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Pinion Angle Problem?
#1
i am looking to drop the rear of my car with springs, lowering blocks or a combination of the two. Looking for about 2” total. Questions is, will I run into a pinion angle problem?  302 w/ C4 if that’s makes a difference. 
[Image: C0-E50304-D840-46-A1-B086-2-E732-E5-B388-C.jpg]
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#2
(01-26-2019, 07:32 PM)CoolCat33 Wrote: i am looking to drop the rear of my car with springs, lowering blocks or a combination of the two. Looking for about 2” total. Questions is, will I run into a pinion angle problem?  302 w/ C4 if that’s makes a difference. 
[Image: C0-E50304-D840-46-A1-B086-2-E732-E5-B388-C.jpg]

Dang! Can't answer you question, but what a nice organized garage! Wish mine looked like that.
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#3
A magnetic angle finder / protractor will provide the true answer.
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#4
(01-26-2019, 07:32 PM)CoolCat33 Wrote: i am looking to drop the rear of my car with springs, lowering blocks or a combination of the two. Looking for about 2” total. Questions is, will I run into a pinion angle problem?  302 w/ C4 if that’s makes a difference. 
[Image: C0-E50304-D840-46-A1-B086-2-E732-E5-B388-C.jpg]
CoolCat33,                                                                                                                           Lowering blocks should not change your pinion angle, lowering springs will raise the pinion some.   However the stiffness of the springs would be a player too.                                                        The PROBLEM part always is the relationship between the angles between the engine/ transmission angle and the pinion angle and how much the pinion angle changes with spring wrap at speed.      Suggest you  measure these angles with the suspension loaded before you make any changes.     Once you change either the springs or add blocks or both, re -evaluate the situation, everything in the rear will be fresh and you could easily add some pinion shims to correct the pinion angle if necessary. a lot depends too on how you drive the car.                                                             Boilermaster
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#5
In theory what you want is the pinion angle to match the trans yoke angle within 1 or 2 degrees. If not you then change the pinion angle with shims to be close to the trans yoke angle. Also important is the angle between the drive shaft and the pinion which is measured from the pinion angle and driveshaft angle. Here is a good article about the topic:
www.hotrod.com/articles/91758/amp/

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        [Image: 20160929_171923_edit2_small.jpg]

1971 M-Code Mach 1 w/Ram Air, 408 stroker, 285/291 0.558" roller cam, Blue Thunder intake, TKO600, Hooker headers with electric cut-offs, FiTech EFI w/ RobBMC PowerSurge pump
Strange center section with Truetrac, 3.5 gear and 31 spline axles, 4-wheel disc brakes
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#6
In theory what you want is the pinion angle to match the trans yoke angle within 1 or 2 degrees. If not you then change the pinion angle with shims to be close to the trans yoke angle. Also important is the angle between the drive shaft and the pinion which is measured from the pinion angle and driveshaft angle. Here is a good article about the topic:
www.hotrod.com/articles/91758/amp/

Sent from my SAMSUNG-SM-G930A using Tapatalk

        [Image: 20160929_171923_edit2_small.jpg]

1971 M-Code Mach 1 w/Ram Air, 408 stroker, 285/291 0.558" roller cam, Blue Thunder intake, TKO600, Hooker headers with electric cut-offs, FiTech EFI w/ RobBMC PowerSurge pump
Strange center section with Truetrac, 3.5 gear and 31 spline axles, 4-wheel disc brakes
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#7
(01-27-2019, 10:10 AM)tony-muscle Wrote: In theory what you want is the pinion angle to match the trans yoke angle within 1 or 2 degrees. If not you then change the pinion angle with shims to be close to the trans yoke angle. Also important is the angle between the drive shaft and the pinion which is measured from the pinion angle and driveshaft angle. Here is a good article about the topic:
www.hotrod.com/articles/91758/amp/

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CoolCat33,
Agree with Tony Muscle,
Don't get too caught up with the angle measurements unless you do a before and after measurements.
The measurements are static and what the pinion actually does to cause any viberation are dynamic because of the spring wrap under load.
Expect to see a 4 to 5 degree downward angle at the engine/ transmission and about a 3 degree upward angle at the pinion, thus leaving the LOAD to make up the rest and have the two angles be parallel and cancel each other out.
Actual problems arise when the angles do not cancel each other out or when there is excessive runout in the joints, flanges or driveshaft.
if you try to get the angles exactly parallel with the suspension under load and no spring wrap
(dynamic) you would be more apt to have a problem than just trying to duplicate your before measurements, providing you do not already have a pinion angle problem.
Thing of the spring wrap as being engineered in dynamic angle.
Boilermaster
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#8
One other thing, you want at least a one or two degree angle so the bearings in the u joints move. If they don't move the needles will flatten and the cups and pinions will wear grooves in them. They last longer with some movement. The differential u joint usually gets enough movement from driving around, but the one at the transmission not so much.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#9
If your drop is done correctly, the angle will not change. The relative positions will change, but that should not cause a problem.

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"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
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