Pinion angle--revisited. With Caltracs thrown into the mix.

So you shift into neutral, and the vibration goes away?

 

Yup. Only vibes when in gear and force on the drivetrain.

And if I put in neutral while moving, and then rev the engine up to 3000, no drone. Just nice smooth exhaust sound.

 

When on the highway, and you shift into neutral, wouldn't the drive shaft still be spinning , since you have a spool?

 

Drive shaft is spinning but the force pushing the pinion is off so it goes back to its relaxed position. Which is within the angles that don't bind the u-joint.

 

yep.. the driveshaft certainly doesn't stop spinning just because you slip in into neutral and I'd say that you pretty well narrowed it down at this point.

Have you thought about shimming the trans mount a tad bit.. or even the cross bar.. to see if the sound can be increased or decreased with slight angle changes at that end?

 

I have thought about shimming the trans up to level it out. But first, I want to get under there and get good measurements of all the parts and angles. Just to see what I am working with.

I am currently in the stock configuration at the rear end, no shims, etc.

I may find that I can shim the rear in 2 degree increments and do something at the transmission end of things in smaller 1 degree increments.

Honestly, just like with the carbs, I don't need perfection, just peace and quiet. If I can drive it without my teeth hurting at the end of the day, and not having to retorque all my bolts, I will be happy.

 

Have you pulled your 3rd member to inspect the gears. Maybe you are experiencing a form of gear whine.

Another thing to look at is the condition of your driveshaft. I know you said you had it balanced but I found that even though balanced I still had problems. I decided to replace my u-joints and found that the front driveshaft yoke was out of shape resulting in binding of the cups themselves. I had a new driveshaft built and it made a world of difference. Make sure the u-joint moves freely and the "ears" are parallel to each other.

Another good place to measure transmission angle is using the face of the crank pulley.

When doing this, just keep in mind that the angle you are most concerned about is the driveline working angle. 3* pinion angle doesnt mean anything if the resulting angle between it and the driveshaft is greater than 4*. Same with the transmission end. You may end up changing everything around to get where you need to be.

 

Just finished measuring everything. Still reading the theory trying to determine which direction to move the rearend. Kinda confusing. But I want to do it one more time and be correct.

Engine sits with the rear down at 5*
Driveshaft is dead level at 0*
Pinion sits front facing down at 4*

So, I am probably wrong, but I think I have 9* of total angle looking like this \___/

I think I need to pull my rearend front face UP 6* giving me 3* negative.

Before I do this, going to re-read all the literature.

 

The more I read, the more I think I might be correct in previous post.

And NO WONDER this car has been so noisy!!!

It looks like I need to have the setup look more like

_____/ not \_______/
/

 

That's about where I was after my bud welded the perches on my axle. I didn't even try to drive it like that, instead opting for some 8° shims to get the pinion nose up...

 

OK! Not perfect, but WAY BETTER!!! bananaman:bananaman

When the exhaust cools down, I will go back out and measure what my angles are now.

I might even go up to an 8* block, depending on my numbers.

Now it is silent until 45 mph, then it picks up a slight vibe, but it goes away at 55-60. At 65 there is just a slight mirror vibration and very light power pulsing.

Maybe first, I will rotate drive shaft 180* before I do anything else.

After I re-measure, I will see if I have gone too far, or just 75% of the way there and need to add a couple more degrees.

Or I might just need new u-joints.

Or shim up the Transmission a bit.

Either way, it is much more pleasant to drive!

 

I found some excellent information on this site. http://www.iedls.com/

I had the same problem that you are complaining about and I ended up shimming the transmission up to where the front u-joint was as close to the stock location as possible and shimming the perches. My understanding after several conversations with a local driveline repair guy is that with a leaf spring suspension on a car, the pinion should not point up past the driveshaft angle, ie: positive pinion angle. If it does, the trans/eng angle is pointed too far down. This is a simplistic statement, but I have run round and round in an attempt to get rid of all vibrations that I possibly can and this guy's recommendations worked even though I had a hard time getting my head around it since the pictures I drew looked just like yours.

 

Thanks for that link! They are a well known shop with a good reputation.

Well there is part of my problem. Mine sits 5* back. So it looks like my next step WILL be shimming up the transmission a touch.

That may minimize the amount of shimming I need at the rear.

Still, if engine is raked back, the pinion SHOULD face upwards to be nearly parallel with the engine. Which mine was NOT.

 

What would I use to get 2* shim up under the transmission? Just steel stock or washers?

 

I used front end alignment shims until I got it where I wanted. Washers will work too.
I know it doesn't sound right, but the pinion should point down about 2°. I used a digital smart level to make sure I didn't get confused with + and -

3° eng/Trans angle and 2° pinion angle will give you a 1° difference which will compensate for slight differential roll up under acceleration. With the CalTracs, that roll will be very slight anyway but it should be smooth. Shimming the transmission is a lot easier than the axle too.