Need help troubleshooting transmission noise

Michael B

Greetings!

I have come over to this forum in search for some knowledge / insight as to a noise coming from my transmission.

I have posted this within a write-up within the Thing forum "1973 VW Thing "Face Lift" Many Pictures!” and thought I might ask for assistance over here.

From my post on the Thing forum:

So, back from installing the transmission for the 3rd time and it’s still making the noise that I’m trying to rid it of. Thus far the trans builder (Kevin @ KCR Transmission) has taken everything apart and found nothing conclusive!? Kevin has been very understanding as to my feelings towards this issue/problem and I’m very thankful for that. If I come to find out that this noise is of my doing, then I do what I can to compensate Kevin as best I can. I think what I may need to do is take a short video of my noise and let some of the people of our community have a listen, and maybe give some constructive insight as to its origin. I will see about getting a video today and add it to this topic.

Please listen to the video and maybe offer some thoughts.

Link

tncsparky · Posted: Thu Nov 19, 2009 10:32 am Post subject:

So it only happens in 4th at about 55mph?
Did you give kevin a ride before he tore it apart?
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Michael B · Posted: Thu Nov 19, 2009 10:42 am Post subject:

vwracerdave · Posted: Thu Nov 19, 2009 12:15 pm Post subject:

Check your wheel bearings and CV joints.
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167luckycharm · Posted: Thu Nov 19, 2009 12:48 pm Post subject:

I'm no expert, but this is what I gather...
The noise occurs in all gears, most prominent during deceleration; problem may be in the pinion bearing when unloading of the pinion gear. If it is a brand new item, it's possible that there's a manufacture defect, but hard to tell unless it is opened up for inspection.
I bought a '67 transaxle that was stored for many years (nosecone up) and had no way of testing it under load until I installed it in my '58 bug. I needed to find a bus nosecone first and modify the hockeystick for proper shift alignment. Finally able to drive it, long after the purchase of the transaxle, and found the same noise during deceleration. Problem was the pinion bearing (and getting my money back).
Are the ring gear carrier bearings brand new too? I believe there's the option of reusing bearings when building a transaxle to maintain proper clearance/preload tolerances, but ultimately, it's up to the discretion of the builder to decide if used parts are within specs for worthiness.
Best of luck to you,
John
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Michael B · Posted: Thu Nov 19, 2009 1:25 pm Post subject:

167luckycharm · Posted: Thu Nov 19, 2009 2:19 pm Post subject:

Mike,
Also wanted to add in my message a big thanks for including the video of the drive/ride-along. My car had the same solid trans mounts and the sound reminded me of how my car sounded like.
As for the trans builder being able to detect the faulty bearing during the build process... I don't know what criteria he uses when selecting used parts or buying new parts from a supplier. The last transaxle I just finished was built with used swingaxle differential bearings that I bought from locash (Lester). They were in really nice shape and I installed them after a thorough cleaning with solvent. The pinion bearing is the original unit, and as of today, I have not installed the tranaxle to test it out.
I have learned that these bearings are under a considerable amount of load and preload once installed and in operation. When checking for rough spots prior to installation, a bearing may feel smooth while free spinning by hand while out of the transaxle. Once installed, however, the tolerances gets tighter, and adding loads begin to magnify any tight/rough spots.
Have a talk with the trans builder again, maybe bring him along for a ride too. I'm sure he'd like to know what the symptoms are in real-time or first-hand. He could do more trouble-shooting during the experience and would be able to rule out other potential areas by process of elimination. Whatever you do, be sure to log down the steps taken, remedies attempted, with trial-and-errors encountered. By all means, report back with your findings and make sure we all get confused, er enlightened with the results.
The truth is out there...
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tncsparky · Posted: Thu Nov 19, 2009 2:49 pm Post subject:

in the video i could only hear it when you hit 55 or so.
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Michael B · Posted: Thu Nov 19, 2009 6:47 pm Post subject:

74 Thing · Samba Member Joined: September 02, 2004 Posts: 7391

Can it be something to do with your solid mounted tranny or maybe your suspension/torsion bushings?

You can always put the tranny into another VW to see if it is the tranny or something else in the vehicle-I know a lot of work but just throwing it out there since it can be frustrating at times.

If it is wheel bearings or CV's I can typically hear this with the engine off coasting downhill.

Bruce · Posted: Fri Nov 20, 2009 12:32 am Post subject:

90% of that noise is from your solid mounts. Put rubber in and be done with it.
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Ed Carp · Posted: Sat Nov 21, 2009 12:20 pm Post subject:

check your cranksaft thust. reason i say that is when you pushthe clutch in you are thrusting the crank all the way to the rear. possiblbly your problem is in the motor with excessive crank thrust. also when you are decellerating the crank thrusts the other way.
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Bruce · Posted: Sat Nov 21, 2009 3:44 pm Post subject:

It's not the engine or crank. That noise is gear noise. Amplified by the solid mounts.
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vwracerdave · Posted: Sat Nov 21, 2009 6:08 pm Post subject:

Bruce

Would a "AV" Thing transaxle have fine tooth 3rd & 4th or the 002 course tooth 3/4
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2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63

Watch my racing video's http://www.youtube.com/user/okvwracer/videos

Bruce · Posted: Sat Nov 21, 2009 10:53 pm Post subject:

Dave, the AV has exactly the same gears as an AT Bug 'box. Fine tooth, brazed on dog rings, 002 type.
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nsracing · Posted: Sun Nov 22, 2009 2:07 pm Post subject:

Michael B · Posted: Mon Nov 23, 2009 8:26 am Post subject:

nsracing · Posted: Mon Nov 23, 2009 9:07 am Post subject:

The needle bearings rarely go out if ever.

But the nose mainshaft bearings...(ballbearings) do go out. This is what is growling in your trans.

We mount the trans directly to the frame on racecars. YOu don't hear no stinkin's growling noises. Rolling Eyes

What did Kevin at KCR say about it??

kcr · Posted: Mon Nov 23, 2009 7:30 pm Post subject:

It is a horrible noise. When he brought it back the first time I was surprised to see it come back. We went through it and put in a new pinion bearing for good measure. He brought it back again and I went for a drive in it. I could hear the noise as soon as he put it in second. It sounded like something hitting on something else. I look under the car and the nose cone was hitting on the body. I thought that might be it. I guess not. I grabbed the crank pulley to see if it had excessive end play and seemed to be fine.
Next time he brought it back, I replaced all forward gears, the r/p, a new mainshaft bearing, and another new pinion bearing although there was nothing wrong with the any of the parts in it. I did not replace the small mainshaft bearing in the case. We DO remove them and inspect them. If it was that bearing making that kind of noise, I would think the mainshaft would be thrashed where it rides on the bearing or the bearing would be spinning in the case. Neither of those symptoms were evident.
So, I changed damn near everything and he says the noise is almost worse.

His cv flanges have alot of wear on the splined area, but I wouldn't think that is the noise.

nsracing · Posted: Mon Nov 23, 2009 7:55 pm Post subject:

Kevin,

That nose bearing on the mainshaft is ballbearing. Any little wear on it will growl. Ask me how I know? Laughing

YOu have changed out everything else except that and did not do anything. Change out that nose bearing and see for yourself.

For pinion bearings, I just surface grind the inner race and put the stock preloads on it. YOu can pinch that bearing till the cows come home.

That nose bearing though I have learned a lot more since I came upon this exact same problem.

Cheers.


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