressure to the clutch pack.

Quote:

How do you determine if the Heat Exchanger is malfunctioning?

If it is leaking, usually. Unless it is blocked, that won't cause it to overheat. It is a very simple device. If there is sufficient flow, it transfers heat.

Quote:

Can it be that the Heat Exchanger is not working properly and making the transmission system overheat?

Not from a slow leak. If it is blocked, yes.

Quote:

I read almost of the transmission issues through this forum but I still think my situation has to do with heat or electronic issues not mechanical, what do you think?

I don't agree. It is mechanical, or electrical (control), in my opinion.

Quote:

At the current stage, should I get the transmission fluids replaced?

You could do it, but I wouldn't expect miracles. It is like a faint-hope clause, you can always try, but if that doesn't help be prepared to spend $$ on the transmission. Furthermore, new fluid may kill it completely.

Quote:

Will reprogramming the module unit help?

Unlikely that it will help.

Thank you for your reply. few more questions though;
(1) The electrical control unit is it internal or external of the transmission? are you reffering it to EGS control module? how do I perform the diagnostic?
(2) So don't waste my $$ to change the fluids and deal with until it stop moving?

I am referring to various control modules, wiring, and sensors. Some are internal to the transmission, some are external.

Whether or not you change the fluid is your decision. You can wait until the transmission fails completely, or you can change it. If you change it, it may improve the situation, or make it worse. You will know after you change the fluid, if you decide to change it.

One of the BMW techs on the board (Weasel, killcrap) may have a specific suggestion on further diagnostics using special tools.

Perhaps I should just take it to the dealer and spend few hrs of labor for diagnostic.
I will also reach out to Weasel.
Thanks.
Hey, my symtom started after my summer trip to Whistler from Seattle.