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Positive Pinion Shackle Flip

C

Cricket

3/4 ton status
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Nov 29, 2004
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Has anyone else done the DIY flip on a 10 or 12 bolt and ended up with a positive pinion angle.

My pinion is now nose high. From what I measured with a magnetic angle finder I would need a 14 degree shim to get the pinion nose down and opposite/equal to the t-case output/driveshaft angle.

14* sounds like an awful lot to me.
 
That sure does sound like a lot; could you maybe get a picture of the pinion along with the installed shackle flip? Maybe a picture of the leaf springs/spring perches as well. I'd like to see what's going on here...
 
Wow, when i did mine, it pointed my pinion right at my tcase...ofcourse i have a blazer. Your long wheelbase means less angle, but wow, 14* sure does seem much. Ive never had any problems with the angles being off or pinion being pointed right at the case...
 
Either that or I'm reading the angles wrong. I checked again and came up with a little different measurement

At zero* on the driveline I show a 5* angle on the t-case output and a 7* angle on the pinion output. In order to get the pinion down through the driveshaft centerline I'd have to come down 7* for parallel and another 5* for an equivalent angle.

Technically the angles are within a few degrees of each other but the pinion is up instead of down.

These are the best pics I could get in below zero temps at night.
 
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i had long bed 1/2 ton with 14ff and 5 leaf 52" springs. i did a ord 4" flip and needed 1" block to level truck to front. then pinion was nose high. so i found a tapered 1" block from a 70 3/4 ton gmc rear. but used it backwards to kick pinion down to perfect no vibes.
 
It is okay for your pinion to be up or down around 3 degrees. Any more than that and you'll start getting some bad vibrations from 15-35 mph. My K5 took a 6 degree shim to get it to perfection.
 
bigblazer87 said:
It is okay for your pinion to be up or down around 3 degrees. Any more than that and you'll start getting some bad vibrations from 15-35 mph. My K5 took a 6 degree shim to get it to perfection.
Click to expand...

unless you have real soft springs and bad axle wrap . than it is much worse.
 
sweetk30 said:
unless you have real soft springs and bad axle wrap . than it is much worse.
Click to expand...

Of course, it just depends on each person's vehicle. It seems that even with a 4" block and 8" springs, I don't get any hints of axle wrap, which surprised me, to say the least. I have my pinion down 3 degrees to compensate for any, should axle wrap arise.
 
When I did my shackle flip I installed 5 leaf 57's form an 85 Bronco. The Bronco had these thick ass cast shims that I installed back wards to correct the angle. I never did check it with an angle finder but it worked out perfect with zero vibration.........
 
With 33's and 3.73 gears I'd get an bad oscillation at 60-65mph.

Now with 35's and 3.73 gears it comes in around 65-70.

I know the pinion angle has changed with the flip bracket because the springs have been moved down in the rear rotating the pinion up, I'm reading a nose up 7 degree difference between driveshaft and pinion yoke. The pinion is up high enough that I'm worried about gear oil getting to it.

Guess I'll just have to dink around with shims.
 
the angle on your pinion and the angle on your t case need to be within 4 degrees of each other.
 
55Willy said:
the angle on your pinion and the angle on your t case need to be within 4 degrees of each other.
Click to expand...

1-2* :whistle:
 
Btw i wouldnt worry too much about it getting oil, some guys pint ther pinions way up. If it is that much of a concern you can always add more oil with zero side effects...:D
 
79k20350 said:
If the anlge are within a few degree its ok whether the opinion is UP OR DOWN.

http://www.pirate4x4.com/tech/billavista/PR-shaft/worksheet sc.jpg
Click to expand...
This is what he's talking about:

Geometry.jpg


Taken from tech article on Pirate: http://www.pirate4x4.com/tech/billavista/PR-shaft/index2.html
 
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