Spring perch angle

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   I've got a 68 AMX with a Ford 9 inch. The rear end came out of an old Mustang that the preveous owner installed don't know what year. To make along story short I pent the spring perches and collapsed an axle tube sunday at the track. Moser can build me one with a couple day turn around, one of the questions is the spring perch angle, can anyone help me with this so that I have proper drive shaft alignment. I'm trying to fix to make Cordova.
 Thanks.

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Grey Ghost Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Oct/11/2009 Location: Route 66 Il. Status: Offline Points: 158	Post Options Post Reply Quote Grey Ghost Report Post Thanks(0) Quote Reply Topic: Spring perch angle Posted: Aug/18/2014 at 10:04am
	I've got a 68 AMX with a Ford 9 inch. The rear end came out of an old Mustang that the preveous owner installed don't know what year. To make along story short I pent the spring perches and collapsed an axle tube sunday at the track. Moser can build me one with a couple day turn around, one of the questions is the spring perch angle, can anyone help me with this so that I have proper drive shaft alignment. I'm trying to fix to make Cordova. Thanks.
	Lets go racing!

jeremy0711 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Dec/12/2008 Location: Southern IN Status: Offline Points: 1547	Post Options Post Reply Quote jeremy0711 Report Post Thanks(0) Quote Reply Posted: Aug/18/2014 at 12:17pm
	I doubt that you will get an answer to that here. Maybe try to set it to the stock amc 20 instead of the ford settings. Tranny and other driveline options change what answers that you are seeking. I see shims in your future as that is the only option for conversions without a mockup on the car.

304-dude Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082	Post Options Post Reply Quote 304-dude Report Post Thanks(0) Quote Reply Posted: Aug/18/2014 at 12:39pm
	My 71 TSM has pinion angle information, but I would expect 68-70 AMX to have a wee difference since the wheel base is shorter. Since my Ford 9 inch housing is truck style with different height aftermarket perches, I set mine at zero for easier adjust-ability for lowering and using Jeep TH400. Remember Ford 9" pinion height will be not the same as AMC20 depending on tube diameter and perch height. Having short wheel base compounds pinion angle as well. If you match to AMC20 you may end up being worse off than just shimming from zero degrees. That is what I have done for my setup, though the springs are lowered along with a Jeep TH400.
	71 Javelin SST body 390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker

Grey Ghost Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Oct/11/2009 Location: Route 66 Il. Status: Offline Points: 158	Post Options Post Reply Quote Grey Ghost Report Post Thanks(0) Quote Reply Posted: Aug/18/2014 at 3:13pm
	I just finished pulling rear end out, before I started I tried to find were it is sitting at now with an angle gauge. With the drive shaft mocked up at the rear yoke (btw the u joint and rear of drive shaft are destroyed) I had a zero angle on the shaft and a 9 degree angle up on the pinion, this I know is way to high, I just want to get close, it already had been shimmed. This may have been part of the reason for the failure.
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Buzzman72 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Sep/15/2009 Location: Southern IN Status: Offline Points: 2725	Post Options Post Reply Quote Buzzman72 Report Post Thanks(0) Quote Reply Posted: Aug/18/2014 at 3:33pm
	Now, I'm certainly no expert...but wouldn't the proper pinion angle be determined by the angle of the transmission output shaft, so that the angles would work together? And wouldn't the pinion angle, in relation to the output shaft angle, determine the angle on the spring perches? IOW, if the output shaft angle is 9 degrees downward [picking a number out of thin air], wouldn't that require the pinion angle to be at 9 degrees upwards? And then, would that not also determine the angle for the spring perches? Or am I missing the point completely? http://www.macsmotorcitygarage.com/2014/07/26/video-driveshaft-angle-and-phasing/ Edited by Buzzman72 - Aug/18/2014 at 3:37pm
	Buzzman72...void where prohibited, your mileage may vary, objects in mirror may be closer than they appear, and alcohol may intensify any side effects.

AMXFSTBK390 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Oct/22/2013 Location: SF Bay Area Status: Offline Points: 3489	Post Options Post Reply Quote AMXFSTBK390 Report Post Thanks(0) Quote Reply Posted: Aug/18/2014 at 5:22pm
	I owned a 1968 Mustang FSTBK GT390, top loader, 9" rear end for six years. The pinion angle was 4 degrees down and the crank shaft/ output shaft was 4 degrees up with the weight of the car on the suspension with the car at rest. Under acceleration or when cruising on the freeway the pinion angle under load should be zero degrees. In theory this is a perfect scenario. Most American muscle cars of the 60's had a carburetor angle of 4 degrees because the engine was tilted back 4 degrees. Hence, the crankshaft/trans output shaft were at a 4 degree angle to get a proper differential pinion angle. Ideally, you want the two angles to be parallel. Under load with the axle rotaing upwards the driveline to differential should be in a straight line, this is the best way to transfer the engines power to the rear wheels without vibration. Depending on what the car is used for, traction bars, 4-link rear suspension, leaf springs all need to be considered when setting up the optimum pinion angle. I have done this numerous times with custom built chassis' with no issues. My 1936 "Special Construction" has a 302, AOD, 4-link rear suspension with Ford 8", and the pinion angle was set at 2 degrees parallel. Rides smooth as silk. As suggested, shimming the rear perches may be the best way to dial in the optimum pinion angle. You also may consider larger/beefier perches.
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