External Transmission cooler?

[teknik_ranger]

Has anyone ever put an external trans cooler on their X? I've got a 2000 X5 with a 4.4l and that 5hp24 trans. 155000 miles on it when the trans failed. Pulled it apart and found that the friction discs were alright (replaced them anyway), but found that all of the o-rings were hard and brittle, and there was a axial needle bearing that failed between the a/b clutch and the c clutch. Fluid was black and smelled burnt. I've owned the X for 7 months and obviously the previous owner didn't maintain it!!!

Nearest I can tell is that the o-rings failed because of heat, which caused the a/b clutch to slip making the bearing overheat and fail. So I'm planning on putting an external cooler (and possibly a external filter) on it but wanted to know your thoughts. Also I'm going to wrap the exhaust since the cat's sit right next to the trans...excess heat sucks.

[JCL]

You already have a thermostatically controlled heat exchanger for the transmission fluid. Standard from the factory. It has the added benefit of heating the transmission fluid on cold starts, to reduce wear. Overcooling would negate that benefit.

Your failure wasn't necessarily due to a lack of maintenance. There have been more transmission failures than we would like to see, statistically, but there is not a common cause or theme for them. Changing fluid has not been shown to improve transmission life. You saw with your transmission that while the fluid was burnt, the clutch plates weren't. That suggests that the clutches weren't slipping for any length of time, rather it is more likely that something broke and it overheated suddenly. Look to that bearing.

I think one data point would be to consider posts from withidl, who towed 8300 lbs with his 2000 4.4, over the continental divide, for tens of thousands of miles. No transmission issues. Lots of posts here to read about. Due to that and similar examples, I really don't think heat is the problem with the transmissions, as long as the cooling system components are working as designed. Rather, I think that the failure of individual items (actuators, seals, snap rings) leads to premature failure prior to wear out. I think that the complexity of the transmission is the single biggest issue with it.

[teknik_ranger]

I knew about the heat exchanger being thermostatically controlled, but how often do these fail? The cooling system may have caused premature wear due to the fact that I had to replace a water pump recently. The old one that I pulled off was a re-manufactured and looked to be inferior quality.

I know also that there is a lot of taboo about whether or not it is better to have a stand-alone external cooler or run it through a radiator first. I am just wondering about anyone doing it.

Also, if anyone has...any problems with the shift points because of the transmission temperature sender? I know that when it's cold it has a different program and shifts are a little firm.

[JCL]

To answer your question, I have been on this board since it started, and I don't recall much discussion about additional external transmission coolers being installed. I think it may be a solution in search of a problem. I just don't think that transmission failures are commonly caused by excessive heat on the X5. I do agree that excessive heat is a common reason for transmission failures, just not on the X5.

[TriX5]

I think CivDiv has an external cooler on his.

[civdiv99]

Yeah, I've been using a B&M supercooler (#70268) for about a year now. Install wasn't a big deal. One day I was poking around under the BMW and decided since the 3/4 inch think B&M looks like it'll fit nicely behind the fan with no cutting, etc., why not? I can always revert back to OEM (I cut and sealed the lines to the OEM cooler in a manner that let's me get a mulligan), but right now I like having trans pan temps down in the 150s in summer driving. I wish I'd have checked the temps before - my all kinds of not scientific: "wow - that's hot" pre-check is not sufficient to draw a conclusion on. Anyway, this was more of a "I think I'll do that on Saturday, and see whaddup" exercise rather than a solution to a problem. I ran it all year (well, I still do) including near zero winter temps, and have not had any inclination to change it back. Really, the only info applicable to most folks is trivia "hey, what trans cooler fits easy between the fan and radiatior?"

[civdiv99]

Man that thing looks grubby.........

[fmugur]

Civdiv, I am thinking to add one as you did to get rid of the harsh 2-1 downshift which seems to happen only when the temperature is above 97 degrees Celsius. That's my alternative after unsuccessfully rebuilding the tranny and I am not willing to spend another 5K to have a new tranny installed.
What are your recommendations for this project? How did you mounted it on the radiator? Is that the best place to install it or you would do it different if you have to do it again? What about the oil pressure, what connectors did you use to be support that pressure.
Thanks,

[HPIA4v2]

Originally Posted by fmugur

Civdiv, I am thinking to add one as you did to get rid of the harsh 2-1 downshift which seems to happen only when the temperature is above 97 degrees Celsius. That's my alternative after unsuccessfully rebuilding the tranny and I am not willing to spend another 5K to have a new tranny installed.
What are your recommendations for this project? How did you mounted it on the radiator? Is that the best place to install it or you would do it different if you have to do it again? What about the oil pressure, what connectors did you use to be support that pressure.
Thanks,

97C tranny fluid temp? just curious.

I've been wondering about bigger trans cooler, not sure; mine shift OK (up or down) but after 30-min or so I feel minuet vibration and feel like the car is 1-gear above what it suppose to be, but when I punch it it down shift fine, no jerk, just wonder if higher temp makes the tranny fluid viscocity change out of it's range a bit. BTW, after coolant flush (every 2-3 yr interval) the symptomms disappear for a while so I know it seems related to temp, no code according to BT tools. sorry I don't have GT1.

[fmugur]

Any substance changes properties with temperature and I guess in this transmissions the oil properties change significant around 220 F.
I think civdiv in another thread was looking for tranny temperatures.
This morning I connected INPA to the car and drove to work with it.
The weather here is cooler in the last few days. This morning I left the garage with 44 F degrees in both engine and tranny. During the trip I could see the tranny temperature being lower than the engine but catching up. The engine temperature stabilized at 215 F while the transmission temperature was going above the engine temperature.
The range was between 228-239 F while the engine was at 215-217 F. Outside temperature was about 28 F.
I noticed the jerking 2-1 happened only when the temperature was above 230 F or so.
Now, the therm inlet and outlet in realoem is confusing to me. I am not sure if it refers to the heat exchanger or the transmission since the diagram is under Radiator section.
I don't think I have the oil tubes revered in the heat exchanger but after this morning reading I wonder if that's the case.



Is number 1 or number 2 the return line for the transmission in the diagram below?