engine and drivetrain Squealing Noise From Under Car

[BrianR]

I have a squealing noise coming from under my car. It is not engine related as it only happens when I'm moving. It is not the clutch, it is briand new and still does it when clutch is engaged. It was doing it beffore I changed the clutch.  I't sometimes gets real loud and sounds like a bearing. Center Bearing? Looks original and I have one on order. How about the speedometer cable. I tried to lube from above, but it looks like it is in two sections. Is that correct? Question about center bearing replacement. Does anyone know what size wrench to remove nut that holds the two sections of prop together? Any other ideas?

 

Thanks

Brian

[Mike Self]

Sounds like a center driveshaft support bearing that's on it's way to CD's neighbor's pool.  You need to hasten its journey.  Those bearing failures usually start out by squealing when you first start driving (bearing is cold, what little grease is left isn't warmed up yet) and then goes away.  As the failure progresses, the squealing lasts longer and longer until it's all the time.  You can pretty much eliminate a tranny problem by letting the car coast in neutral--if the squeal continues, I'd suspect the center driveshaft bearing.

 

Two other things to check: 

 

1.   if you have A/C and still have the original compressor bracket with an idler pulley, check the pulley bearing.  I diagnosed a center support bearing failure that turned out to be that little 6202 bearing in the A/C idler pulley.  Easy to replace as it's held onto its bracket with a circlip.

2.  As you mentloned, the speedometer cable.  If your car has the " emission service" warning light atop the dash inside the seat belt warning light pod (75s & 76s), the speedo cable is in two pieces, with a gearbox interposed that trips the warning light bulb every 30k miles.  So you'll need to lube both sections of cable.  However, when the speedo cable starts squealing, the speedo needle starts twitching; if yours is steady, chances are that's not the problem, unless it's the lower cable.

 

cheers

mike

[Rocan]

Mike, do you have any more info on the speedo cable? mine twitches at low speeds and makes a rattling noise. The noise wasn't there when I got the car or when I removed the cable from the gauge the first time, but after the second time it started making a rattling noise and jumping a bit at low speeds. I'd prefer a one piece cable (two piece + gearbox sounds like more crap I don't need )... can it be retrofitted? 

[Mike Self]

Re the speedo cable on your '76. 

 

You can replace the two piece cable/gearbox with a one piece cable assembly from a pre-75 car; just have to remove the old cables and gearbox, thread the new cable through the holes in the bodywork and reconnect at both ends. 

 

About the noise:  is it coming from the speedometer itself or the cable?  To determine, you need to drive along (do this on a deserted street or a big parking lot) with one hand up under dash fondling the speedometer cable.  If you can feel it twitching noticeably inside its sheath, then chances are good it's the cable. 

 

To make sure it's the cable, remove the instrument cluster from the dash, file down a piece of copper or aluminum heavy gauge wire (or something else easy to file) so that it's square on the end, and will fit into the speedo's drive slot.  Chuck the wire into an electric drill, then power up the drill in reverse and watch the speedo. If it still flickers and makes noise, the problem is in the speedo.  And if that's the case, drop me an e-mail and I'll send you an old column I did on troubleshooting and repairing wonky speedometers.

 

cheers

mike