DIY 4Matic Front Differential

8/13/2019 DIY 4Matic Front Differential

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Items needed:

Mityvac Hand Vacuum Pump or mityvacBrakeBleeding Kit. These come in a wide variety of models.

The gun can be made of plastic or metal. I have usedthis one for many years for brake bleeding and thoughtit would also come in handy for this job. This is theplastic version which is very inexpensive, available atauto parts stores, or online, for under $20.00.

Lower Unit Gear Lube Pump, is designed for marine

outboard motors but widely available at most auto partsstores and online also. It fits most gear lubricantbottles, usually under $10.00.

Extra hose piece to extend Gear Lube Pump hosereach. Same size that comes with mityvacfits OK. Itwould be interesting to experiment with a smaller

diameter hose to extract fluid out of differential. I thinkone could get even more out with a thinner sectionhose, widely available at most hardware stores.

8 mm socket Hex drive with corresponding ratchet andextensions universal joint recommended - or Allenwrench.

Fill/Drain plug copper seal washer from dealer.


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Hydraulic jack and proper jack stand or lift if you arelucky to have one.

Last but not least, Synthetic Gear Lubricant from thevariety of Daimler approved lubricants. I used Mobil 1LS 75W-90. Look for the Mercedes-Benz star on cap ofbottle as shown on picture.

Drip pan.

Steps

I had replaced the rear differential fluid a couple of weeksearlier on my MY 2000 4Matic Wagon and I felt I needed todo something about that front differential, before it wouldtake my sleep away.

I decided to do an exploratory job to evaluate feasibility, andended up doing it right then and there!

I knew there was no drain plug but only a fill plug. I hadalready planned to try the mityvac for this task. I will referto said drain plug as fill/drainplug for this write up.

Overall its a very easy job that should not take more than 20

or so minutes excluding setup and cleanup time. Since I hadnot prepared in advance to do it, I missed a couple of things:

Get the fill/drain plug copper seal washer from the dealerand an assortment of hoses in different diameters for themityvac. I reused the copper seal and the standard size


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hose I had worked very well. I dont know the torque valuefor the plug, which is not that critical, since its not a pressurelubricated unit.

The fill/drain plug is easily removed through the passengerside wheel well with a ratchet and proper extensions which Ibelieve is the easiest or from underneath the car with an

Allen wrench. Access is very good from either one.

Most important step is to get as much hose in through theopening as possible. I could get about 10 inches (25 cm)with the standard hose supplied with the vacuum pumpwhich has an outside section diameter of about 6/8 (10mm).

I was impressed I was able to easily pump out a goodamount of old dark (and stinky) fluid, about 420 ml (13.52 fl.oz). Specification capacity is 0.5 US qt (460 ml). I believeusing a smaller section diameter hose would allow to geteven more fluid out.

This job was done on a cold vehicle with an ambienttemperature of about 45 F (7 C) and light rain. You can wellimagine a warm differential fluid and warmer weather thereshould be an improvement in the amount extracted! I let thatto other fellow forum members to find out and report back!

Enjoy your Mercedes 4Matic!


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DIY 4Matic Front Differential