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Derek

Let's talk driveline angle.

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So since I put in my CD009 I decided to do some checking into proper driveline angles. The transmission output shaft is right around 2.7 degrees which is good from what I read. but the pinion angle in it's factory position is 4.9.  Anyone ever delved into this? I did some searches but I didn't see much about it.  Is there a reason why Nissan put so much angle in there? I have a Ron Tyler style mount and I can top hang the diff and dial in the angle but before I do that I wanted to hear what you all had to say on it.

 

Thanks

Derek

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I had no idea the stock angle was so much, trucks sometimes have a lot more than that but generally they are not going very fast.  I always shoot for anything between 1 degree but no more than 2.5 and as parallel as I can make the trans and diff.  RT's mount is great in that you can shorten or extend the snubber to find the right angle, the transmission is a lot harder to point than the diff.

Now you're going to laugh but it works very well, the bmw trans is different that the Datsun 5spd so I had to have room to lower the diff to get a good angle.  This rear cross member started out as just a stop gap solution so I could test the angle and keep the progress moving but it worked so well I welded it properly and it has thousands of miles on it now.

 

DSCN0625.JPG

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Actually I was already thinking what I would do if I wanted to rework the cross member. That looks like a practical solution for sure.

 

I think the stock angle on the motor was right around 3 degrees.  When I was working on the 6 speed install I kept looking at the pinion angle and thought it was odd.  There is a fair amount of data out there on the principles but my understanding is no more than 3 degrees on either angle and no more than 1 degree difference between them. There is more to it than that but that's the general gist.  The 5 degree pinion angle is way out.  I have heard of dropping the pinion flange so that under hard pulls it lifts into position but it's 2 degrees out of spec even before torque is applied.

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There are some old threads on using laser pointers. I don't think you'll find a spec as to what the angle should be, but you will find some info on how to adjust. I am just horrible at math, so I did the laser pointer thing and basically shined lights from the diff and the trans on a piece of paper in the middle and then moved the trans mount until I could move the paper back and forth and the distance between the dots hardly changed at all. Basically held up the piece of paper, marked the dots with a sharpie, moved paper and tried to line up the dots again at the new location. When I got a minimum of movement of the dots, I called it good and welded up my engine and trans mounts to keep that angle.

 

You can do this more accurately with trigonometry if you're less retarded than me. Regardless, my math avoidance workaround was successful, no vibrations with V8 offset to pass side, T56, R200, very short driveshaft (cyl head is ~1.5" from firewall) I want to say CTC on the driveshaft u/joints was 19". The problem with just the vertical angle measure is that the trans and diff might not be parallel to the center line of the car, and they are probably also not perfectly in line with each other.

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I saw those and may make one at some point to check horizontal alignment. Tremec makes a pretty good app for taking measurements with your phone and it does the math for you.  The 5 degree pinion angle is so far out that until I get some clarification on that I'm not going to change anything. It seems they had to have had a reason for designing it with 5 degrees tilt . I wonder if it was trying to correct a vibration problem. My 73 has the stack of steel plates under the diff X member so there was for sure some sort of issue.

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Just thoughts. I noticed it as well when I was down there. I would be curious as to the reason as well. I thought symmetry was the reason. The rear setup is fairly symmetrical except for the differential offset. The front is also line up down the center other than the tilt of the engine. Driveshaft then is twisted at an angle to accommodate the mismatch. I think you would have to delve into the evolution the rear Nissan IRS design and where the inspiration came from to determine if it was intentional, happenstance, or poorly copied. 

 

I recall asking my driveshaft shop and they said as long as both ends were flat and there was angle it would be fine, best would be if the angles were the same, but not always done or possible.

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2 hours ago, grannyknot said:

I use to use the red pointer lasers until I found these digital inclinometer , they make the job so easy, they are down to $20-30.00 now.

 

The Tremec app works really well. And it's free:)

 

I exchanged a PM with Madkaw over on classicz because I saw a post he made on it. He said he measured his and it was 2 degrees so the plot thickens. Everything I read says no more than 3 degrees. I'm going to double check my measurement and see what gives.

 

Here is a video showing the importance of having the same angles on the transmission and pinion.

 

 

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12 hours ago, grannyknot said:

I use to use the red pointer lasers until I found these digital inclinometer , they make the job so easy, they are down to $20-30.00 now.

external-content.duckduckgo.com.jpg

This is what I used . I tried a laser , but it was really hard to come up with a rig that fir and sat square against the surfaces . I run the Subbie diff with a redrilled pattern on its larger yoke flange . Lots of surface to sit this on . I used a square off of the tail shaft along with this . Pretty consistent readings . 
i was looking for sources of driveline vibration so I wanted to make sure the lines were not intersecting .

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I think the laser is appropriate for horizontal alignment. but an inclinometer is a much better choice for vertical.

 

The 5 degrees I measured was with my Subbie 3.9 diff installed. I have since put my stock diff back in to test out how the 3.364 ratio plays with the CD009 but like an idiot I didn't check the pinion angle.  I'll be pulling the drive shaft again soon and I'll check the angle again and see what I get.  

 

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14 hours ago, seattlejester said:

I think you would have to delve into the evolution the rear Nissan IRS design and where the inspiration came from to determine if it was intentional, happenstance, or poorly copied. 

There has to be some angle; the angularity is what rotates the needle bearings in the u-joints. Without the angle the power will be applied to the same few needles over and over and they will fail quickly. Occasionally you'll see this come up when someone makes their own mounts and decides to "fix" the driveshaft angles by not having any. Sounds good but doesn't work, unless you're running a torque tube without u-joints like a Vette or a 944. 

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Agreed.  I think the more critical number is that the output shaft of the transmission and the input shaft of the diff are the same or nearly so. The video shows pretty clearly how an elliptical  movement can be generated by miss matched angles. The Tremec app measures the output shaft angle, the drive shaft angle and the pinion angle and then gives you a report if they are within specs. 

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I was doing the installation instructions for the CD009/L6 bell housing. I started on the cross member section and that is when I researched drive line angles. As soon as I walked over to the car an looked at the pinion flange I realized that it was a lot more than 3 degrees.   

 

I'm going to bring it down to match the engine and see how it goes.

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Posted (edited)

So I made a laser alignment tool based on a few Ideas I gleaned from the forum. I made a slip collar that fits over the CD009 output shaft that holds a 45ACP laser bore setter. I'm using this for the horizontal alignment.

 

IMG_3126.jpg.4078b6f00ed6a5401b86d937dbf15479.jpg

 

Works well.

 

IMG_3125.jpg.c4463034f6d6ca0fb375745fe8faa9f0.jpg

 

I made a target that has a couple of alignment lines. The bottom is parallel/perpendicular to those lines so you can use a level to get it plumb. I then proceeded to drill so many holes in it that it's almost useless:)  The key word here is almost. 

IMG_3124.jpg.ca710885010ab7a0fdbb682a162fecff.jpg

 

That was a far over to centerline as I could get it. I need to rework either the Diff mount or the trans mount to get it any further but it's only about a half a degree so I may live with it.

 

I'm running the Technoversions RT mount and I switched to the top mount instead of the stock bottom. This brought the pinion angle down to 2.8 degrees. The transmission is at 2.9 degrees so I'm pretty satisfied.  Hard to tell if it made much of a difference but the math says it should.

 

Edited by Derek
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24 minutes ago, madkaw said:

So the trans is 2.9 up?

Motor tilting back/down. Pinion flange pointing up.  Technically that means the pinion shaft is tilting down according to the literature I read.

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I tried that laser deal,  but didn’t get the right laser and didn’t have a precise mounting jig for the trans . I think I trust my angle reader , but it doesn’t verify if the there’s a lateral issue . 

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8 hours ago, madkaw said:

I tried that laser deal,  but didn’t get the right laser and didn’t have a precise mounting jig for the trans . I think I trust my angle reader , but it doesn’t verify if the there’s a lateral issue . 

Yea that's why I made the slip adapter. The other methods with a magnet didn't seem to be accurate.

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