Mercedes DCS Transfer Case Rebuild Kit A2511251400

If your Mercedes ML350, GL450 or R350 4MATIC clunks from under the center console when you pull away, rattles on and off the throttle, or has a whine that climbs with road speed, the chain in the single-speed DCS transfer case is the usual suspect. This kit has the parts for a full rebuild of that case: an HV-091 / HV-523 style drive chain, four ball bearings, three needle bearings, three oil seals, four sealing rings and a bushing. It is listed against case number A2511251400 and the A2512800700, A2512800800 and A2512800900 family.

What the transfer case does on a 4MATIC ML, GL or R-Class

The transfer case bolts to the back of the 7-speed automatic and splits engine torque between the rear propshaft and the front axle. On these trucks a chain carries the front share from the main shaft to the front output sprocket, and an open center differential lets the axles turn at different speeds in corners. Transmission Digest points out that the case has its own small oil sump, separate from the transmission, and that on chain-drive ML models the chain wears and stretches when that oil is not changed around every 40,000 miles. A stretched chain slaps the inside of the housing as you get on and off the throttle, and that is the noise owners hear. Because the case holds so little oil, the bearings on the same shafts see the same neglect as the chain.

Symptoms of a worn DCS transfer case

• A clunk or knock from under the center of the vehicle when pulling away or shifting into Drive or Reverse
• A rattle or slap on acceleration and again when you lift off, from the chain hitting the case
• Whine or growl that rises with road speed, from worn bearings
• Grinding or a skipping feel under hard acceleration once the chain is badly stretched
• Oil seeping at the input seal, at the output seals, or at the seam between the transmission and transfer case
• Warning lights for the transmission or stability system after the chain has been slapping for a while

How to confirm it before you buy

Noise is the number one 4MATIC complaint and it is easy to blame the wrong part. Put the truck on a lift and listen with a stethoscope at the transfer case, both differentials and the propshaft center support bearing. Transmission Digest suggests disconnecting the rear driveshaft when needed to take that support bearing out of the picture. Check the transfer case oil level and condition too; dark, metallic oil and a low level point at this kit. If the noise is coming from inside the transmission itself, start with our 722.9 common problems guide. Scanning all modules with a Mercedes full-system scan tool will also show whether there are stored faults that point elsewhere.

Fitment

Listed fitment is the M-Class W164 and W166, the GL-Class X164 and X166, and the R-Class W251/V251, 2005 to 2015, with the standard single-speed case. It does not fit trucks with the Off-Road Package; those use the two-speed case with low range and a locking center differential, a separate design. Mercedes revised the transfer case more than once in this span, so read the part number on your case and compare it with A2511251400 and the A2512800700 through A2512801200 numbers before ordering, or send us your year and VIN and we will check it. The GLK uses a completely different integrated unit; that part is our 722.9 GLK transfer case planetary. Other Mercedes transmission parts are on our 722 series parts page.

Install notes

• The transfer case comes off the back of the transmission with the front and rear propshafts and the front axle shaft unbolted. Support the transmission before removing the case.
• Split the case halves carefully and keep track of shims and snap rings. Clean every sealing face down to bare metal before applying fresh sealant.
• Inspect the sprocket teeth and the chain guide. A chain that stretched long enough often wears the sprockets and can break the guide off its studs, and new parts here will not save a worn sprocket.
• Press in the new bearings and seals squarely and lubricate every lip before reassembly.
• Refill only with a Mercedes-approved transmission fluid for the transfer case; the capacity is small, so measure it rather than guessing. Our 722.9 fluid type guide explains the approval sheets, and this is a good time to service the transmission with a 722.9 service kit.

Will this kit fit my ML350 with the Off-Road Package?

No. Off-Road Package trucks use a two-speed transfer case with low range and a locking center differential. This kit is for the standard single-speed DCS case only.

Can I replace just the chain?

You can, but the bearings and seals have the same miles and the same oil history as the chain. Since the case has to be split either way, doing chain, bearings and seals together saves a second teardown.

What fluid goes in the transfer case?

A Mercedes-approved transmission fluid made for the transfer case. It is not shared with the transmission sump, so it has to be drained and filled on its own. Confirm the exact approval and capacity for your VIN in your service data.

How do I know the noise is the transfer case and not a differential?

Listen at each component on a lift with a stethoscope. A chain rattle is loudest at the transfer case on throttle changes, while a differential or center support bearing noise usually changes with load and speed in a different spot. Disconnecting the rear driveshaft can isolate the center support bearing.

How do I confirm my case matches?

Read the part number on the transfer case housing and compare it with A2511251400 or the A25128 numbers listed. If the tag is unreadable, send us your year and VIN and we will check it before you order.

• 722.9 Common Problems and Fixes
• 722.9 Fluid Type and Capacity
• 722.9 Identification Guide
• Complete ATF Fluid Types Guide