I just don't get messing with a transmission cooling system when one is not a trained ZF technician and there is not historical data that indicates overheating has been a problem certainly not a chronic issue.

I understand trans coolers are used in some applications but that doesn't mean it is good practice on other brand vehicles, as much chance it is a bad idea as a good one. In the discussion, comments bounce around different transmissions so there is no consistency of input to even a given transmission.

Be sure to go back and read JCL's input early on about ZF transmissions---per the forum threads overheating has not been a problem. I agree with his observation and that is also my personal experience with all 117,000 miles in Texas.

My suggestion is to spend the money on something else like PM or the rest of the cooling system if not in great shape.

:iagree:
Like pulling all the leaves out from and between the rad, ac condenser, etc. Having all your preventative maintenance completed, including cooling systems up to snuff will go a long way to keep temps where they need to be.

Doing my own preventative work I pulled the alt off a 528 last fall to replace the dreaded oil filter housing seal and pull out a pound of acorns from the back of the air duct at the rear alt housing. Damn chipmunks......:wahwah::wahwah:

As these trans age, there will be more failures. Welcome to "old cars"!

Explain to me why it is not good practice? Why should one need to be a trained ZF technician to understand that keeping the transmission fluid in a more optimum temperature range will help extend the life of the transmission, help to keep it operating efficiently and help extend the life of the fluid? Running transmission fluid at over 100 degrees (yes I have proof) isn't going to help anything. Everyone is aware they are a particularly fragile transmission especially when approaching 100k and over - could this be the reason why?

There is also no risk over overcooling since the thermostat is in place to avoid this.

Before I added this transmission cooler I had 3 issues...

1. Harsh 2-1 Downshift
2. Getting stuck in 3rd gear
3. Randomly changing down gears

I have now done 20,000 miles in it since fitting the cooler (half of which have been done whilst towing) and I have had NO further issues at all. To me that's a result and worth every penny.

I believe I tapped into the line labelled 1. on realoem.com. I will double check tonight though when I get home.

Yes, the fittings did push directly in - do yourself a favour when you fit them and take the lines off the car completely. It's the only way you are able to get enough purchase on them to ensure the fitting goes all the way in as they are very very tight. You cannot do it on the car you just don't have the space or the capability of being able to hold them whilst you do it. If the fittings don't go in properly they will absolutely without a shadow of a doubt come off once the car is running......trust me on this I know and fluid isnt cheap when you lose a load.

Thanks V8 :thumb up:

Good tips on the lines off the vehicle. Let me know when you can confirm the exact return line hose.

I'm with you on the cooling philosophy, old school. It can't hurt cause the thermostat is in the system and one day, if radiator issues rear their ugly head, it could help provide an extra measure of temp margin for the tranny while one limps it off the road.

While I had no issues pulling the 4,000# trailer on a 1200 mile trip a few months ago at speeds in the 75mph (~125kph) range and a few modest hills where it downshifted out of top gear/lockup, the two worst enemies of the internal combustion engine, IMHO, are heat and dirt and I'm happy to do a little extra to guard against heat.

Mike

I agree with Brian on this one there really is not a problem with trans cooling with how the factory system is set up. 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. I get that some want additional levels of cooling but at most the results of improvement are marginal. 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.

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.

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.

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.

IMO a cooler is masking the core problem in normal driving circumstances.

The transmission cooling is designed for the optimum operating temperature range for the transmission. If the temperature is varying beyond specifications there is something not working properly in the existing components.

The exception can be if one is towing a lot or beyond the maximum towing wt. or repeating drag racing starts without letting the fluid cool. If I recall correctly the max temp. spec. for the 5HP24 is 200 degrees. If the transmission temp is above that during normal driving something is not working properly.

I notice you were towing. Was that the case prior to the cooler?

Transmission symptoms can be misleading. IMO if ones transmission is not operating properly it is time to get a diagnosis from a well recommended transmission shop familiar with your model transmission.

http://www.xoutpost.com/bmw-sav-foru...s-summary.html

Question: Is this a case of needing the latest trans software and Transmission adaptive memory refresh after a fluid change that created a new dynamics with the normal shift operations?
Legal disclaimer: My ZF trans knowledge base is VERY LIMITED.

Well if that's the case it's doing a very good job of masking it for 20,000 miles!

This is were we could really do with a sample of temperatures to see if my findings are normal or not. 200 degrees F is 93 degrees C which is 2 degrees under where mine started acting up.

Yes, I bought it primarily as a tow vehicle - I just enjoyed driving it that much I ended up using it more and more as a daily when I fancied a change from my 330d.

As I mentioned further up the posts - it would probably have been a transmission out job anyway as I'd exhausted all other options. I've got a spare box with knackered clutch packs if it ever came to it but I'd rather I got as much mileage out of this box as possible if it is on it's way out.

All done when it went in for a torque convertor under warranty.