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Originally Posted by X53Jay4.8is
Even when they designed the X5 it was designed with the expectation that towing would be part of the equation hence the internal trans cooler.
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Strictly speaking the standard item is a heat exchanger. It's never going to do the best job in the world of making much of an impact to reducing the temperature of the gearbox fluid since it uses the 108+ degree coolant to try and take heat away from the fluid.
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Originally Posted by X53Jay4.8is
I get that some want additional levels of cooling but at most the results of improvement are marginal.
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I wouldn't say resolving my 3 issues and lowering the temperature of the fluid by nearly 30 degrees was marginal - it saved me having to remove the transmission and start ripping it apart to try and find an issue that might not even have been there. Also since this fix has lasted for over 20k it definitely can't be classed as a temporary improvement either.
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Originally Posted by X53Jay4.8is
You can definitely spend your money elsewhere on these X5s for better improvement than the the trans cooling. If you are having a problem with cooling then something is not operating correctly on the vehicle and this is where more diagnosis is needed to fix the failing part or parts.
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I went through a process of diagnosis and found the same re-occurring issue. As soon as it hit 95 degrees that's when issues occurred. I changed the gearbox thermostat and the heat exchanger before venturing down this route anyway but neither of these helped. The only thing that was left to change was the radiator itself but since the car itself wasn't showing any signs of overheating I couldn't see how this was going to resolve anything.
Do a search on Google for '5HP24 hard downshift' - you'll find lots and lots of results. Not only people with X5s either, people in Range Rovers etc where the same box is also used all experiencing the same issue. It even seems to have earned itself a nickname of 'tranny slam' it's that common an issue.
Who knows.....perhaps the gearbox is more tolerant of the higher running temperatures when it's newer but as things inside start to wear the the viscosity of the fluid becomes more crucial so it starts to show issues. I'd definitely prefer spending £150 on what I did than £2000 on a reconditioned box which would have been the next route.
What would be interesting would be to see what temperature other peoples gearbox fluids run at. I'd only managed to find a couple of peoples temperatures to compare with mine and they seemed to tally up with what mine was running at - only problem with this is short of fitting a separate temperature sensor inline the pipes or in the sump of the gearbox the only way getting a temperature reading is achievable is if you have some kind of diagnostic equipment like a Snap On or via INPA which alot of people don't have access to.