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Diff pinion angle ?


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#1 biga064

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Posted 02 September 2010 - 08:50 PM

Hi Just put a digital protractor on my diff pinion and it read 89.6 degrees , Back of transmission read 85 degrees .do i need to get the diff pinion close to the gearboxes 85 ? If box is 85 degrees what does pinion need to be ? Thanks for the help .

#2 TerrA LX

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Posted 02 September 2010 - 09:05 PM

You want the G/box centreline to be zero, ATM it seems you have 15deg.

You want the pinion to come upto zero under load, this will incur a few or several deg negative offset static, this means the pinion will be pointing to the ground and when accelerating it will rise.

http://www.buickperformance.com/Pinion.htm

Edited by TerrA LX, 02 September 2010 - 09:02 PM.


#3 biga064

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Posted 02 September 2010 - 09:14 PM

You want the G/box centreline to be zero, ATM it seems you have 15deg.

You want the pinion to come upto zero under load, this will incur a few or several deg negative offset static, this means the pinion will be pointing to the ground and when accelerating it will rise.

http://www.buickperf....com/Pinion.htm


Hi how do you get 15 degs ?

#4 TerrA LX

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Posted 02 September 2010 - 09:26 PM

zero would be parallel to the ground, 90deg would be pointing at the ground.
My math is #@$^%& ATM, should have said 5deg sorry.

#5 76lxhatch

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Posted 02 September 2010 - 09:31 PM

In one scenario you would be looking to get the angles similar, but without knowing the relative heights you could have too little or too much angle at the unis.

Don't worry too much about absolute angles - measure them relative to the driveshaft angle, so that you have a difference in angle either end. You want say 2 degrees at the front, and maybe 3-4 degrees (down) or 0-1 degrees (up) at the rear to account for movement so that the angles match at maximum acceleration. Ideally these angles should also be in opposite directions but unfortunately that's not always practical in a lowered car.

#6 TerrA LX

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Posted 02 September 2010 - 09:36 PM

Oh and don't measure them off the ground, measure from the G/Box output shaft centreline.

#7 wot179

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Posted 02 September 2010 - 10:07 PM

The easiest way to check the diff pinion angle is to put the diff on jackstands and jack the front of the car up so that the car sits level.

Your sills should be level,use this as a reference point.

Pinion should be pointing towards the ground about 3 degrees.

#8 SS Hatchback

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Posted 02 September 2010 - 10:17 PM

I had around 5 deg down on gearbox measuring from the output shaft as Terry mentioned, i changed it to around 3 deg down and my diff now points up 1 deg , no vibration now

#9 ls2lxhatch

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Posted 03 September 2010 - 12:07 AM

The gearbox and pinion angles should cancel each other out. If the gearbox is down 5 then the pinion should be up 5 when loaded to cancel out the gearbox angle. You need to allow for diff rotation under load which will make the pinion rise.

The amount the pinion angle changes under load depends on many factors. As a starting point from this website.

Factory bushings: Set Pinion Angle 3 degrees to 4 degrees downward from cancelled angle.
Poly bushings: Set Pinion Angle 2 1/2 degrees to 3 degrees downward from cancelled angle.
Solid bushings: Set Pinion Angle 1 degrees to 1 ½ degrees downward from cancelled angle.

This article explains what you are trying to achieve and how to measure the angles.

Edited by ls2lxhatch, 03 September 2010 - 12:08 AM.


#10 rodomo

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Posted 03 September 2010 - 12:54 AM

I'll just add that Holden motors (which includes the gearbox mainshaft) lean backwards from the factory.
Dr Terry, from memory, has posted the angle.

So..........calculate this angle into your measurements.

#11 biga064

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Posted 03 September 2010 - 05:37 AM

Thanks guys for the info !!!!

#12 Cook

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Posted 19 November 2019 - 03:59 PM

Hi all.  I'm just trying to find out that engine angle for a 308 that Dr Terry had previously posted but can't find it on the site.  Anyone steer me in the right direction.  Cheers Ron



#13 Cook

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Posted 21 November 2019 - 10:43 AM

Anyone recall this angle?  Cheers Ron



#14 Dr Terry

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Posted 24 November 2019 - 10:09 AM

Hi Guys.

 

I don't remember ever posting the angle figure, but I believe it is around 3 to 4 degrees.

 

You can measure it at the front pulley. Put you level on the front pulley or harmonic balance face to see how far off the vertical it sits. It will be the same number.

 

Dr Terry



#15 yel327

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Posted 24 November 2019 - 12:03 PM

I found the engine installed angle for HT-HG Holden:

 

6cyl 3spd (M15) and auto (M35 or M40) - 4degrees 18seconds.

6cyl 4spd (M20 or M22) - 4degrees 58seconds.

 

253/308 3spd (M15) or auto (M35/M40) - 4deg 18seconds

253/308 4psd (M21) or 350 (M21 or M35) - 4deg 58seconds.

 

The Engineering Technical Specifications morphed into what was called Features Manual for HQ onwards, so haven't found this same info, but I can only assume that Torana 253/308 will be the same approx. 4deg built into the carby face so it sits flat when the engine is tilted backwards just over 4deg. 



#16 Cook

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Posted 24 November 2019 - 12:36 PM

Thanks again gents.  Confirms what we have been able to identify on my other thread.  Cheers Ron 



#17 claysummers

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Posted 24 November 2019 - 02:23 PM

That’ll be degrees and minutes’, not seconds”. Anyway 4.3 - 5 deg.

Any specs on pinion angle yel? Dr T?


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Edited by claysummers, 24 November 2019 - 02:25 PM.


#18 Dr Terry

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Posted 24 November 2019 - 02:39 PM

Diff pinion angle will vary from car to car & will also depend on the car's usage.

 

The whole idea is to have the front & rear unis working at roughly the same angle under slight power on. i.e equal & opposite.

 

The pinion angle has to have some "pre-load" built into it, because the nose of the diff will lift further under full acceleration.

 

A leaf spring car will react completely differently to a 4-link car & a drag car will need more pre-load again.

 

This is where you need the advice of an experienced diff guy.

 

Most diffs start out with a few degrees pre-load, around dead level is often used. In many cases it's actually trial & error.

 

Dr Terry 



#19 claysummers

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Posted 24 November 2019 - 09:22 PM

Thanks Dr T


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#20 yel327

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Posted 25 November 2019 - 05:50 AM

That’ll be degrees and minutes’, not seconds”. Anyway 4.3 - 5 deg.

Any specs on pinion angle yel? Dr T?


Sent from my iPad using Tapatalk

 


Spot on. just having a Lysdexic moment! It is degrees and minutes. I would have used the symbols but don't know how to create a superscript degrees symbol here.

 

I haven't see any factory mention of pinion angles in any GMH Technical Literature yet.






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