Have Gear Rollover Noise? Check this out...

[bookite03]

Maybe I'm just lucky...I did a C6 to ZF5 with SMF swap on my truck almost a month ago. The trans had some rattle and rollover noise but I learned to drive with it and got used to it. Reverse was the worst...BIG growl. Actually got to the point where I could "drive around " the noise.
Fast forward to yesterday, was working on clearance issues with my Gear Vendors and cab floor and prying and moving the transmission and t-case around quite a bit. Put it all back together and magically my rollover noise was 10x worse. Borderline ridiculous ( ask Leeland lol). So today I ended up noticing my downpipe from the turbo was resting on my transmission bell housing. So we loosened the exhaust up and got the clearance I needed. Test drive...now I had more noise and horrible vibration in the cab. Re-checked and found the down pipe was now hitting the firewall. Made another exhaust adjustment...verified the downpipe wasnt touching anything at all.

Made another drive and...HOLY CRAP! Almost zero rollover noise, quiet smooth shifts. Pretty much sounds as good as a friends 94 PSD 5-speed with the DM flywheel.

I guess the lesson of the day for the turbo guys is to check your exhaust clearance really close. That noise that you think is rollover might just be your downpipe.

 

[jrad235]

I've also found that if you have noise at idle, bump the RPM up a little. I bumped mine up to around 800rpm and now I only get just a bit of grumble when stopping too fast or FIRST thing on a cold day. Otherwise, just as quiet as the day it rolled off the factory floor.

 

[6.9poweredscout]

Mine doesn't make noise moving above 10 mph, but at idle it makes terrible noises, and if you hold the brake while at idle in gear moving and get a load on the trans it sounds like its going to rattle to pieces.

 

[bookite03]

I bet that bumped idle also helps out starting in 2nd gear. Funny thing about my truck is I swore it was rollover in the beginning. It was mainly growly at low speeds, not coasting in 4th and 5th. Also had that light rumble sometimes in neutral. Just couldn't believe the light rubbing of that down pipe could cause that much noise.

Just passing along my $0.02 and experience here...

 

[franklin2]

The way to determine if it's roll-over noise is let it idle in neutral with the clutch out. Observe the noise. Then push in on the clutch and hold it to the floor. The tranny will stop turning, and any noise that goes away and then comes back when you let out on the clutch is roll-over noise. This is with the truck not moving.

I am sure all of you get some noise from the tranny when doing the above test. Probably a DMF truck gets a little bearing whir, and a SMF truck will always be a little louder. You can also do the idle rpm experiment this way, by letting the clutch out in neutral, and then slightly step on the throttle to see how it affects the noise.

 

[Zaggnutt]

Forgive my ignorance, but is having this noise a sign of a problem? Also, if you have verified this noise is roll-over is there any way to fix it? I guess my main question is: what does it mean if you have roll-over noise?

 

[franklin2]

Forgive my ignorance, but is having this noise a sign of a problem? Also, if you have verified this noise is roll-over is there any way to fix it? I guess my main question is: what does it mean if you have roll-over noise?

It means you probably have a solid flywheel conversion if you have it. When the diesel fires it hits very hard, 4 times per revolution on a 8 cylinder. This hard hit smacks the gears and other components in the tranny, making a rattling noise. The factory got rid of this by using a 2 piece flywheel called a dual mass flywheel. The engine turns one piece, the other piece of the flywheel is connected to the tranny, and connecting the two pieces together are clutch discs and springs, to dampen the hard hits of the diesel engine.

 

[Zaggnutt]

OHHHHhhhhhhh I get it! Okay, I didn't realize that was a side effect of converting to the solid flywheel.