Crunching/grinding noises on hard acceleration... Gearbox?

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BenT
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Posts: 86
Joined: Fri Nov 19, 2021 9:26 pm
Engine size/power: 1.6 CR TDI (102bhp)

Crunching/grinding noises on hard acceleration... Gearbox?

Post by BenT »

Hi all, hoping someone might be able to shed some light before I pull the thing apart!

I heard a "pop" when I pulled out of a junction earlier today, and now when I accelerate firmly in 1st, 2nd or 3rd gear there's an audible grinding/scraping sound coming from the nearside. There seems to be a light scraping in 4th and 5th but much less pronounced. I think I can feel it on the overrun, but putting the clutch pedal down stops it.

Has anyone experienced this sort of thing before? Mine's a 2012, CAYD engine with an LZY 5 speed gearbox on 156,000 miles. I put a new clutch kit in it a year ago after the master cylinder became incontinent... Otherwise, it's driving fine, selecting all gears as it should, just sounds rough!

The driveshafts are still bolted tight, wheel bearings seem fine, can't hear the exhaust blowing or see/hear any leaks anywhere. If it is the gearbox, might be a good excuse to sneak a complete 2.0 engine/gearbox into it ;)

Thanks in advance :D
BenT
Caddy Fan
Posts: 86
Joined: Fri Nov 19, 2021 9:26 pm
Engine size/power: 1.6 CR TDI (102bhp)

Re: Crunching/grinding noises on hard acceleration... Gearbox?

Post by BenT »

Problem found!

One of the upper gearbox mount bolts had snapped (hence the clunk when I pulled out of a junction). Here are some pictures to weep over. Whether I didn't torque them correctly when I replaced the clutch I don't know. Or, perhaps I did't quite line the mounting points up properly. Haynes was very specific about getting this right!

I really hope this isn't helpful to anyone, one day :oops:

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To add insult to injury, the "hardened steel" removey tool think snapped off in the bolt as I was trying to extract it. New mount and bolts on the way :cry:
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dan@biali
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Joined: Sun Mar 06, 2011 11:32 pm
Engine size/power: 2.0 Stage 3+ TFSI

Re: Crunching/grinding noises on hard acceleration... Gearbox?

Post by dan@biali »

Is it possible they are stretch bolts and should be replaced every time you take them out, hence why one has now snapped?
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BenT
Caddy Fan
Posts: 86
Joined: Fri Nov 19, 2021 9:26 pm
Engine size/power: 1.6 CR TDI (102bhp)

Re: Crunching/grinding noises on hard acceleration... Gearbox?

Post by BenT »

They do look like stretch bolts actually! I vaguely remember having trouble torquing them to spec for some reason too. Whoops. Makes it all the more remarkable that cars roll of the production line and seldom suffer from bolts coming loose...
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