New SBC DD... A question and my initial impressions

[c-hawk]

I just installed a new 3600 12cb yesterday in my 01. 5. The install went pretty smooth... no problems at all really. (That 5600 sure is heavy though. )



On the initial test drive, everything was good. The clutch was very smooth, it was very quiet under all circumstances, there was just the tiniest bit of rattle when the clutch was depressed. Shifting was still good, maybe just a tiny bit slower then it was with the oem clutch. Pedal pressure feels like it's twice (or more) what the stock unit was. That was the only real surprise i had as i was expecting a "light increase in pedal pressure".



Ok, on to the question. With about 30 miles on the unit, i noticed that it has a pretty loud rattle (acompanied by a slight vibration) when ideling in neutral with the clutch engaged. If i raise the rpms just a little, it goes away. If i press the clutch pedal in, it goes away also.



I'm wondering if this is normal??? If so what causes it? I understand where the rattle comes from when the clutch is disengaged with the two disks and floater plate, but i can't picture what would make it rattle when it's engaged in neutral at idle.



The performance is still great. Shifts good, engages good (although it seems slightly more grabby then it was at first).



Thanks for all the help.



Chris

 

[Hammer]

That was the only real surprise i had as i was expecting a "light increase in pedal pressure".

:-laf :-laf :-laf

Light pedal pressure eh... .

At times when I depress the pedal on my EEP double Chris I wonder what they used to determine the words "light pressure" LOL.



Seriously. .

I would chat with Peter in the AM as you should have no rattle while its in neutral idling and it sounds like something may be wrong and its not normal. Most all of the doubles I have been around or driven when in neutral are like any other unit,just there and not making noise. The SBC doubles have came along way in the past few years and are a good stout unit with a good company behind them,of course you know that already.



I know the weather is not at all going to help but have you been out and seated it in yet?. Find a dry stretch of roadway and slip her in third,give it some rpms and walk her out. When the clutch is about all the way engaged,drop the loud pedal. It will usually help seat the units in and at times when I have been being to easy on mine I will have to re-educate it by finding a 5 liter who needs a good view of my tailgate.



If you have any questions feel free to call me or drop me a PM. BTW,it will never shift as fast as the old trucks slushbox,LOL... ..... Andy

 

[JCleary]

Rattle in neutral with the clutch engaged is a trait common to all dual discs.



It is caused by the fact that the clutch discs do not have springs on them, so all the torsional spikes caused by the Cummins get directly transmitted to the input shaft on the transmission.



You'll also notice some growling in the trans, especially when in 5th gear under a load.



You can install a Fluidampr and get rid of about 80%-90% of the noise.



I switched back to a single disc. My driving doesn't really require a dual disc, and I wanted to get rid of the noise. So far my OFE is holding strong. No 3rd gear 4wd launches for me any more, however.

 

[BPonci]

John is correct. I installed a fluidamper and it tamed down the noise.

 

[Tomeygun]

I switched back to a single disc. My driving doesn't really require a dual disc, and I wanted to get rid of the noise. So far my OFE is holding strong. No 3rd gear 4wd launches for me any more, however.

Did you not like the daily drive of the DD? Cause I know my HP needs the DD, and I want to 1/4 the truck, but without the ability to launch in 3rd, I get toasted on the line...



I bought the 1&3/8ths input shaft already, So Its a matter of time, But I am starting the think that daily driving the DD can be quite a challenge. Any thoughts?

 

[c-hawk]

Rattle in neutral with the clutch engaged is a trait common to all dual discs.



It is caused by the fact that the clutch discs do not have springs on them, so all the torsional spikes caused by the Cummins get directly transmitted to the input shaft on the transmission.



You'll also notice some growling in the trans, especially when in 5th gear under a load.



You can install a Fluidampr and get rid of about 80%-90% of the noise.

I talked to peter a few minutes ago and he says this is in fact very normal for a twin disk with out dampened hubs.



Otherwise, very happy with the clutch. Completely happy really. Just glad i don't have to yank that 5600 again.

 

[DTroy]

Tomeygun. .



I wouldn't hesitate to put a DD in a daily driver (that needs it).



If you have the hp, then go with the DD.

Yes, there is more pedal effort. And if you get stuck in stop and go traffic, it's not so fun. But it's still manageable.



The DD is actually a little less grabby than the FE was. And I've done a 3rd gear hi range launch on dry pavement. The DD didn't miss a beat. As well as a dirt drag and some sled pulls. I give it a thumbs up.



If your only concern is comfort, then stick with a good single.

 

[moremph]

Been driving a 3850 dd for 2 years now and i love it. No questions when it comes to "will it hold" while beating it.



Chris



If you put a new "updated" master/slave unit that peter sells it will take care of some of that pedal pressure. I now drive my s10 5spd a lot and the dodge a couple times a week and when i get in the dodge it feels easier to push then the s10 "weird i know" but it does.



Chris