Borg Warner Gearbox Noisey Under Light Load

[GILow]

Hello Cruisers,

I have noticed that our Borg Warner Velvet Drive sounds sort of loose and rattely under very light load. The symtoms only appear at idle revs, in either forward or reverse, as soon as any load/throttle is applied it all sounds fine. In neutral there are no noises, no matter what the engine revs.

The gearbox was fitted in the late 80's so I guess it is getting on a bit, but it only has 2000 hours and the oil looks good. It is a 1.5:1 reduction box connected to a fairly lumpy 96HP Nissan diesel. A visual inspection seems to show everything as nice and tight.

There seem to be no strange noises under load in either forward or reverse, and when freewheeling under sail with the engine off, you can hear the gearbox but it sounds tight and smooth enough.

Is this normal, or is this a sign of impending doom?

Matt

[goboatingnow]

Drive plate ( damper) between the engine and gearbox maybe worn. These are often spring loaded and the springs get weak

Dave

[GILow]

Oh dear, that sounds like opening up the bell housing to me... nasty. Not a lot of room to move the gearbox backwards, which implies moving the engine forwards, which would be a hell of a job.

From what you know is it likely to cause some kind of failure or breakage if not attended to, or does it just continue to sound loose?


M

[shakey doug]

G'day,
My money is with Dave!

[goboatingnow]

Originally Posted by GILow

Oh dear, that sounds like opening up the bell housing to me... nasty. Not a lot of room to move the gearbox backwards, which implies moving the engine forwards, which would be a hell of a job.

From what you know is it likely to cause some kind of failure or breakage if not attended to, or does it just continue to sound loose?


M

Depends on the make, some youll loose drive and hence will have to be replaced. in some it may be one or two springs loose and the damper will continue to work for a long ( some!) time. YMMV

dave.

[jstevens]

+2 on Dave's pointing to the damper plate.
As he said, you could operate in this condition for an extended period of time, but it is likely causing damage to the VD. Before you decide to risk further operation I would check the ATF in the VD. If it is not bright red (or whatever color ATF you use) that is likely caused by metal being shaved off the forward and reverse ring gears. If you don't see a problem I would still have the ATF analyzed by a transmission shop to be sure there is no damage to the VD.
Several years ago I had a similar backlash noise at low RPMs. I have a V-Drive and all of the mechanics I had check it thought the problem was there. Walter, the V-Drive manufacturer, said they had no problems with gear backlash. So I continued to operate the engine for several years until one day coming into a dock I found out I had no reverse gear. I was fortunate that the VD could be re-built, only the ring gears and oil cooler had to be replaced. Still $$$$.
My advice is to pull that damper plate and have it replaced. Most modern damper plates no longer use springs.

John

[dannobee]

Most Velvet Drives use a damper plate with springs, even the modern ones, and it's common for them to wear out.

The noise isn't likely inside the gear box, but you'll still need to remove it to replace the damper plate.

[GILow]

Originally Posted by jstevens

+2 on Dave's pointing to the damper plate.
As he said, you could operate in this condition for an extended period of time, but it is likely causing damage to the VD. Before you decide to risk further operation I would check the ATF in the VD. If it is not bright red (or whatever color ATF you use) that is likely caused by metal being shaved off the forward and reverse ring gears. If you don't see a problem I would still have the ATF analyzed by a transmission shop to be sure there is no damage to the VD.
Several years ago I had a similar backlash noise at low RPMs. I have a V-Drive and all of the mechanics I had check it thought the problem was there. Walter, the V-Drive manufacturer, said they had no problems with gear backlash. So I continued to operate the engine for several years until one day coming into a dock I found out I had no reverse gear. I was fortunate that the VD could be re-built, only the ring gears and oil cooler had to be replaced. Still $$$$.
My advice is to pull that damper plate and have it replaced. Most modern damper plates no longer use springs.

John

Thanks John, I found your blog on this very matter when I was searching around and your experience was enought to make me realise I couldn't afford to leave this one to chance.

[GILow]

Thank you all, I will do as you all suggest and and swap that damper.

Oh goody, more time working on the engine... :^(

Just spent A$3K on the injectors, now this. And I don't even LIKE using engines on boats, I just need the darn thing to get the boat in and out of the pen. (Oh, and of course if the mast falls off, if the wind fails, if there's a medical emergency on board... etc.. etc...)

Sigh.

Matt

[SkiprJohn]

I agree I think its the damper plate.

A way to check is to isolate the noise if you can get a stethoscope down there or a long handled screwdriver to your ear.

Damper is located between engine and trans inside the bell housing.

[gjordan]

I had the same problem with a Mercedes engine, and velvet drive in a steel boat. All the advice I got was to change out the damper plate, so I did. I had good engine access , so it was not a hard job. When I discovered that it didnt solve the problem, I was not a happy camper. Finally an old salt came over and listened to it and said,"turn the idle speed up a little" and it was nice and quiet after that. I wish I would have talked to him before I spent a couple of hundred bucks, and waited 2 weeks for the new plate to be flown in. You might want to try turning your idle up 50 or 75 RPM, and see if it makes a difference? Try the simple cheap things first, before putting out the big bucks. ___My 2 cents worth.____Grant.

[AnchorageGuy]

There is a possibility that the damper plate is the problem. BUT, our Borg Warner sounded like it was full of rocks whenever it was in idle and ran just fine for over 17 years and tens of thousands of miles. It's still going strong for the new owner of the boat. I'm just sayin'. Chuck