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Re: Advice on MGA 3rd gear noise mystery

To: SCC <>
Subject: Re: Advice on MGA 3rd gear noise mystery
From: Martin <>
Date: Mon, 04 Jun 2001 12:12:31 -0500
When the noise is most loud in 3rd have you tried up shifting into 4th
maintaining constant speed? Does it quit? If so you must have chewed
up 3rd gear or the 3rd gear part of the laygear.

SCC wrote:

> Driving home from a Chicagoland MG club tech session yesterday (thanks,
> guys!  very informative), I noticed third gear was making a sound, as
> follows:
> * Frequency of sound is proportional to engine speed while under throttle.
> Throttle off, sound diminishes greatly.
> * No trace of sound in any other gear (including reverse)
> * Sounds like fanblade (metal) contacting rubber or plastic, but it isn't
> (fanblade is clear)
> * Could also be described as a vibration or warble as if a shaft is
> misaligned
> * Similar to a high frequency version of thumping one would hear with warn
> suspension bushings, for example.
> * Sound is difficult to locate, but is definitely not from the rear of the
> car.  Driver or forward.
> 1962 MGA 1600 Mk. II
> I was about to yank the engine and transmission, but then someone who knows
> a lot more about MG's than I (which would be most people, actually) said it
> could just be a worn universal joint.  I would have thought that would
> affect more than just 3rd gear.  But I thought I'd better ask the list (of
> experts) for opinions on where to look for the problem before I cover my
> garage in my poor LBC's innerds.
> The only thing that's been done to the car recently, none of which I can
> think would be remotely connected, is Petronix ignition, fan shroud
> installation, 165 degree thermostat, and lube for the steering rack.  I
> checked all fluids, and everything is in order (no fluid older than, say,
> 300 miles).  30 weight Castrol GTX in the transmission, 20w50 Castrol GTX in
> the engine.  Yesterday was unseasonably cold for Chicago, and the car was
> cruising at 160 degrees (lowest it's ever been since I've owned it --
> usually hovers at 180), but seemed to be running fine at the lower
> temperature in general.
> The only other issue the car has (and has had since I got her) is an
> occasional backfire when cruising at 60+ mph, and a tendency to stall
> occasionally when decelerating from cruising speed under engine braking
> until she's really warmed up.
> Any help would be GREATLY appreciated!
> Scott

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