Trailing Arm Cracks

[TMike]

My TR6 has just returned a from media blast and I have discovered cracks on both trailing arms. The cracks are located on the bottom of the trailing arms near the hub (same location on both TAs). Is this common? Any advice on repairs?

 

[trrdster2000]

Mike, I don't think this was a major problem on the TA, but if push comes to shove I have a pair I can inspect to make sure everything is OK and will make you a good deal. They don't weight much, just a little bulky.

Wayne

 

[TMike]

Thanks Wayne, that sounds great. I plan to remove the TAs this weekend for a closer look. I'll let you know what I find.

 

[KVH]

I've not heard of aluminum cracking like that, and wonder if you're just looking at minor surface imperfections in the casting. I was told that is common with aluminum. If they could just crack, that could be catastrophic, and it would be one heck of a liability and a good reason, regardless of age, for BL to close shop well before the TR7s showed up. I'd be curious what you find.

 

[TMike]

That is certainly possible. I'll report back after removal and thorough inspection.

 

[M_Pied_Lourd]

I had stress cracks in the actual brackets that I found when I sandblasted mine.

Cheers
Tush

 

[mallard]

I agree with KVH that they might be casting marks and not cracks. Get them as clean as you can to be sure. Tush I've never seen that kind of crack in the mounting brackets, was the car raced at some time?

 

[M_Pied_Lourd]

Hi Keith, No it wasn't raced. It was a pretty original car when I first got it. I have seen a few other guys report the same. If you are doing a resto, I definately suggest to sandblast/strip to inspect. The crack wasn't visible until I cleaned them to bare metal. I replaced mine with the RG ajustables anyway but just thought I would share my experience.

Cheers
Tush

 

[mallard]

I also have the adjustable brackets on my car from Good Parts. I'll have to take a look at my originals.

 

[TexasKnucklehead]

I once had a 72 tr6 and a loud squeek started. Turned out the forward left bracket was broken in two about where that crack is. I replaced with one from a junk yard.

 

[MDCanaday]

The only one I have seen cracked had been hit pretty hard by an Impala....no way to magnaflux.
you might spray it with penetrating, oil wipe dry , and dust with talc.Perhaps this 6 has seen some hard track time??
MD(mad dog)

 

[hondo402000]

that would be called Dye penetrant method, I would get some red food coloring, clean the area well, maybe sand it with some 280 grit sand paper, clean it good with carb cleaner, let it dry for about 30 minutes, put the red food coloring on with a Qtip, let it Set for about 15 minutes, wipe it off with a clean paper towel then dust it lightly with talcum power, if you see a sharp red line then its a crack

Hondo

 

[TMike]

Ok, thanks to everyone for the posts. After getting a closer look, both TAs are cracked in similar locations. Although I have no way to know for sure, there is no indication that the car has taken a hard hit. Especially one that would have resulted in both TAs being cracked in the same location. Not sure about track use, but there are no obvious signs.

It doesn't appear that this is a widespread issue, but I can tell you that I would have never found these cracks had I not had the TA media blasted. I have uploaded photos so that others can inspect their TAs for similar issues. I have these TA to a TIG Welder to see if repairs can be made. If not, I'll be contacting Wayne about purchasing replacements.

 

[TR4A_IRS]

Those cracks look downright scary!

 

[JerryVV]

I wonder if at some time a garage lifted the car with a two post lift and placed the lift arms under the TA where the shock mounts? If they did I wonder if lifting in this way caused these cracks? That is odd that both are cracked as they show.

 

[trrdster2000]

Mike, What a surprise to see those. I see our normal breaking on some of the flange bits where the axle goes through, but never have seen what you have. They must have tried to do a Duke's of Hazard jump. Let me know and I will give mine and extra look before we come up with something to make you happy.

Wayne

 

[Foura]

I wonder whether the car has been bottoming on the bump stops for a while? If the car has the original soft 4A springs and they have sagged, it could have been continually hitting the bump stops and caused the cracks. The bump stop is in front of the wheel and could cause the trailing arm to crack like this. Or has it landed really hard after flying over a railway crossing.....?

When I was rebuilding mine, one of the trailing arms had a chunk broken off. I got a replacement one and my son-in-law who is a helicopter engineer had both crack tested and sprayed with a protective coating that they use on the helicopters. Should see me out.

 

[TMike]

Your lift arm theory is arguably the best so far. Since the car was largely original when I purchased it, I don't believe that it was raced. Also, having disassembled the entire car, there are no indications that the it has been in a major collision. At least nothing that would have caused both TAs to crack in the same location.

As others have suggested, if this was a common problem, we'd likely have heard about catastrophic failures. But, since these cracks could go undetected until the TAs are thoroughly cleaned (hence sandblasted), who knows how many cars have similar problems, or at what point that a failure might occur. If you are doing a restoration, I'd definitely sandblast the TAs and inspect. If you are not restoring, I'd seriously consider getting the car off the ground and inspecting the best that you can.

 

[TMike]

Rocky, you may be on to something. I do have a bump stop (inside fender well) that would indicate a pretty hard bottom hit. Other side of car didn't show any indication, but is still cracked. Springs appear to be original and the car would squat significantly during takeoff.

 

[TMike]

Thanks Wayne. Dukes of Hazard may be right and the car was red

Does anyone have thoughts about repairs with TIG Welding?