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Old 11-29-2012, 11:53 PM
oltom oltom is offline
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Location: Floida
Join Date: Nov 2012
Posts: 18
Mein Auto: 530i
D-G Drum failure Root Cause

Hello ALL
This post for info only. If previously posted please forgive. Just purchased a 2001 530i with 77K on the clock. Transmission is working fine with NO codes present. Before purchase I knew of this problem area. Before being left on the side of the road I decide to tackle this problem. After talking with numerous associates from ZF transmissions this is what I learned. Yes the D-G drum is light weight and needs to be replaced but the root cause is in the main valve body. Pull up the explode view of the trans. valve body. Find the main valve body part number. Find part number 50.010 or ZF part number 1060 327 138. Locate bore number 50.100. This is the modulation pressure port. It's job is to regulate transmission pressure and does so by continuous rapid cycling. Over time the piston laps or wears the bore of the valve body making it egg shaped, as a result constant pump pressure (approximately 850psi) slips past part 50.100 and puts constant pressure on the clutch pack. The end result BAM! If you've installed a new D/G drum and did not address this, it's only a matter of time.
The good news is that you don't have to pull the tranny to change this part. Drop the pan, the lower valve body plate the neck of the transmission filter goes through is the culprit. When swapping out the piston components no o rings are required. The best price I could find is $140 at CTSC (California transmission supply company). If you don't have a $140 look up Valve body's is all they do. They have a modification fit which includes a reaming fixture tool to over bore the port and an over size piston for the hole. Price for this tool unknown to date.
This also appies to Audi, VW Passet, Porsche, and several others.
My contacts: Lory transmission (ZF rep) Miami, Fl.
Eriksson Industies Old Saybrook, Conn.
Need a new tranny... check out Trans Specialties Wayne, NJ.,
Price $2000 plus tax, shipping $125, and $750 core. This tranny indules ALL modification/upgrades and includes a torque converter.
Good Luck and pass this on.
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