Hum, Grind, Clunk?

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Apr 1, 2008 | 07:53 PM

Mia

Thread Starter

Burning Brakes

Joined: Oct 2007

Posts: 946

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From: Lake Geneva WI

Hum, Grind, Clunk?

Hello, I noticed a kinda of hum, grind/clunk which appears to be located near the tranny and or drive shaft.. It is really hard to say which.

Anyway, I took an extended drive today on the interstate, perhaps 100 miles round trip at speeds around 70-80... The hum, could be my new tires for all I know. However, coming to a stop and decelerating off the off ram then coming back into stop and go traffic it seemed like there was kinda of a jump or jolt and clunk in the drive train. It felt like the drive shaft or tranny was gonna fall off. The drive back was fine.

Now I have noted here before that I have a small transmission fluid leak, but I checked that and keep it topped off. I've not pulled the tranny yet for a rebuild or service, so I am wondering if I have more trouble than I thought?

Any ideas on what to look for? This is a T350 auto on a 79 Vette, stock, original. Stock L48 motor and torque converter. Thanks!

Apr 1, 2008 | 08:00 PM

weimer20

Burning Brakes

Joined: May 2007

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From: Ventura California

Hmmm.... Does the humm change in pitch as related to the speed you are driving? Happening in all gears? When you top off the fluid in the trans, are you filling it with the engine running?

Apr 1, 2008 | 08:04 PM

Mia

Thread Starter

Burning Brakes

Joined: Oct 2007

Posts: 946

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From: Lake Geneva WI

Quote:

Originally Posted by weimer20

Hmmm.... Does the humm change in pitch as related to the speed you are driving? Happening in all gears? When you top off the fluid in the trans, are you filling it with the engine running?

I did not really notice until we were consistently cruising at hyway speeds. So I guess the later gear is all I noticed, ie., 3rd.

Yes, filling and checking with engine running and hot. It's only losing it after it is parked. And then it spits out like a table spoon or less each time. So it is not losing a huge amount. Also, the transmission does not feel like it is slipping. It feels quite responsive actually.

Apr 1, 2008 | 10:00 PM

ENG40

Racer

Joined: Nov 2007

Posts: 320

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From: Upstate New York

Did you check the u joints? It might be chewing up the needle bearings in one of the caps.

Apr 1, 2008 | 10:02 PM

Mia

Thread Starter

Burning Brakes

Joined: Oct 2007

Posts: 946

Likes: 0

From: Lake Geneva WI

Quote:

Originally Posted by ENG40

Did you check the u joints? It might be chewing up the needle bearings in one of the caps.

Good idea.. From the sound and localization of the sound, it sure seems like that might be it. Thanks! I'll have to look at that this weekend!

Apr 1, 2008 | 10:13 PM

Glass Act

Melting Slicks

Joined: Jul 2005

Posts: 2,545

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From: 406ci SB, AFR 180 Heads - 490 HP @5,600 RPM 529 lb-ft @ 4,100 RPM

Sounds like bearings, but also check your wheel nuts, as you mentioned new tires.

Apr 2, 2008 | 06:26 PM

weimer20

Burning Brakes

Joined: May 2007

Posts: 945

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From: Ventura California

Quote:

Originally Posted by Mia

I like the suggestion regarding checking the universals on the driveshaft. Loose lug nuts is also a possibility that has been suggested too. I'd certainly go that route first. I would doubt it's the trans at this point.

Apr 2, 2008 | 06:54 PM

Mia

Thread Starter

Burning Brakes

Joined: Oct 2007

Posts: 946

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From: Lake Geneva WI

I think I will check wheel bearings and the u-joints first.... Now I have a nice weekend project to work on. Gives me an excuse to repack the bearings while I am at it. Thanks again guys!