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Spit Vertical Link failure new v OEM


13254
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The conundrum from hell, have now inspected both sides, both verticals are OEM and both trunnions are same manf with steel bottom disc seal - I think may have been newly fitted about 10 yrs /20,000 miles ago.

Visually both VL threads look great condition zero corrosion  as do the trunnion threads I can see however..

Left  VL in trunnion has virtually no play however where rubber VL seal mates VL shank above thread  there is a narrow line of corrosion running  1/3rd way round - potential stress corrosion cracking scenario? - I have read on other forums some saying they can break here but others say snapping only ever occurs on the threaded portion and I've only seen pictures of failure at the threaded - I don't want to scrap a part unless necessary -anybody confirm this?

Right VL in trunnion has about 2mm of rattle, measurement  of OD of VL thread with vernier  gauge suggests a reduction diameter / wear at top there is also slight undercut of shank above thread,  no corrosion to worry about really.

I will be buying a new trunnion to see if it takes out the play but I suspect not

I don't want to go trunnion less

If I buy from one of the  main suppliers are all the dodgy VL of the past now  gone ?  I presume all the VL come from same manf. can anybody confirm where these come from i presume not manf. UK! are these forged as OEM or cast? Are the threads rolled or cut ?

I don't want to go new unless I have to as there is then the  knock on problem with new stub axle accuracy problems - arghhhh

Thanks

 

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  • 1 month later...
1 hour ago, Gt6s said:

Mostly seen broken at the very end of the thread even on very fresh ones. Go trunnionless.

 

What do you feel about the geometry changes and change in suspension leverage ratio that trunnionless brings?

Nick

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On 08/06/2021 at 23:30, 13254 said:

are these forged as OEM or cast? Are the threads rolled or cut ?

Forged as OEM with rolled thread. Not sure whether those currently sold are forged or cast but the thread ms are definitely cut.

Nick

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17 hours ago, Nick Jones said:

What do you feel about the geometry changes and change in suspension leverage ratio that trunnionless brings?

Nick

Don't see it as a big problem Nick

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I don't think that there is an easy answer to this one.  Put simply, the only options are:-

 

1) Go trunnionless.  There are differing schools of thought on this.

2) Fit a new (remanufactured) VL with an inferior cut thread.

3) Try some new/secondhand trunnions - but sounds like your issue is in your VL.

3) Find a better seconhand VL - rocking horse poo nowadays.

 

I went down the trunnionless route on two of my three small chassis cars.  I have not looked too closely at any geometry changes, but they seem to have lasted well over time.  I have yet to repair a loose trunnion on the third car.  I will be scouring my box of used bits, but expect them to be pretty much exhusted of anything decent by now.  My lean would be towards trunnionless again, apart from the cost. 

 

Edited by mikeyb
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The replacement VL may or may not be forged.  But is there an issue if it is cast. I would suggest no.

The early (up to the late 30's) crank shafts were forged but then a decent casting process found the casting worked well. Nearly all automobile cranks are now cast.

The benefits of forging is that the grain flow is continuous and gives strength - and then you drill a hole or machine a face and knocks that idea into a cocked hat.

Thread rolling is indeed the top preference in threads that need that extra bit.

The threads on the VL are not under that much load. They don't appear to shear off or do anything silly.

The root of the thread should still be nicely rounded if you have a decent die/tap. The thread run out is a problem area when cutting with a die as it tends to end abruptly - in general engineering terms this is not a good idea as it becomes a stress raiser. It could be fettled with a file and emery.

But then consider- do they really fail at this position due to the thread run out. You would need to analyse the crack face of a failed VL to make an assessment - and I am sure this has been done.

So unless you ask the questions of the manufacturers as to what process they use then you are stuck with the 'over the counter' offerings.

I would go with either -

1  - take your VL to a suppliers of trunnions and try them out to get the best fit.

2 - if the above fails then buy a new VL and try out the trunnions in the shop.

 

Roger

 

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On 16/07/2021 at 07:38, mikeyb said:

My lean would be towards trunnionless again, apart from the cost. 

 

Tell me !  I own 3 sets of them. Wait till you get into Quaife diffs I have Two (Genuine) and a Blackline Chinesium one

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I don't see any issues with the trunionless option. Fitted mine maybe 10 years ago. I've not touched them in all that time. I don't see any issues with the slight geometry differences. I've had it set up on a 4 wheel aligner at a reputable company loaded the seats with weight and allowed me to give them the specific geometry setup I wanted. Cost wise the trunionless are barely more expensive than new trunions,VL's and the seals. A fit and forget solution in my opinion

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