DMF FAIL?? Help please

[ADV]

My dad has a 92 fsuperduty N/A with a zf5 the last time he drove it he was pulling our tilt deck trailer with a 8000 pound fork lift on it and when he started to go up some hills he said it felt like the clutch is slipping but he did not smell burnt clutch. He dripped the trailer about half way home so he could still drive the truck home it moves but slips allot now.

Is this a DMF fail?

 

[franklin2]

How many miles are on the truck and the clutch that is in it? If the clutch was ever serviced, the DMF should have been replaced at the same time. It's a wear item just like the clutch.

 

[rjjp]

Is this a DMF fail?

The DMF is a fail...

Start the truck, put it in reverse then move the shifter half way from reverse to neutral (to defeat the syncro), then slowly lift the clutch off the floor until it FAINTLY starts to grind, then measure the distance from the pedal to the floor, to determine the clutch reserve.

Take the inspection cover off and see if you can wobble the flywheel (rotationally), may need something to pry with.

 

[TWeatherford]

It could be either, but if it were me I'd replace both (or lucky mod the flywheel, and replace the clutch) while I was at it. Unless the clutch was recently replaced or something. Definitely go with a single mass flywheel or lucky mod, and its a good time to go with a 12 1/4" or even a 13" flywheel if it'll fit (can't remember). You need a clutch disk with springs in the middle, and the larger flywheels provide not only more friction surface area but room for more springs, which will quiet gear rollover.

 

[rjjp]

Here:
If release system is greater than 11 mm, and the clutch is suspected, check for clutch reserve as follow:
1. Set the parking brake control (2780) and put the transmission in neutral.
2. With the clutch pedal fully depressed, shift into reverse, then shift half way between reverse and neutral to defeat the synchronizer.
3. Allow the clutch pedal to fully return and adjust the position of shift control selector lever and housing (7210) to obtain light contact between the gear teeth. A slight grind will occur.
4. Slowly depress the clutch pedal until grinding stops. Measure the clutch pedal travel from this position to the full down position (clutch reserve position).
This clutch reserve dimension should be at least 1 1/2 inches. If the reserve is less than 1 1/2 inches, and there are no hydraulic control system concerns, remove the transmission and check for excessive clutch wear. On the 7.3L diesel and 7.5L engines, check for contamination of clutch release hub and bearing (7548) and binding on the bearing retainer. Replace the clutch assembly or clutch release hub and bearing as required.

 

[gatorman21218]

When you shut the truck off can you hear anything rattling?

 

[RLDSL]

My dad has a 92 fsuperduty N/A with a zf5 the last time he drove it he was pulling our tilt deck trailer with a 8000 pound fork lift on it and when he started to go up some hills he said it felt like the clutch is slipping but he did not smell burnt clutch. He dripped the trailer about half way home so he could still drive the truck home it moves but slips allot now.

Is this a DMF fail?

That sounds EXACTLY how my DMF acted the day I hooked up to my carhauler and it folded. No clutch smell, but slip sliding like crazy when trying to accelerate . had to limp the thing along to go pickup a car and then after unhooking it was real weak, but no clutch smell, which it can't really have since that internal overload section is metal to metal, it;s extremely tight and only meant to give way to protect the tranny gears, but they get fatigued over time by heat etc and if you put a non stock replacement clutch in, they become the weak link in the chain