Reality of trailing arm bolts?

[Redsquall]

How important should replacing the tabs be when they seem slightly bent and still rotatable?
has anyone here actually had it break on them?
im looking for level headed advice as I have an auto transmission and it sound like a major job to replace.
thank you

[Michael]

A broken TAB can literally kill you if it happens at speed. It's basically like a broken ball joint on the rear wheel. I check mine every time it's in the air and you are right, it's a bear with the auto. If I ever have to drop the autobox for any reason, I'm replacing the TABs with some of Dave's offerings from DMCMW whether they need it or not.

I have seen (in pictures only) cars with broke TABs. Fortunately they were low speed and caused minor damage and the driver was unhurt. I'm sure there are a few threads with pics here on the subject.

I have never replaced my TABs but I believe you can do it on the auto just by removing the mount itself and not actually dropping the tranny altogether.

[Jonathan]

The reality of TABs?

There's never been enough specific information on failures to say definitively what will or will not happen.

It isn't consistent for the most part. The advice is to replace them if they are frozen in place, i.e. rusted in place, or they aren't frozen (like yours) but rotating them shows that they are bent.

I also have an auto and understand changing them is a pain in the butt. I don't know that from my own experience as I've never done the job. I have every single nut and bolt and replacement fastener sitting and waiting in one of my parts boxes, but it all just continues to sit there.

There are other factors that can contribute to them failing, such as they got scratched, etched, dinged or banged up in some way and this damaged portion becomes the point where the metal fatigues and fails outright. Rust can do that for you if the failure point is a rust pitted spot. Temperature will also affect the metal failing. Ambient temperature that is. If the metal is cold because it is cold outside, the materials strength is reduced and the likelihood of failure increases.

Changing them out is a good idea, sure. It is also somewhat of an insurance policy. There are a few areas on the car like this, where changing out old parts proactively may help you avoid a potential problem. Fuel lines are another major one. No guarantee that it would have failed if left alone though, there just isn't the information available and there is too much variability on each car's history to make one all encompassing rule.

And as with changing or working on fuel lines, there is a risk that you could make matters worse. Not saying brand new, properly installed replacement TABs or fuel lines are a bad idea, but getting there and the cost and work to do so needs to be evaluated. As with any kind of risk management decision like this, you weigh the likelihood of failure (probability) and the consequences of failure (severity) against the costs (real or imagined) of doing the work or doing nothing (or at least just inspecting/monitoring only).

[jmettee]

I had mine break while driving about 35 mph over a railroad crossing. The rear starts to randomly "steer" since the upper & lower control links are all that's controlling the wheel. At higher speeds, it's a good chance of complete loss of control.

If it's bent, it's weakened & in failure mode - should be replaced ASAP if a bend is seen. For mine, it wasn't bent, but the bolt was original & of poor quality surface finish....it rusted from both sides & failed in the middle of the bolt. Looking at the bolt, it's a classic fatigue failure with the bolt bending forward & rearward with the drive thrust/braking.

Bottom line: Replace them. I've done it on both auto & manual cars, it's not terrible & definitely worth doing as opposed to wrecking the car or hurting you & your passengers.

[Delorean Industries]

A trailing arm failure at speed will result in your death almost certainly. The amount of weight over the rear will over come the upper/lower rear link bushings without being tied at the forward mounting point. The wheel will climb against this new direction of travel and cause the failure side to drop and dig in.

This is why I designed a safety system for all of our builds. I now incorporate a three point hoop method of binding the arm in case of failure as done in F1 and other sanctioned motorsports. The two radius arm reinforcement points are attached to the outer most point of the TAB bolt limiting the aft travel if sheered to a minimum and giving the driver the ability to stop. This is accomplished with a high tensile strength cable arrangement. Not to be confused with brand X ground trap updates by the transmission as many have though they were on our cars.

[content22207_2]

A trailing arm failure at speed will result in your death almost certainly.

A tad dramatic.

A broken trailing arm bolt at speed would definitely be a challenge, but not necessarily fatal. I've been trained to safely steer an 80,000 lbs vehicle to the side of the road in case of a front tire blowout. Surely a broken trailing arm bolt wouldn't be world's more difficult. Like a front tire blowout, I'd stay off the brakes until control is re-established. Don't know if I'd hit the accelerator however (with a front tire blowout your first reaction is to floor the accelerator to compensate for slewing towards the blowout). I'm guessing the rear end would slew towards the broken TAB because the wheel would pivot rearward, like the back wheel of a hook & ladder. Probably need to steer into it like losing your rear end on ice.

Grade 9/Class 12 bolts only cost a couple of bucks apiece -- just replace them.

Bill Robertson
#5939

[iflights]

I found this information helpful when I was asking that same question...

http://www.dmcnews.com/Techsection/tabolts2.html

[axh174]

im looking for level headed advice as I have an auto transmission and it sound like a major job to replace.
thank you

I have an auto transmission and I replaced my original TABs with a set of Toby TABs. The best advice I can offer when replacing the TABs is to get a 75-degrees (at least) offest boxwrench. This wrench can easily fit between the transmission and the TAB head and allow you to easily get the TAB loosened.

Using the offset boxwrench, I didn't have to remove either of the transmission mounting brackets, however I do recall having to remove the TAB bushing plate and bushing in order to get enough of an angle to get the TAB completely removed because the tranny was in the way. For me, this was not that big a deal since I was replacing the TAB bushings anyway. A word of caution, though: if I recall correctly, the bushing retaining plates are bolted to the frame such that small nuts are used between the frame and the bushing housing. If a nut slips out of your hand, it can get lodged/lost in there and potentially cause reassembly problems.

As for torquing the TABs to their proper spec upon re-installation, my torque wrench was too large to fit between the TAB nuts and the fiberglass body for proper torquing, and I had to make use of a torque adapter.

[PJ Grady Inc.]

They must absolutely be replaced when bent along with the bushings. If you double nut the pivot bolt there is no need for exotic materials like the Monel Toby tab's but there is nothing wrong with overkill. That best why to keep them from loosening/bending due to the twisting movements of the suspension oer bumps and undulations.
Rob

[content22207_2]

Monel Toby tab's

Inconel. Same stuff used for bolts that hold airplane engines on (Toby Peterson worked for Boeing -- he used a Boeing supplier to make his trailing arm bolts).

Bill Robertson
#5939