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What's wrong with my 915 gearbox? - Competition


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Well, as you know I have had a nasty noise since the "bring a car run." It has got steadily worse so it needs proper investigation. Matthew at @Type911 put me in touch with Pat who is not far from me and I went to see him today. (This is where I met him https://anthonygodin.co.uk/ - Wow! But that's another story). 

On the way down the noise was horrific to the point where I was actually worried about driving the car. We went for a drive and Pat agreed that it was definitely the gearbox and it sounded bad. We had coffee, I nosed at all the amazing machinery in the showroom and then I, gingerly, drove home.

Hopefully Pat will be doing a rebuild in 4 or 5 weeks time. In the meantime I thought a little competition would be fun.

The person who guesses closest to what is wrong and what needs replacing wins a prize (not a big one but an actual one). The symptoms are a loud grinding noise in 3rd, 4th and 5th gears at pretty much any speed. Less so in 2nd and not at all in 1st. The noise goes away when I lift off the accelerator. Gear selection is not affected.

Good luck!

 

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I know exactly what it I is Phil. ...............Happened to me many times

it’s your bank account washer, specifically the one that fits between your current account and your debit card.

they are notorious for wear and eventually bankruptcy with these Porsche cars. All I can suggest is that you 3d print a decent funnel to keep the account at the correct level. 😉

  • Haha 1
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45 minutes ago, Type911 said:

Is it fecked?

That will probably be the winning answer.......:rolleyes:

9 minutes ago, Beaky said:

Thrust shaft bearing, Pressure plate thingymegig, syncro's on reverse

Stringing a load of gearboxy sounding words together doesn't count :lol:

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@Leicestershire 's answer seems to be the only sensible one so far if not a bit scary judging by aftermarket specialist prices!! I hope that's not the problem or at least standard jobbies are less costly.

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17 hours ago, Leicestershire said:

Pinion, crown wheel, bearing & retainer. 

Agree - worn retainer or bearing allowing pinion to move. Hopefully something simpler as not a cheap fix!

http://forums.pelicanparts.com/porsche-911-technical-forum/506374-transmission-sound-3rd-4th-gear.html

Good luck

Edited by Roy M
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1 hour ago, sopor said:

Apols if this is a silly thought but have you checked the oil level? 

I think if oil level it would be noisy all the time and in all years.

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  • johndglynn changed the title to What's wrong with my 915 gearbox? - Competition
  • 1 month later...

Car went off today to have the gearbox rebuilt. Hopefully will be opened up by the end of next week so last chances to join me in my misery and hazard a guess at what's at fault.

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I'm going with pinion bearing at rear of gearbox has collapsed . From the tail of the box moving to the bell housing you have 5th and reverse then a pair of bearings that supports the pinion and input shaft at the rear, 4th , 3rd ,2nd and finally first. Then you have the 4 point bearings and retainer crown wheel and pinion etc.  By the sounds of it the noise deminishes as you come down the ratios suggest the issue is the support for the gearsets furthest from the retainer plate have an issue. If not that 1st gear needle roller as the noise disappears when 1st is selected . Remember gears are in constant mesh the drive is transmitted by the sliding sleeve keyed to the spider locking into the dogteeth . 

But I have seen this before when 1st gear input shaft has lost a tooth. Very noisy in all other gears until 1st is selected as the large 1st gear free wheeling hammers around when it is idling. As this is part of the shaft the gearset is rather spendy. 

Hopefully something cheaper.

 

D

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29 minutes ago, PorscheApostle said:

I'm going with pinion bearing at rear of gearbox has collapsed . From the tail of the box moving to the bell housing you have 5th and reverse then a pair of bearings that supports the pinion and input shaft at the rear, 4th , 3rd ,2nd and finally first. Then you have the 4 point bearings and retainer crown wheel and pinion etc.  By the sounds of it the noise deminishes as you come down the ratios suggest the issue is the support for the gearsets furthest from the retainer plate have an issue. If not that 1st gear needle roller as the noise disappears when 1st is selected . Remember gears are in constant mesh the drive is transmitted by the sliding sleeve keyed to the spider locking into the dogteeth . 

But I have seen this before when 1st gear input shaft has lost a tooth. Very noisy in all other gears until 1st is selected as the large 1st gear free wheeling hammers around when it is idling. As this is part of the shaft the gearset is rather spendy. 

Hopefully something cheaper.

 

D

Edit Sorry it's late and Ive had a few whiskeys 😂 Reading that back that's arrrr5e about face. Likely to be your 4 point pinion bearing Phil . From 5th and reverse you've got 1st 2nd 3rd 4th at the 4 point  pinion bearing  side so certainly sounds like the pinion 4 point bearing has failed . Best of luck 

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42 minutes ago, PorscheApostle said:

I did a vid a while ago, please excuse the thick spitting image Yaarpie accent , hope this explains it better than my bumbling drunken post.

 

Very interesting, thanks for posting that 👍 I didn't realise you were the "new" RSR, I will have to swing by sometime.

I really do hope it's just bearings.

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2 minutes ago, Phill said:

Very interesting, thanks for posting that 👍 I didn't realise you were the "new" RSR, I will have to swing by sometime.

I really do hope it's just bearings.

Yeah Russell Lewis (RSR Engineering)  hasn't worked in place for a few years now. He's working from home. He had a feature in classic Porsche last month. 

It's just Me, Bart and Ollie now. 

D

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