1966 pinion angle - Vintage Mustang Forums

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post #1 of 5 (permalink) Old 05-17-2017, 05:22 PM Thread Starter
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1966 pinion angle

1966 mustang vibration c 4 trans. Replaced third member with a professionally rebuilt one, 100% new.
Replaced trans output shaft bushing, new rear drums, rebuilt and balanced driveshaft but used old trans yoke, new
Crager wheels and balanced on Hunter Road Force machine. Need your opinion on the pinion angle.
With rockers level and weight on all wheels pinion angle is zero from level,90*. Driveshaft angle 3* from level,
93*. Trans output 5* from level, 95*. Calculated pinon angle,90* - 93* = -3*. Trans angle 95*- 93*= +2*.
This gets me a 1* differential. This difference looks acceptable to me. How does this look to you? Am I reading this wrong?
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post #2 of 5 (permalink) Old 05-17-2017, 06:21 PM
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This is a tough one to explain on a keyboard. From out of the back the trans , the driveshaft angle should be "down". Meaning the driveshaft goes lower than the yoke. At the diff , the angle should be "up". Meaning the drive shaft goes above the pinion yoke , but the yoke and driveshaft are not in a "straight line". To work properly , ( as I'm confident you know from all of your noted effort to fix this) U joints need "angularity" to function properly. A common problem is when the pinion angle is "higher" than the driveshaft angle which produces two "positive" angles instead of a positive and an offsetting "negative angle". "I think" that is what you are explaining IS present , yet you still have the vibration. If that is true , you may want to look at the axles themselves. I had one with a VERY slight bend that gave me fits in my drag race car at 120 mph trap speed.

'66 GT350H-3 time cover car - Car Craft July'77,Modified Mustangs and Fords Feb2011 ( w/article), Mustang Monthly June 2014. Bracket raced by me for the last 43 years. Yes it is a real one.
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post #3 of 5 (permalink) Old 05-17-2017, 06:49 PM
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1966 pinion angle

I had a bad vibration issue years ago. It turned out to be the U-joint caps measured about .080 shorter than the width across the saddle where the caps fit into the yoke. As a result, they would favor one side which caused a vibration. It's worth looking into.
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post #4 of 5 (permalink) Old 05-17-2017, 07:44 PM
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Your old trans slip yoke could be worn. I'd replace it.

1966 Restomod/track car, 1973 Q-code Mach 1, 1989 GT, 1997 F250 diesel, 2005 retired OSP Crown Vic, 2015 Focus ST-2
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post #5 of 5 (permalink) Old 05-19-2017, 05:14 PM
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Tremec has a free app for Iphone and Android that uses your smart phone as an angle finder. It has you take 3 readings (engine, driveshaft, rear) and then it will tell you if you pinion angles are in spec or not. It was very helpful to me when I was trying to get my pinion angle in spec. It's called Tremec Toolbox.

'67 Mustang coupe, 289/T5
'68 F100, 390/3-speed on the column
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