To clarify, when you say the pinion is up, do you mean the pinion yoke is pointed up? If it is, your angles are good as is.
If the yoke is pointed down then shimming is needed. I say all of this because people often confuse the pinion angle direction. If you haven't already done so, download the Tremec toolbox app and run your numbers through the driveline angle selection. If you need shims, at one time shims were available with a counterbore (for center bolt head) on one side and a raised nub on the other side to keep the axle centered. I'm not sure if they're still made that way.

 

I have this horrible harmonic type vibration at 3k rpm or 50-55mph. That's what led me to believe my angles are off. yes, the pinion yoke is pointing up. I have greaseable u joints i'll try greasing them and see if that helps solve my issue. I thought the pinion and tail shaft need to be opposite angles so they run imaginary line parallel of each other.

 

I thought the pinion and tail shaft need to be opposite angles so they run imaginary line parallel of each other.

That is the age-old rule of thumb and it's good.

Really what matters is the "Working Angles" at the universal joints.

Using your numbers, your working angle at the trans tail is 1.5°

The working angle at the rear pinion is either 1.0° or 1.5° ... depending on the .5° or 1.0° pinion.

Working angles are best when they are as equal as possible and more then .5° and less than 3.0°

As for terminology on this, if the rear yoke is pointed toward the floor (of the car) that is referred to as a "down".

If the yoke is pointed toward the ground, that would be referred to as "up".

The reference terminology views all angles as the slope from front to rear on the driveline.

Anyone can feel free to correct me if I am wrong on anything here.

 

my pinion is pointed up so i guess that means it's down approx 1*. the tailshaft is up 3.5*

I got a bad vibration at 50-55 i'm trying to sort out, it's getting old.

 

My guess? if the vibration is at a certain MPH I would look at some other possible causes such as tire balance.

I had the vibration from bad angles on my drive line. In my case it was really only evident while I was under acceleration at any speed. My angles at the time were far worse than what you have.

 

I have tried two sets of rear tires/wheels and had the fronts rebalanced which did not fix the issue.

The driveshaft has no markings of any of the weights falling off and the driveshaft has only been removed by me and i haven't dropped a cap off. I have greasable zirq fittings or however you spell it. I'll try pumping the u joints with grease see if that helps.

 

your angles sound right to me....especially considering that if they were off you have more of the vibration under load. you want the exact, but opposite angles assuming a perfect world or maybe independent rear suspension. but with the leaf spring, youll have a little axle wrap under a load, so you offset that by having about 2 degrees less in your pinion angle...by the above context, measuring "front-to-back" that would be more "up" like you currently have it set. any chance you have other issues like wheel weights fell off, bad u-joint, etc? if a shop did anything removing your driveshaft, theyre known for losing pins in the bearings.

I battled the shims trying to get mine right...i fabricated longer dowel using long bolts to make it work. ended up not using any shims at all...but i modified a LOT of other stuff. lowered the car, shimmed my trans, etc.

 

if you have the rubber pads....might be worth tightening the hell outta the rear-most bolts, then snug+locktite the fronts and see if that buys you .25 degree or so....i dont think your angles are off, but if they are that should be enough to put you in the safe operating range....or maybe im crazy. get a 2nd opinion on that one hahaha. that would lower your working angle at the pinion-driveshaft u-joint. if it even reduces the vibration, at least youll know youre heading the right direction.

 

Like @allanjs mentioned, the Tremec app has a tool for this. It isn't "perfect" but it does let you know you are in the ballpark and makes calculating the angles idiot proof. Finding a surface to read the angles accurately with your phone is the challenge. The app is free

How are you measuring your angles? magnetic dial or electronic angle finder? And where are you measuring them from?

I ask because that information may help someone with more knowledge than me. I am interested in your situation, I may or may not have a driveline angle issue. I have made a lot of changes recently and need to get a few more miles on mine before I make any more changes or adjustments.

I'm using a digital degree thing I got off amazon. I have rechecked numerous times to ensure it is getting the same readings. I've checked the tail shaft, the seal on the end of the transmission, the oil pan and all get me to 3-3.5* 'up'. Then the rear end measuring off the pinion flat face where the u joint caps bolt in. also checked against the rear housing cover and got the same readings 1* down on that one.

 

Like @allanjs mentioned, the Tremec app has a tool for this. It isn't "perfect" but it does let you know you are in the ballpark and makes calculating the angles idiot proof. Finding a surface to read the angles accurately with your phone is the challenge. The app is free

How are you measuring your angles? magnetic dial or electronic angle finder? And where are you measuring them from?

I ask because that information may help someone with more knowledge than me. I am interested in your situation, I may or may not have a driveline angle issue. I have made a lot of changes recently and need to get a few more miles on mine before I make any more changes or adjustments.

 

I prefer spicers website...but yeah measuring with your phone will have you all over the place. Spicer Driveline Operating Angle Calculator

and invest in a digital angle finder. got mine on summit for about $20

 

well i'll chime in on this since ive been monkeying around with pia pinion angles in my cobra for 20 years ,i wish the driveshaft in my cobra is as long the one in the camaro its about 28in total in the cobra so pinion angle is crazy to set up , first off the car must be level the suspension loaded with the cars weight , the engine should be level in the chassis , if the springs or control arms have factory rubber bushings set the pinion angle to 3 to 4 degrees downward , if the car has poly bushings set it to2 1/2 to 3 degrees downward if it has solid bushings set it to 1 degree downward , source baseline suspensions.com i used this and have set mine too much down will cause the ujoint at the diff to bind under heavy braking ive got the broken ujoint to prove it

 

interesting. i have cal tracs essentially so i doubt there is much leaf spring wrap but i could be wrong. I think my driveshaft is 49" in length center of cap to center of cap.

 

Your driveline angles look good.

I have this horrible harmonic type vibration at 3k rpm or 50-55mph.

3k @ 50-55mph... what is your rear gear ratio?... and rear tire diameter?
What happens if you drive in 2nd or 3rd gear at 3000 rpm?... Do you notice the same vibration?... or is it just speed related to 50-55mph?

What is the diameter, material, and tube wall thickness of your driveshaft?

If you are running a stock driveshaft, I leaning towards 1/2 critical speed driveshaft vibration.

 

Your driveline angles look good.


3k @ 50-55mph... what is your rear gear ratio?... and rear tire diameter?
What happens if you drive in 2nd or 3rd gear at 3000 rpm?... Do you notice the same vibration?... or is it just speed related to 50-55mph?

What is the diameter, material, and tube wall thickness of your driveshaft?

If you are running a stock driveshaft, I leaning towards 1/2 critical speed driveshaft vibration.

Rear gears at 3.90s. tires are probably 26.5". 1st or second at that rpm do not have a vibration just 3rd/just speed related.

 

Here's a bit of an update. I greased up the u joints and i'd say the vibration was at least 1/2 way gone if not more. I'll throw some more grease in them next time I get around to it to see if it needs anymore and where it's at. Who would have thought greasable u joints need grease???????????? well at least i'm moving in the right direction I feel like.

 

I dont know for sure, but i wouldnt think that would do much unless its buffering the gap from worn out ujoints or missing needle bearings. ultimately masking the problem. but somebody else might know better than me.

 

i had a shop replace my pinion seal (cuz some reason when i do it it kept leaking), and the shop replaced it, still leaked. but i did a full overhaul on my rear diff (fixed it that time). but my story is that drive shaft/ujoint only had about 1k miles on it with spicer ujoints. the shop was the last to remove it. once i pulled it, the bearing cap fell off.....i found about half my needle bearings were missing. the shop claimed they didnt pull the cap off so it couldnt have been them. but we all know the truth.

anyway, even missing half my needle bearings, i didnt have any vibration, but that ujoint was pretty chewed up.

 

i had a shop replace my pinion seal (cuz some reason when i do it it kept leaking), and the shop replaced it, still leaked. but i did a full overhaul on my rear diff (fixed it that time). but my story is that drive shaft/ujoint only had about 1k miles on it with spicer ujoints. the shop was the last to remove it. once i pulled it, the bearing cap fell off.....i found about half my needle bearings were missing. the shop claimed they didnt pull the cap off so it couldnt have been them. but we all know the truth.

anyway, even missing half my needle bearings, i didnt have any vibration, but that ujoint was pretty chewed up.

dang thats disheartening for me to hear lol. I will be honest my u joints went without being greased for a LONG TIME. once i finish this disk brake swap I'll probably get back to addressing the ujoints.

 

DS removal 101 would have you either using a rubber band or tape wrapped around U joint caps...but yeah shops get lazy. I don't use U joints with zerk fittings.

 

I don't use U joints with zerk fittings.

X2 - and worth saying again.

 

I used 4º shims to rotate the rear end. I actually used two 4º shims on each side. I placed one shim on top of the spring and one facing the other way on the bottom so the shock plate would sit level. At first it may seam like using two shims on each side cancel each other out, but I assure you it doesn't. I also eliminated the rubber spring pads so I had to add a 3/8 inch thick steel spacer to the spring pack and a longer bolt.

To solve the alignment pin problem I used a nut as a spacer under the head of the spring pack bolt and a double nut on the other end. This way the bolt protrudes through the shim and indexes the holes in the spring perch and the shock plate.

Shimming the rear end solved my vibration problem.

 

wow that is quite the process, thank you for sharing the elaborate post. Do you experience any issues running just spacers and no rubber pans in between the leaf springs?

 

Here is a good video on the subject of pinion angle.

 

The out of phase U joint idea was something engineers felt worked on paper....in real world it was a fail.....and it took 3 years to admit it was a fail