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Transmission intermittent whirr sound

Posted: Mon Sep 09, 2019 2:58 pm
by pressonregardless
Went for a two hour drive to explore this weekend. Turned down an "old vintage road" no painted lines, one lane bridges, extremely bumpy, seldom used and dropped my speed due to the rough conditions, mostly 2nd gear and bottom of third gear speeds (30 mph). So bouncing around violently at times, after about 10 minutes, I hear what sounds like a "loose gear that tipped or fell rubbing against the output of the transmission. This noise is speed dependent, not affected by engine RPM, nor any gear, nor clutch in or out.

I pulled over and depressed the clutch then selected 1st, 2nd, 3rd, 4th, 5th gear. Then went for reverse and herd a sound like the car is slow rolling and you try to go into reverse. I was stationary. I depressed the clutch again and waited about 10 seconds, selected reverse again and it went into gear and backs up the car.

So, I continue on this very bumpy road and 1/4 mile of complete quiet and hit a bump and Whirrrrr again. Limped home by stopping the car and selecting Reverse when ever the sound appeared. Going to drop the GL-1 and inspect or metal.

I have searched both "Fiatspider.com" and "Mirafiori.com" and nothing like this shows up. Suggestions? ?

Re: Transmission intermittent whirr sound

Posted: Mon Sep 09, 2019 5:52 pm
by miker
I would check the rubber guibo between the back of the transmission and the driveshaft. This would be a part that rotates no matter which gear, forward or backward. It's also a known wear item.

Re: Transmission intermittent whirr sound

Posted: Mon Sep 09, 2019 9:13 pm
by bartigue
Ditto mike

It doesn’t sound like a transmission issue. Sounds like a failure in the driveshaft rotoflex (guibo) or center support or u joints

Re: Transmission intermittent whirr sound

Posted: Tue Sep 10, 2019 2:39 am
by rridge
Agree. With any strange noise from the drivetrain start with a close inspection of the rubber donut. Then check for excessive play in the center bearing support. While under there pump some grease into the nipple on the front driveshaft which lubes the sliding spline.

U-joints also need a check for play. I once found a U-joint that had a poorly formed seat for one of the circlips which allowed the center cross to shift side to side.

Before you drop the car back down check the lube levels in both the trans and differential. Both usually have magnets on the drain plugs. And then there is the clutch throwout bearing, pilot bearing...

Re: Transmission intermittent whirr sound

Posted: Tue Sep 10, 2019 1:00 pm
by hayesbd
Since you note that hard vertical bumps initiate the problem and a torque reversal temporarily alleviates it, I recommend also taking a look at the engine and transmission isolators in addition to looking at the usual suspects (giubo, pillow block, etc.)

Brian

Re: Transmission intermittent whirr sound

Posted: Wed Sep 11, 2019 12:42 am
by pressonregardless
Today put the Spider up on jack stands and began an inspection. Found some PO added extra "rubber matting" for sound-heat control and over the years, it slowly slipped down and was "grabbed" by the flex disc (Guibio). It looked like it was formed out of a floor mat, cut to fit under the foam rubber boot.
Since I have it "in the air" I dropped the Transmission pan to clean it. Found some tiny brass specks, no steel. Physical inspection of the transmission internals all look normal. So tomorrow, button up, add 1.75 Qt of GL-1.

Fingers crossed!

Re: Transmission intermittent whirr sound

Posted: Wed Sep 11, 2019 2:22 am
by davedecker4
pressonregardless wrote:
Wed Sep 11, 2019 12:42 am
It looked like it was formed out of a floor mat, cut to fit under the foam rubber boot.

Fingers crossed!
I hope that cures it. But...what and where is the foam rubber boot? I'm not sure if I have that part.

Re: Transmission intermittent whirr sound

Posted: Wed Sep 11, 2019 8:39 am
by kgfiske
Is this what he referred to?

Re: Transmission intermittent whirr sound

Posted: Thu Sep 12, 2019 10:53 am
by pressonregardless
Yes, the foam boot was in place, but in average shape. I'll be ordering a new one from AR.
Ended up changing the transmission, rear end, and engine oil. Transmission (Napa GL-1) was about 10 years and 20K old. Slightly dark from new, a few very fine brass grains on the plug and pan, no steel ! ! So, guess it was the heavy rubber mat beating on the drive shaft. Flex Disk was firm and looked almost new. (Driveline rebuilt about ?? 6 years ago??).
Will make a test drive today, thanks to all for your input!

Re: Transmission intermittent whirr sound

Posted: Thu Sep 12, 2019 8:53 pm
by bartigue
Brass bits are the synchronizers shedding material b/c of speed shifting or someone resting their hand on the shifter while driving. Don't do either!