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F250 Clutch SMF Vs. DMF

 
  #31  
Old 02-04-2011, 06:12 AM
dishman5000
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if you buy the clutch from advance buy it online they do free shipping over $75 and also yahoo" advance auto parts Coupon codes" to use at checkout I think there is on for $50 off a purchase of $200 or a 20% off and a few otherones
 
  #32  
Old 02-04-2011, 09:12 AM
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i think its more like any low idle RPM operation like slow going across a field..... alot of stop and go traffic ect.
 
  #33  
Old 02-04-2011, 10:04 AM
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Actually a diesel can produce a rotational pulse at any RPM, the motor just has to be relaxed at that RPM ... meaning no load. no RPM change, etc...

And it's not a shock ... it's a pulse!

-Enjoy
fh : )_~
 
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Old 02-04-2011, 11:34 AM
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ic so at any rate the DMF isolates this from the driveline.
 
  #35  
Old 02-04-2011, 11:47 AM
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Transmission ... Mainly the input shaft.

A DMF has nothing to do with anything after the transmission.

Without a DMF the transmission absorbs the pulse, thus beating it to death.

-Enjoy
fh : )_~
 
  #36  
Old 02-04-2011, 12:48 PM
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Originally Posted by Festus Hagen View Post
Yes, the SMF will beat your ZF to death ... Yup, it may take years, but it'll happen!

Most of us will likely never live to see it happen, depends on how much you idle your SMF Diesel.

The DMF does not absorb drivetrain spikes ... The springs in the DMF are no where near strong enough, under load the DMF locks up and becomes like a SMF.

The purpose of the DMF is to absorb the rotational Pulse caused by a idling Diesel Motor, thus what causes Gear Roll Over thus what will in time beat your ZF's gears & splines to a pulp!

This did not become an issue until technology started playing parts and components were being made closer to their maximum yield. (i.e. Smaller and lighter)

Best way to explain the issue is ...
Take two fingers on one hand and give the Peace sign ...
Take one finger on the other hand and stick it between the other two ...
Then shake the hand with one finger ... It will beat the insides of your two fingers on the other hand!

Same thing happens to the gears & splines in a Diesel Transmission.

-Enjoy
fh : )_~
LOL! So it will beat it to death IF both you and the truck live long enough to see it happen!

In my case, since the most of the truck is 25 years old (the engine is 22 years old and tranny is only 15 years old), and since I don't view the truck as some kind of precious family heirloom to be passed down through the generations, I don't think I'll worry much about it...

FWIW, when I swapped the 7.3 out of an '88 into my truck (replacing the original '86 6.9) the gear rollover noise decreased very noticeably. Enough that I was able to reduce my idle from 800 RPMs back down to around 650 or 700. Anybody got any theories why that would be? I re-used the same clutch, pressure plate, and flywheel off the 6.9...
 
  #37  
Old 03-02-2015, 10:36 PM
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man i tried posting something smart sounding but i'm new to all this. but so far what i've read about the dmf is that it original purpose (maybe that's changed) was to reduce the vibration transmitted to the clutch caused by low rpm and high torque because as technology was developing engines with more torque output at lower rpms current clutches were found inadequate for the developments in the engines.

so it seems that the DMF wouldn't be the be all end all technology to reduce such vibrations. i'm new to all this stuff but couldn't you just get a beefier clutch setup with a SMF and do just fine?

recently either my clutch or my DMF (or both) crapped the bed, thus i am at the point to decide: DMF or SMF.

i remember reading that the ZF5 was designed with high tolerances between gears for heat expansion after warmup etc. so it seems that Overthrow is/was expected in these transmissions.
i only bought my '86 6.9 less than a year ago, only 100k miles on it, i'm the 3rd owner and it sounded like hell man! it's so loud and it has a DMF. and what is the noise from? overthrow? thats as far as i can tell.
my solution was to just disengage the clutch at lights or when i needed to idle.

so if low rpm is going to eat up the gears in the ZF than why not do the SMF with the soft clutch cause holding that DMF clutch in at stop lights was starting to make me walk in an arch.

i also hear that ZF5s are damn near bulletproof.
i'd say: if you can afford it go with the dmf, it's manufacturer specified.
i'm going with the SMF because i find it weird that some people on here act like the DMF is the Holy Grail, or the achille's heal of these transmissions and i wanna find out for myself. oh, and i'm poor..

so long as it lasts me long enough to afford a non-obsolete truck i'll be happy.
don't get me wrong, i love my 6.9 and i have faith that it will run long enough for me to go through the SMF i put in it.. then maybe i'll try a DMF.
 
 
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