Pinion angle
 

When building my '71 Suburban, I changed all body mounts, engine mounts, trans mount, trailing arm and track arm bushings with polyurethane. I added a 700r4 and shortened my two-piece driveshaft by 3". I also changed only the front springs with 2" lowering springs. I am getting a slight vibration at certain speeds and I am thinking it could be the pinion angle is off after changing these things. Any thoughts? Could these mods have affected the pinon and trans angles?

Re: Pinion angle
 

Have you checked your driveline angles?
This is a good angle calculator from Spicer.
https://spicerparts.com/calculators/...gle-calculator

Re: Pinion angle
 

Adding a 700R (longer trans) and shortening the DS changed your DL angle. measure it (link posted is a good one)

You may need to add an angled shim on rear end...

Re: Pinion angle
 

Between the transmission swap and the today's not exact factory engine and transmission mounts it's likely your angles need adjustment. The link goes the drive shaft work I did on mine. Post 348.

Two years later I ended up installing 2 degree shims in the rear axle mounts after converting to a one piece drive as part of installing a Gearvendor. Unfortunately I didn't document the swimming of the shaft very well.

http://67-72chevytrucks.com/vboard/s...698377&page=14

Re: Pinion angle
 

Actually, shortening the front shaft doesn't change the DS angle because the carrier bearing is in the same location. The fact that you went from rubber to polyurethane mounts may contribute to your feeling something now that you didn't with the rubber mounts. Also, did you have both shafts with the carrier bearing balanced when the shaft was shortened? I dont think any of the changes you've made would affect the
pinion angle enough to cause a vibration. On page 4-24 of the service manual it describes rotating the rear shaft 4 splines to the left side of the vehicle. Model CE31403 rotates only two splines to the left. That phases the rear shaft to the front shaft regardless of the pinion yoke position. You should have both front and rear shafts with the (preferably new) carrier bearing balanced assembled together with new u-joints at a DS shop.

Re: Pinion angle
 

My bad, missed the 2 piece DS part in OP's post

Assuming the shortened shaft was rebalanced??

Still would be a good idea to check DL angles

Agree poly mounts do transmit more harmonics/vibration as rubber does a better job of absorbing those

Also look for any sounds of "grounding" (exhaust hitting x member or something)

Re: Pinion angle
 

I did the trig on the effect an additional 4" on the transmission or to put another way 4" shorter drive-line.
This assumes the drive-shaft had a 3 deg down angle.
The longer transmission increased the angel .2 degrees. That's point two degrees.

After shorting the drive shaft the angle was 3.2 degrees.
It appears to be within tolerance.

Re: Pinion angle
 

The front shaft was shortened. Anything that happened or happens ahead of the carrier bearing has no effect on the DS angle. Only from the center u-joint back, (the rear shaft) has any measurable angle down to the pinion. It was not disturbed because the carrier holds its position, it's nearly level from the carrier forward. You can cut that front shaft down to 6" long and it wont change the pinion angle...Our two piece drive shafts are thus...Say, while your doing that trig, maybe you can figure how much the rear axle rotates down for every inch the truck is lowered? That would only be coil rear trucks with trailing arms. ;)

Re: Pinion angle
 

I agree with the two shaft analogy. First shaft changes nothing.

I was only attempting to clarify the question how much lengthening the transmission changes the angle of the joint.

Re: Pinion angle
 

Guys, you are hammering me on details not on the actual angle differences adding 4" makes....
I just used the 3 deg as an example. I could have used Collinear and the results wouldn't varied enough to measure the differences with the protractors used to measure these angles.

If I use 1 deg for the math the difference is .1 deg. That's one tenth of a degree when you add 4 inches to the transmission. It also changes both u-joint angles the same amount.
Show me your math and I will show you mine. LOL.
Cheers

Re: Pinion angle
 

Would think the added length would add more angle than that. The way I understand it for a shaft with three ujoints one has to be less than 1 degree and the two left should match within 1 degree. Basically, one has to disappear. Actually measuring the angle would be better than using calculations.

Re: Pinion angle
 

One shaft only in my example. 55.5" between joints. With three shafts, yes it would be more angle as the distance between point would be much less.

Re: Pinion angle
 

E=MC-squared? They threw me out of public school for riding my pony down the halls and out the back doors. I had to one up my friends challenge after he rode his dirt bike down the said hall and out the back door...So I missed math class...I did later get a GED and enjoy a successful career building America. "Stay on subject Hill!" ;) Happy Thanksgiving everyone! :mm:

Re: Pinion angle
 

:lol:
To Ironangel
A thumbs up.

Re: Pinion angle
 

I am going through something similar with my build and highly recommend this magnetic AccuRemote Digital Electronic Magnetic Angle Gage Level/Protractor/Bevel Gauge

it's really easy to over think this so don't let it

the differential needs to point up at the same angle as the transmission points down, so if the trans angles down 5° try to angle the rear end up 5° or as close to that as you can

then there's the 3° rule which basically means the driveshaft shouldn't angle down from the transmission more than 3° as it slopes down to the rear end

same from the rear end the driveshaft should not slope up more than 3° to run up to the transmission

this gauge makes it easy to measure stuff, you can stick it to the driveshaft right by the rear end and see what it says, then remove the driveshaft from the rear end and measure the angle of where the U joint goes in to the yoke and see what the difference is, again should be 3° or less

Re: Pinion angle
 

This is correct! Especially what you said first, "it's really easy to over think this so don't let it" I think that 90% of these vibration and pinion angle posts are balance problems and not DS angle problems. I cant stress enough how critical it is to have these two piece drive shafts balanced, fully assembled with the center carrier installed by a properly tooled up shop. The 1/2 ton trucks with automatic transmissions that have the Tear Drop sometimes called clam shell type carrier bearings, are susceptible to another problem that my drive shaft technician only recently brought to my attention/knowledge. And that is that these rigid "clam shell" carriers that are made from billet aluminum and bearings attached with epoxy resins will only work with drive shafts with slip joints on both sides of the carrier itself. The factory installed type clam shell carriers use a very flexible rubber insert to hold the bearing allowing it to move laterally inline with the shaft. As the rear axle moves up and down, the pinion pushes and pulls the rear (solid) shaft the transfers this lateral motion to the front shaft. That's why a slip joint is used at the transmission, and a flexible rubber clam shell carrier is used...So you guys using these "Billet Carrier Bearings" without using a rear shaft that has the splined slip joint in it are shooting yourselves in the foot! That will wipe out transmission guts (no end play) break and tear up center supports as well as wipe out pinion bearings...PS Gregski, you got a beer on ice at Ghostriders Bar & Grill Cheers! ;)

Re: Pinion angle
 

You have two beers on ice brother, Cheers! ;)

Re: Pinion angle
 

Several posts have stated that angles ahead of the carrier bearing have no effect on the DS angle. This is only true when the engine/transmission angle and the front drive line angles are in the same direction. As shown in Ironangel's drawing.

If the engine and front drive shaft are at opposite angles then changes in transmission length may cause the angles to change enough be out of spec.

When I replaced my factory T400 with a T350 and a Gearvendor it changed the angles enough to require me to install 2 degree shims in the rear axle mounts and put a spacer under the carrier bearing. Admittedly that is a much longer change in transmission length

Before I did the Gearvendor swap I installed one of the billet poly carrier bearings Ironangel discusses. To bring the angles in spec I had to adjust the engine/transmission angle as follows.

Transmission 3.5 degrees down
Front shaft 0 degrees
Rear shaft 2 degrees UP
Pinon angle 2 degrees DOWN
I jacked the rear of the transmission up and slid a 1/2" piece of plate under the mount, lowered the transmission back down and after double checking my ride height, I took a new round of readings.
Now the transmission angle is 2 degrees and the front shaft is 1 degree. Victory at that end! The second shaft was now just shy of 2 degrees. Now with a one degree difference between the transmission and the front shaft angles, and with the pinon and the transmission at the same angle I should be good as long as the other two u-joint angles aren't too extreme This arrangement puts the u-joint operating angles at:
Front 1*
Center 3*
Rear. 4*

I just wanted to bring this up so no one goes away thinking there is no need to check the angles forward of the carrier bearing.

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WOW!:eek::eek::eek: Didn't realize how detailed this post was gonna be or how many opinions there would be. Gotta get a pinion angle finder now....
Thanks guys!

Re: Pinion angle
 

This post has definitely gotten complicated! I'm working through this with my 2-piece driveshaft now. I used 4 inch lowering springs and had the front driveshaft shortened when the 700r4 was installed. After a while I realized that there was no slip in the rear section and the driveshaft had destroyed the center bearing. I just had the CPP cross member and tubular trailing arms installed along with the poly center bearing and their rear slip driveshaft. Everything looks like it will work and now I just need to have the center yoke replaced, since there is metal missing where the c clips go, and get the unit balanced. I'm hoping this will do the trick and I won't have to do any angle measuring!

Re: Pinion angle
 

Your end result is exactly what I was stating in my post. With 3 cardan ujoints, two need to be in phase and third at zero. Within 1 degree is acceptable and actually recommended at zero degrees. A zero operating angle is not recommended.

While a maximum 3 degree operating angle is recommended for optimal life and reduced vibes. It is not set in stone. The joint will not self destruct or destroy itself in short time if that is exceeded. No 4x4 I have ever owned has been kept to that. Never remember changing ujoints regularly on any of my lifted trucks and they have all been daily drivers.

I think some may not understand the difference between the operating angle and the trans/driveshaft/pinion angle. Good to see a post that mentioned it. 3 degrees references operating angle. While the components create the operating angle they are not the angle that is most important.

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Just did mine I used an app on my phone for angle finder

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When you had the front section shortened, did you take both pieces in to the shop or just the front piece? And did you pull the whole assembly out as a whole or pull the 2 pieces out separately?

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IMHO I find the tremec phone app comes up with different #'s each time. More because the phone case (better to use it without a case) you have to hold STEADY against the point you measure. A $5 magnetic analogue angle finder, for me, is more stable and "hands free" so the needle settles for an accurate reading. One option for getting trans tail angle is hold the angle finder against the flat front of damper as it is dead nits the same angle as engine/trans

Lowered truck often needs an angled shim on rear end to get DL angles back "within" spec and also flat shims between trans and rear mount. This is where using an angle finder tells you wtf "your" angles are and which direction the tail of trans needs to move and rear pinon

Re: Pinion angle
 

So are you guys saying that changing from a TH350 to a longer 7004R trans and having the front section of a 2 piece driveshaft will change the angles to the point that a vibration will occur. I have a C20 totally stock suspension with rear leaf and 4.10 gears. Very noticeable vibration at ~45 to 50 MPH. Both shafts were rebalanced when shortened. Shimming Carrier bearing, 2 and 4 degree axle shims, many hours later and nothing really changes. Is not wheels, tires as these have been changed.