Never more than 5000 lbs with my X5. Much more than that with heavier vehicles. I had a professional license (class 3, air brake endorsement) but those were generally single trucks, not truck/trailer combinations.

I think you are stretching to say that the increased towing capability in Europe is just an air duct. We don't know that. What I find interesting is that it is a no-charge option. You are also taking E70 information and applying it retroactively to your E53, which is a totally different platform.

If it was just transmission heat that limited the X5 towing capability, then the manual transmission model wouldn't have the same limit.

I did not say that it was good to 7700 lbs, I said that I recalled a Europe-only option for that trailer capacity, years back. You don't have that model, and I haven't seen a parts list as to what is different when the E53 had that option.

You just need to be very clear that you are planning on being significantly overweight, you can't reason it away.

In hindsight, my previous post was a bit convoluted. If you look on RealOEM, the increased towing capacity parts for an E70 include an airduct, an essentially identical rear diff with a different part number (which is only $200 more expensive than the stock unit so it couldn't possibly be so radically different - as I said, maybe a finned cover), an additional water radiator (which comes standard on the "hot weather package" cars), and a 220A alternator.

Yes, I realize that the option code just posted is for an E70. I tried searching and couldn't find anything on the E53. I will call BMW tomorrow to see if they can provide any other info. I was applying the E70 information retroactively more as an exercise than anything. I don't think it's unreasonable to do that considering that the base E70 has the same towing limitation as a base E53. Of course, that could be attributed to cooling issues which, when taken care of, increase the towing capacity because the chassis was engineered stronger than the E53. That's the question that carries the day. Is the E70 chassis stronger than the E53 in the towing department? I will certainly check with BMW on that one.

That said, after seeing Withidl's 8,500lbs setup being towed some 40,000+ miles, a setup he's had up to 9,300lbs (which is a number which I wouldn't dare approach - 7,700 is about the most I'm willing to go up to) I'm not too worried about the chassis or about being over the stated non-weight distributed limitation even without the increased towing capacity options. Those options, at least for the E70, add zero strength. But, as I said previously, that could be because of the chassis. If the E53 did, as you recall, get that option and assuming nothing on the chassis is strengthened, I find it hard to believe that the E53 cannot do at least something over 6,000lbs and stay within spec.

The deciding factor will be how the thing tows. If she's solid, great. If not, I'll probably buy a used Cummins or, at least, an F-250.

Just found the E53 option code. JCL was correct. The option code increases tow capacity to 3500kg (7,700lbs) with a 12% gradient maximum. Actually, the standard towing capacity is also rated at a 12% gradient maximum. The increased towing capacity option was available for the V8 and I6 Diesel cars so I think it's now safe to say that concern here is power rather than chassis strength. As far as the chassis and suspension goes, it looks like the E53 is actually good for 7,700lbs per the manufacturer.

JCL, any input?

See below:

http://www.bmw.be/be/fr/newvehicles/..._datasheet.pdf

I sold my E53 six years ago. Beyond that, I don't know why I remembered 7700/7900 lbs optional tow capacity that was only valid on another continent, but there you go.

Other input?

Good dig out on the old Euro spec sheet.

At least we are now dealing with the E53. I wouldn't keep referring to the E70, it is irrelevant. We need to know what the E53 Euro option code included. Because it was a zero cost option, I suspect it wasn't much. I can't recall the code number, but I suspect it wasn't 233 as the E70 is.

The E53 code specifically requires 18" and larger tires. So it looks like tire loading, and possibly dynamic stability, are issues.

The E53 code specifically excludes the manual transmission 3.0, which doesn't make sense if it just a chassis limitation. I suspect the driveline is not up to it, in BMW's opinion. BMW lets most of their Euro vehicles tow 3500 lbs, with far less HP than the X5 3.0 has. Even my 114 hp Volvo wagon towed 1600 kg/3500 lbs.

While the manufacturer has made reference to 7700 lbs, with specific options that you don't have, they have never permitted that load in North America. So, it may be a combination of mechanical changes and/or legal liability issues. The US hitch is also different, so that could be part of it.

I looked at your pictures of the trailer in another thread. That is a lot of trailer behind a 3.0, in my opinion. You will need to make sure your trailer brakes are working well. And all this speculation about ratings is not as important as driving habits when towing fully loaded, stopping for brake checks when descending mountain passes, etc.

Jeff

Some Points:

1. The Wheels. I saw the bit about 18" wheels. I will have 4.8is wheels on the car and will outfit them with the highest load rated tire I can find so no problem there.

2. The Driveline. The E53 code excludes both the manual and automatic 3L but not the 3Ld, which makes me believe it is a power thing. But, I see what you mean about BMW allowing smaller and lower powered cars tow 3,500lbs. That said, it might be a clutch thing on the manual. It might just be a transmission thing. I'll have to check into it more. I'm actually going to check whether the diesel transmission is the same as the one on the petrol engine. If it is, then it's got to be a torque/power thing. Otherwise, I'll just be more confused and have more questions. As I said, I'll be on the phone with BMW tomorrow to check on this and on the other options that come with this option code. I know that one such option is Trailer Stability Control; an option which is presumably an on/off type thing that can be accomplished with a GT1 as it functions through the ABS/ASC/DSC or whatever. Again, however, I'll have to confirm with BMW.

3. The Hitch. Yes, the Euro hitches are different. I'm going to ask BMW about this and will also touch base with Westfalia about it. Many say Westfalia's actual rating is higher but that they label it at 6,000lbs because that's what BMW says. I'll have to confirm with them as it's currently hearsay.

4. Mechanical Changes/Legal Issues. I'll also talk to BMW as to why this option was not offered on the U.S. cars. Could have been a marketing thing - could have been a more legitimate reason. I'll have to confirm.

5. The trailer. Yes, the trailer is a sizable piece of equipment. However, it is shorter in length and height (well, and weight, obviously) than Withidl's Airstream. I understand that the Airstream is more rounded, but at 6-12" taller, I'd say the aero drag is approximate (albeit probably a bit, but not much, more on my trailer).

6. The Driver. You're absolutely correct about the driver. It is driver habits, preparation, and monitoring that will carry the day. Of course, those won't make up for towing an unspeakably stupid load on an X5 (e.g. 12,000lbs). However, assuming everything checks out with BMW about the Euro tow capacity option, I should think that 7,500lbs would be a load that a diligent driver can handle as the chassis (again, assuming the equipment is up to Euro spec.) can handle it. This is going to be the deciding factor.

7. The Actual Drive. As you probably saw in the other thread, I won't be towing the trailer fully loaded at the first instance. I'm going to see how she tows unloaded, then loaded with the car, then fully loaded. Actually, I'll probably go unloaded, then loaded with full kit without the car, then fully loaded with the car. If the X5 can't do any one of those due to the drag, it's Cummins or 1/2 ton time. If the latter, I've got an open deck I can still putz around with in the mean time.

Just checked the transmissions.

Automatic:
It looks like the European X5s got Getrag transmissions (A5S 390R - YZ) while the American X5s got some other brand (GA6HP26Z). Europe also got a different torque converter.

Manual:
It looks like both European and American X5s got Getrag manual transmissions. They are different, but not very. I'll have to check with Getrag on this.

American: GS6X37BZ - THEE & GS6X37BZ - THEX (RealOEM lists these as "GS6X37BZ/DZ" just like the DZ designation for the European models - likely, then, it's the "37" vs. the "53" that is the difference; could it be gear ratios? Strength? Who knows).
European: GS6X53DZ - THGE & GS6X53DZ - TJGB

Two problems: 1)none of these parts are labeled "For Vehicles with Increased Tow Capacity" so I don't know whether these parts were different on those vehicles and 2) I've got more questions now that I did before. Therefore, this was basically a useless exercise. What I need to do is talk to BMW and get precise part numbers.

The GM 390r transmission was for the six cylinder, in all markets. The ZF 6hp transmission was for the V8 models, in all markets. The diesels changed from early models to later models due to torque capacity of the GM transmission.

Trailer stability control is in the DSC, not the trailer package. I even have it on my E83, which is an E46 platform. It is activated by the factory wiring harness being connected, but it is already there, just dormant. Coding isn't required, as long as your vehicle software recognizes the towing harness.

You don't need a Cummins, that's an engine. You may need a 3/4 ton pickup.

Cummins-powered [Dodge 2500] is what I meant. Not sure if you were being sarcastic there.

You really think a 2500 won't cut it?

No sarcasm, I should have used a smiley. I know that Dodge Rams have optional Cummins engines. It isn't the pickup I would choose.

A 2500 is a 3/4 ton pickup. I don't think a half ton pickup, whether an F150 or GMC 1500 or Ram 1500, will cut it. I work with Cummins engines. If you are looking at used, several years old, fine. If you are looking at new, check the recent history after the emissions controls were added.

Right, my mistake. I'm looking at the older models. But how old are we talking here? I'm looking at nothing older than late 90s. I can pick up a Cummins 2500 Dually for something like $6,000 on Autotrader. Sheesh.

I can't afford the new ones, anyways - way too expensive; especially for a car I'll only use a dozen times a year.

What would you recommend? I would like something that's somewhat built well on the interior in addition to a bulletproof drivetrain (so, basically, not a Ford unless I could get a screaming deal on one). I'm thinking either Chevy or Dodge. Thoughts?