The nose of the pinion should be pointing up but it depends on your perspective of the world.  It does point down from the pinion towards the back of the car.  You need to concentrate on matching the engine/transmission to the pinion and not concern yourself with the driveshaft unless the car is severly lowered.  Most engines/transmissions point down about 3 degrees but some of the aftermarket crossmembers for the T5 can set it lower in back leaving you with 4 degrees or more of driveline angle.

For most cars, if the engine/trans is at 3 degrees, the pinion need to be at 2 or 2-1/2 to allow for spring wrap under load.  If you raise it up to 4 degrees, it will be worse.

Now, if you pinion is actually down in front, you will have problems.  Did you install new perches on the Lincoln axle?  If the perches were installed wrong and your pinion at the u-joint is lower in front than in back you are way off on angle.  Please clarify by what you mean by pinion "down".  There are a lot of other sources of vibration and althoug it is hard to tell without a means of measuring vibration, a driveshaft angle mis-match produces vibration at two times the RPM of the driveshaft.  If the driveshaft is out of balance or if you have a u-joint that is not centered properly, this will produce vibration at 1X driveshaft speed.

A few things to check:

1.  Measure driveshaft runout at the front and rear of the driveshaft

2.  Verify u-joint phasing.  If you had a new shaft built or your existing shaft shortened for the t-5, they may have gotten it wrong.

3.  If you didn't shorten the driveshaft you may be binding up the driveline

4.  Test at 80 MPH in 5th gear and then repeat at the same speed in 4th gear.  If the problem is exactly the same then it is somewhere in the driveshaft instead of clutch, for example.

5.  Some aftermarket rear crossmembers for T-5's do not properly support the back of the transmission and can induce a shake at certain speeds that feels like the driveshaft.

You may want to drop the pinion by 1/2 degree and then try to raise it up by 1/2 to see which way it needs to go.  The trans angle is a little steep - stock is often closer to 3 degrees.  I might be tempted to start there before shims in back.  If you can, temporarily install some washers to see if you can raise the back of the transmission up by 1/2 inch or so and then test (or until the engine/trans is at 3 degrees).  If they don't help you can pull them back out and if it gets worse, I'll have to ponder on that for a while.  You've done some good testing and measurements so far which helps narrow down the list of problem areas.  

A natural frequency of the exhaust system can be excited by normal driveshaft vibration and it feels just like the driveshaft.  In some cases, you might be able to install a wooden wedge temporarily between the pipes and the crossmember.  This can often move the natural frequency up to a higher speed and if it does change the speed where the problem occurs it points more towards an exhaust structural resonance than the driveshaft.

I hate to ask questions about some of the basics like driveshaft length, etc., but sometimes it is the un-asked question that finds the problem.

WIth that info, it seems like the front of the pinion may want to come up 1/2 degree.  But, a way to see if that will help is to keep the car in 4th to get more "compression braking".  Take it up to 80, hold it at steady speed, and then let off the gas.  If it gets worse under deceleration then the pinion is indeed a little low.  If it is the same between acceleration, steady speed, and deceleration this would tend to indicate that it has nothing to do with angles and that you have another problem.  What rear ratio are you running and what is your approximate tire diameter.  Tomorrow AM I'll run some numbers to see what frequencies/speeds are in play.  If you have a chance to brace the exhaust, that will be helpful.  Any wobble in the pinion or is there any play in the yoke/transmission?  Often a driveline angle problem will be felt at many speeds and not necessarily at higher speeds.  The forces produced by unbalance or an unbalance induced by a bend or by play in a bearing support increase at a rate of the square of the speed of a shaft.  At 80, your driveshaft is spinning at pretty high speed.  You mentioned that the vibration gets worse beyond 80.  I'm not recommending high speed driving but if testing shows that it gets worse and never gets better at higher speeds that would help to determine if there is a true force such as unbalance or angles or if you have some resonant amplification of a responsive structure like the exhaust.

You can get some wierd stuff with tires and tire diameters that can cause some sort of cyclic vibration but the more common cause of this phenomenon is a vibration beat established between a vibration source and either another source (like two engines on a prop plane) or between a source and a resonant system.  If they system is lightly damped like an exhaust system it wants to vibrate at its natural frequency and if the driveline forcing frequency is close, it will cause the two different frequencies to add and subtract from each other and a beat will ensue.  This MAY help to identify this as resonance and the most responsive structure under the car is the exhaust system.  This is not related to the acousics but the structural natural frequencies.  You can feel them if you lightly hold the pipes and impact them with the base of your palm.  Just like ringing a bell.  Have to run for a plane but report back on some of the other tests.

Great update and glad you got it fixed.........

Dumnernhell wrote:

Guys, i just finished the Hotrod Power tour where I chased a vibration in my car for over 2500 miles. Everything was smooth as silk up to 60 mph and then from there on up it was just a steady vibration and roar throughout the car. During the trip from MS to I replaced the front tires, balanced the rears and checked the front wheel bearings with no improvement. When I arrived in Eau Claire we put the car on a lift and 14 hours later we had new axle bearings(they were shot!) and rear tires, two new u-joints and a rebalanced driveshaft, a new bushing in the trans tailshaft along with a bunch of new car bugs worked out. Back on the road all was sweet until I hit the 60 MPH mark and the vibration and noise were back. 15 hundred miles later I parked the old heap in the garage and pulled the axles to check the bearings - check- all good. Tires and wheels balanced OK. Then when I removed the driveshaft I noticed a lot of slop in the yook where the universal joiunt sits. BINGO! the yoke had signs of u-joint failure in the past and the u-bolts indicated the yoke was distorted. I replaced it with a brand new yoke and now its as smooth as can be.
The u joint was not fitting tightly in between the two tangs that retain the cups and allowing it to rotate off center and setting up harmonic resonation which was destroying the new trans bushing and who knows what all else.
 

  Eau Claire Wisconsin?
 

One thing you want to make sure of is that you don't have too much driveline offset between it and the pinion/trans. Generally you want no more than 3 degrees of offset though Dana/Spicer does have tighter specs depending on which type of yoke (1310/1330/1350, slightly less offset for the smaller yokes). Additionally you want at least 1 degree of offset for proper U joint motion/lubrication..

If your pinion is at 2.3 up and your trans is at 3.9 dergrees down I would say that it looks like you have too much trans angle. If you brought your trans angle up to 3.3 degrees, you would have one degree of difference which seems to be a number many people agree is good for a powerful street engine with leaf springs. When a load is applied the pinion will rise to align closer with the trans. As long as you have the proper offset and the powertrain is parallel with the diff, you should be golden.

I hope this helps.

Lil' Hoss wrote:

Cougrnut, I have wondered about the output shaft in the T5, I bought it as a rebuilt race ready unit with hardened gears and shafts, It is quiet and smooth so I haven't taken it apart to check anything............... yet. 

As for the Versaillies spring perches, they do have larger holes but what I have done is machine the wedges from a steel block, drill the centering hole for the center bolt then center up the axle and weld the wedge to the perch, Guaranteed it is not shifting. 

I have com to the conclusion that the driveshaft is causing the vibration, thinking back I used to feel the vibration in the shifter the most, when I replaced the slip yoke I intentionally swapped ends with the driveshaft and now I feel the vibration further back, so I have decided that I am having a new steel driveshaft made to see if that is the issue, if it isn't then I guess I have a 3.5 inch aluminum driveshaft to use in the car I am restoring for my wife. 

 

If your shaft was balanced I don't think you should swap ends

"If your shaft was balanced I don't think you should swap ends"

A balanced shaft should not make any difference as to which end is front or back 

"Here's a thought. Shouldn't the drive shaft slip a lot further than 3/4 of an inch inside the trans?"

Yes, and it does, it has 3/4 inch travel, it is engaged 4+ inches. 

 

Last edited by Lil' Hoss (6/26/2015 8:34 PM)

Was balanced without the yoke, unless the shop installed a yoke because I didn't take it along and they didn't say anything about it. But you do have me wondering now. I may have to swap ends to see if it makes a difference. If it does then the vibration will move to the front and I still have a problem and time for a new shaft. 

Last edited by Lil' Hoss (6/27/2015 7:18 AM)

Lil Hoss, here's a question fer ya......when installing the front yoke....does it slide in easy or do you have to bump it in with a hammer or something?
Reason I ask...a friend had a vib issue and his was hard to slide in. He pulled a bushing from inside the tailshaft. (Required a special tool his dad just happened to have) It was egg shaped!! Replaced that and now yoke slides in/out easily.
Don't know for sure yet(he hasn't tested car) butt it stands to reason THAT could cause a vib condition.

I know I'm jumping in Late, but.... When I ran leafs on the Mach, I had the 5 1/2 leaf mid-eye springs. My Trans was 3* Down , so I shimmed the Pinion 3* UP and my vibrations went away. Equal but Opposite Angles. I had also heard of folks saying Trans 3* down and Pinion at 0* so it can rise under acceleration...My Pinion did not rise under acceleration, in fact when I was Drag Racing, with Slicks I did not need Traction bars after I put the 5 1/2 leaf springs in...meaning they are STIFF. Since I have gone to the Triangulated 4 Link in the Rear, my Trans is still 3* Down and I set the Pinion Angle with the 4 Link to 3* Up and still good. Maybe I just got lucky, but it works.

Last edited by Mach1_Ron (6/29/2015 6:54 AM)