RostamDastan

Hi KristyKustom,

May I ask at what speed do you go up/down the grades? Also, do you use paddle shifters or let the transmission pick the gears?

I'm in the east coast. Going uphill, I leave the transmission in D. I've wondered whether or not its better to manaully shift. I've experimented with different speeds going uphill (40, 50, and 60 MPH going up 10% grades in Appalachian). Coolant temperature does not change. I don't have access to transmission temperature. GL consumes a lot more diesel at 60 MPH. These are shorter grades, maybe 2-3 miles. I'm assuming grades are longer in the West.

Going down, I shift to 2nd or 3rd gear, reduce the speed to 30 MPH, and start the descent. When the speed gets to 40 MPH, I apply the brakes to reduce the speed to 30 MPH. I repeat this process, until descent it over. It usually requires 5 or so brake application to go down a 2-3 mile grade.

Any feedback is appreciated!

Thanks!

DennisG01

Rostam,

Tranny temp (unless your diesel is different than mine - '08 320) is one of the "pages" in the center dash display. You just have to toggle through to find it.

SFCabs

Wow, where? I've never seen it in any the display by the speedometer or in the nav unit of my 2008 GL320.

I've enabled the hidden menu by hitting the reset button 5 times which shows you the voltage but I haven't seen transmission temperature in there either.

clvincent

i dont remember seeing trans temp in my 08 display either, please tell us the sequence you use to get to that

DennisG01

My apologies, guys. I haven't been using the truck in a while and I was remembering wrong. I was thinking of the engine coolant temp and mixed that up with tranny temp in my head. Sorry for the confusion!

KrustyKustom

I leave my GL in D 95 percent of the time. Mainly if I manual shift it is because I am in a tight area, like a campground and come up to a immediate steep hill. It will want to go a gear high which lugs it.

I use a ProPride anti sway equalizer hitch. Great results.

Also super regular maintenance on the GL. I drain and refill the transfer case at every oil change, differentials at 15k intervals.

The airmatic is the cats pajamas though. Never thought much about that feature until I towed with it. It really adjusts for the load so well you do not feel any porposing or "heavy" front axle feel you get on a steel non adjusting suspension.

Removed underbelly pans as I live in a hot climate, seems to help.

114k miles so far!

RostamDastan

Thanks for the info KrustyKustom! I appreciate it. Would you mind sharing the rough speed at which you go up and down the grades? I'd like to know whether I am going too fast or too slow

Callisto1

I can second the advice from KrustyKustom, at least as far as towing an Airstream @5000 lbs +/-. Just stay on top of the fluid changes, and use quality stuff.
Just returned from a 5000 mi trip up the east coast and back through Applachian/Smoky Mountains. Zero problems, and I don't use sway bars or an equalizer. If you have a trailer that catches the wind, maybe you need those.
Prior to trip, I changed out my tranny pan for the Weistec, (see earlier post) which also meant replacing about half the fluid. (I used Pentosin) I did not drain the torque converter, since I had done a full flush 20k earlier.
I also removed both belly pans under the engine to encourage better airflow.
While I do not have a tranny temp gauge, I never saw my coolant temp rise above 92-93C, even when towing up 7% grades on the highway, and as high as 9% grades on back roads. Normal highway temp without a trailer is 90C in South Florida.
I plan to go in Friday to replace fluids in engine, both front and rear differentials, transfer case, and tranny/filter. I will post a report on how all the fluids look after the summer of trailer wear and tear.

KrustyKustom

Sure, I tow a 30 Airstream and my towing weight ranges from 6700 lbs to 7100 lbs (depending on water tank). I hit I70 which has some gnarly grades and keep it about 50mph. I like to settle in to about 2400 to 2600 rpm and accept whatever speed it allows. Usually 5th or 4th gear on the big grades. Only grade that threw me for a 3rd gear was Wolf Creek pass! Wow..thats steep.

Thoroughly impressed with the GL as a tow vehicle.

RostamDastan

Thanks KrustyKustom!

I agree. GL is an impressive tow vehicle. Would have been the perfect tow vehicle had it had an exhaust brake. But its big brakes are really good. I once lost my trailer brakes coming down a 10% grade (we have a 26' Avion, weighing about 6000#) and GL's brakes alone controlled everything really well.

Callisto1

After towing our 26 foot Airstream about 3500 miles this summer, and maybe another 1000 earlier this spring, I second KrustyKustom’s advice from 3 years ago. CHANGE YOUR FLUIDS FREQUENTLY! The diesel GL (and probably the ML) are fuel efficient workhorses; and great tow vehicles that in my case didn’t even need a WD hitch or anti sway bars. However, it does put tremendous strain on the vehicle drivetrain, so fluids should be changed much more frequently than MB recommends. And you should do that yourself because with dealer service you never get a real report from the tech who did the work.

RECAP:
My 2010 GL350 has 73k mi, and is driven on short 5-10 mile trips in South Florida for 10 months a year totaling roughly 4000 miles. (It it not driven at all many days.) Then for about 2 months in the summer, we drive to NC mountains 850 miles each way, and once there most days drive 30-100 mi on the Blue Ridge Parkway or other 4 lane roads at modest speeds (40-60 mph). So the car has a warm weather short driving history most of the year, then some long distance easy diesel speeds that more than double the annual miles in just 2 months.

Always serviced by local dealer at recommended intervals while under warranty. Mistake. They forgot to fill the Adblue. They didn't change the fuel filter. They kept changing wheel speed sensors when it was the entire ignition control module that had intermittent failures.(They admitted later they didn’t realize it was a diesel. Really?) Also, as far as I’m concerned, the Mobil1 only protects the DPF, not the engine, so I don’t want them changing my oil. Last 3 years, I either did my own service or used the dealer in NC for big stuff when it happened while on vacation up there.

In June of 2016, I changed differential oil, but a mixup with my DIY garage had them order the 234.15 blue ATF instead of the 234.14 red. So I didi not change the tranny fluid or transfer case. 1000 miles later, in NC mountains, the oil cooler went kablooey and needed immediate repair. I took it to NC dealer, and while there asked them to also do a FULL FLUSH of the transmission and torque converter, and drain and refill the transfer case. Ultimately a $5000 job (because the engine mounts had melted) left me a little stunned, so I did not notice in the 4 page single spaced invoice that I was only billed for 6 liters of ATF; and that under the transfer case service line,they billed billed for gear oil.
Bottom line, differentials were drained and filled by me at June 2016 at 60k, and maybe again by dealer a few weeks later at 61k. Transfer case and transmission were SUPPOSED to be drained and filled at 61k. I suspect they only did a half drain/refill on the transmission, and MAYBE the transfer case as well. June 2017 at 68k, just before long trip towing the airstream, I replaced the tranny pan (but did not drain the tc) with the Weistec pan that has cooling fins and holds 2.5 liters more. Pumped about 7 liters of Pentosin 234.14 into the tranny and let it drain out until heavy drizzle according to MB specs.

REPORT AFTER SUMMER OF TOWING
This year we didn’t go directly to NC mountains, but took 3 weeks to tow a 1968 Airstream up the coast as far as Washington DC for 4th of July, then back down through VA, TN and KY to NC mountains. Then parked trailer in NC for a month before towing back to SoFla.
Good news is GL towed the airstream like a champ. No sway, no laboring, no excessive bouncing or porpoising from bumpy roads. Truly a joy to drive.
Bad news is what the fluids looked like when I drained them.

The transfer case fluid was in the worst shape after only 12,000 mi (if we believe the dealer did change the fluid at 61k.) On the color grade scale of ATF where cherry red is perfect and black is awful... transfer case fluid was to the wrong side of awful. Looked more like engine oil. Same report at KrustyKustom.
Next worst was the front diff. Pretty burnt as well, and a lot of silvery fine particles in there. None of which would stick to a magnet, so I’m, not sure what the metal is. I myself put in 80w 90 Mobilube, not my first choice but what I could get at the time and approved under MB spec. It is also possible dealer changed diff oil at 61k because my invoice shows a charge for gear oil. They originally recommended 85w 90 for the front, but have apparently revised that to 75w 85. At this point, seems like a craps game to me regarding what weight to use. Today I refilled using LiquiMoly 85w 90. The rear diff, where I also used the 80w 90 mobilube, was nearly perfect. There were a few silvery fines that didn’t respond to a magnet, but otherwise, rear diff fluid looked great.
Last up, the tranny itself. Fluid was a little burnt. “Time to change” on the color scale, but not "OMG time to rebuild!!” And no fine particles on the magnet. Bear in mind though, most of this fluid had less than 6000 miles on it after I replaced the tranny pan.

Conclusion: If you tow, change your transfer case and front diff every year. It only takes only 1/2 liter ATF and 1.3 liter gear oil. And check your tranny fluid for signs of early deterioration.
Best of luck!
Next up, I am hoping to start a thread about adding a larger tank for the transfer case, since that seems to take the most abuse.

clvincent

Totally agree on not trusting the dealer on changing fluids when towing or not

I buy my own fluids/filters and have my indy do them

Oil at 5000
Air filter, transfer case fuel filter at 15,000
Transmission every 20,000 and diffs every 25,000 but may bump that earlier since you guys are and are seeing some dirty fluid

My truck had a book of dealer service records when i bought it
and it was obvious that the PO had approved anything mercedes wanted to do
Thousands of dollars in repairs and fluid changes
Yet diffs and transfer case were never done, what a crock

johny75

My mechanic who is a MB diesel guru says to remove all those panels anyway as these engines tend to run too hot in general. In general not having any covers anywhere at least shows you early problems that otherwise might be concealed for some time. .. and the engine noise is not any bigger,.. trust me!

goalie_k

I took the engine cover off this past weekend and did notice a faster recovery time when things heated up while towing up to the White Mountains. Next step remove the belly pans.

smiledr996s

I am not currently towing but hopefully will in near future. Was curious what fluid change recommendations would be for trans,TC,and f&r diff? As well as brand and weight.

I had had been following 40k for trans and TC and 80k for differentials.

Also curious how many are using the weitec pan and thoughts on it.

Thank you.