Deadeye
11-10-2005, 09:57 PM
6splb7 had a question about dmf help:
http://dieselplace.com/forum/showthread.php?p=772006#post772006
Here is the explanation of the dmf problem, the SMF rattle, and the potential solution(s):
As I am sure most of you know, the semi trucks have large diesel engines and most are manual transmissions. They have a similar rattle issue as our pickups. The semi's don't use the DMF. With their SMF they will have the same rattle in neutral with the foot off the clutch pedal. The cause is called diesel spike.
At low idle the diesel engine rpms spike. When the clutch is engaged to the input shaft it transfers the spike thru the input shaft to the syncros, gears, etc. when the clutch pedal is pushed in the spike does not go into the tranny. Given very extensive idling, there will eventually be some tranny damage.
This is one reason GM, Ford, and Dodge have tried using a DMF. The purpose is for the flywheel to absorb the spike, reduce the noise, and protect the tranny. The problem with the DMF is that there is just too much torque and constant spikes for them to last. My understanding is that most Dodge and Ford handshakers have been switched over to SMF for the same reason that I am working with SBC on one for the Duramax: the DMFs don't last.
On the semi trucks the input shafts have an "anti-rattle and spline saver" hub. This is designed for some spacing to absorb the spike at low idle rpms so that the spikes don't move into the transmission.
South Bend Clutch is beginning a design process for a similar product for diesel pickup trucks. They plan on doing the Dodge first and hope to have it done by spring. Then the will make some for Fords and Duramax's.
It is too early to determine much about how these will work on pickups, or what the cost will be. If I understood correctly, there will be no need for changes in current SBC clutch kits for these spline savers.
In the meantime, I would recommend keeping the clutch pedal to the floor at idle. If you get out of the truck and leave it running there are three other options: 1) forget about it and just let it rattle 2) put the engine on hi-idle this will eliminate the spike, or 3) use a pipe or rod to hold the clutch pedal down.
The third option is one I have done for quite a while. In the next couple of weeks I will have a simple product for this purpose that should be pretty easy to put in and take out.
http://dieselplace.com/forum/showthread.php?p=772006#post772006
Here is the explanation of the dmf problem, the SMF rattle, and the potential solution(s):
As I am sure most of you know, the semi trucks have large diesel engines and most are manual transmissions. They have a similar rattle issue as our pickups. The semi's don't use the DMF. With their SMF they will have the same rattle in neutral with the foot off the clutch pedal. The cause is called diesel spike.
At low idle the diesel engine rpms spike. When the clutch is engaged to the input shaft it transfers the spike thru the input shaft to the syncros, gears, etc. when the clutch pedal is pushed in the spike does not go into the tranny. Given very extensive idling, there will eventually be some tranny damage.
This is one reason GM, Ford, and Dodge have tried using a DMF. The purpose is for the flywheel to absorb the spike, reduce the noise, and protect the tranny. The problem with the DMF is that there is just too much torque and constant spikes for them to last. My understanding is that most Dodge and Ford handshakers have been switched over to SMF for the same reason that I am working with SBC on one for the Duramax: the DMFs don't last.
On the semi trucks the input shafts have an "anti-rattle and spline saver" hub. This is designed for some spacing to absorb the spike at low idle rpms so that the spikes don't move into the transmission.
South Bend Clutch is beginning a design process for a similar product for diesel pickup trucks. They plan on doing the Dodge first and hope to have it done by spring. Then the will make some for Fords and Duramax's.
It is too early to determine much about how these will work on pickups, or what the cost will be. If I understood correctly, there will be no need for changes in current SBC clutch kits for these spline savers.
In the meantime, I would recommend keeping the clutch pedal to the floor at idle. If you get out of the truck and leave it running there are three other options: 1) forget about it and just let it rattle 2) put the engine on hi-idle this will eliminate the spike, or 3) use a pipe or rod to hold the clutch pedal down.
The third option is one I have done for quite a while. In the next couple of weeks I will have a simple product for this purpose that should be pretty easy to put in and take out.