GTV transmission driveline whine diagnosis - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 7 (permalink) Old 11-07-2012, 10:18 AM Thread Starter
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GTV transmission driveline whine diagnosis

What's the best way to diagnose where the whine from the driveline is coming from?

Car: 1969 GTV1750 with a ton of miles.
Just replaced the transmission and rear dif fluid with Redline 75W90NS
Don't know if it whined before I did this, as the car wasn't drivable when I got it (brakes needed rebuild)
Transmission doesn't grind when shifting.
I don't really notice the whine until 4th gear. Also hear it in 5th.
Sound does change when on gas vs off gas.
Whine mostly goes away when in neutral and rolling. (ex: rolling along in 4th, put car in neutral and glide)
Have a hard time hearing if its coming from the front or rear, but it sounds like its coming from the transmission.
I can't detect any slop in the driveshaft, but the car did come with a replacement driveshaft support and bearing... don't know why... or maybe I do now...

I don't feel any vibration from the drivetrain.
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post #2 of 7 (permalink) Old 11-07-2012, 12:40 PM
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I'd like to hear other's views too, as I haven't had this on my (only) 105, but in a transaxle car, a very distinct whine that can be stopped and started at will by going just in and out of the throttle (crossing the "neutral" point if you will) is normally the pinion shim being worn. I had this on the Milano/75 I bought used back in '92 and had the dealer replace the shim as a condition for the purchase. (This shim locates the fore-aft position of the pinion gear compared to the crown wheel.)

The implication being that if it is this, the pinion bearings may need to be replaced and/or re-shimmed at the correct distance, which is hardly a trivial job.

But I won't claim this is definitive however...
/Neil
PS Some may say that the NS variant oil isn't right for a non-LSD diff, if that's what's on your car.

74 GTV
Alcala de Henares, Spain
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post #3 of 7 (permalink) Old 11-07-2012, 01:26 PM
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what fluid were you running prior to the change? the fluid could cause a whine depending... a worn throw out bearing will whine as well or the center driveshaft bearing.
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post #4 of 7 (permalink) Old 11-07-2012, 02:05 PM
Richard Jemison
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Whine

1st 75-90 NS is the correct lube for the trans.

The whine is likely from the input bearings or output end bearings if from the trans.
Most likely is differential wear..

Richard Jemison
RJR Racing

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Last edited by Alfar7; 11-07-2012 at 02:08 PM.
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post #5 of 7 (permalink) Old 11-10-2012, 05:34 AM Thread Starter
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How can I tell where it's specifically coming from? Are my choices only to really start replacing bearings and hope the sound goes away?

I can drop the trans sometime this winter. Salt on the roads already up here. Do I have to split the transmission cases to replace the input/output bearings? I'd like to replace the seals anyways.

I do have a "spare" transaxle, but its an unknown.

As for prior noise... no idea. No idea what the fluid was in the transmisison and gearbox, either. Bought the car relatively cheap after a short test ride because the brake MC was leaking like a... well, leaking badly. I knew what I was getting, and was ready for some work.
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post #6 of 7 (permalink) Old 12-09-2012, 07:17 PM Thread Starter
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Just a quick update on this... figured out the noise is coming from the rear diff. Took it for a longer drive with my wife, who's hearing is better than mine. I do have a "spare" rear axle, but I don't know the condition of it. Guess I should take a look.
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post #7 of 7 (permalink) Old 12-13-2012, 04:49 PM
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easiest way to tell if it's diff vs. tranny is get up to a speed where you hear it under light load and shift to the next highest gear...add some throttle. if the pitch of the whine is same regardless of what gear you are in - it's more than likely the rear end.

i.e. is the whine related to wheel speed or engine speed
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