Broken TC Rod

Suspension, including wheel, tire and brake.
Gigawatts
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Joined: 17 May 2015 13:41
Location: Houston, TX

Broken TC Rod

Postby Gigawatts » 18 Jan 2016 15:42

Hey Guys

I bought this 72 510 wagon a few months ago, and I have only driven it a handful of times. I hit a pothole going about 30 mph; heard a bang and the sound of metallic objects flying away from the car. When I started to lightly brake, the car would turn hard to the left even with me counter-steering to the right. I later found out the driver's side tension control rod had snapped right where it looks like the bolt threads into the main shaft.

It has a ka24de swapped in and I noticed the front sway bar is missing when looking at the TC rod. After reading on here, I assume the previous owner removed it to clear the KA oil pan and just never replaced it with a bar that fits. The car drove and cornered fine. Maybe I didn't drive it hard enough to notice, or maybe I never would have noticed the sway bar was missing.

The car is lowered. It has the small libra 175/50/13 wheels, what looks like 2" blocks on the rear, and I'm sure the front strut/spring has been modified or swapped from another car. The frame rail under the driver door is about 4" from the ground. I am thinking the lowering may have contributed to the TC rod failure. Also, it looks like the TC rod bushings are rubber and are pretty new.

I would like this to be a fun car to drive and perform well all around and it will be 95% street driven. I don't know a lot about suspension geometry. When I want to make a car corner better, I usually just read forums and do what everyone else is doing. Would it be recommended to source a stock TC rod to replace it or buy an aftermarket set like the futofab or technotoytuning ones? I don't know how to set the toe/caster/camber. Whatever I get, I will most likely just try to set the length to what the stock rods were and then take the car to an alignment shop.

I'm leaning more toward buying an aftermarket set, since I don't want another stock one to break on me.


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Thanks for looking!

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okayfine
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Re: Broken TC Rod

Postby okayfine » 18 Jan 2016 15:59

Looks like poly bushings on your T/C rods, which is a known issue:

Go here:
https://drive.google.com/folderview?id= ... =en&pli=1#

That is The 510 Archives, 3.8GB of Datsun 510 information, including complete backissues of all three national 510 newsletters. In the DQ folder, find:

DQ Volume 2 Issue 2 - T/C Rod Modification - A lowered suspension and urethane bushings can lead to T/C rod failure. A small modification can help prevent it from happening to you.

This will give you all the background on what happened to you. OE T/C rods are fine, very very few break like that without the presence of poly T/C rods. Aftermarket adjustable T/C rods will do as well, but your problem isn't the T/C rod, it was the bushings.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

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PoorMtnKid
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Re: Broken TC Rod

Postby PoorMtnKid » 18 Jan 2016 17:46

I has the same issue with the poly bushings, went back to stock style and never had a problem while driving the car. I actually got a good deal on some aftermarket T/C Rods so I have the stocks hanging out collecting dust if you need one.
looking for pass. side arm rest

Gigawatts
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Joined: 17 May 2015 13:41
Location: Houston, TX

Re: Broken TC Rod

Postby Gigawatts » 19 Jan 2016 15:54

Yea, that's it. The black threw me off and I was thinking they were soft like rubber. They are so hard, I can't really compress them with an adjustable wrench. In the second picture, I am actually trying to compress it, lol.

I think I should stay away from the poly altogether, and I will give the futofab one's a try. Thank you for your offer PoorMtnKid, I will let you know if the futofab ones are too harsh for me. How are your aftermarket ones, is it noticeable?

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Thanks guys!

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Byron510
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Re: Broken TC Rod

Postby Byron510 » 19 Jan 2016 16:55

Damn - that's scary. I have not met a person who has personally had this happen to them, but the thought sends chills up my spine!

The polly bushing, if that stiff, would seem to limit the natural movement of the pivot as well as the compression. The latter is desired, but the former is curtail to the function of the TC rod.

It's little wonder the part failed when you think about it.
I have used the EE TC kits for many years in many applications and have found no issues at all. The EE kit allows free rotation of the TC rod through all it's travel while limiting compression that gives the spongy feel under braking (when using sticky tires and big brakes).

Glad you shared this with us, hopefully you find a better alternative.

Byron
Love people and use things,
because the opposite never works.

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funwithmonkeys
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Re: Broken TC Rod

Postby funwithmonkeys » 19 Jan 2016 21:11

I have the futofab ones. They are well made and went in easily. I don't really notice the harshness some people speak of but I have some very stiff springs in my car so most every bump is a bit harsh.
If no one from the future comes back to stop you from doing it then how bad of a decision can it really be?

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510wizard
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Re: Broken TC Rod

Postby 510wizard » 20 Jan 2016 09:34

I would differently have the other one magafluxed or replaced, who knows if the other is starting to crack. I too use the EE TC kit or equivalent ones for over 40 years, no problems. Be safe!

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bertvorgon
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Re: Broken TC Rod

Postby bertvorgon » 21 Jan 2016 08:12

Back in the 70's, when I first started with my turbocharging, I had the turbo in my 1972 wagon. One Saturday, myself and another friend blazed up up our Sea to Sky highway, then went up an old gravel road to an abandoned mine. Then, as it was late in the day, we just blazed back once we got on the pavement. I was carving every turn on the way back. This trip put just over 200 Km on the car.

The NEXT morning. I get in the car, and turn out into my back alley, and the T/C box pulled off the car....the front wheel INSTANTLY turns at almost a right angle to the car. I shudder to think of what might have happened if that had failed on the highway at 100+ KMH.

The T/C rods must be replaced as the others suggest.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

1973 2Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1968 Vintage 3HP Mini Bike
1971 Vintage 13' BOLER trailer

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PoorMtnKid
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Re: Broken TC Rod

Postby PoorMtnKid » 21 Jan 2016 10:34

I really did not notice any difference in the T3 ones I have to be honest, but I might be in the same boat as funwithmonkeys. Im running 300lbs springs.
looking for pass. side arm rest

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JordanTr
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Re: Broken TC Rod

Postby JordanTr » 21 Jan 2016 19:15

I've got close to 30k km on the T3 TC rods on my car. Somewhere in that time I also upgraded the front LCAs to have heim joints as well. There wasn't a step change in NVH when I added the T3 TC rods but the car was exactly a smooth car before so take that with a grain of salt.

I did notice that a bit of added caster with the TC rods made quite the difference in handling and the front end was much tighter.
Jordan | '72 2 door KA project | '94 240sx RB26DETT | '97 Silvia RB25DET | '90 Audi 90 Quattro 20V (DD)

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Baz
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Re: Broken TC Rod

Postby Baz » 21 Jan 2016 22:34

The polyelastomer bushes we use have a softer durometer than all we have tested.
Even on Rally & offroad we have not had reports of TC ( radius rods) failure.

In the early days of the red poly bushes the snapping of the rods was common.

For safety reasons most rally 510s use a wire tether cable from the TC bracket to the LCA.

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Baz
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Re: Broken TC Rod

Postby Baz » 21 Jan 2016 22:45

On our wide track front end we built a proto type TC rod setup.
We wanted the pivot point further forward , longer length and higher mounting point.

Purpose was to reduce caster change over bumps.
And to make adjustment easy.

Bracket is bolt on using existing points & crush tubes where needed.
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510longroof
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Location: Hamilton Ontario Canada

Re: Broken TC Rod

Postby 510longroof » 21 Feb 2016 11:39

I'm a little late to this discussion but anyone from the rust belt or whose car was ever driven during the "Brine season", road salt, should take these apart and inspect them for rust damage. I bought a low mileage, 18K, 710 once and had one of these snap due to rust. On a highway exit ramp of all places. It decayed to thinner than a pencil before it let go. The damage was within the bushing so did not show until the failure.
A lot can happen in 40+ years and in the case of suspension parts, it's better not to find out the hard way.
71 510 wagon
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74 CB360T project


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