Mismatched Tie Rod Ends and Accidents

[123rover50]

I keep hearing reports of mismatched TRE,s causing fatal accidents but have seen no evidence of such.
Is this anecdotal or an urban myth?
There is still plenty of thread screwed in and as long as the clamps are tight the rod cant unscrew.
If the rod did slowly unscrew there would be a discernable difference in the feel of the steering surely. This would be looked at before it came undone.
There is the same amount of thread engaging with either TRE so it cant just strip.
Am I missing something here?

Didiman.

[tomalophicon]

I keep hearing reports of mismatched TRE,s causing fatal accidents but have seen no evidence of such.
Is this anecdotal or an urban myth?
There is still plenty of thread screwed in and as long as the clamps are tight the rod cant unscrew.
If the rod did slowly unscrew there would be a discernable difference in the feel of the steering surely. This would be looked at before it came undone.
There is the same amount of thread engaging with either TRE so it cant just strip.
Am I missing something here?

Didiman.

I haven't heard anything about it, but not everyone does something about their car when it starts to play up, i.e the steering feels terrible!

[Lotz-A-Landies]

Are we talking about Series tie rod ends?

If yes, then you are definately missing something, the early Series 1 and series 2/series 2a have threaded shafts with a raised collar for the last 3/4", this collar has a diameter greater than the outside diameter of the thread and therefore when fully threaded tie rod ends are fitted to tie rods for the shouldered ends there is minimal (if any) clamping pressure on the thread.

If you compare the two types of tie rod end, you will observe that the shafts are the same length, but the early type has 3/4" less thread (the length of raised shoulder), and relies in large part by the clamping pressure on the raised shoulder.

If you have an early tie rod, remove the tie rod end and with a right angle scribe check out how little thread is actually inside the rod.

In any case why would you use the wrong tie rod ends when the correct ones are readily available from suppliers who know there is a difference? (Not ones who have reduced the two types to a single pair which will be incorrect for a significant proportion of sales.)

I have no trouble getting the correct tie rod ends from All Four X 4 at Kotara NSW.

BTW, the problems happens not by unscrewing, but by the thread stripping with lateral forces. As for evidence, one of the members of the now defunct series one garage had a mate die because of the problem. ( I guess that is still in the realm of myth. )

[Blknight.aus]

it can also happen on poorly maintained fully threaded rods...

if the rods internal corrosion gets bad enough the threads just strip out. Ive seen one actually snap the rod where the rod end was threaded in, Admitedly a much abused vehicle and fortunately due to the overall state of neglect with a very limited speed so the end result was little more than a spilt hay load and some smart assery along the lines of "well that went well, lets not do it again"

[isuzurover]

My father's IIA once had one TRE strip the threads out of a track rod. Fortunately he was driving slowly, and of course could still steer one wheel, so was able to stop safely on a side street.

IRC though, that it was a S3 track rod and TRE, and the threads stripped due to corrosion, rather than TRE mismatch.

I have found it hard to get good quality IIA TREs, so in the past have machined down an old track rod, to convert a SIII/Defender TRE to a IIA type.

[PAT303]

I had a tie rod end pull on my first 2a that sent me off the road,land cruisers pull the ball joint on the track rod,both will leave you with no steering and I would change them if I had either vehicle as a matter of coarse. Pat

[JDNSW]

As Diana says, it is apparently not a myth, although most failures have probably not led to accidents, let alone fatal ones. If you have a flat surface clamping on a threaded surface, the problem is that the contact area is very small, and consequently the clamping friction is very low. And the slightest movement will free it further. It is unlikely that movement is gradual - on a corrugated road, I would expect movement, once both ends are free, to progress to where failure is likely within a few kilometres, and in most cases the driver would not notice. I suspect the only reason that it is not more common is that a large proportion of the fleet has the TREs firmly locked by rust, regardless of mismatched threads. But this does not seem a very secure way to operate!

You can argue that if only one end is mismatched, as long as the other end stops the tube from rotating, there is no problem. However, this is a doubtful safety factor, as once the end can move, even if only a little, the thread will wear quite rapidly.

As a final comment - in the event of an accident resulting from a failure caused by mismatched threads, any competent insurer would certainly void cover.

John

[123rover50]

Its not mismatched threads that seem to be the problem.
The pitch and all match, it appears to be the clamping force of the clamps.
I feel the clamps are there only to stop rotation and the longitudinal clamping force of the clamps would be minimal. This is the function of the threads. So far failures appear to be from rust and corrosion not from the rod unscrewing or stripping sound threads.

[Lotz-A-Landies]

Its not mismatched threads that seem to be the problem.
The pitch and all match, it appears to be the clamping force of the clamps.
I feel the clamps are there only to stop rotation and the longitudinal clamping force of the clamps would be minimal. This is the function of the threads. So far failures appear to be from rust and corrosion not from the rod unscrewing or stripping sound threads.The tread in the completely threaded and shouldered series TRE are the same, but how much wear will there be in the threads of a 50+ year old vehicle?

I guess the issue becomes, when should you replace tie rods and not just the TRE!

[isuzurover]

...


I feel the clamps are there only to stop rotation and the longitudinal clamping force of the clamps would be minimal. This is the function of the threads. So far failures appear to be from rust and corrosion not from the rod unscrewing or stripping sound threads.

Without the clamps being 100% secure, you will get fretting of the splines, which will eventually lead to failure.

[JDNSW]

Its not mismatched threads that seem to be the problem.
The pitch and all match, it appears to be the clamping force of the clamps.
I feel the clamps are there only to stop rotation and the longitudinal clamping force of the clamps would be minimal. This is the function of the threads. So far failures appear to be from rust and corrosion not from the rod unscrewing or stripping sound threads.

The threads as you say, are the same. The failures result from the clamping being ineffective because the area of contact is inadequate. This can result in either the joint unscrewing or wear on the thread due to movement weakening the thread and consequent failure.

The problem is simply that you cannot rely on clamping being effective where you are clamping a thread against a flat surface. OK, you will get away with it a lot of the time, maybe most of the time - but do you really want to rely on "most of the time" when talking about steering?

John

[JDNSW]

The tread in the completely threaded and shouldered series TRE are the same, but how much wear will there be in the threads of a 50+ year old vehicle?

I guess the issue becomes, when should you replace tie rods and not just the TRE!

If the clamp has always been secure (and hence no movement on the thread), there should be no significant wear, even after fifty years. Rust is a more likely problem (or bending due to impact!).

Replacing the tube should be on condition.

John

[chazza]

There was case reported in LRO International some years ago, of a father and son dying in their S1 when they lost all steering and crashed through a stone wall. The investigators put it down to the wrong TRE somewhere in the system.

Remember also that the rods have slots cut in them, so when the clamp is done up the end not only grips on the shoulder but it causes the female thread to grip on the male part.

I used Loctite anti-seize on mine to stop rust; galling and fretting and I guess regular inspections are a must,

Cheers Charlie

[Psimpson7]

There was case reported in LRO International some years ago, of a father and son dying in their S1 when they lost all steering and crashed through a stone wall. The investigators put it down to the wrong TRE somewhere in the system.



I recall that story, but thought the cause was the fact that the track rod had rusted through as opposed to a TRE issue...

[123rover50]

I dont have a problem with using the shouldered TRE,s. I bought them off Alex at the Series one shop for the rebuild of Borumbah and Tristan but I have yet to hear any hard evidence of mismatched ends causing these fatalities .It appears to remain an urban myth.
Perhaps a comparison using a strain gauge and testing to destruction would give a result.
I posed the same question on the UK forum with no replies. At least here there is some discussion even if no definitive answer.

Keith

[B.S.F.]

Last year?... after driving the car daily for about ten years including several outback trips on very rough roads,I started to get kickback at the steering wheel. Upon inspection I found that the longitudinal steering tube was too short and clamped one TRE on the thread. That was the only TRE that had worked loose.All the TREs were of the shouldered type.In all fairness it must be said that because of the short tube only about 3/4-1" of the thread was engaged.
W.