Just installed a used but very good condition Spohn torque arm. I have the model that bolts to the chassis. The pivot has a poly bushing on one end and a ball end on the other:


The arm is installed what I believe to be correct, I have zero drive line vibes so the u-joint angles are correct and the pivot piece is straight up and down. All fasteners are very tight.

Here is the problem:
I can feel and hear road bumps from the rear end more
I can feel and hear drive line slack in both directions more
In 5th and 6th gear at low RPM's, I can feel something weird in the back

It feels like someone banging on the floor with a dead blow hammer. It is not severe, its just something that was not there prior to the Spohn TA.

Is this normal?
Anything I can do to minimize this?
Thanks

 

Even if you have it set-up correctly you will have more road noise and feel the shifts more. Mines an auto, so I only have a little thump when I first take off.

 

Is this due to the "slop" in the ball joint. The ball joint I have is in great shape but, however it has the normal clearances required for proper operation.

 

The only thing I can quess, is that the noise is related to the front mounting point and the way it must move under accel/decel. When you give it a fair amount of gas pedal, does it feel like the back of the car is doing the anti-squat thing? If so, I believe you have it set-up correctly.

 

You're going to feel more road vibration.
It's the downside to chassis-mounted torque arms.
I've had the same issue with both my BMR setup (on my 95) and Spohn (on my 93)

Your exhaust is not bouncing off of it is it?

 

The exhaust is fine, plenty of clearance. Well I am glad to hear that it is normal.

I wonder if the ball end can be replaced with a poly bushing just like on the other end of the swivel link? Maybe some thin but durable insulators can be sandwiched between the chassis mount and the chassis?

 

Sure, but doesn't that defeat the purpose of having a chassis-mounted
torque arm on there?

 

Possibly, but this is not an all out race car.

 

then you probably bought the wrong type of tq arm for your application. It sounds like you would probably be happier with a traditional trans mounted arm to keep the noise down.

Its kind of the point to a chassis mounted tq arm... its very rigid and solid so it transfers vibrations and noise.

If you dont like it then you should probably sell it and go with a trans mounted arm. Just installing a poly mount will defete some of the purpose of a chassis mount and will probably not quiet it down that much.

 

Thanks guys, I only gave $200 for it so its not a loss. I am sure I will get use to it.

 

When you say "ball end", do you mean you bought the "rod end" on the torque arm? If so, you had a choice between the rod end and a conventional poly bushing. The poly will definitely be quieter, but not completely silent. Once you hook the arm to the floor pan, you can feel everything that happens to the rear axle. I think I can guess the approximate backlash in the gears at this point, because the more backlash you have, the bigger the clunk I get when I put the TH400 in gear. To me, the rod end version of the arm is not a problem as far as noise, but then with duals dumping under the car, and nothing more than Borla XR-1's for mufflers, most noises are hidden by the exhaust.

 

Injuneer,
Yes I mean the "rod end". It came on the arm when I bought it used. Your statement makes perfect sense to me.

I am going to experiment with some thin rubber washers at the bolt holes, by keeping the insulators thin it should not badly impact performance. I totally understand that any above a thin insulator will absorb power but even at the worst it could not be as bad as the stock TA.

 

Okay, i have now gotten used to it.