gustaf.dgm

Hi All,
Looking for help from someone that hopefully already went down this road.
I have a '15 GL350 that we recently purchased that did not come with a hitch from the factory.
I wanted to go down the factory path so I purchased what I believe to to be the correct hitch part number (166-310-11-37). The car was at the body shop getting the rear bumper repainted and I asked the shop to install the hitch since they were taking the cover off. The shop called me and said that the hitch will not fit mount up; they claim it is too short.
He called the dealer and they claim a different hitch is needed (166-310-01-00) which when I look it up seems to be more of a kit but I can't find what all the contents are.
Has anyone crossed this bridge before? Are there some additional pieces I need to get to make this work?

Mike450

The hitch itself is only a portion of the factory tow package.

If you want full OEM trailer brake control, lights, and anti sway features, you need the hitch, the wiring harness that runs to front of car and the 7 pin connector for hookup.

Dealership quoted me $2200 installed. The drivers side entire interior of truck needs to be removed. ~5 hour job.

gustaf.dgm

Thanks Mike450.
I'm planning on doing the electrics myself and wanted the body shop to do this while they were in there.
Right now just trying to figure out what pieces I'm missing to get it mounted or if there is really some different hitch which I think is unlikely.

Mike450

I believe there is a thread from a year or two ago here with part numbers quoted.

fabbrisd1

1st - you have a GL350 - correct ? Please understand that it is very possible with the AdBlue tank - that you may need a "different" hitch than the gassers - not all online info from non-MB sources may not be correct - I have even seen diagrams with Euro hitch - if you had started with a dealer with your VIN# - you would have started with correct part# - and you would not have gone down the wrong road

2nd - I "think" that correct part # "might" also include the body harness - and frankly that is not necessarily a good thing - since installation of that harness requires about 5 genuine shop hours to install with access to Star system.

3rd - If you need wiring just for lights/brakes - Modulite add-on is just fine - if you want "full" MB towing function (which are good thing) - frankly you need the narness - which comes with ZERO instructions

Good Luck - keeep the beat !

gustaf.dgm

So I just picked up the car this morning and the body shop showed me what the issue is. The current reinforcement bar has tabs on each side that are brackets - fuel tank shield on the passenger side and exhaust heat shield on the driver side. The tow bar does not have these so I assume that there must be separate brackets that attach on here.
I've attached pics of the reinforcement so you can see what I am talking about.
Anyone have a part number for these? I can't seem to locate them on some of the genuine MB parts diagrams that I've found.

fabbrisd1

I wish you the best of luck in your search - I mean that sincerely.


Please post the part#'s for these "missing pieces" that will make the Gasser hitch fit your GL350 - with your persistence if they are out there you will find it.

Good luck - you might end up having to buy the correct hitch for your GL350 - heaven forbid that !

Ericlojo

You should not need a special hitch for the GL350. I have 2014 GL350 and the install was standard and is indistinguishable from a factory install. I don't know why the standard parts won't fit your vehicle. Just call a dealer and give them your VIN and ask what hitch kit you need.
The hitch will come with all the pieces you need, basically the hitch itself and a wire harness. The harness runs to a SAM in the rear of the vehicle and also runs all the way to the front dash.

Unfortunately I did not have the time to do this myself. I did weeks of research and dealt very closely with the dealer on my install. I had to verify and re-verify that all the SAM updates were done correctly (took them two tries).

L-L

I understand that this thread is old, but I am struggling with My 2015 GL350 Bluetec Diesel.
Dealer quoted me $2600 parts and installation. They also provided me with part number 166-310-01-00, which I also believe is for hitch and harness only.
Yet CURT makes a hitch (part#13173) that fits 2014 GL350 Bluetec but they do not have it as compatible with 2015 GL350 !!
A. Anyone used CURT hitch on 2015 GL350 Bluetec?
B. Did you guys figure out what is included with MB part 166-310-01-00?
C. Is there any other parts needed, ie new SAM, other modules, special coding, deactivating ESP, just enabling option 550 (trailer pack)?

Any help will be much appreciated.

mikapen

Here's a picture of the parts of a factory hitch kit. Note the bars that are inserted into the chassis for reinforcement. Aftermarket hitches don't have these and are not as strong, but I do see that they are braced against the rear crossmember, which is good.
Earlier kits had a replacement rear SAM, later ones needed to be programmed by the dealer.

L-L

Thank you Mikapen for your detailed email.
Well what is still strange to me is that CURT sells a hitch compatible with 2014 GL350 but not for 2015 GL350. Maybe it is just because they didn't test it on 2015s.
The specific Curt #17137 hitch is rated 7500lb towing capacity with 900lb tongue weight which is impressive.
In any event, do you know if 2015 GL350 requires SAM replacement or just reprogramming by the dealer?

Thank you
L-L

Yeffsy

I installed the factory wiring on my 2015 GL350. When I purchased mine it had the factory hitch installed, but not the wiring. I wanted the factory transmission shift point changes and the sway control that this adds. On this thread, they're installing an aftermarket wiring harness. To install the factory harness I followed this thread and a couple of others. For the wiring, I had to purchase: a trailer hitch wiring harness, a control unit wiring harness, and a trailer recognition control unit. They're all on the routing diagram in that tread. I pulled the middle row of seats, the passenger front seat, most of the panels on the passenger side, and pulled back the carpet. Then I routed all the wiring and had my dealer plug it all in and program it. I couldn't find details of where to plug everything into the fuse blocks, CAN connections, SAM connections, etc.

Jeff

L-L

Thank you Yeffsy for all the info. Very helpful.
I came across that specific cabling diagram before and indeed it is the only one I found online. Since you have the exact year/model as mine, do you by any chance still have the Part Numbers of each component you had to purchase? (ie "Trailer hitch wiring harness", the "Trailer recognition control unit", and the "Control unit wiring harness").
Also my understanding is that all the parts needed are:
A. Hitch with Trailer hitch wiring harness - 166.301.01.00
B. 850W Cooling FAN/Blower - 099.906.40.00
C. Trailer recognition control unit - ??? part #
D. Control unit wiring harness - ??? part #
Also...as per the local MB dealer, the below parts are also required (note "E" - if you will change the cooling fan you might need that part)
E. Vacuum Line - 166.430.16.29 (only when the cooling fan is replaced)
F. Some kind of Rear Shield - 166.520.05.23

Are parts A to D what you had to purchase? Do you have the part numbers of C and D.

Thanking you in advance,
L-L

Ricardoa1

Installation and programming is obviously needed. Nobody has mentioned the other upgrades before, so if you find them necessary go for it.

I commend anybody who undertakes the full factory retrofit, but at the value most of these vehicles are, most less than 30k and not even gonna mention diesel values, Is spending 2-4K on the hitch a sound idea anymore? Maybe when the truck was 50k it might have been more manageable. Trading for a tow prepped vehicle might make more sense now. Anyways...I’m almost wrapping up my install and can honestly say I’ve spent no more than $550, and have the factory hardware and working lights with aftermarket solutions and the option of a wireless brake controller. I’m a factory components sucker, I hate hack jobs, but when the truck is worth 23k in trade I’m not gonna be paying for the labor of tearing a whole interior apart, If you can get a tech to to he job for less than 2k you have a good deal, its easy a 3k labor only job at the big cities dealers, the parts kit cost $1000. Furthermore, do you really want to tow heavy stuff with this vehicle? Have you seen at the rate rear tires are eaten up by the factory camber setting? Rear air bags will only pump up so much, you will chew up the tires on a heavy load with max tongue weight and max load. Can you do it sure, will your tires like it? Get a solid rear axle vehicle for big jobs. Sway assist is neat feature for heavy loads and shift points can be manually adjusted via the paddles. But again do you want to go max tow where sway and stability control shines. So if doing small stuff, do you really need the extra software features?

Sorry for the reality check. Value on this venture is subjective, but I’m careful how I spend my money on a fast depreciating asset. But you are the consumer an it’s your money after all.

car-parts.com is your friend. Find a local wrecker with a ML or GL that has pulled the tow bar and longitudinal braces. Make sure they include the bolts and exhaust shield bracket. Avoid a receiver with a chain loop for the safety chains, get ones with the welded plate. The impact foam is $90 shipped new, so don’t worry about that being part of the deal at the yard.

And If you are worried about cooling cause your are in a hot climate then an obd tool to monitor trans temperature is of utmost importance.

gustaf.dgm

This picture is not the trailer hitch kit for the X166 body. This might be for the X164 but not the X166 as the tang for the wiring connection is mounted to the receiver gooseneck. Re: the support bars I know that the W166 uses support bars but do not think that the X166 uses them.

RostamDastan

This is the first hitch that MB put on GL. Its rated at 750# tongue weight. Shortly afterwards, they replaced it with a defective hitch, where the hitch receiver tube would break under load (probably a cost cutting measure). After that, they put the Oris hitch that is used now, which is a good hitch. All 3 have had the support arms, which make for a secure hitch/unibody connection and improves weight distribution with weight distribution hitch engaged. BMW, Porsche, Land Rover, etc do not have these support arms -- Hitch is connected to unibody via 8 bolts. MB has those 8 bolts plus the support arms. Much better design.

L-L

Thank you all for your replies and info.
It seems that MB has two part numbers for the hitch. One is 166-310-01-00 which is supposed to be a kit, and the other part is 166-310-11-37, which I believe it is just the actual hitch.
The question, something that none of the local MB dealers know the answer for, is what is included with the 166-310-01-00 kit. The price difference is between $250-$400 depending on the MB dealership.
Is it just the hitch and support bars?....Does it include the wire harness from the hitch to the trailer recognition controller....or maybe also the harness from the trailer recognition controller to the SAM module, fusebox and green plug that travels to the driver's side for potential brake controller? Is the trailer recognition module also part of the 166-310-01-00 kit? I called 4 Local MB dealers and nobody knows. I even emailed MB parts USA and I received a reply to contact the local MB dealerships since they didn't know.
I wouldn't might the Curt 13173 hitch (7500lb/900lb) but Curt states that is compatible with 2014 GL350 but NOT for 2015 GL350, which is strange.
Thank you all.

RostamDastan

I'd call the MB dealership in Arlington, VA. Its a huge dealership and they are very well versed in towing info -- I believe the service department manager (?) tows a race car with his GL. They installed the break controller on our GL several years ago. Our local dealership did not know how to do the install, and refused to do it even after I brought in a MB PDF file with instructions on how to do it!

Ricardoa1

The 37 number is just the impact bar/tube with the welded receiver and the 8 square mount points to the frame, at that price it’s highway robbery when the kit comes with the longitudinal braces, foam and exhaust shield brackets, which is necessary for the installation plus all the bolts and hardware.

See if this kit is still available from the dealer, it has a parts detail. Including electronics... Says for a ML but it should be compatible with the GL. Part numbers appear to be identical.

Trailer Hitch Kit

#166-310-01-95
Take advantage of your ML-Class`s considerable hauling capacity with our CLass III trailer hitch. Designed especially for Mercedes-Benz with a corrosion-resistant surface treatment. Class III hitch - 5,000lbs tow capacity - Wiring harness included. - No SAM change required. WIS # AN31.10-P-8080GQ - Additional Parts Required: A1664700181 (bracket). This is NOT INCLUDED in the hitch kit and MUST BE ORDERED SEPARATELY - Gas vehicles, the install requires two (2) brackets. - Bluetec, the install requires one (1) bracket. - Brackets are not provided in the kit, but four (4) extra nuts to secure the brackets are included. - WIS instructions for installing detachable components for this retrofit (AN31.11-P-8080-05GQ) lists, for step 4, to fasten assembly plates. The `assembly plates` are the brackets. Included in Kit / Qty for install / Description: A1663100118 / 1 / Long Member A1663100218 / 1 / Long Member A1663101137 / 1 / Cross Member A1663150065 / 1 / Elastomer Fitting A1664407013 / 1 / Wiring Harness A1665404410 / 1 / Wiring Harness A2469005501 / 1 / Control Unit N000000003275 / 8 / Nut N000000003749 / 2 / Screw N000000006409 / 4 / Bolt N000000006964 / 4 / Bolt WIS instructions are under review in Germany (for clarification of installing brackets) We have requested brackets be included in the kit going forward. Until this is confirmed by Germany, the brackets must be ordered separately.
List Price: $970.00 | Your Price $824.50

L-L

Hello all,

Well, I finally got all the parts. I have a few questions regarding the wiring harness from the controller to the rest of the vehicle.

A. The hitch module/controller has 3 plugs. The RED coupling from the vehicle's wiring harness connects to one of the three plugs. The BLACK coupling from the hitch wiring harness connects to the 2nd plug of the controller. But, I can't figure out what goes on the 3rd plug of the hitch controller/module . According to the diagram I have, it is supposed to be a BLUE coupling (diagram below-22.4) which is also supposed of be part of the vehicle's wiring harness. Is there a BLUE coupling at all, or the 3rd plug on the hitch recognition module/controller remains unused/empty?

B. Also I came across 2 different wiring diagrams. One shows the Fuse box behind the passenger's side middle seat. Also it shows the brake controller wires passing under the passenger's seat and under the driver's seat, before ending under the driver's side under-pannel . The other diagram I found, shows the fuse box behind the driver's side back seat. Also it shows the brake controller wires passing under or through the dashboard.
Do you remember which of the two methods you had to use? (My 2015 GL350 has the F4 Fusebox behind the driver's seat, yet I am not sure if the wiring diagram below (pic) is the correct one for the specific year/model.)

C. In the F4 fuse box, how many wires did you have to install, 5 plus the blue fuse holder OR 4 plus the blue fuse holder?
I received the harness from MB but it seemed to be a return so I am not sure if they send me the correct harness. (there are only 4 wires plus blue fuse holder, to install in the fuse box. (the wiring diagram I found online shows both the BLUE coupling for the hitch module and 5 wires plus blue fuse holder for the F4 fusebox - see pic below)

Thanking you in advance.

Ricardoa1

I don’t believe the third is used socket is used. Most controllers I found used that sold the pigtail only has two plugs connected.

ianlp

Hi,
It seems I have the same 2015 GL350 that did not come with the trailer tow hitch. I have been thinking of installing the factory tow hitch and I was wondering if you could be so kind to send me the complete parts list required. Much appreciated.

Best regards,
Ian

L-L

Hey Ian,
Sorry for the late reply.
So...I did A LOT of reading and exchanged A LOT of emails with local dealers as well as MBUSA. MB provided almost zero support since they didn't know.
This is how it goes:
There is a lot of work to be done. MB provided me with several quotes. For everything...around $4500-$5000 (you will understand below what I mean by "for everything" - including parts J,K,L below and at least 8-10 hours of labor).
Part number 166-310-01-00, IS A KIT. I tried to find out what is included BUT NOBODY from MB knows. My understanding is that it includes the actual metal hitch, longitudinal bars that attach to the hitch and slide in the chassis for load balancing, Trailer recognition module, and maybe the 2 harnesses. But again it is not clear, thus I bought every part individually. If you can find out what is included in the kit, then it will cost you much less than purchasing everything individually. I bought some parts used and some new from Mercedes of Miami Online Parts (best prices). https://parts.mercedesbenzofmiami.com/
ALL the parts (individually listed) needed are:
A. Hitch 166-310-11-37 (I bought mine used, but it was like new and included the longitudinal bars and 2 brackets that are needed-see below for the brackets "C")
B. Longitudinal Bars (I am not 100% sure about the part number, but if you check the MB of Miami Online Parts, you might find the exact part numbers- I think it is 166-310-04-18 but also I thing there is a Left and Right with different part numbers. Maybe I am wrong.
C. 2x Brackets - 166-470-01-81 - The brackets hold the blue tank and the exhaust shield. When you remove the impact bar behind the rear bumper, you will understand where the brackets are used.
D. Harness (from 7-way hitch plug to Trailer Recognition Module) - 166-440-70-13
E. Trailer Recognition Module - 246-900-55-01 (you need to install this on the right of the trunk, behind the panel with the net. The mounting bracket is already installed (silver).
F. Harness from Trailer Recognition Module to the rest of the vehicle - 166-540-50-35 (travels to the CAN, SAM, Fusebox F4, and under the steering wheel for the brake controller. Passing this harness is the biggest hassle of the project.
G. Protective impact foam - 166-315-00-65 - It goes on the actual hitch, after is installed and before you re-install the bumper.
Now, there are more parts but they have to do with the cooling system...meaning to keep the engine temperature normal while towing. These are:
H. 850W Cooling fan/engine blower - 099-906-40-00
I. Under shield - 166-520-05-23 - replaces one of the shields under the car for enhanced air flow.
J. Vacuum Line - 166-430-16-29 - I did not use this line yet, since I did not change the engine blower/fan (from 600W to 850W) yet, so I am not sure where it goes.

Also the car needs programing to enable code [550] - Trailer hitch package, which is about 1-2 MB hours ($200-$400). MB technicians have to do the programming. (I believe permission from MB Germany is needed)

I bought the hitch, longitudinal bars, brackets and trailer recognition module online...used but as I said above, they look like new. I got all for about $600.
I bought the harnesses, foam, and vacuum line form MB of Miami for about $240. I did not get the engine fan or shield yet, which are about $1400 for OEM. Aftermarket fan is about $600 plus $120 for the shield. That is ~$720. So about $1400 for both OEM or $720 for OEM shield and aftermarket engine fan).
I strongly believe though, that the MB KIT (166-310-01-00) includes many of the above parts, except maybe C,H,I,J, and maybe one of the harnesses. I suggest to try and find what is included in the kit, before purchasing all the parts individually.

I hope that the above info helps. Also, many thanks to Yeffsy (Jeff). Without his help I wouldn't be able have a clear view of the parts needed, thus I wouldn't be able to help you.

L-L

ianlp

Hi L-L:
Thank you very much. Let me look into the details you have so kindly provided.
Best regards,
Ian

Galen Foster

you make some very good points. Hard to argue with your logic. When mentioning taking panels off which ones regarding wire harness install. I’ve seen videos of the hitch installed but have not seen anyone tackle the harness.