ddruker

Question for other folks who tow.

One of the things I initially did not like at all about the GL was the cruise control and how it does not allow the GL to coast going down hill. On all of the other cars and trucks I've ever owned, the cruise control keeps the vehicle at the desired speed on the flat or uphill, but allows the vehicle to coast and to go faster than the preset speed going downhill.

The GL is clearly keeping the preset speed at all times. Anyone know what it is doing to slow down? It's not obvious that it's either applying the brakes or using engine braking.

Initially when towing I found this to be a great feature - it sure makes downhills easy - but then I got to thinking it could be causing problems when towing.

Do you use cruise control while towing downhill? My concern is that it is effectively riding the brakes going downhill - and also causing the trailer to ride its brakes. For sure the brake controller notices the GL slowing and applies the trailer brakes.

Since then I've been letting it do it's thing on minor grades, but turning off cruise control on steep or long grades and manually downshifting and applying the brakes periodically when needed. With the big airstream behind me, there is quite a bit of aerodynamic braking going on anyway.

Any other thoughts ?

mdadgar

The GL is applying in the brakes in cruise to limit speed. I love this feature.

I tow downhill in cruise. Trailers want to be towed. When coasting downhill, the trailer is pushing the tow vehicle. That's bad. Cruise braking will limit this.

- Mark

a2j

If transmission starts to shift up and down, regardless if you're towing or just driving in mountains, shift it to gear where it's not doing that anymore. But with diesel, this issue almost does not exist because of low-end torque.

rhornet

Since all of you have had no problems with towing your great looking unit how was the trailer brakes installed I know that there is a connector under the dash, but of course it doesn't match the brake controller. I would assume there is a fuse missing under the hood fuse block. If anyone knows about this I woulds appreciate the in lightment. The fancy MB dealers don't seem to want to share any information or want to share an arm and leg for something that should be a simple installation. Please help? Thanks

ddruker

Search a little bit on the forum and you will find instructions for how to plug your electric brake controller into the green plug under the dashboard. You don't need a fuse - it's all ready to go. You just need to make up a connector between your brake controller and the green plug - all the instructions are already in one of the towing threads.

I use a prodigy controller and it works great.

rhornet

Thanks for the reply, I am new to the forum and am having trouble finding the instruction on how to plug your electric brake in I know I have to go get the male green plug from the MB dealer. thanks

ddruker

Search the forum for Tow Green Plug...

In the post below, download the pdf file attached to one of the postings - it contains instructions and the parts list you need to get from the dealer.

https://mbworld.org/forums/gl-class-...reen-plug.html

If you are using a Tekonsha controller, search the forum for Tekonsha and you will even find a post that includes which wires on the green plug map to which wires on the connector that comes with your Tekonsha controller.

Search is your friend.

- Dan

amg8451

I know its an old thread but I just wanted to give input on my towing experience. I am towing an 18ft FunFinder travel trailer, about 5600lbs gvwr when fully loaded. I just got back from a trip to Sequoia National Forest, and the GL was awesome at towing the trailer. I kept it a steady 60-65 mph and got and average of about 12mpg. Going up the pass on I5 in the Los Angeles county area the truck did great. I have towed this trailer before with my ML55 from California to the south rim of Grand Canyon. The ML55 did fine, it had plenty of power, but with the 5spd tranny, the ML seemed like it was gear hunting a whole lot. the ML was always downshifting shifting from 5th to 4th. I did not notice the tranny in the GL shifting as much as the ML did. I seemed like the 7spd tranny in the GL knew what gear it had to be in.
For the brake controller, if you do not want to mess around with hunting for the cable, get a wireless brake controller (Tekonsha PRODIGY® RF). The wireless brake controller worked flawless for me. So easy to setup.

Exotic-metal55

What kind of adaptor is everyone using to stop the trailor lights from flashing while towing? I have the 7 pin plug on the GL and boat trailor with LED lights.

ddruker

I'm also interested if anyone has found a solution that works. I tried wiring resistors into my Airstream brake circuit per a handout from MB USA, and it did not work - they were still flashing.

Exotic-metal55

What mirror extensions you running on your GL550?

Dynamic

I don't know how you do it getting 16 mpg with that big trailer. I was towing two snowmobiles on an open aluminium trailer total weight less then 1200lbs. at 75mph I was getting 15 MPG when I normally average 23 MPG at same speed without a trailer.

This was really an eye opener for me and any future trips that I will plan when towing my boat or snowmobiles. I normaly get 18 MPG on my Ford F350 diesel, when towing boat or snowmobiles it will drop down to 16.5 MPG

gbigpapa

Try this one:
http://www.towready.com/content/prod...575&part=20141

Here is a link to a previous discussion on the same topic.
https://mbworld.org/forums/gl-class-...ng-lights.html

cmarshack

I bought this one and it works great!

http://www.uhaul.com/MovingSupplies/...Module?id=4089

2010GL550

As mentioned above, when using cruise control the vechilce will apply the brakes when decending a hill. Forgive me if this is a silly question, but are the brake lights activated when this happens? I don't tow, but have noticed the sudden slow-down and was just curious.

gbigpapa

Yes, the brake lights on the vehicle are activated when this happens.

mooeymoose

I have a 2012 GL450 with the tow package. It is rated at 7500 lbs in towing and a 600lb hitch weight. I want to buy a 25 ft airstream that states Hitch Weight (w/LP & w/o options, water & cargo) (lbs.)833Unit Base Weight (lbs.)5,612Gross Vehicle Weight Rating (lbs.)7,300

The hitch weight seems to be the limiting factor. Now, my understanding is a weight distribution attachement only transfers weight to the front axle for stabiltiy reassons. The hitch weight will not change with this. The other aspect that confuses me it the airstream is the hitch weight reported appears to be when it is loaded. I would think the hitch weight can vary a lot on an RV depending on what and where you load the trailer. Can't I can just load my trailer in the rear and lower the hitch weight thus keeping the trailer under the 7,300 and lowerinig my hitch weight to 600 lbs. I would think I would also get a weight distribution attachement for safety reasons but I also hear this my be a problem with the air shocks.

Can someone tell me if I understand this correctly and if there are any options so I can tow this trailer.

Thanks

Safetyfirst50

Can someone tell me if I understand this correctly

Andy at www.canamrv.ca will answer all your questions.

Mevans6453

+1 for Andy at Can Am, he setup my 2011 GL350 and 2012 Airstream International 25 - just yesterday. Returned home today and the ride was everything I expected and more.

In fact, my girlfriend wanted to try and drive with the Airstream hitched up on the way back. The roads were open so I figured it would be a good training ground. She ended up taking us over the border and the bridge through traffic while I played DJ.

Great trip, great setup. Anyone who thinks you need a Ram 2500/Cummins combo to tow an Airstream is just plain wrong.

Mike

UNderdog

I am in the Dallas area. Does anybody have experience with (or know of) a local shop that will reinforce the GL hitch? Preferably a shop that has seen a GL or ML or if not any shop that is competent with this type work. I have an '08 and after researching I think welding gussets on each side of the receiver and also welding a brace on the back of the receiver which then bolts up to the rear cross member is the way to go. Thanks, Randy

s4play

How many feet is that trailer?

What is your weight with race car in the back there?

Max4Speed

2014 GL550 towing....

nickydinardo

We are considering buying a Keystone Bullet (~28ft. @ 4,685# dry weight and 550# hitch weight)... http://www.rvtrader.com/listing/2016-keystone-rv-bullet-east-coast-243bhs-114482682
Can anyone tell me if I can have full confidence in pulling this with my GL?
I'm a little nervous as this my first Trailer. Any tips and/or thoughts would be very much appreciated.
Thanks,
Nick

s4play

What are you guys using for the actual ball hitch point? I just bought a heavy duty CURT 45900 channel style unit which is one heavy sucker. Does it matter what ball hitch system you use and is there any precautionary connections with chains that I need to make just in case the ball fails? Or is that never an issue?

ddruker

Nicky - lots of us tow trailers of similar size and weight to that without drama... I did modestly reinforce my hitch receiver for peace of mind, I don't know it it was truly necessary. You will want to watch your hitch weight and be careful to carry cargo in your trailer not your truck if you wish to stay within spec for your gl.