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Discussion Starter · #1 ·
I know this has been asked before, and I did search through some of the other threads.
I have a 55, with an LS3 and 4L65E. I took the rear end out, had it shortened and am putting it back in. My car is on jackstands, and has 2" dropped spindles. ( I'm not sure either of those make a difference, but will yield to you all.)
My degrees are: Intake 6.9-- Starter 5.5--- Transmission pan 1.8--- and the top of the car is 0.2. All are higher at the front of the car.
I think I have 2 problems. The intake on an LS3 is difficult to set up with my angle finder as it is an uneven surface. I put a piece of flat steel on top of the intake, but that didn't help any. I have a mini starter, and I really can't get a good reading there either as there is not a smooth or flat surface.
For the time being, I am thinking of raising the rear end up 3 degrees. I have a 9". I have a triangulated 4 bar, so I have a lot of adjustment.
Where do I measure the rear end-- where the driveshaft bolts to the yoke?
Any thoughts and input on all of the above is greatly appreciated.
Thanks-- Terry
 

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Trifive Automotive Electrical Wiring Expert
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Measure the end of the transmission tail housing either using a square or subtract 90 degrees. Measure the frame rail to determine how much the car is out of level.
 

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Parallelism.

Bottom line - Ultimately, you want the up/down angle of the crankshaft, and hence the ouput shaft of the transmission, to be parallel with the up/down angle of the pinion gear.

They don't have to line up with each other, just be parallel to each other. The up/down angle of the driveshaft is arbitrary, within operational limits.

If you are content with the position/placement of the engine in the chassis, and do not intend on changing that, then your 1.8° at the trans pan measurement is probably the closest equivalent of the crankshaft angle.

Without moving the car from it's rests, set the pinion angle to 1.8° and you will be good.

BTW, when measuring these angles, the frame doesn't necessarily need to be level, but it does help if weight is on the rear suspension, for a more realistic comparison of the two angles.

It sounds like you can make pinion angle adjustments pretty easy with your trick 4 link.

Also, in the future, if you verify these angles, depending on any attitude changes that may have taken place with the car, you might read, say 4°, at the trans pan. For parallelism, the pinion must naturally read 4° at that time also.

Remember, the actual angle is secondary to parallelism. Some carburetion guys are more into duplicating factory intake manifold angles, but if it was critical, gassers would be having float level or fuel delivery problems, which they really don't.

:anim_25:
 

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Discussion Starter · #4 ·
Don
The output shaft of the transmission and the tail shaft are both 83.3 degrees. I'm fairly confident as my angle finder has a magnetic base and I stuck it on the output shaft. The frame about at the back of the rear seat location is 0.3 degrees, as is the frame under the trunk floor, just in front of the gas tank neck, so I think I am fairly level on the frame. Thoughts?
Thanks- Terry
 

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TJV....When you measured the 1.8* at the transmission pan, at what angle was the frame?......Optimally, the engine should be 4* down in relation to the frame (but those are stock figures)

You should zero your level on the frame first, then take your other angles.
 

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Discussion Starter · #6 ·
Dave
I zeroed my level before I took any measurements. I got the Sears digital angle finder that you recommended a long time ago. The engine, transmission, etc. has been in the car a year, so no changes there. It is just Hard to get a good reading off the LS3 intake. I will crawl under it tomorrow and recheck. I cracked a rib a couple of days ago, so am slow to get under the car.
Terry
 

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Discussion Starter · #7 ·
Big Block--- thanks--- good input. I still am not sure where to measure the rear end angle.
Terry
 

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A challenge.

On some rear axles it is easier to fit-up vertically to the yoke or flange, vs horizontally. As was metioned earlier, just add or subtract 90° to come up with the resultant angle.

We have an Explorer 8.8, which has this round flat flange that a yoke bolts to. Very easy to measure, albeit vertically.


http://www.trifive.com/forums/picture.php?albumid=3170&pictureid=26703


With a GM style rear, I've heard of placing a length of round bar or tubing in the half moons of the yoke, and resting the angle finder against the tubing to make the (vertical) measurement.
 

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Also remember the angle is + on one side - on the other. Meaning, if your engine is 1.8 degrees down, the pinion will be 1.8 up. Be sure to measure the pinion angle with the weight of the car on it as well, not hanging on jack stands.
 

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Discussion Starter · #12 ·
Rick
You are correct. The transmission pan is 1.8 degrees and the output shaft was 83.3 degrees, or I am assuming 6.7 degrees. That may be a little strong, so I may have to put a shim or 2 under the transmission on the mount which should raise the engine also....???
 

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Yes, if your frame was level you'd want it at 86 degrees. You said it was actually at 0.3 degrees but you didn't say which way. So you actually should be shooting for 85.7 or 86.3 degrees.
 

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Also remember the angle is + on one side - on the other. Meaning, if your engine is 1.8 degrees down, the pinion will be 1.8 up. Be sure to measure the pinion angle with the weight of the car on it as well, not hanging on jack stands.
I agree... rear needs to be loaded with car weight.. good rule of thumb.. what ever tail shaft of trans is pointing down rear needs to be pointing up same degree while loaded.
 
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