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Velvet Drive tranny with "marble sound" in starboard 454 only???

N

northern_lights

Member
I pulled an earlier thread relating to this....but not quite the same issue as I am having. To set the background. Twin 1986 454's Model 350's with Velvet Drive transmissions. Starboard tranny at idle sounds fine. However, put into gear at lowest rpms (600 rpms) and it sounds like hell?!? However, increase speed to 800 rpms......sound goes away. In reverse...no noise. Port engine is fine under all conditions. I have always had a single marble sound when just in gear on Stbd side...but now its gotten noticebly worse.

I have not called in my local mechanic yet for fear he will say "that's normal" or "you need a new tranny" ??? What do the "Pros" think??? fyi....fluid is new and full.
 
For the VD to be quiet at 600rpm in gear, several things need to be just right. The torsional dampner needs to be in good shape, with no loose springs. The engine needs to be in good tune. Meaning equal power out of all cylinders. See if a vacuum gauge reads steady. Have you done a stb tune up recently? In any case, 600 is a bit low, I'd do 750 rpm in gear.
 
I'm with DDave about the tune up. With little load the gearbox is loafing and you may be experiencing something like backlash. Even when the engines are running well, I get this when running with a current. Speeding up/Increasing the load on the engine/gear makes the noise go away. Try this: At dead-slow take the Stbd. engine out of gear...putting more load on the Port. Noise go away?
 
As noted above, 600 RPM is low for in gear idle.

if the noise has gotten noticeable louder, I'd plan on changing the damper plates soon. They are only good for so long and if yours are original, I'd say they have provided a useful life of service.
 
Had same issues early in the season. Took tranny apart everything was ok, replaced damper plate while i was there..Tune up engine, compression was 145-150 all cylinders, realign shaft and tranny coupler but noise was still there with under 800 RPMs in gear. At the end i gave up and learn to live with it..I put around 35 hours after that and noise still the same not better or worse..
 
hmmm, a trend here. Three of us have tranny noise on the RH engine only. Maybe they are more sensitive to RH rotation.
 
As we say in San Francisco Bay Area...."Shake rattle & roll no more". I adjusted the rpm idle to 900 and the rattle went away and the shifting smoothed right out. Plus the engines just sound better. thanks all for input. I appreciate it.
 
You are shortening the transmission life by shifting at 900 RPMs. I'd live with the noise and put the idle back where it belongs. The noise is quite common, if it bothers you that much, turn up the radio.
 
linesix said:
You are shortening the transmission life by shifting at 900 RPMs. I'd live with the noise and put the idle back where it belongs. The noise is quite common, if it bothers you that much, turn up the radio.
Click to expand...

hmmmm; OR, maybe, its a trade between gear wear due to chatter and clutch wear. I've been into some pretty old VD's for service and its impressive how long these clutchs plates wear. You will see a lot of warped clutches, but thats due to running on low fluid, with slipping/overheating discs. If they don't "bang" into forward, I don't think the rpm is too high.
 
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