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Pinion angle and rear axle alignment #1047104 08/04/11 11:38 AM 08/04/11 11:38 AM
Joined: Dec 2004 Posts: 182 USA N Nitrofish OP member
Nitrofish OP member N Joined: Dec 2004 Posts: 182 USA	I have some questions related towards pinion angle. Is pinion angle the difference between the angle of the pinion and driveshaft or the difference between pinion and transmission output shaft? Here are the angles I'm currently working with. Trans output shaft is 2.5* down (so the output shaft is pointed down slightly from parallel, with the harmonic balancer slighly up). Driveshaft angle is 4.0* down as the trans output shaft is higher the differential pinion. The pinion is currently 0. What is my pinion angle? Once again trans is 2.5 down, driveshaft is 4.0* down and pinion is 0* Also when aligning the rear differential I assume that the trans output shaft aligned directly with the differential pinion is the correct alignment. As the incorrect alignment would be centering the wheels/tires in the wheel wells which would throw off the alignment between the trans output shaft and differential pinion. I'm I correct that the output shaft and pinion should be aligned and NOT that the wheels/tires should be centered in the wheel well?

Re: Pinion angle and rear axle alignment [Re: Nitrofish] #1047105 08/04/11 12:53 PM 08/04/11 12:53 PM
Joined: Oct 2005 Posts: 164 Savannah, GA mopar400 member
mopar400 member Joined: Oct 2005 Posts: 164 Savannah, GA	I believe you are (4-0=4 Deg. down) I double checked w/ THIS DOC.in tech archives. From what it says your drive shaft is considered a positive when down at rear. Kevin 1965 Fury II 1970 Challenger 440, 509 cam, 11:1 w/ 452 iron heads, 6.99 1/8, 11.29@ 120mph 1/4 (1999 Magnolia Drag strip track champion) 1992 Jeep XJ Crawler

Re: Pinion angle and rear axle alignment [Re: Nitrofish] #1047106 08/04/11 07:18 PM 08/04/11 07:18 PM
Joined: Oct 2003 Posts: 7,506 Az Crizila master
Crizila master Joined: Oct 2003 Posts: 7,506 Az	Quote: I have some questions related towards pinion angle. Is pinion angle the difference between the angle of the pinion and driveshaft or the difference between pinion and transmission output shaft? Here are the angles I'm currently working with. Trans output shaft is 2.5* down (so the output shaft is pointed down slightly from parallel, with the harmonic balancer slighly up). Driveshaft angle is 4.0* down as the trans output shaft is higher the differential pinion. The pinion is currently 0. What is my pinion angle? Once again trans is 2.5 down, driveshaft is 4.0* down and pinion is 0* Also when aligning the rear differential I assume that the trans output shaft aligned directly with the differential pinion is the correct alignment. As the incorrect alignment would be centering the wheels/tires in the wheel wells which would throw off the alignment between the trans output shaft and differential pinion. I'm I correct that the output shaft and pinion should be aligned and NOT that the wheels/tires should be centered in the wheel well? Pinoin angle is -4 degrees. The axle should be centered ( end to end ) in the chassis. Fastest 300

Re: Pinion angle and rear axle alignment [Re: Nitrofish] #1047107 08/04/11 07:40 PM 08/04/11 07:40 PM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	Quote: I have some questions related towards pinion angle. Is pinion angle the difference between the angle of the pinion and driveshaft or the difference between pinion and transmission output shaft? Here are the angles I'm currently working with. Trans output shaft is 2.5* down (so the output shaft is pointed down slightly from parallel, with the harmonic balancer slighly up). Driveshaft angle is 4.0* down as the trans output shaft is higher the differential pinion. The pinion is currently 0. What is my pinion angle? Once again trans is 2.5 down, driveshaft is 4.0* down and pinion is 0* Also when aligning the rear differential I assume that the trans output shaft aligned directly with the differential pinion is the correct alignment. As the incorrect alignment would be centering the wheels/tires in the wheel wells which would throw off the alignment between the trans output shaft and differential pinion. I'm I correct that the output shaft and pinion should be aligned and NOT that the wheels/tires should be centered in the wheel well? Like was said already... center the housing in the car... dont worry about the output shaft and pinion being in line... make sure the axle is SQUARE in the car (if the ladder bar cross member was installed correctly you can square off the cross bar to the axle housing)

Re: Pinion angle and rear axle alignment [Re: Nitrofish] #1047108 08/04/11 10:19 PM 08/04/11 10:19 PM
Joined: Mar 2007 Posts: 3,289 West Coast, USA jbc426 master
jbc426 master Joined: Mar 2007 Posts: 3,289 West Coast, USA	Pinion angle is in relation to engine/trans output shaft centerline. According to the angles you stated, your differential pinion angle is 2.5* nose down in relation to Engine/trans. Did you take the measurements with the car loaded and at the ride heigth you want? Driveline angle = -4* Indicates your rearend input shaft centerline is below your engine/trans shaft centerline...Good, That's normal on our cars. In this case, the driveshaft has to angle down to hook up with the rearend, because it is below the engine/trans. My rear diff is slightly offset to the passenger side from the factory by about 1/4". Axle flanges are about 1/4 of an inch offset to the passenger side. The rear end itself is square to the cars frame. I left it alone. Last edited by jbc426; 08/05/11 02:07 AM.

Re: Pinion angle and rear axle alignment [Re: Nitrofish] #1047109 08/05/11 01:39 AM 08/05/11 01:39 AM
Joined: Aug 2003 Posts: 43,333 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,333 Bend,OR USA	If this is a stock chassis car, rear end and trans in the original location and stock rear sub frames, I would use the original spring boxes(and do) to measure to the axle housing to get it square, within 1/16 of a inch As far as the pinion shaft and trans. output shaft it is not neccesssary for them to be in perfect alignment, as already said. The U joint need a difference in angles to make the needles bearings rotate in the cups to preveny bernelling( SP?)As far as the trans and pinion angles I have never measured the trans angle in over 40 yrs of racing and building stock type drag cars, I do measure the differences in angles between the rear of the driveshaft and the pinion shaft, I like to see the pinion straight or nose down and the drive shaft pointed up towards the trans and anywhere from 3 to 7 degrees difference between the two, depending on which type rear suspension is being used Last thing, I like to make the rear end go forward as far as I can(and not hit anything )to get as much weight behind the rear axle as I can for better traction My Duster rear end is moved one inch forward from stock and he rear wheel wells where stretch five inches(three inches forwrd and two inches back from original) to make it look stock 6763803-MVC-054S.JPG (284 downloads) Last edited by Cab_Burge; 08/05/11 01:41 AM. Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: Pinion angle and rear axle alignment [Re: Crizila] #1047110 08/06/11 01:39 AM 08/06/11 01:39 AM
Joined: Jan 2005 Posts: 3,699 Newport, Mi Evil Spirit master
Evil Spirit master Joined: Jan 2005 Posts: 3,699 Newport, Mi	Quote: Quote: Once again trans is 2.5* down, driveshaft is 4.0* down and pinion is 0* Pinoin angle is -4 degrees. The axle should be centered ( end to end ) in the chassis. HUH? Trans at 2 1/2* down, pinion at 0* = pinion angle is 2 1/2, NOT 4. Free advice and worth every penny... Factory trained Slinky rewinder.........

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