Spit Vertical Link failure new v OEM

[Benjamin Swatton]

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

 

[Gt6s]

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

 

Edited July 14, 2021 by Gt6s

[Nick Jones]

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

[Nick Jones]

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

[Gt6s]

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

[Nick Jones]

Ok…… Messed up my suspension tune and geometry big time.  Got most of the way back after much messing about but not as good as it was. Needs stronger springs now.

Nick

[mikeyb]

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 July 16, 2021 by mikeyb

[Hogie]

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

 

[Gt6s]

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

[mikeyb]

On 17/07/2021 at 17:16, Gt6s said:

Wait till you get into Quaife diffs I have Two (Genuine) and a Blackline Chinesium one

I can boast a Salisbury and a Phantom, lol! 

[thescrapman]

On 19/07/2021 at 19:14, mikeyb said:

I can boast a Salisbury and a Phantom, lol! 

Which car is the Phantom in?

[mikeyb]

It's on the garage floor currently!

Small chassis 3.89 if I recall...

[TimW]

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

[Benjamin Swatton]

 After a bit of delay to proceeding's,  recently I spent most of a tedious tiring grubby day at a used parts supplier to find some good used OEM Stanpart VL's. .

Having gone through approx two dozen VL pairs it was interesting to note approx  2/3rds were actually found to be relatively modern pattern parts with the cut threads, also all VLS  were full of  grease and not oil! I came away with 2 pairs of the best condition OEM rolled thread VL's that I could find and an assortment of used trunnion's that weren't too wobbly..

Having grit blasted them and purchased 2 brand new trunnion's for comparisons, it's now time for closer inspection, cracked testing and selection of the least worst!

 

 

[Benjamin Swatton]

Below are two pics of the VLs one for each side of car for comparison of conditions. The ones painted black  are the ones removed from my car. So visually you can see the purchased one are an improvement generally... However two the six VLs I have in total have a suspected crack across corrosion pits running circumferentially partly around shank area - difficult to see but 3rd photo shows , unlikely i will use these but for curiosity and to be sure I will be using a cracking detection kit. Now I'm glad I bought 2 pairs..

[Benjamin Swatton]

Meanwhile I have selected the best trunnion with least play for each side - mostly by sight but for curiosity I set up a dial gauge wobble test as per photo.

What is intersting is that both BRAND NEW trunnions from a popular supplier had the same amount of wobble as used originals of indeterminate origin! There are several conclusions you can draw from this but I'm glad I gathered a selection of used part's.  

[thescrapman]

I think I know which 2 I would go with, LH top picture and RH bottom picture.

Really need to go through all my spares at some point.

[Benjamin Swatton]

First time using dye penetrant Flawtek crack test. Now undertaken and after 1 hour appears to show all 6 VLs are surface crack free.  I will select those that have the least corrosion pitting

[Nick Jones]

Interesting.  Bit surprised you don't seem to be getting any trace from the rust pitting?  IMO the area where you want to be most fussy about the rust pitting is at the bottom of the thread groove in the upper turn of the thread.  This is where they mostly break.

Also bear in mind that if the horizontal axis is stiff (ie the nylon bush), this puts a significant bending moment into the link, just about where the top of the thread is, as the suspension moves, so very important these move as they should.  This is one (maybe even the biggest) advantage the trunnionless-design has - free movement in all directions.

The drawback with the trunnionless design is that it moves the suspension pivot point outboard and increases the leverage ratio, reducing the effective spring rate.  Maybe ok if setting up from scratch at that point, but a disappointment if you were expecting your previously perfected arrangements to still work as before, afterwards.

Nick

[Benjamin Swatton]

I had another look to be sure - nothing in the thread grooves.

I was told that these fail on the shank at the height where seal and trunnion mate as thats where corrosion line often is as per my car's VLs

Photo shows the very slight pigment in the corrosion spots.

Either way I will be able to select 2 good VLs

 

[Hogie]

Hi,

Dye pen is not the best method for checking FerroMagnetic steel.  Magnetic Particle is the top choice.

However you do need a decent magnet system to make it work.

Like Nick I would have thought there would be a greater pink background rather than stark white.

So this begs the questions -

How did you clean the VL?

How did you remove the excess penetrant  from the surface.?

The cleaning process should include some form of hot Trichl....... for an hour or so.

The penetrant should be cleaned off by using a dry paper towel to get the majority off and then a damped paper towel (damped in the remover fluid). This would leave a pink background.

Apply the developer in a very thin coat and watch it as it dries. If there is any cracking the dye will show this as a fine line BUT will start to smudge quite quickly and lose its definition.

If you apply a thick coat of developer (yours looks thick but I may be wrong)  then you will not see a fine line

or the corrosion pits as it will start to smudge from the onset. 

As stated above the cracking should occur at the end of the threaded area.

Also check the profile of the thread form. If they do not look symetrical then that will add to the sidesays play.

 

Roger 

 

[PeteStupps]

On 05/08/2021 at 10:05, Hogie said:

Dye pen is not the best method for checking FerroMagnetic steel.  Magnetic Particle is the top choice.

This is what I had done with mine last year, very luckily a neighbour does crack testing professionally so had the kit and expert eye. Photo below is out of focus so not much use, but he could see clear evidence of a crack just above the threads (I think that's where it was, I could see it when he pointed it out but wouldn't have spotted it myself). Photo was taken after the electromagnet was removed, so line was less pronounced.

 

[Benjamin Swatton]

I followed the instructions exactly that came with Flowtek 3 part crack test spray which included the cleaner which was used with cloth, trichloroethylene was not used as only using what kit had. If any thing is wrong the white is too thick but either way I'm not using either of the two VL that I was suspicious of .  I'm not getting trich or I may as well get it done professionally using other methods..which I may yet do..

The scrap dealer mentions they break at corrosion line at shank, others mention they break at the thread but is that because thread has corroded ? -we need to be clear on this as i would not use a corroded thread anyway - so show me the breakage photos...

[Benjamin Swatton]

Got the stub axle's hydraulic pressed out at local garage , did spray some GT85 lubricant in first they came out easily except left most one that bent its thread on the way out.

As Hammerite ive found no good for yearround use and goes off in tin a's does POR15 which is too expensive, so I'm trying Bonda Rust zinc primer the tractor/truck/boat people like, Then halford sprit based gloss enamel.

[Benjamin Swatton]

Decided to repeat the Flawek crack test on two of the VLs  below that look like they should show up either cracks on shank or threads or dye in corrosion pores. I will test twice.

first time I will pre clean in cellulose then follow Flawtek instructions using supplied iso propanol spray but then will increase time for dye to penetrate to 1 hour (instructions says 5mins and upto 20mins for fine cracks as I did last time) will also then put on less developer  as it was a little thick last time.

The second test will involve a 24hour pre soak in Cellulose thinner to draw out contaminants in any cracks I will then repeat Flawtek test process again.