ZF-5spd Single or Dual Mass

Just picked up rebuilt trans the other day and before installing, I'm considering changing back to a dual mass flywheel to eliminate the roll over noise. What was the original problem with the dual mass flywheels? Why does everyone want to change to single mass?

single mass= less parts to go wrong.
clutches are a PITA!!!!
do it once and be done with it!

This truck had the factory dual mass in it when I bought it. Zero gear roll-over noise. Then after several years of use it started making a noise when you first started the engine. It would always go away with a quick tap on the gas pedal. The guy at my state inspection garage told me the noise was coming from the dual mass flywheel and that I should replace it with a single mass. I followed his advice and while the clutch worked just fine and start-up noise was gone, the gear roll-over noise has been terrible. "New" dual mass flywheels / clutch / pressure plates are getting harder to find and more expensive than SM conversions. I liked the dual mass much better however the lack of replacement parts indicates they may not be around much longer. I'm also wondering if the rebuilt trans will make more or less roll-over noise.

If the dual-mass flywheel comes apart while the engine is turning, the escaping bits can grenade the transmission case. Since there's no separate bellhousing, you're looking at replacing the whole case.

At least on a ZF the front is easier to replace than the rear? When I do my ZF swap I'll be going single mass. Normal flywheels just work, at IDI RPM no worries about grenading one. Not sure how loud this rollover noise is but as much as I hate noise I'll deal with it to have something that just works. What is it about the ZF5 that makes noise as compared to a NV4500 or other similar use trans that doesn't have these problems? Any particular ATF or oil that quiets it down and still lubricates the pocket bearing and other crevices sufficiently?

The problem with the smf kits out there is there's 2 different ones for the same engine, one has double the springs in the hub and doesn't make any noise, the other just has 4 springs and I think it's considered the HD version, I'm using a regular Luke kit and it's dead silent, don't go cheap and no name brand and you'll be fine, also don't mistake the gear growing noise while lugging as roll over noise, all smf make growling noises while lugging.

catbird7 said:

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Just picked up rebuilt trans the other day and before installing, I'm considering changing back to a dual mass flywheel to eliminate the roll over noise. What was the original problem with the dual mass flywheels? Why does everyone want to change to single mass?

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Because people are cheap. The one other reason is if you have a truck that is making a lot of power, the dual mass has a safety clutch pack in it that will slip to protect the tranny and the driveline. They make single mass systems that are larger than the dual mass for the big power guys also.

The dual mass has parts that wear. It should be changed when the clutch is worn out and needs to be changed. There never was a recall or any chronic problems with them that I have ever heard of. People who have horror stories about them had many many miles on them, they were way beyond their service life. If you want a nice quiet truck, put the dual mass back in.

Dual mass flywheels are nothing new and not only found on zf equipped idi trucks. There other cars and trucks that use them also. If I had the money, I would put one back in my truck.

ifrythings said:

The problem with the smf kits out there is there's 2 different ones for the same engine, one has double the springs in the hub and doesn't make any noise, the other just has 4 springs and I think it's considered the HD version, I'm using a regular Luke kit and it's dead silent, don't go cheap and no name brand and you'll be fine, also don't mistake the gear growing noise while lugging as roll over noise, all smf make growling noises while lugging.

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with how cheap the LuK smf is, its almsot harder to find a cheaper no name part! i got my smf flywheel conversion kit from Luk off Rockaupo for like 360 buck shipped!

I've noticed there's two sizes of SMF kits. What's the difference and how do you determine which to use? Is it determined by the size of your clutch?

There are two different discs available for the single mass setup. I've been through the same pain with rollover noise, and swapped my clutch and trans more times than I care to admit. Anyhow, get the disc with more springs in the hub. Once I did that, my rollover noise was almost entirely eliminated. (only time I hear it is if I lug the engine a bit creeping through a parking lot). I originally installed a Sachs "HD" clutch which had HORRIBLE rollover noise. Went to a LUK standard duty kit, which actually had more springs in the hub of the disc, and it's silent now. You can search my "new transmission time" thread for more info...I had quite the saga getting my pile sorted out after the DMF setup failed, requiring a new trans, 2 new clutches, and several trips to the lift to remove and install it all. Also, here's a couple photos of the discs. The 10 spring disc is the one that makes everything quiet. The 8 spring disc makes some noise but works fine.

The clutch disc I just revmoved has 10 springs and the transmission had terrible roll over noise. Night and day difference between the solid mass with 10 spring clutch disc and factory dual mass flywheel set-up. Maybe, now with the rebuilt trans the roll-over noise would be less however I'm going to check into the cost of reinstalling the dual mass flywheel.

A little trick you can try. If you are sitting at the stoplight and it's going crazy with the noise, just ever so lightly push on the throttle to raise the idle speed. On mine that got rid of a lot of noise, so I turned the idle speed up a little bit and it's much more bearable now.

Got the dual-spring-row setup here (10 springs in total), in 12-1/4" size too, dead silent. Only time she growls is as Reklund described, if upshifted a bit too early. Running Pennzoil Synchromesh oil tho, not ATF - it's the fancy GM-spec stuff that you pay dearly for, but if it can quiet a typically loud 4-speed and also make her shift easy even stone-cold it's a winner in my book.

Yes I am over trying the oils also, though I am too cheap to try a synthetic. Straight 30w is too thick in the winter, 10w-30 is a little better but still a little stiff when it gets really cold. I also found the thicker oil would drag my idle speed down a little bit and of course that made it noisy. As it would warm up the oil the idle speed would get faster and the noise would go away. So I went back to the Dexron in mine.

ZF REQUIRES synthetic.