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ragpicker
Paul Ricard


Joined: 14 Apr 2013
Posts: 3147
Location: North East England


PostPosted: Sat Jul 08, 2017 8:46 pm    Post subject: Reply with quote

Unusual problem this weekend. The lower gearbox mount lug pinged off as I was setting off from work. I heard and felt it, thinking it must have been one of the new coil springs cracking. When I checked I found this:







What an absolutely terrible design. The thinnest bit of alloy fin is used as the gearbox mount lug!

Anyway, I was puzzled with what to do as a solution. Fortunately a friend gave me the number of a mobile aluminium welder - a rare breed!



Access isn't as bad as you would think and within an hour he had built the area up with new weld to strengthen it and got it fixed. Hopefully stronger than new!




Looks like its fixed, tomorrow i'm going to attach it back onto the mount and see. £65 for a job which could have saved me £800 for a second hand box!

Result!

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kas750
Paul Ricard


Joined: 31 Mar 2013
Posts: 3401
Location: Chorley lancashire

2006 Porsche 911

PostPosted: Sat Jul 08, 2017 8:56 pm    Post subject: Reply with quote

The mount on mine snapped as well..Again I heard a ping that sounded like a coil spring snapping!!!
The only clue was the exhaust tail pipe at a weird angle..
Again welded in situ and now all good..
I love my 986..The best Porsche model ever... and I've owned a few
 
  
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ragpicker
Paul Ricard


Joined: 14 Apr 2013
Posts: 3147
Location: North East England


PostPosted: Sun Jul 09, 2017 4:26 pm    Post subject: Reply with quote

Totally agree with you Kas750. I've owned a few too now and the lowly old 986 is every inch a true Porsche.

Just to finish this bit off, here's a pic of the gearbox completely fixed..

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Demort
Estoril


Joined: 21 Mar 2015
Posts: 3502
Location: Sussex


PostPosted: Sun Jul 09, 2017 4:47 pm    Post subject: Reply with quote

Surprised

2 of you have had this and ive never even seen it !

Excellent idear for a repair though .. ill remember it for when i do come across this Thumb
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ragpicker
Paul Ricard


Joined: 14 Apr 2013
Posts: 3147
Location: North East England


PostPosted: Sun Aug 20, 2017 1:48 pm    Post subject: Reply with quote

I was trailbraking into a left hander 2 days ago when I heard a 'clink' and a thud. As I was late for work I carried on cautiously but noticed that the car was pulling to the left and there was a horrible noise like the front wheel rubbing under heavy braking.

Today is the first time I've been able to get the car on the lift and have a look:

Broken tuning fork:


Slipped coffin arm bush insert:


Drop link broken:


As you can see, there's an awful lot of damage happened due to the failure of the tuning fork. As you can see from the following pictures it is clear that the polybush didn't allow any 'give' next to its anchor point which led to it fatiguing and then failing:




Without the tuning fork keeping the centre of the wheel pinned in position, under heavy braking the wheel was moving back and rubbing on the leading edge of the front wing. The only think really keeping the hub where it should be was the coffin arm but this was clearly overly stressed in order for the bush insert to move out of the arm.

Needless to say I won't be buying polybushed tuning fork arms again. Good old OE bog standard replacements from now on. I'm obviously going to replace the pair even though only one is damaged along with a new coffin arm.

Could have ended in tears....

nooo
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Demort
Estoril


Joined: 21 Mar 2015
Posts: 3502
Location: Sussex


PostPosted: Sun Aug 20, 2017 2:19 pm    Post subject: Reply with quote

You where very lucky there as thats a pretty bad component to have fail .. interesting what the cause of it is though .
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Marky911
Suzuka


Joined: 04 Jun 2009
Posts: 1069



PostPosted: Sun Aug 20, 2017 4:08 pm    Post subject: Reply with quote

Top work Raggy, as ever. Especially the suspension refresh though. Cool

What a freak failure on that tuning fork. As Demort says, lucky escape there.
 
  
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pothole
Monza


Joined: 04 Oct 2011
Posts: 168
Location: Location Location


PostPosted: Mon Aug 21, 2017 1:46 pm    Post subject: Reply with quote

Interesting failure. Noted for the future as I will probably rebush my 987 at some point. Will stick with the inner and outer coffin arm bushes I think.
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ragpicker
Paul Ricard


Joined: 14 Apr 2013
Posts: 3147
Location: North East England


PostPosted: Sat Aug 26, 2017 7:06 pm    Post subject: Reply with quote

All sorted with new tuning fork arms both sides and a new coffin arm on the nearside:



It took about 20 minutes to put these back on, its lovely when everything comes off easily, but it wasn't all plain sailing.. First I had to contend with the two 'identical' arms that an eBay seller sent me Rolling Eyes



To be fair to them, they sent me a replacement part out by 10am the next day, so it wasn't too bad.

Next episode will be the installation of the new underdrive pulley!

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kas750
Paul Ricard


Joined: 31 Mar 2013
Posts: 3401
Location: Chorley lancashire

2006 Porsche 911

PostPosted: Sat Aug 26, 2017 7:12 pm    Post subject: Reply with quote

I'm interested in the results of the underdrive pulley.
Great work as ever. thumbsup
 
  
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ragpicker
Paul Ricard


Joined: 14 Apr 2013
Posts: 3147
Location: North East England


PostPosted: Mon Aug 28, 2017 3:55 pm    Post subject: Reply with quote

Today I spent the morning installing the underdrive pulley. This is a first for me as its one of the few mods i've never done.

A forum member (jimk04) has been producing and selling the pulleys. He kindly sourced me the correct belt to go with it. £125 later it arrived and the product looked good.

For those who aren't that familiar with the 986 anatomy, the front of the engine is accessed through a fire wall behind the drivers seat:


Here you can see the two pulleys we are interested in - the large silver pulley at the bottom is the crank pulley which will be replaced, the smaller black one above it is the tensioner pulley which keeps the belt under tension and stops it falling off. Both have a 24mm bolt in them.


To remove the crank pulley you can buy the porsche tool which prevents the pulley from rotating when you undo the bolt, or you can place something through one of the holes in the pulley and into the TDC boss to stop it turning. Then with a long 24mm ring spanner, or a shallow 24mm socket you undo the bolt.

The original crank pulley, note the notch cut out of the centre hole:


Compared to the new pulley:



Using a dremel you have to grind down the TDC boss to provide clearance. You can see that the notch on the pulley fits over the notch on the crank pulley mount. This is there to ensure that the pulley turns even if the bolt holding it in is loose, thereby making certain that the ancillaries are powered by the pulley. To this effect, whilst you should make every effort to re-tighten the bolt during re-installation, there is a safety net there.

Here is the amount of TDC boss needed to be removed:


Pulley offered up:


And re-installed with a bit of loctite on the bolt:


And thats it! Simply put the new, shorter belt on, fire up the engine to ensure everything is seated properly and then put the fire-wall back. Bobs your uncle, Fanny's your aunt and Robert's your mothers brother!

Has it made any difference?

Well, the most surprising difference initially was how quiet the engine sounds now. Maybe its because its a new belt, maybe because things aren't spinning as quickly, but it is a huge improvement in that regard!

There is no change in how heavy/light the steering feels.

There does appear to be a small but noticeable improvement in punch across the rev range. Certainly not an amazing amount but its there. The bum-dyno says its probably 5-7whp. There was no change in water temp either.

I'm absolutely amazed at the reduction in whirring noise in the cabin though, its worth it for that alone! I think all in all its a good little mod and I would definitely do it again.

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crash7
Monza


Joined: 28 May 2011
Posts: 248



PostPosted: Tue Aug 29, 2017 5:43 am    Post subject: Reply with quote

Could I ask how much clearance you have between the ground down boss and the pulley? - Cheers Thumb
 
  
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ragpicker
Paul Ricard


Joined: 14 Apr 2013
Posts: 3147
Location: North East England


PostPosted: Tue Aug 29, 2017 6:34 am    Post subject: Reply with quote

crash7 wrote:
Could I ask how much clearance you have between the ground down boss and the pulley? - Cheers Thumb


Hey! I think i was a little too enthusiastic with the dremel and have about 4mm clearance. As there is no back and forth movement of the pulley you could get away with less than 1mm. The hole for the boss seems to be never ending, its very difficult to grind too much off.

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