Torque arm blues
03-23-2006, 05:09 PM
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Torque arm blues Maybe one of the suspension gurus here can help me out a bit. I installed my new Spohn torque arm and panhard bars today hoping to help with my excessive wheel hop issues, no luck. I followed Spohn's recommended setup and install, bolted everything back together pulled in to the street to check my progress and was immediately met with window shattering wheel hop at any launch over 2000 rpm 
Am i doing something wrong or is there an option to remedy this? I know i need new shocks and a set of LCA's wouldn't hurt either, but i want a little input from you guys before i start spending more hard earned cash with poor results. Sorry for the post length just really at my wits end. Any help is greatly appreciated
Am i doing something wrong or is there an option to remedy this? I know i need new shocks and a set of LCA's wouldn't hurt either, but i want a little input from you guys before i start spending more hard earned cash with poor results. Sorry for the post length just really at my wits end. Any help is greatly appreciated 
03-24-2006, 01:35 AM
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FYI - I bought LCA's and tried those first with no luck. Added the Spohn TA and that fixed my problem. You might need the stiffer LCA's too. As others have suggested, make sure the TA is adjusted properly first.
03-24-2006, 04:36 AM
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And don't bother using the shitty, incorrect instructions that come from Spohn on how to set your Pinion Angle.
They tell you to measure the angle of your DS and then measure the angle of rear. Measuring the angle of the DS doesn't tell you jack **** that you need to know to properly set the angle.
The DS could be at any angle depending on the load on the wheels and thru the full range of the suspension travel. Take for example a truck that has a lift kit installed - do you really think the DS angle is anywhere near being the same as a truck without a lift? Measuring the actual DS angle does not tell you anything about the angle of the engine/tranny as it can swivel on the tranny yoke U-joint independant of the tranny angle.
Here is the CORRECT way to set PA as I recently found out straight from a GM engineer after trying the 20 some different ways that are described:
1) Have car on alignment rack that supports car by tires or raise car in such a manner as to put load on all (4) tires as if car was on ground.
2) Remove DS (making sure to make a reference mark on pinion yoke and corresponding mark on DS rear yoke to allow for same position when you bolt back up)
3) Using an angle finder, first measure the angle of the engine/tranny combo by placing gage on output shaft tailshaft housing face. Record this angle and note whether it is pointing down to ground or up (most likely will be pointing down).
4) Using an angle finder, then measure the angle of the rear by placing gage on face of pinion yoke where U-joint straps interface. Record this angle and again note whether it is pointing up or down.
U-joints are designed to work best in conjunction with one another when the angle imparted to them on each end of the DS is the same, yet in opposite direction. Think of an imaginary centerline thru your crankshaft/tranny output shaft and another thru your rear pinion shaft. If you were to draw these (2) lines they would need to be PARALLEL to each other (not in-line but parallel) to allow the best operating conditions for the u-joints and the least vibration.
So it follows:
5) If your tranny measurement is 2 degrees pointing DOWN - then your rear angle should be 2 degrees pointing UP. This would yield a zero degree pinion angle and is where your car is set up from the factory. For strip cars with high HP/TQ and good tires, you can impart a -1 to -2 degree angle relationship between the rear and tranny angles. This is due to the fact that the rear rotates thru an arc upwards under high loads - so if you give it a negative angle to begin with, when it finally is done rotating upwards - the angle will come back to zero.
So if you wanted to do this, and the tranny angle is 2 degrees DOWN - then you would want to set the rear angle to 1 degree UP for -1 and zero for -2.
6) Re-install DS aligning the positioning marks on rear yoke that you made in step 2. Torque U-joint strap bolts to 14-19lb ft and use loctite on the bolts.
Sorry if I sound harsh in the beginning, but alot of us are having vibration problems after modding rear gears, suspension components; and having 20 DIFFERENT suggested methods for setting a PA is truly exasperating
I like the quality/function of the Spohn components - just wish they would not publish incorrect PA instructions with their T/A's.
-Jay-
They tell you to measure the angle of your DS and then measure the angle of rear. Measuring the angle of the DS doesn't tell you jack **** that you need to know to properly set the angle.
The DS could be at any angle depending on the load on the wheels and thru the full range of the suspension travel. Take for example a truck that has a lift kit installed - do you really think the DS angle is anywhere near being the same as a truck without a lift? Measuring the actual DS angle does not tell you anything about the angle of the engine/tranny as it can swivel on the tranny yoke U-joint independant of the tranny angle.
Here is the CORRECT way to set PA as I recently found out straight from a GM engineer after trying the 20 some different ways that are described:
1) Have car on alignment rack that supports car by tires or raise car in such a manner as to put load on all (4) tires as if car was on ground.
2) Remove DS (making sure to make a reference mark on pinion yoke and corresponding mark on DS rear yoke to allow for same position when you bolt back up)
3) Using an angle finder, first measure the angle of the engine/tranny combo by placing gage on output shaft tailshaft housing face. Record this angle and note whether it is pointing down to ground or up (most likely will be pointing down).
4) Using an angle finder, then measure the angle of the rear by placing gage on face of pinion yoke where U-joint straps interface. Record this angle and again note whether it is pointing up or down.
U-joints are designed to work best in conjunction with one another when the angle imparted to them on each end of the DS is the same, yet in opposite direction. Think of an imaginary centerline thru your crankshaft/tranny output shaft and another thru your rear pinion shaft. If you were to draw these (2) lines they would need to be PARALLEL to each other (not in-line but parallel) to allow the best operating conditions for the u-joints and the least vibration.
So it follows:
5) If your tranny measurement is 2 degrees pointing DOWN - then your rear angle should be 2 degrees pointing UP. This would yield a zero degree pinion angle and is where your car is set up from the factory. For strip cars with high HP/TQ and good tires, you can impart a -1 to -2 degree angle relationship between the rear and tranny angles. This is due to the fact that the rear rotates thru an arc upwards under high loads - so if you give it a negative angle to begin with, when it finally is done rotating upwards - the angle will come back to zero.
So if you wanted to do this, and the tranny angle is 2 degrees DOWN - then you would want to set the rear angle to 1 degree UP for -1 and zero for -2.
6) Re-install DS aligning the positioning marks on rear yoke that you made in step 2. Torque U-joint strap bolts to 14-19lb ft and use loctite on the bolts.
Sorry if I sound harsh in the beginning, but alot of us are having vibration problems after modding rear gears, suspension components; and having 20 DIFFERENT suggested methods for setting a PA is truly exasperating
I like the quality/function of the Spohn components - just wish they would not publish incorrect PA instructions with their T/A's.
-Jay-