Pinion Angle - What Should It Be Set At? November 21, 2010, 10:27:10 PM I am in the middle of setting up the pinion angle in the ’83 and have a question with regards to the direction that the pinion needs to point. I have read all kinds of differing opinions on the degree that the pinion angle should be set at and whether or not the pinion should point up or down. The car has adjustable LCA's (Griggs) and UCA's (Global West) so I can adjust how the rear end sits in the car from front to back and in rotation or pinion angle.I took my handy Craftsman buttstuffog angle indicator with a straight edge and measured off the lower pulley on the crank. It read 7.0 degrees of downward angle (the front of the motor is higher than the rear of the transmission). I moved the angle finder to the drive shaft and it is measuring 4.0 degrees of downward angle (the front being higher than the rear). For me this gives a net angle of 3.0 degrees difference between the output shaft of the transmission and the drive shaft (DS). I measured the pinion angle on the back of the pinion using the straight edge and came up with 1.0 degrees. This also gives me 3.0 degrees of difference between the DS and the pinion. So what I have is the engine centerline going downhill from the front of the car to the output shaft of the transmission, the DS centerline going downhill from the transmission to the rear end, and the pinion going uphill from the pinion to the rear end cover.My question is should the pinion centerline and the motor centerline be running in the same direction or should they be opposite like they are now? I went here:http://www.maximummotorsports.com/content/install/pdf/rear_susp/MMTA1-2r2.pdfand found on page 9 a diagram that shows the center lines running in the same direction and the angles needing to be the same. This is on a Mustang but I would think it would be the same for our cars. I also found this article on drivetrain.com which was a good read and also states that “Ideally, the operating angles on each end of the driveshaft should be equal to or within 1 degree of each other, have a 3 degree maximum operating angle and have at least 1/2 of a degree continuous operating angle.”http://www.drivetrain.com/parts_catalog/drivetrain/driveline_angles_and_phasing_problems.htmlI am pretty convinced that I need to rotate the pinion upward but I am not 100% sure. Any input would be appreciated. Darren Quote Selected
Pinion Angle - What Should It Be Set At? Reply #1 – November 22, 2010, 05:53:35 PM I know nothing about what you are trying to do, but here are the specs from the 84 shop manual. Quote Selected
Pinion Angle - What Should It Be Set At? Reply #2 – November 23, 2010, 02:56:14 PM Basically you have to get the u-joints on the drive shaft at the same angle (+/- 1/2 degree is acceptable) so that you do not get vibrations. If one is out more than the other then you can get what some call sympathetic vibrations in which the frequencies will intermittently cancel one another out. So you end up with a vibration that is cyclical or in other words a vibration then a pause then vibration then a pause then a vibration then a pause...This is what I had in the Bird prior to the 302 motor dying a tragic death. I did a lot of research while I had the vibration including swapping out the TKO for a buddy's when his car was down (did not help on bit) and it continued after the motor died. I am trying to get the pinion angle figured out so that when this 351W fires up I can just drive the car and enjoy it as the vibration kept me from driving the car before as it was so frustrating.Thanks for the info above as I am sure it will come in handy but it does not help with what I am trying to do as my Bird no longer has any of the factory drive train or suspension.Darren Quote Selected
Pinion Angle - What Should It Be Set At? Reply #3 – November 23, 2010, 04:51:00 PM Look at your joints. The straighter they are the better you will be. Do you have vibe problem? Your pinion will have to face upward I would think. Quote Selected
Pinion Angle - What Should It Be Set At? Reply #4 – November 24, 2010, 10:32:21 AM I had a problem the last time the car was together with the 302 which was several years ago. I got really aggravated with the car so I put it up and did to touch it for about five years, just glad I did not do something stupid like sell it. I battled a cyclical vibration in it from the time I finished building it in 1999 until the motor died in 2003. I tried all kinds of stuff to get rid of the vibration from pinion angle to clocking the DS. I pulled the Tremec TKO, stripped it down, and shipped the internals to a Tremec shop and had the shafts checked for straightness and if I remember right the farthest one was out was 0.003" which was within factory tolerance. I even borrowed a buddy's TKO and put it in the car but nothing changed. I had new gears and bearings installed in the rear end at Ford but that did not solve the problem. The vibration was speed induced as it would do it in 3rd, 4th, and 5th and in neutral. It was more noticeable on the gas i.e. with the drive train under load. The speed at which the vibration would occur could be changed with pinion angle but not by much, maybe +/- 5 mph. With that being said I figured out it was an issue from the output shaft of the TKO to the rear wheels. I had the custom aluminum DS checked by the shop that made it and another one and both said it was balanced and good to go. The wheels were spun up at two shops and they were balanced well. I checked axles for excessive run out and they were fine.I never really gave the whole drive train geometry much thought until this time around. The car now has a Griggs K-member, 351W, same TKO but with an SROD bell housing instead of the Lakewood scatter shield, and the suspension is all new with coil overs, new control arms, and CC plates. So just about everything has changed. If you are wondering the SROD was a four speed transmission that came out of the 82-83 GT Mustangs and it just so happens that the bell housing fits a Tremec 3550 and TKO, not sure about the new Tremec 500 and 600's. The bell is a tapered design like the T-5 bell housing so headers and what not fit a lot better than a Lakewood. I battled header fitment issues with the Lakewood so I sold it and got this instead.I started reading up on drive line geometry and found out that I was only addressing the angle between the pinion and the DS when I should have been looking at both angles between the tranny & DS and the pinion and DS. From what I have read on several sites and books "the operating angles on each end of the drive shaft should be equal to or within 1 degree of each other, have a 3 degree maximum operating angle and have at least 1/2 of a degree continuous operating angle". I was only addressing the pinion angle and not looking at the transmission angle as well.So long story short I am trying to get the angles figured out before I fire the motor up so it will be fun to drive this time.Darren Quote Selected
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