Towing with GL450
Senior Member
Joined: Feb 2011
Posts: 350
Likes: 106
From: Palo Alto, CA
2011 GL 350, P1 Package, HID headlamps, Blind spot assist, Parktronic, Wood steering wheel
Cruise control when towing
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 ?
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 ?
Senior Member
Joined: Feb 2010
Posts: 331
Likes: 3
2011 GL350 Bluetec, Irridium over Black Leather
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.
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.
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
Senior Member
Joined: Jun 2012
Posts: 409
Likes: 22
2008 GL320CDI (310k), 2017 GLS450 (170k), 2024 Sprinter 2500 (40k)
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.
Newbie
Joined: Sep 2011
Posts: 3
Likes: 0
From: Grand Junction
GL 550
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
Senior Member
Joined: Feb 2011
Posts: 350
Likes: 106
From: Palo Alto, CA
2011 GL 350, P1 Package, HID headlamps, Blind spot assist, Parktronic, Wood steering wheel
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.
I use a prodigy controller and it works great.
Newbie
Joined: Sep 2011
Posts: 3
Likes: 0
From: Grand Junction
GL 550
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
Senior Member
Joined: Feb 2011
Posts: 350
Likes: 106
From: Palo Alto, CA
2011 GL 350, P1 Package, HID headlamps, Blind spot assist, Parktronic, Wood steering wheel
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
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
Member
Joined: Apr 2005
Posts: 111
Likes: 1
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.
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.
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PLATINUM SPONSOR
Joined: Jun 2008
Posts: 3,834
Likes: 65
From: Texas
2003 CL55
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.
__________________
E63 Biturbo, UPD Cold Air induction kit, UPD performance crank pulley and UPD adjustable rear suspension with ride height adjustment.
CL55 UPD Cold Air Boost kit, UPD 3000 stall converter, UPD 77mm SC clutched pulley and beltwrap kit, Custom long tubes, UPD crank pulley , UPD suspension kit, UPD SC pulley, Aux. HE, Trunk tank w/rule 2000 pump, Mezeire pump, UPD 5pc idler set, Aluminum rotor hats.
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instagram @ultimate_pd
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E63 Biturbo, UPD Cold Air induction kit, UPD performance crank pulley and UPD adjustable rear suspension with ride height adjustment.
CL55 UPD Cold Air Boost kit, UPD 3000 stall converter, UPD 77mm SC clutched pulley and beltwrap kit, Custom long tubes, UPD crank pulley , UPD suspension kit, UPD SC pulley, Aux. HE, Trunk tank w/rule 2000 pump, Mezeire pump, UPD 5pc idler set, Aluminum rotor hats.
www.ultimatepd.com
instagram @ultimate_pd
facebook.com/ultimatepd
Senior Member
Joined: Feb 2011
Posts: 350
Likes: 106
From: Palo Alto, CA
2011 GL 350, P1 Package, HID headlamps, Blind spot assist, Parktronic, Wood steering wheel
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.
PLATINUM SPONSOR
Joined: Jun 2008
Posts: 3,834
Likes: 65
From: Texas
2003 CL55
What mirror extensions you running on your GL550?
__________________
E63 Biturbo, UPD Cold Air induction kit, UPD performance crank pulley and UPD adjustable rear suspension with ride height adjustment.
CL55 UPD Cold Air Boost kit, UPD 3000 stall converter, UPD 77mm SC clutched pulley and beltwrap kit, Custom long tubes, UPD crank pulley , UPD suspension kit, UPD SC pulley, Aux. HE, Trunk tank w/rule 2000 pump, Mezeire pump, UPD 5pc idler set, Aluminum rotor hats.
www.ultimatepd.com
instagram @ultimate_pd
facebook.com/ultimatepd
E63 Biturbo, UPD Cold Air induction kit, UPD performance crank pulley and UPD adjustable rear suspension with ride height adjustment.
CL55 UPD Cold Air Boost kit, UPD 3000 stall converter, UPD 77mm SC clutched pulley and beltwrap kit, Custom long tubes, UPD crank pulley , UPD suspension kit, UPD SC pulley, Aux. HE, Trunk tank w/rule 2000 pump, Mezeire pump, UPD 5pc idler set, Aluminum rotor hats.
www.ultimatepd.com
instagram @ultimate_pd
facebook.com/ultimatepd
Newbie
Joined: Sep 2012
Posts: 10
Likes: 0
From: Chicago IL
07 MB GL320 CDI
We normally get about 25 MPG on the highway with the Diesel GL350; towing the Airstream we saw an average of 16 MPG. We definitely got funny looks from the full sized diesel pickup truck crowd when we were in RV parks along with comments along the line of - "you're towing with that little thing?"
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
Junior Member
Joined: Jul 2009
Posts: 58
Likes: 4
From: Seattle, WA
2007 GL450
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
Member
Joined: Sep 2009
Posts: 171
Likes: 10
From: SoCal
GL450; Audi Q7 sline; GX470-SOLD, E55-SOLD, Range Rover Supercharged-Sold
Senior Member
Joined: Dec 2012
Posts: 251
Likes: 20
GL550
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.
Junior Member
Joined: Jul 2009
Posts: 58
Likes: 4
From: Seattle, WA
2007 GL450
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.
Newbie
Joined: May 2014
Posts: 1
Likes: 0
2012 gl450
Towing a 25 foot airstream with a 2012 GL450
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
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
Last edited by mooeymoose; May 17, 2014 at 04:41 PM. Reason: correction
Newbie
Joined: May 2014
Posts: 5
Likes: 0
From: Florida currently. Have lived in 8 states and 3 countries.
2020 GLE450, 2020 C43, 2021 F350
Can someone tell me if I understand this correctly
Andy at www.canamrv.ca will answer all your questions.
Andy at www.canamrv.ca will answer all your questions.
Newbie
Joined: Jun 2014
Posts: 1
Likes: 0
From: Indianapolis, IN
GL350
Can-Am - Just Returned
+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
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
Member
Joined: Aug 2008
Posts: 84
Likes: 18
S65 GL320CDI GLS63 80 Series Landcruiser
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
Member
Joined: Feb 2003
Posts: 227
Likes: 0
From: Bay Area
01 S2000, E46 M3, 99 ML320
Newbie
Joined: Oct 2015
Posts: 3
Likes: 0
2011 MB GL450
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
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
Member
Joined: Feb 2003
Posts: 227
Likes: 0
From: Bay Area
01 S2000, E46 M3, 99 ML320
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?
Senior Member
Joined: Feb 2011
Posts: 350
Likes: 106
From: Palo Alto, CA
2011 GL 350, P1 Package, HID headlamps, Blind spot assist, Parktronic, Wood steering wheel
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.
Last edited by ddruker; Oct 2, 2015 at 09:58 AM.
