Spohn Torque Arm Usefulness?
09-28-2004, 12:59 AM
#1
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Spohn Torque Arm Usefulness?
How effective is the spohn tq arm that mounts to the body? What kind of 60' reductions did you see?
I hear that fbodies like mine with a 9" rearend have pinion angle problems? How much difference does pinion angle make?
Is the tq arm noisy? How low is it? Weight difference between it and stock?
I hear that fbodies like mine with a 9" rearend have pinion angle problems? How much difference does pinion angle make?
Is the tq arm noisy? How low is it? Weight difference between it and stock?
09-28-2004, 02:59 PM
#3
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
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Re: Spohn Torque Arm Usefulness?
Pinion angle affects the life of the u-joints, trans rear main seal/bearing and differential pinion shaft seal/bearings. It also affects the amount of energy lost in the drive train. And, if its way off, it will cause the u-joints to bind, producing unpredictable torque reactions in the rear axle assembly, that are going to destabilize tire traction.
The objective is to keep the trans mainshaft and the pinion shaft at the same angle, producing equal angles between the DS and the tranny output shaft, and between the DS and the pinion shaft. The measurement is sometimes "shortcut" to provide enough negative pinion angle so that when the nose of the pinion shaft rises under high torque loads, the pinion shaft and the DS sort of form a straight line. The 9-inch complicates the process, because the pinion shaft sits lower on the differential than on a 10- or 12-bolt. And the 9-inch pinion shaft is offset to one side from the centerline of the car.
A high quality TA allows you to control the pinion angle by eliminating the deformation and deflection present in the stamped sheet metal stock TA. Moving the front mounting point off the tranny tailshaft eliminates stress on the tranny tailshaft and on the tranny mount. It fixes the front of the TA more rigidly, and make the pinion angle easier to control.
Whether you need the beef of a Spohn TA will depend to some extent on how much power you are putting to the pavement. There are people who have run 10's on a stock TA, so its not essential that you go to a high $$$ TA setup. On the other hand, there are people running a lot slower who have managed to destroy the stock TA. And, you are going to stress the drive train a lot more with poor pinion angle control.
Can you measure the ET improvement.... probably, if you are getting a lot of wheel hop related to drive shaft mis-alignment. But its no magic cureall that guarantees 3/10's or anything like that. A quality TA is just part of the upgrades required to eliminate yet another variable from the traction and drivetrain wear/stress/power loss equation.
The objective is to keep the trans mainshaft and the pinion shaft at the same angle, producing equal angles between the DS and the tranny output shaft, and between the DS and the pinion shaft. The measurement is sometimes "shortcut" to provide enough negative pinion angle so that when the nose of the pinion shaft rises under high torque loads, the pinion shaft and the DS sort of form a straight line. The 9-inch complicates the process, because the pinion shaft sits lower on the differential than on a 10- or 12-bolt. And the 9-inch pinion shaft is offset to one side from the centerline of the car.
A high quality TA allows you to control the pinion angle by eliminating the deformation and deflection present in the stamped sheet metal stock TA. Moving the front mounting point off the tranny tailshaft eliminates stress on the tranny tailshaft and on the tranny mount. It fixes the front of the TA more rigidly, and make the pinion angle easier to control.
Whether you need the beef of a Spohn TA will depend to some extent on how much power you are putting to the pavement. There are people who have run 10's on a stock TA, so its not essential that you go to a high $$$ TA setup. On the other hand, there are people running a lot slower who have managed to destroy the stock TA. And, you are going to stress the drive train a lot more with poor pinion angle control.
Can you measure the ET improvement.... probably, if you are getting a lot of wheel hop related to drive shaft mis-alignment. But its no magic cureall that guarantees 3/10's or anything like that. A quality TA is just part of the upgrades required to eliminate yet another variable from the traction and drivetrain wear/stress/power loss equation.
You need to start teaching automotive theory courses or something!!! Great post.
09-29-2004, 12:31 PM
#7
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
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Re: Spohn Torque Arm Usefulness?
Dazzle 'em with brilliance..... or baffle 'em with bull$hit. Which is it? 
I think mine may weigh as much as 35#.... can't remember. I do have that big bulky "4" Mufflex" front mount, which weighs a lot more than the tubular mount that he sells now. I've though about changing out the front mount since I don't run any exhaust through that spot any more.
Chirping between gears.... shouldn't cost you a lot of ET, as long as its just a "chirp" and not a long period of spinning the tires. Do you have LCA relocation brackets? That's what ironed out ALL the traction problems with my setup.
I think mine may weigh as much as 35#.... can't remember. I do have that big bulky "4" Mufflex" front mount, which weighs a lot more than the tubular mount that he sells now. I've though about changing out the front mount since I don't run any exhaust through that spot any more.
Chirping between gears.... shouldn't cost you a lot of ET, as long as its just a "chirp" and not a long period of spinning the tires. Do you have LCA relocation brackets? That's what ironed out ALL the traction problems with my setup.
Last edited by Injuneer; 09-29-2004 at 12:46 PM.
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