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Old 01-30-2019, 11:01 PM   #61
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My trailer is 7500 GVWR, but this is irrelevant. Trailer ready for comping is 7,000-7,200 lbs. I towed it through Rockies in 110F heat and many times through Sierras. This is Jayco. Airstream would be much easier to tow due to better aero profile. I am sorry JohnandJan, but your information is incorrect.

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(...) At any rate, an X5 with the 3.5 engine does not have enough power for a 7300 GVWR trailer.
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Old 01-30-2019, 11:03 PM   #62
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For another p.o.v. ... as a 'AS beginner' with a 2011 X5d we bought in a 2016 23 FB, with published hitch weight 440 lbs and unit base weight 4806 lbs. X5 ratings are 600 hitch weight and 6000 GVWR (maximum trailer weight when vehicle is empty (no payload); any load carried in the vehicle reduces maximum trailer towing capacity). The theoritical load, therefore, is 1194 lbs for driver, passengers, vehicle cargo and AS cargo.

BTW, in Canada the 23 TB is 'stamped' 6300 GVWR?

I switched to a Cayenne D which has 7717 lbs 'towing capacity, however, with 616 lbs hitch weight rating I think I cannot go 'bigger' than the 23 FB.
The 7716 lb tow rating is a common Euro rating for vehicles of this size, as it equates to 3500 kg. Above that kg weight rating the regulations are different, so many manufacturers use that as their ceiling. That includes BMW with the X5. In the US, BMW sell a North American style hitch with a lower rating, so that becomes the North American vehicle rating by default. Of course, there are aftermarket hitches available if one wants to use the full design capacity of the vehicle.

I would strengthen the receiver hitch as required, and pay attention to the rear axle loads on the tow vehicle. That would be a prudent and safe approach.
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Old 01-31-2019, 08:52 AM   #63
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A lot of “nopes” here.
Assumming your Tacoma is a 6 cylinder, you will struggle greatly getting up western mountains and continental devide at altitude. You will also realize your trailer is much heavier than your vehicle. You can probably do it , but it will be a struggle. We struggled pulling a 19 Bambi with our 6 cylinder Tacoma in the West fighting altitude and headwinds. We spent a lot if the time in 2nd and 3rd gear. When we upgraded to a 23 ft Grand Safari, we got a Tundra with
the big 8 cylinder engine and that was the proper vehicle for towing.
You will absolutely need a hitch equalized setup to safely tow. Whatever vehicle you choose will need this. This is not the same as an antisway setup.
A friend has an X5 bmw and a 25 ft Airstream. After a few trips with the BMW, he decided to no longer tow with it and began renting a big pickup for trips because the truck towed better and the BMW was struggling to tow.
Don’t underestimate the challenge of towing into a 3 day headwind at 6000 ft + elevation
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Old 01-31-2019, 10:14 AM   #64
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A lot of “nopes” here.

Assumming your Tacoma is a 6 cylinder, you will struggle greatly getting up western mountains and continental devide at altitude. You will also realize your trailer is much heavier than your vehicle. You can probably do it , but it will be a struggle. We struggled pulling a 19 Bambi with our 6 cylinder Tacoma in the West fighting altitude and headwinds. We spent a lot if the time in 2nd and 3rd gear. When we upgraded to a 23 ft Grand Safari, we got a Tundra with

the big 8 cylinder engine and that was the proper vehicle for towing.

You will absolutely need a hitch equalized setup to safely tow. Whatever vehicle you choose will need this. This is not the same as an antisway setup.

A friend has an X5 bmw and a 25 ft Airstream. After a few trips with the BMW, he decided to no longer tow with it and began renting a big pickup for trips because the truck towed better and the BMW was struggling to tow.

Don’t underestimate the challenge of towing into a 3 day headwind at 6000 ft + elevation


So our MDX is a 2011 with the 3.7 L V6 with 300 hp and we had no problems going over the continental divide towing a 25’ AS. We were usually in 4th or 3rd gear (3rd gear puts us at 55-60 mph, 4th about 70-73 mph). Granted it was just two of us and we were loaded light (empty waste tanks, water tank 1/4 full, one propane tank empty, no heavy gear in MDX) but is the 3.5 L engine in the BMW that much different?
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Old 01-31-2019, 10:33 AM   #65
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So our MDX is a 2011 with the 3.7 L V6 with 300 hp and we had no problems going over the continental divide towing a 25’ AS. We were usually in 4th or 3rd gear (3rd gear puts us at 55-60 mph, 4th about 70-73 mph). Granted it was just two of us and we were loaded light (empty waste tanks, water tank 1/4 full, one propane tank empty, no heavy gear in MDX) but is the 3.5 L engine in the BMW that much different?
Similar peak hp. The BMW is turbocharged, which means no appreciable power loss at higher elevations, and more torque, especially at low rpm. It is also possible to increase the hp using a BMW reprogram of the engine’s computer.
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Old 01-31-2019, 02:08 PM   #66
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I am driving BMWs since almost 20 years. I've never heard about any particular problems with transmissions in BMW SUV. There were a couple of BMW transmission "failures" (E39 530d, E60 M5, etc.), but nothing with SUV.

Bother to share the source of your claims?
In general that CLASS of SUV is not equipped with a heavy duty transmission cooler or other features that come with a tow package. This can cause wear and premature transmission failure over time under many towing conditions.

I base this on anecdotal evidence from owners of improperly equipped SUVs directly and from Internet forums. I suggest that anyone contemplating towing a heavier class of Airstreams thoroughly research the issue.

By no means did I intend to single out the BMW.
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Old 01-31-2019, 02:13 PM   #67
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Not sure about other SUV, but BMW X5 35d is equipped with transmission cooler as a standard feature. I do not know, what "a heavy duty transmission cooler" means, but I am watching fluids temperature when towing very closely. I do not think transmission temperature is an issue with X5.

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In general that CLASS of SUV is not equipped with a heavy duty transmission cooler or other features that come with a tow package. This can cause wear and premature transmission failure over time under many towing conditions.

I base this on anecdotal evidence from owners of improperly equipped SUVs directly and from Internet forums. I suggest that anyone contemplating towing a heavier class of Airstreams thoroughly research the issue.

By no means did I intend to single out the BMW.
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Old 01-31-2019, 04:35 PM   #68
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Not sure about other SUV, but BMW X5 35d is equipped with transmission cooler as a standard feature. I do not know, what "a heavy duty transmission cooler" means, but I am watching fluids temperature when towing very closely. I do not think transmission temperature is an issue with X5.


Ours has a transmission cooler as well. Was standard my model year but now optional.
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Old 01-31-2019, 04:55 PM   #69
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Quote from OSU "I tried it with a BMW X5 5.0 10,000# anti sway bar set up and it was like the tail wagging the dog the sway was ok just felt unsafe. I kept the car & upgraded to a 2017 Yukon Denali 6.2l Wow what a difference"

Quote from OSU "Again the BMW is a unibody chassis you need a truck frame chassis"

-----------------------------------------------------------------------------------

OSU - Is that Yukon a standard model or is it an XL model?

What year 4.4 X5? What weight distribution/sway control hitch? What CAT scale weights for trailer axles and X5 axles? What tongue weight and receiver capacity?

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Old 01-31-2019, 11:42 PM   #70
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In general that CLASS of SUV is not equipped with a heavy duty transmission cooler or other features that come with a tow package. This can cause wear and premature transmission failure over time under many towing conditions.

I base this on anecdotal evidence from owners of improperly equipped SUVs directly and from Internet forums. I suggest that anyone contemplating towing a heavier class of Airstreams thoroughly research the issue.

By no means did I intend to single out the BMW.
I realize that you are not picking on the X5, but for background info, it actually doesn't have a transmission cooler in the traditional (air to trans fluid) sense. It has a heat exchanger with a thermostatic control. One side of the heat exchanger has the transmission fluid, and the other side has coolant. This is sized for sufficient transmission cooling in all expected ambients, up to the 7700 lb tow rating used throughout the world, but it has another benefit in that it also heats the transmission fluid when starting from cold. The engine coolant warms faster than the transmission on a cold start, and most component wear happens when cold. By heating the transmission fluid with coolant, the transmission comes up to temperature sooner, reducing transmission wear, and also allowing the transmission to use the special cold shift program for less time. It is a nice system.

The vehicle also uses adaptive shifting. There is no need for a tow mode with a manual control. The transmission computer compares throttle position and fuel readings with actual acceleration from the chassis system, and thus knows when the engine/transmission are under high load. It is designed for steep hills and trailer towing per BMW technical training materials. If the computer senses high loads, it adapts shift points and so on.

There are a number of additional towing features designed into the base vehicle, including trailer stability control when a trailer is connected, etc.

All of this is included in every X5 model, there is no optional tow package.
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Old 02-01-2019, 12:40 PM   #71
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I realize that you are not picking on the X5, but for background info, it actually doesn't have a transmission cooler in the traditional (air to trans fluid) sense. It has a heat exchanger with a thermostatic control. One side of the heat exchanger has the transmission fluid, and the other side has coolant. This is sized for sufficient transmission cooling in all expected ambients, up to the 7700 lb tow rating used throughout the world, but it has another benefit in that it also heats the transmission fluid when starting from cold. The engine coolant warms faster than the transmission on a cold start, and most component wear happens when cold. By heating the transmission fluid with coolant, the transmission comes up to temperature sooner, reducing transmission wear, and also allowing the transmission to use the special cold shift program for less time. It is a nice system.

The vehicle also uses adaptive shifting. There is no need for a tow mode with a manual control. The transmission computer compares throttle position and fuel readings with actual acceleration from the chassis system, and thus knows when the engine/transmission are under high load. It is designed for steep hills and trailer towing per BMW technical training materials. If the computer senses high loads, it adapts shift points and so on.

There are a number of additional towing features designed into the base vehicle, including trailer stability control when a trailer is connected, etc.

All of this is included in every X5 model, there is no optional tow package.
Sounds like a good system. BMW is certainly innovative.
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Old 02-01-2019, 01:08 PM   #72
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Sounds like a good system. BMW is certainly innovative.
You gave up way to easy, especially when you we're right! This has some innovation, but transmissions have been cooled this way since at least the 50's. It a cost savings measure plain and simple. In most cases the end user will never thermally stress the system and the manufacturers can get away with this. This is why tow packages come with an auxiliary transmission oil cooler. It allows the radiator to only have to cool the engine, thus giving the cooling system more thermal capacity. Jeff has admitted this is entertainment to him (Which I now get)!
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Old 02-01-2019, 03:38 PM   #73
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You gave up way to easy, especially when you we're right! This has some innovation, but transmissions have been cooled this way since at least the 50's. It a cost savings measure plain and simple. In most cases the end user will never thermally stress the system and the manufacturers can get away with this. This is why tow packages come with an auxiliary transmission oil cooler. It allows the radiator to only have to cool the engine, thus giving the cooling system more thermal capacity.
Most automotive transmission I have worked on have had fluid/air coolers. A fluid/fluid heat exchanger is fundamentally different. And it certainly isn't cheaper.

A fluid to air transmission cooler is typically stacked in front of or behind the engine coolant cooler, or run in lines between the other circuit lines. There is typically one fan, not separate fans. There isn't accurate temperature modulation, there is simply turning the shared fan on low or high. The liquid to liquid heat exchanger allows warming, which reduces wear on a cold start, but it also provides thermostatic control which is much more precise. It allows the designer to use much closer specs and clearances in the transmission components, because they have better thermal management. That is also partly why these transmissions run the fluid so long (lifetime design, although some may decide to change it due to their own belief system)

More basic vehicle designs with optional tow packages come with auxiliary coolers simply because they were spec'd by the design team with lower cost and lower capacity cooling systems up front, simply to save money. It isn't a bad approach, it saves them money. But a separate transmission cooler isn't a feature, it is a remedy for a design limitation.
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Old 02-01-2019, 04:05 PM   #74
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This has some innovation, but transmissions have been cooled this way since at least the 50's.
A good question would be, why does the transmission require all this cooling? Slipping was normal, and they were called slush boxes for a reason. Early automatics were notorious at generating heat. That continues on some basic designs, but modern automatics are designed for much higher efficiency. Heat is wasted energy. You burned fuel to make it. It is a weakness of the design.

Fortunately, we are not using 1950's transmissions. Start with the torque converter. Design it to go into lock up as soon as possible, so there isn't wasted energy going into the vanes spinning and heating up the fluid. Design the transmission to bypass the torque converter, lock up, and use direct drive after starting off from rest. Now look at the shift events. Modulate engine power at the moment of shifting to drastically reduce slippage in the wet clutches in the automatic. BMW does this with changing ignition timing via integration with the engine computer. Now there is far less heat going into the fluid. It is so efficient that the transmission needs heating to operate efficiently. This isn't just BMW, the ZF transmissions in other vehicles (like the RAM pickups) are the same. And it isn't new. My X5 version debuted in 1999, with all of these features. That was 20 years ago, for those counting

Times move on.

If you want entertainment, read the RAM 1500 forums where posters found that their new automatics had transmission heating modules (on the ZF models) and were flabbergasted. They thought it was a mistake. Everything they knew was likely based on what they or their teachers learned in the 1950's.
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Old 02-02-2019, 04:43 PM   #75
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Invisihitch

I have an X5 with an invisihitch. I did my research. It was a tough choice given all the variables.
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