GKK

On my 91 Vette, I've been hearing a howling noise consistent with the Vettes speed.

I changed the rear end fluid but, still hear the howling noise and thought maybe it's the tires making the howling noise but, I'm now convinced the noise is coming from the rear end gears.

The howling is heard at speeds of 60 mph or under on straight roads. I don't hear it on the freeway.

Also, the wheel bearing hubs are not worn.

Are the Limited Slip clutch disks worn and how difficult or expensive is it too fix?... Thanks

JrRifleCoach

Well based on the fact that you have narrowed the noise down to the rear end,
Have changed the fluid,
The WB are not worn,
And that the LSD clutches have nothing to do with noise until turning....

Sounds like you need a new rear end.
What do ya think?

Of course we don't know how many miles on the car.
Or how old the WB and U-joints are.

I thought I was loosing a diff and it turned out to be the trans...

hemivett

Wheel bearings make a grinding noise that's can sound like howling, (depending how bad they are) and almost always do it at 60. Try jacking it up high enough to get a big (5ft) pry bar, or 2x4, and lift up on it, if you see movement, the bearing is gone. h

GKK

My 91 Vette has 130k and is very well maintained.

Do the Ring and Pinion gears wear down causing the howling noise?

hemivett

I just did mine (120,000) 1 bearing fell apart in half!

Ring and pinion gears do make noise when worn, or improperly installed. Some guys think they can install gears, by just replacing the ring and pinion. When in fact there is a whole science to getting them in properly. You can save a bunch of money by pulling the pumkin yourself. Just unbolt your driveline, and 2 halfshafts, then unbolt the pumpkin from the carrier. Now you can take it to a rearend shop, and this is a good time to change the gears, if you want. h

GKK

Thanks, hemivette.

The Pumpkin removal doesn't seem difficult so, I'll check that out.

hemivett

It is really easy. Someone who doesnt know what they are doing, can have it out in an hour. Remember when you unbolt it from the carrier, to have some sort of oil pan under it, or gear oil will go everywhere. Peace. h

DinoBob

Howling usually indicate a worn pinion bearing.

GKK

Thanks, DinoBob!

I'll have that checked out!

WVZR-1

I would certainly think a stethoscope could aid in the diagnostics here!

Time and mileage would indicate it's time for six bearings, three seals and a close inspection of the differential pinions and the cross-shaft. A clutch pack? Might be overkill.

hemivett

If you are sure the bearings are good, then pull the pumpkin, and take it in. Your problem has to be in there somewhere, and without special tools, and a whole bunch of know how. The service is NOT capeable by the average guy.

This is a dumb question, but have you checked the fuid? h

WVZR-1

The OP mentions I believe what I'd interpret to be a "fresh or recent" change.

There's other things the OP mentions that I didn't address because he hinted he was going after the rear but he mentions "not heard" on freeway and under 60MPH. He mentions "straight" roads but doesn't mention the surface. Not knowing the branding of the tires, the tire pressures and the composition of the roadway you can't go right after the rear. That was the reason I mentioned "stethoscope". Low tire pressure on some brands are very noisy, it does dissipate with speed and changes with composition of the roadway. Just say'n?

GKK

The slight howling noise is really heard at 40mph on smooth asphalt roads traveling straight.

Yes, I recently changed the rear end fluid using 75w-90 Royal Purple synthetic with additive included.

I first thought it was the year and a half old Yokohama S. Drive tires but, it just sounded like a rear end howl. Most people wouldn't even notice it unless they were listening for it.

I know this sound because I had a 91 RS Camaro with a similar noise that ended up being the Pinion bearing.

With the many U-Joints, Wheel Hub bearings and other C4 IRS components, I decided to ask the experts here first.

hemivett

Ya, most people can tell the difference between tires, and mechanical. I still think pulling the pumpkin, and taking it in is your best bet. If you want an upgrade look for a Dana 44. h

GKK

Yeah, I'll pull the pumpkin and take it in since I know the Ring and Pinion clearances have to be set just right!... Thanks, for all the advice!...

WVZR-1

You mentioned "most can" - I believe that's quite "optimistic" !

Once it's out and on the bench it becomes a "do" and not a diagnostic procedure. I mentioned "time and mileage" indicates but I'd do some diagnostics before I just tossed it on the bench!

Ain't no fun scratchin' your head after the do and figurin' out "what's next"!!