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MG MGB Technical - Noisy overdrive

My OD works perfectly, cuts in and drops out exactly as it should but I’ve noticed recently in 3rd OD it sounds noisy, it’s probably also noisy in 4th OD but as I mostly use it with the top down I can’t hear it. The noise is a droning that sounds similar to tyre noise.

The gearbox oil level is correct and I’m using 20/50 engine oil as per the manual. The gearbox is quiet and the synchro works well in all gears.

What’s the likely cause and should I be worried?

On another note, I was out yesterday enjoying a rare bit of sunshine, I was traveling at approx. 50mph quite some distance behind the car in front when I heard a small crack and immediately notice a stone chip about 3 inches from the centre of my eyeline. Just bad luck you may say but as I only fitted this windscreen about 4 months ago to replace a genuine Triplex screen that had a stress crack in the top right corner but was otherwise perfect, I’d say it was very bad luck. I sometimes think I must have been a bad person in some former life!

Bob
R.A Davis

Bob, Who fitted the replacement screen? My last one was fitted by one of the bigger companies and it lasted just 3 hours. They had not cottoned on to the fact that slightly too long a screw can hit the edge of the glass. Finished up doing it myself as they didn't have a hacksaw!!!!
Allan Reeling

Allan - Can I assume that you are not going back to them in the future?
Cheers - Dave
DW DuBois

Allan

I fitted the screen myself, I use a couple of G clamps, one on each pillar and progressively wind them down. As long you put plenty of tape over each pillars to protect them it’s reasonably easy and controllable. I also pay particular attention to the screw lengths.

Just went to take a picture of the chip and what was probably just about an MOT pass is now definitely a failure. The paper towel behind is to make it stand out.

I must have been Attila the Hun in that previous life.

Bob


R.A Davis

Is it just a chip or is that a crack running across the screen?

Does the MOT allow chip repair? In the US, I would visit a glass shop and they would fill the chip. Just had one done on my GT and you cannot see it at all.
Bruce Cunha

Bruce

It started as a small chip but overnight it’s developed into a crack going from top to bottom of the screen. I’ve had chips filled in the past with varying degrees of success.

The MOT test allows small chips within the arc of the driver’s wiper and larger damage outside this but a crack from top to bottom is a failure.

The initial chip was made by something very small judging by the sound of the impact and I was surprised by the damage, the chip having now grown to a crack from top to bottom makes me wonder if the glass had been correctly manufactured. I assume the glass is tempered before it’s laminated, I wonder if this was done properly. It could also be I’ve got some stress in the screen, I was careful to ensure the spacers at the bottoms of the pillars went back in the same places but there’s no guarantee they were right to start with.

The good thing is they only cost £69.95 from the club, or is that a bad thing meaning they’ve been cheaply made?

Bob
R.A Davis

Noisy OD when engaged and quiet when disengaged indicates pretty bad wear on the planet gear bearings / pins.

Not good news and could fail.

Check the OD filter for bits of metal.
Chris at Octarine Services

Since you were out driving, I would bet the window cracked when it cooled off. That is a shame as that is a time consuming project to replace.
Bruce Cunha

This thread was discussed between 21/08/2017 and 23/08/2017

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