Technical Engine is angled at 5.8 degrees

Once again, thanks to everyone who helped out on my brake problem. Now I decided to revisit a drive line vibration. It turns out the engine is slanted down at the tailshaft and the angle is 5.8 degrees. Not sure how it got set there except that an angle finder says the top of the intake manifold is only .5 degrees from level. I probably worked from there and called it good (too many years ago).
The rear transmission mount is shimmed as far as it can go without the tranny hitting the tunnel so unless some serious modifications are made, the engine pretty much going to be slanted like this. Is it possible to shim the rear axle to the same angle and get a smooth running drive line with such a steep angle?

 

It should work out okay if you raise the pinion angle to match the engine angle. It is not so much about what the angle is, but that the engine/trans centerline angle is the same as (parallel with) the pinion centerline angle.

Ray

 

As long as the u-joint included angle does not exceed 5 degrees. If you can't get the angle right because the car is too low the other option is to use a double cardon joint at the front and tilt the pinion angle down 1/2-1 degree in relation to the driveline. If you have any questions ask here and I will answer within a day or two.

 

How does one go about measuring the included angle? Is that the difference between the tailshaft angle and the driveshaft angle?

 

I've always heard and also seen as long as your pinion is matching but opposite, like 5 degrees down on trans means 5 up on pinion

 

That's what I understood.

 

Don't trust the intake manifold angle. The carb pad may have an angle that is not parallel to the crank centerline. Attach your angle finder to the front of the block, front of teh harmonic balancer or some other surface that you are sure is the same as the crank or 90 to the crank.

-Abone.

 

Most engines are set at an angle, so the carb is near level at its base. Nothing wrong with
having the crank center line at an angle either. Thats the way they were designed to
operate.

............................ Jack

 

The carb pad is what the factories level to. If it is level, you just adjust the rear end pinion angle to compensate. Tail shaft down, pinion up is correct. I don't know what engine/trans combo you are running but if I remember correctly, Ford angled their stuff more than GM.

 

Get the TREMEC app for your smart phone, works great! It'll find out how much of an issue you really have....if no phone, find a friend with one....also, I found the best place to get the right crankshaft angle is the valve cover flange against the head. TREMEC app wants you to find the crankshaft plane angle....we took several backup measurements to confirm findings....

 

Tremec diagram

 

results

 

Has the driveshaft been shortened/altered?
If so, couple things to consider...
U-joints in phase
Driveshaft balanced before install

 

Included angle is the tail shaft angle or the crank centerline angle and the driveshaft angle. The engine angle is usually down in the rear and the driveshaft can be a steeper angle down and is the case with lifted vehicles. The driveshaft can have an upward angle to the rear and is usually the case with lowered vehicles. The included angle is the difference between crank center line and driveshaft center line no matter if it is up or down.

 

All driveline angles are measured from crankshaft angle to driveshaft angle, and driveshaft to pinion angle. You can also have driveline angle when the pinion is offset to the transmission either to the left or the right. As long as the combination of the angles is with in the u-joints range, you are good to go.

 

Thanks guys! I already have the Tremec app on my phone. Thinking back, I set the carb pad level when I fabricated the mounts for the engine and trans. that gave me the 5.8 degrees downward tilt on the crankshaft axis. I have measured the angle from 2 different locaions: first along the rocker cover flange and second on the round drum-like feature that's part of the slip yoke at the tailshaft on the transmission. 5.8 degrees in both places. I managed to measure the driveshaft angle somewhat but I'm planning on raising the truck up with 3" spacers under each tire so I can slide under there a little better. Either the truck got lower or my belly got bigger, not sure which.
Anyway, I took measurements at the tailshaft, drivshaft and pinion flange and the Tremec App gave me a green light.
My plan is to re-measure more accurately with the truck raised and then also check the phasing. The truck is a 40 Ford pickup built on a Ranger frame with a 4.3 Chevy and 700R4. I had the driveshaft built by an outfit called Brookline Machine. They're very popular around these parts and it was balanced when it was built.
Next is to get a line on the floor that's parallel to the crankshaft and then get a line on the floor that's parallel to the pinion and see if they're parallel to each other. I set this up so many years ago I honestly can't remember how I placed things where I did. I know the engine is offset to the passenger side and the rear end is offset that direction too.
Stay tuned.

 

OK! The truck is up on 3" blocks. The Tremec application says that angle 1 is 1.5 degrees. Angle 2 is 1.7 degrees and the driveline operating angle is 0.2 degrees. The application gives me a green light for driveline angles. Phasing: front U joint 10.7 degrees rear U joint 11.1 degrees.

Next trick is to see if the crank and pinion are parallel.

 

There are a LOT of factors that are not related to the driveshaft that can contribute to vibration.

While it is up on blocks, run it in gear. Make sure that everything looks like it is turning smoothly.

Look for wheel wobble, out-of-round, shake, etc. Unbalanced wheels, poorly balanced wheels, un or poorly balanced brake drums can all do it, too.

Now remember, whether it has a 7.5 or an 8.8 rear, the Ranger rear has an offset pinion, which adds additional driveshaft operating angle.

 

Just thinking out loud here but when do you get a vibration? Sometimes items that are off balance will vibrate more at a certain speeds whereas I would think u-joints at non-equivalent angles would have a "changing" vibration harmonic as it rotates faster and faster.

 

Just curious, how accurate are those apps. that measure the degree of an angle on your phone. I'm assuming you'd have to take the case off to get a flat surface on your phone for an accurate reading.

 

The vibration happens at about 40 MPH. The vibration is of a fairly high frequency, faster than a once per wheel revolution type of vibration. It's hard to describe it but its not constant. it varies in intensity. It builds and subsides even though the speed is constant. The truck drives smoothly until it hits 40 and by 48-50 the vibration is gone

And yeah, you need to take the case off the phone to get a nice smooth hard surface to measure with.

 

Has it had this vibration since you built it or is it something new?

SPark

 

Hey! Give me credit for something, SPark. I designed and built this vibration into the truck from the beginning. Do you think I'm some sort of amateur?

 

The angles become more critical as they get bigger. With the large angles you have, any change in ride heigth will throw the angles off. You will fight this untill you get the angles down. I would shoot for 2* and use a digital angle indicator from HF. They measure to 0.1*.

 

Andy, so what you're saying is that the 5.8 degree initial slope of the engine is just too steep to begin with? It's gonna take a lot of fussing to get the engine any less sloped!

 

Check the fit of your U joints to the yokes, I had a joint that fit when mocked up but after running it a bit, I felt a vibration turns out the joint was wrong and there was play between the end caps and the stopper/ridge on the yoke allowing the U joint to shift in the yoke. once a new/correct joint was installed vibration went away. as already mentioned running the car in gear on GOOD stands, is a good way to check for out of round wheels, tires, bent axles, bad bearing etc.
Godspeed
MrC.

 

If what you're saying is your u-joint operating angle is 1.7* , I doubt that's a problem , tires , wheels , bearings , tailshaft bushing , ..........
dave

 

If you are getting a changing magnitude at a constant speed, check motor/trans mounts also. I don't think your angles are out of whack and a U-joint problem won't give you the changing magnitude at a steady RPM, that you describe. It could even be something else in the driveline, I didn't notice if you are running auto or manual trans, but it could be something setting up a harmonic vibe in the engine/trans. I have that in a engine trans combo that has a manual locking TC, if I leave it unlocked it will wet me know at about 50mph, as soon as I flip the switch the vibe goes away.

 

I can't visualize how all this is fitting together.
Please take some measurements.
Heigth of front and rear joints off the floor.
Angle of the centerline of the engine, driveshaft, and pinion.
The real critical number is the opperating angle of the joints. The crank and pinion can be parallel but the poor joints may be operating at an eleven degree included angle. This will not work.

 

Just made some layout lines on the garage floor. I plumbed straight down with a level from the front surface of the rear axle tubes and scribed a line between the marks. That gave me a line parallel to the rear axle on the floor. Next I plumbed a line down from either side of the companion flange on the rear end. That gave me 2 marks, and I marked the center point between them, that's the center of the pinion shaft. Then I scribed a line 90 degrees to the rear axle line at the point that represents the centerline of the pinion. That line was continued up to the front of the truck.
Next I dropped 2 plumb lines from either side of the slip yoke at the end of the transmission and marked the floor exactly between those marks, that gives the center of the transmission. Then I dropped 2 more plumb marks from either side of the harmonic balancer and marked a point exactly between them, yielding the center of the balancer, which in fact, fell on the centerline of the rear end that was projected up from the back of the truck.
Then I stretched a string from the centerline of the balancer through the centerline of the slip yoke, in essence projecting the axis of the crankshaft back to the rear of the truck. By the time the line was down to the rear axle, it was skewed by about an inch. I'm thinking that needs to be corrected before I do anything else.