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GLA54 AMG X156 2016 Mountain Grey GAN GT Chiptune 20x8.5 ET40 KUMHO Ecsta PS71 245/40R20
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Discussion Starter · #1 · (Edited)
OK guys, first of all please try to understand that in Thailand, they sold like 5 of the GLA45s, so parts are not stocked. (No other non-AMG 4matic A's are sold here either)
Next, after the warranty was over, I work on my car myself at home.

Right, so that "thud" when the rear diff clutch pack engages/disengages goes from inaudible (with fresh rear diff fluid) to the sound of a free rolling watermelon in the boot (when the rear diff oil gets old). I've been doing the rear diff every 30,000KMs or 3 years based on the documentation.

I took a road trip up to Laos to hang out with some friends for a month, and I took the car. The thud was getting annoying loud, so I though, "OK, I'll call my dealer and order A002 989 02 03 09", which takes about 1 month to arrive via sea freight. (No official MB dealers in Laos, just private importers that specialize in Mercs.) I was getting irritated by the thud every time I drove, so I decided to stop by an auto parts store and managed to get my hands on some Redline 75W-85 gear oil, which has MB235.62 on their product sheet. I was pretty happy, same viscosity, and MB235.62.

Up on a hoist the car went, drained the rear diff, very black, this is still before my "scheduled" next change. Spun the rear wheels, replaced the drain washer, then in went the Redline, Xentry to reset the oil change, and activated the solenoid a couple of times and all was good. The engagement thud was much softer and was easily drowned by the radio. No obvious metal bits that I can see in the black oil.

A few hours later I decided to do some hard pulls from stationary (first gear starts)...and the clutch pack in the rear diff starts to slip, blap-blap-blap-blap then it catches by the second gear. I tried this several more times and it kept slipping. I was an obvious slip, you can feel the pulses of power. It didn't slip when flooring it in higher gears. I drove around like this for a week.

So I looked at the bottle of Redline and realized that it is for LSD, and had FMs in it. "That's probably why the clutch pack was slipping", I thought, so back to the auto parts store I went. The only gear oil rated for hypoids and has EP additives was a conventional base oil by a Thai manufacturer, single weight 90, GL-5 rated, EP additives, hypoid, no FM added. So I changed the fluid again. No obvious metal bits in the oil. Went out to do several pulls and the clutch pack in the rear diff was no longer slipping, it was biting normally. The engagement thud was also minimal, so I just left it at that.

Some weeks later, still in Laos, I ran across a bottle of Motul Gear 300, 75W-90, full synth GL-5, no FM added. I thought it would be good to change again, so I can flush out as much of the conventional oil GL-5 currently in there in preparation for the final fill of MB fluid. After the the drain and fill, I did several hard pulls, everything performed normally. No obvious metal bits in the oil. Two weeks passed and I headed back home, swung by the dealership to pick up the bottle of liquid gold, and went home to change the fluid again. No obvious metal bits in the oil. Everything is still normal at this point, even after about 5,000KMs and many hard pulls and aggressive driving.

This brings me to my conclusion, as I believe there are some of us out there who lives in a country where parts availability is an issue, if you're in a bind and need some emergency rear diff oil for your 45, then go for any GL-5 rated oil, 80 to 90 weight, that does not have LSD additive. It got me home, while still having fun. Now the car has an additional 60,000KMs since that trip and the rear diff still behaves normally. My second point is to do with that Redline oil, it is strange that it mentions MB235.62 and has the same viscosity, yet doesn't work at all, it was WAY too slippery. I try to stay away from MB fluids as much as possible in order to save some money, for coolant I use generic HOAT, transmission I use Valvoline DCT (MB236.21) with the MB anti-foam syringe, engine oil I use any MB229.5 rated full synth, brakes I use off the shelf DOT4.
 

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Rear diff oil should be changed at an interval of no more than 10K miles, IMHO.

Thanks for sharing your experiences. Congratulations on your new car. Welcome to the Forum here. Sounds like you're good with your hands. I look forward to hearing about your trips and driving in general. It's been many years (35 or so) since I've visited your beautiful country. Share pictures as you can.
 

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Thanks for the info on the different fluids and the detailed post. Good to know Redline didn't work.

I do have one question: did any more fluid drain out while you spun the rear wheels or after you spun the rear wheels?
 

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Hmm, might have to re read the fine print on the oil guy entry for my favorite version of unicorn juice:

Ford Genuine Fluid XT-M5-QS Full Synthetic Manual Transmission Fluid


Just the best feel in the 6 speed cone synchro box

mebbe it has magic modifiers of the friction kind
 

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Thanks for the info on the different fluids and the detailed post. Good to know Redline didn't work.

I do have one question: did any more fluid drain out while you spun the rear wheels or after you spun the rear wheels?
Its a bit wasteful perhaps, depending on how much subsequently finds its way to hedgetrimmer chainsaw, hinges, etc,
I, would if diy;ing this rumour/wives tale/past practice filled topic

pour in a couple qts of decent grade, same spec "superTech" fluid spin it 21 spins anti clock, and 21 clockwise

then drain that and use it as you see fit. well, "sewer drain lubricant" is poor form, but you get the idea

whatever is left just saw an order of magnitude's worth of dilution.

plenty good enough
 

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Rear diff oil should be changed at an interval of no more than 10K miles, IMHO.

Thanks for sharing your experiences. Congratulations on your new car. Welcome to the Forum here. Sounds like you're good with your hands. I look forward to hearing about your trips and driving in general. It's been many years (35 or so) since I've visited your beautiful country. Share pictures as you can.
Agree, since it's hard to get maint. stuff like this it would be best to buy 2 of everything needed in advance.
 

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Mark, totally hear you about oils and LSD's. Too much slip lubrication or Moly additives and plates don't work anymore . In my 993, I have q Guard LSD- the transmission and LSD totally perform differently or don't perform well depending on oils used.. These are also affected by ambient temperatures.. Some oils which work well during the summer will make it feel like you're fighting the synchros in the winter..
 

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MadDogMark, thanks for the great write up and glad your car is performing well now. How did you activate the solinoid? I've been trying to figure that out for awhile. I've changed mine several times, but have not figured that step out. Thanks.
 
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