almost 200,000 miles on G56

[betterthanstock]

So if the clutch has zero wear, why not replace just the springs in the DMF, with stronger ones, and keep on trucking? Can the DMF be repaired, or is it riveted/welded together and cannot be repaired?

 

[GCroyle]

Dmf

This DMF is from the same basic design as the DuraMax, the common failure on the DuraMax version is that the secondary F/W gets "loose" from the primary side of the F/W. The secondary is piloted by a bushing, the DMF for the 7. 3L Ford used a double row ball bearing between the secondary and primary, I have never personally seen one of those with the same failure but we have seen our share of DuraMax DMF's that have gone out of balance from the bushing wearing out and the secondary shifts position releative to the primary. Remember, the secondary is carrying the entire clutch pack and a loss of centerline alignment will create an out of balance condition that is felt with the engine running, increase RPM and hang on! We do not have any first hand reports on the G56 other than based on the sample that we purchased it uses the same design, however it may have design modifications to help address this issue. We will be taking our new 2007 5. 9L G56 truck apart this month to start development of our system.



Regarding the lack of wear at almost 200,000 miles. Lets give the driver a pat on the back for using the clutch correctly. To achieve this service life it sounds like the clutch was almost always looking at 1st gear starts from an engine at idle speed, then respectfully shifted and the pedal was not used as a foot rest.

 

[steved]

... the DMF for the 7. 3L Ford used a double row ball bearing between the secondary and primary, I have never personally seen one of those with the same failure...

I have a friend with a 97 stroke that paid $3700 when his DMF failed at 120k... not that it is common, but it happens... stock truck, probably towed 25% of it's life...



steved

 

[GCroyle]

7.3l Dmf

Steved,



Let me add a little bit, we have seen Ford DMF's failing for years, solid conversions for these are extremely popular for the entire clutch aftermarket. But the common failures for the Ford DFM relate to the torsion damper (visible springs) and internal (not visible w/friction material) torque limiting clutch, not the double row ball bearing that pilots the secondary to the primary. The springs wear in the pockets, the isolators wear out, the clutch pack in the DMF can be contaminated from oil and the DMF is done. These parts wear out. I counted 128 individual parts in a Ford DMF down to the rivets.