Help! $6500 and 2-3 months in the shop... and the drive train whine persists...

[SPANISHVETTS]

SpanishVettes: I have thought a bit about 3.89. My car is able to hold down the 4.10's, but only just and only in a straight line. Are you saying that 3.89 is quiet where 4.10 is not? It's only a 5% different ratio... so that may be a small enough change to not feel anemic to me. And if it makes all the difference in sound issues... maybe that's the right thing to do.

I have nothing to base this on but gut feelings and 40 years of hot roding + a bit of math. The 5% difference between 4.11:1 and 3.89:1 requires a much more drastic ring to pinion size difference than say the difference between a 3.89:1 and a 3.73:1 would. The 4.11s are close to the limit for the Dyna 44. If you could stick a bigger carrier under the car then the Pinion could be larger, allowing more meshing with the ring gear, which would mean less noise.
Don’t take this as gospel…at best I am a hack taught by a shade tree, and a very opinionated one at that.

You know... if the problem was caused by a new bearing that's defective, having them setup a different case entirely may actually be a good thing. If they just replace my ring and pinion in my current case, I don't think there will be a second rebuild kit installed.

Replace the bearings and seals, it is cheap insurance. We never re-use a bearing, even if in only has a few hours on it!

 

[MoeJr]

Being in the auto field I have found that the deeper gears tend to be noisier. I went from 2.41's in my 77 Grand prix to 3.08s and the 3.08's howl.


I guess I'll never understand why people would go to 4.11's. I know with the overdrive you can get away with it but if the LT4 felt as you say "anemic" then something else is wrong. An LT4 is far from anemic even with ther stock gears. Unless you are a dedicated drag racer 3.45's should be all you need on the street.

Just my .02

 

[Skant]

I guess I'll never understand why people would go to 4.11's. I know with the overdrive you can get away with it but if the LT4 felt as you say "anemic" then something else is wrong. An LT4 is far from anemic even with ther stock gears. Unless you are a dedicated drag racer 3.45's should be all you need on the street.

Well, I didn't mean to imply that my LT4 is slow with the 3.45's. What I mean to say is that it is much faster with the 4.11's. After getting used to its speed with the 4.11's, going back to the 3.45's would feel like quite a downgrade _to me_. My car would feel anemic by comparison to what I've grown used to.

It makes sense to me that a lot of people would think that 4.11's are going too far. In most applications, they would be. But in my application... in combination with the ZF6... the gear ratios end up very nice and not over the top. The ZF6's gear ratios are quite different from the other trannies.

The ZF6 1st gear is 2.64. Compared to 3.06 for a 1984 automatic or 2.88 for a 1984 manual 4+3.

That means 1st gear on a ZF6 with 4.11's is roughly equivalent to an automatic with 3.45's or a 4+3 manual with 3.73's.

And yet the ZF6 with 4.11's is still able to cruise at 1800rpm on the freeway at 65mph. So that's not an issue at all.

In fact, with the stock 3.45's gears, 6th on the ZF6 is almost too high to be usable. It runs 1450rpm at 65mph, and pretty much only has enough torque to maintain speed... it can barely accelerate or climb hills without downshifting to 5th.

So I'm just saying that in terms of the final drive ratios, ZF6 + 4.11 is really a sweet combination.

The only problem I'm battling is a noise issue. And _that_ may ultimately shoot down my usage of the 4.11's if it can't be overcome. Every other aspect about it is really great.

- Skant

 

[SPANISHVETTS]

The ZF6 1st gear is 2.64. Compared to 3.06 for a 1984 automatic or 2.88 for a 1984 manual 4+3.

I did not realize that the ZF had that steep a 1st. This must have some thing to do with the EPA. Not even the General would pull a number that high out of the hat when he has 6 gears to mix and match.

If you cain´t live with the 4.11´s whine get a louder exhaust and upgrade the stereo.:L

 

[Skant]

Alright. The other day the second shop finished putting in the Dana ring and pinion gears, and we took it for a drive.

The freeway warble whine still persists. Same as ever.

Now if you'll excuse me..

... Ahem... *clears throat* ...

AAAAAAAAAAAAAGGGHGHGHAHAHHAHGHGHGHGGHHGHGHHHHHHHHHHHHH!!!!!!

At this point, I've thrown roughly $10,000 at this. And I'm feeling pretty depressed. I must have made some big error in judgement somewhere along the way.

Anyway... it's still at the second shop. The shop owner hasn't given up on it yet. He felt that the car sounded like it was missing sound proofing under the console that was supposed to be there. And he also wanted to do more tests on it and run it on the rack where he could listen underneath.

Indeed, I have thought there was no sound proofing under the console at all... the sound through it doesn't sound muffled. But I was not aware that there was supposed to be something there? Just opening and closing the door that goes over the cup holder makes a pretty dramatic difference in the noises... which implies that there's little or no sound barrier beneath it.

This car has always had a noisy driveline... even before the 4.11's. Until more recently, I just never knew it wasn't normal. I'd never driven another C4 with a ZF6. Now I've driven three other ZF6 cars, and they sounded nothing like mine ever did. Maybe somewhere along the line, the sound proofing was removed. Or perhaps there's another problem. But really... multiple shops have been all over the drive line on this car and have found nothing wrong.

So maybe sound proofing is a good theory.

And it does seem to me like... even if it's not missing sound proofing it's supposed to have... adding some is maybe the answer. The car isn't experiencing any drivabilty problems... it's just a noise issue. And considering how much just closing the little door on the console muffles the noises, it doesn't seem like it would take much sound proofing to deaden it. It is a high pitched sound, after all... and those are the easiest to knock down.

Seems to me that I've heard of some other folks on this forum adding some sound proofing to their cars, and they reported considerable effectiveness.

Now... I am a racy type. I have this maybe incompatible desire to have a car which is both comfortable for a cruise and wicked fast... thus my desire for quiet 4.11's... I hope that a little sound proofing for this doesn't add much weight to the car. I've dropped about 100 pounds off the car elsewhere.

Oh, speaking of quiet 4.11's... even though that one noise persists, the rest of the driveline noises seemed a good bit quieter with the Dana gears versus the Tom's Gears. The driveline seems to make more of a whhhrrrrr sound rather than a whine sound... other than the aforementioned warble whine on the freeway at 65mph+.

Now here's another consideration... the transmission and rear end have been changed on this car (multiple times). Each change has altered the sound of the car... EXCEPT... for that warble whine on the freeway. That sound has never changed its character throughout any of this. It is exactly the same noise. Perhaps it is coming from neither the transmission or the ring and pinion.

I understand that the described symptoms are a match for bad U-joints as well. But both shops have checked the U-joints and say they feel fine. Could they feel fine, but still have a sound problem? Could there be something else?

- Skant

 

[Ken]

I can't remember, and I don't feel like going through forty-four responses right away this morning, but has anybody suggested the insulator for the driveline support? It's the foil-backed, heavy insulating material that to me sorta feels like lead or something.

First of all, is it there? :confused

Secondly, if it isn't there, get some and install it. It is necessary to quell driveline vibration.

 

[Skant]

The second shop did determine that the sound proofing under the console did exist, but it wasn't connected correctly (by the first shop). They fixed that, and it made a world of difference in the noise level. Now it doesn't get all this noise coming up through the center console. This quelled a lot of noises the car was making, and it's pretty pleasant around surface streets now.

This improvement does help with the freeway whine somewhat, too. It cuts down a bit of it. But you still hear it through the rear deck pretty good.

The second shop also put the car up on a lift and ran it that way in order to pinpoint where the sound was coming from (why the first shop never did this...?) They were able to get the noise to happen with the car suspended and confirmed that the sound was definately coming from the pumpkin.

...Gee... all the money I would have saved if the first shop had done that little bit of analysis early on...

Ahem.

Anyway... the second shop has been researching the matter. The experts they're talking to are telling them that putting a Viper rear end into the car will eliminate the problem because the Viper's D44 is a larger carrier and the gears are thusly a better size so they don't whine at a 4.11 ratio.

This seems to be very much inline with Spanishvettes has been saying.

So... anyone familiar with this swap?

I've heard somewhere that it's possible to put the viper 4.11's into the vette's D44 with minor 'clearancing' (ie. grinding away) of the inside of the case.

I wonder if the Viper's D44 is much heavier? I'm still waiting to see how much this option will cost. They're trying to find an empty viper carrier. They've got a source on the viper 4.11 ring and pinion already.

The other way is to try for the sound proofing.

So I guess I have to decide which way to go.

- Skant

 

[MoeJr]

I would go with whatever way is cheaper at this point. right now by reading your post it seems you are just throwing money at the car with no return of satisfaction. i hope all this works out for you in the end.