TRANNY RATTLES!!

[zalez]

Hey everyone,

Ive been having issues with my truck for a while now.

1997 f-350 7.3 powerstroke turbo diesel, dually.
Manual Transmission


PROBLEM: My transmission rattles!!

DETAILS: After my truck warms up and im driving everything is fine.
When i stop at a red light or just make a stop, the tranny rattles
like its going to fall off. "BLAK,BLAK,BLAK,BLAK" The truck shakes as
well. Well when i rev the engine the the rattling stops and truck
sounds normal. Can some help me out or guide me to what the
problem might be. Thanks.!!


NOTES: The tranny rattles on and off. It doesnt happen all the time.

[Patrick Feeley]

If you still have the factory DualMass FlyWheel (DMFW), it a likely culprit. The DMFW has two masses with dampening springs between them. The springs are to dampen vibrations from the engine. Many times the springs fail, the spring retainers fail, or the springs just get weak and the flywheels fail (which can cause vibration, rattling, mimic injectors "missing", and even crack transmission cases).

Replacing the DMFW is expensive just for the parts. Many folks opt to replace the DMFW and clutch with a Single Mass FlyWheel (SMFW)/Clutch kit. The kits are available from a host of suppliers (Luk, ValAir, SBC etc) and are generally cheaper than just the DMFW alone (no clutch). The clutches are not interchangeable between the two setups.

The advantages to a SMFW setup: More reliable, easier pedal compared to the DMFW, you can resurface them, and they're cheaper. Drawbacks: A bit noisier due to "gear rollover" noise and very low rpm and speed (lugging around in 1st or 2nd under 1500 rpm). Some find it objectionable, but I didn't mind (it is a truck).

You can check the DMFW by removing the flywheel inspection cover and look at the dampening springs to see if they are all there with the retainers. Try to counter-rotate the two masses against each other. Measure the distance of the counter-rotation at the flywheel rim. Anything more than 5/8" and it's bad.

Cheers!

[zalez]

Hey Thanks for your reply!!!

Are there any images you can direct me to see what the dampening springs and retainers look like when bad?

How many springs are there supposed to be?

Can i check all this while the tranny is still on the truck?

Thanks,

[Patrick Feeley]

Sorry, I don't have a picture. If you look up in there with a flashlight (tranny does not need removal ... just remove the inspection cover) you'll be able to see them and the end retainers. Just make sure they are all there (I forget how many maybe about 6 - 8?) and check the measurement too. Cheers!

[madpogue]

Originally Posted by Patrick Feeley

Drawbacks: A bit noisier due to "gear rollover" noise and very low rpm and speed (lugging around in 1st or 2nd under 1500 rpm). Some find it objectionable, but I didn't mind (it is a truck).

The first time or two you drive the truck after the job, you'll chirp the tires and/or lug/stall it. Before you know it, the "brain in your leg" will learn the right clutch action to engage smoothly without lugging, and the rollover noise will diminish and/or you'll just tune it out.

Try to counter-rotate the two masses against each other. Measure the distance of the counter-rotation at the flywheel rim. Anything more than 5/8" and it's bad.

This is the key. If any spring parts have come loose, they'll probably fall out when you remove the inspection cover. But this movement is the important thing. And to emphasize what Patrick mentioned earlier, the big risk is that the two masses will separate at speed, with bits of spring/retainer being thrown outward with great centrifugal force. That's what can crack the tranny case. And since there's no separate bolt-off bellhousing, it's the case for the WHOLE tranny that goes.

[Patrick Feeley]

I mostly noticed it when I would downshift into 2nd or 1st going slow (like when the fiver is hooked up). Just kind of startles you at first, but you get used to it (and tune it out). Cheers!