Towing a boat with X5d
 

I just bought a malibu wakesetter and we've been enjoying it for a month or so now here in CO. I'm VERY surprised at how well the X5 diesel tows the boat--I swear it pulls it better than my step-dad's 2015 Silverado 1500.

Question is this: we plan on doing some camping soon at one (or several) of the mountain reservoirs. This means up/down passes etc. I've towed in CO for years, so I know HOW to drive in the mountains, I'm just curious if anyone has any experience with this rig specifically--towing about 4000lbs. No tranny temp gauge, no oil temp gauge etc. worries me a bit as I've always had things to monitor before.

Thanks!

Congrats on the diesel. I am pulling my 210 Sea Ray Sundeck with my diesel and I can even get 15-16 mpg going on flat with 65mph. The Sea Ray is around 5k lbs with the trailer, but is twice as wide and twice as tall than the X5 so the aerodynamic resistance over 60 mph puts more strain that the weight. I can still go our very steep and long Tejon pass with 60-65mph on 6th with 1 or 2 short downshifts to 5th.
These 6 and 8 speed transmissions work like manual ones-the torque converter is locked by default and it will be unlocked only for a brief moments when the engine is out of boost(torque). Once the car is under way it will never unlock, but downshift instead. No TQ slip=no heat in the tranny so this should not be any concern at all.
My '03 4.6is was unlocking the TQ at any sign of uphill and the transmission was usually hot halfway up in a hot day.

oh wow, that sea ray is a lot more boat! Tejon is no joke too.

Great info on the torque converter, what a great way to set that up BMW!

can you get an OBD connected device to display these temps?? Id like that if I was towing. One tranny overheat can destroy seals, kill the trans

I've towed more than that with the diesel, but Ontario is mainly flat, so I can't comment about the mountains
Bimmerfest - BMW Forums - View Single Post - Towing Photos with X5.

http://www.wardphotography.com/Boat/towing.jpg

I have pulled my 3400lb hobby car on a 2000lb 18' trailer with my X5 35D and experienced zero issues.

I had attempted the same pull with my newer (at the time) Silverado 1500. The transmission started slipping after three trips to the track.

The X5 pulls that 5400lbs effortlessly even up an ~8 to 10% grade. It's a pulling machine!

You are right about the overheating, but when the TQ is locked there is no excessive heat source. It is hard to believe, but it is the physics ;) Next time i tow up over Tejon in 90-100 degree heat i will connect some tool to get actual readings.

Pay attention to your trailer brakes. Our 23' Yamaha only has brakes on the rear axle. If I lived in CO (rather than FL) I would add them to the other axle immediately. Brakes on both axles are required by law in many states (including FL) but the boat dealers sometimes ignore to save $400. Also, flush trailer brake fluid often.

I find the X5 transmission will stay down shifted when the transmission starts to get warm. That must pump fluid faster to cool things off. After a minute things go back to normal. It is a nice warning sign.

As ard mentions, Android Torque with a Bluetooth dongle in the OBD port will allow you to set up a custom gauge set to monitor temps.

And are you sure your boat weighs 4000lbs? My very light 23' boat weighs 3200 empty. Add 1200 for trailer. Then another 500 for gas and gear and I am near 5000 lbs.

Yes, 4050 on the truck scale last weekend (I was that curious). That was with about a half tank of fuel which I'll probably try and leave empty when pulling then fill up before we get to wherever the final destination is. It's a very light boat with a hull design that makes a killer wake and 2500lbs of fat sacs which I obviously empty before we're off the lake. Plus the wake plate it basically turns into a 7500lb boat when loaded and setup in the water. Great design. Dual axle trailer with dual axle brakes, the jam brake type with the piston system in the tongue. It brakes VERY well, in fact so well that the car still brakes almost like nothing is back there.

Thanks for the input, I just wanted to make sure this thing is the towing machine it sure seems to be!

This used to happen a lot on my '03 4.6is. I was pretty good at keeping the TQ locked, but at 1 point it just unlocks and pretty soon the transmission was overheated. It had an aftermarket 8 row transmission cooler installed in front of the radiator, but nothing helps while climbing long steep hill at 100 degree day.
The diesel and the 6 speed tranny would not even brake a sweat at the exact same conditions.