Question about driveshaft angles?

This may be more of a question for those of you who have cars that are lowered but in my case the sits 1-2" lower than stock and I have a 200-4R transmission. I would really like to have my driveline angles set properly but I am not able to shim my transmission high enough to get the driveshaft to angle down toward the pinion. Measuring off the engine block I zero the digital level, and since I have adjustable upper control arms I can set the pinion on a zero plane with the crankshaft. However, the driveshaft doesn't point down like most do but rather it goes up to the pinion. I have the angle set at about 1.8 degrees which I believe should be about ideal. It seems to me that it shouldn't really matter whether the shaft angles up or down as long as the angles opposite at the trans and the pinion and they are equal. This is for street/highway driving and I do realize that it could pose a problem at the dragstrip but am really drawing a blank here for options on this. What are your thoughts and/or experience with this? Thanks.

 

What you need is to compare the straight line angles of the trans output shaft VS the pinion line angle. The lines should be parallel under full power, but the pinion line should tilt about 2 degrees down from parallel when at rest. Forget the driveshaft.The drive shaft takes care of itself.
I have two professional books on chassis with the experts showing pictures of angle gauges measuring the pinion and driveshaft. For our A body chassis with one piece driveshaft, it is a big mistake no matter if they wrote a book or are a big hot rod celebrity, it's still usless, possibly dangerous, BS.
Go to www.buickperformance.com and see the real story on what you need to do. Enter the site, then page way down the lists of info; you'll find ACCURATE info listed there.

 

I'll add an explaination here. I just went to the www.buickperformance site to look at the sketches. There are 5 drawings of the trans and rear end with degree markings at different angles.
To get a -2 down on the pinion, that I refered to in my above post, look at drawing #4 and #5. The 4th shows the trans at -2 down and the pinion at +2 up. That means the angle lines are parallel. This is what you theoretically may get under power.
The 5th shows the trans at -2 down and the pinion at 0 level. This is what you should have at rest.
Now consider that your chassis may not be level and the floor or lift may be off level too. Just be sure all the weight is on the tires and springs and try to find a level place to check it.

 

IT'S ME AGAIN!
I forgot, you said you wanted 0 setting for normal driving. Go with parallel angles at rest, and ignore the "under power" stuff.
If the tranny is -4 the pinion should be +4 (or 3 or 1 or etc), as long as they both are parallel at rest.

 

Well, I don't necessarily want a 0 setting, it's just easier for me to set it up this way. Maybe I haven't been very clear on my explanation so I'll try it again. I have the car up on blocks, at rest (of course), I'm not worried about setting it up for being under power, only for cruising. I have a digital level and I am using the oil pan rail on the block for a starting reference. There's no real good place to put the level on the trans so I figured the crankshaft centerline would do just fine. So, I put the level on the pan rail and then zero the level, a nice feature of the digital tools. Then I place it on the pinion, or in my case I am using the u-joint as a reference, and I set the pinion for zero to line up perfectly with the engine block. This is basically what is in the top drawing in illustration #2 on George's site. The way I have the trans mount shimmed right now the driveshaft still goes up to the rearend, or rather, the rearend is actually higher than the back of the trans. With it set this way I have opposite angles on the u-joints, which is what I want. I believe the top drawing in illustration #3 best describes this, only I have a 1.8 degree setting instead of 2 degrees in the illustration. Everything I have read states that 1-3 degrees is good for street driving so I should be good, right? And that it doesn't really matter that the driveshaft angles up to the rearend rather than down to the rearend? I hope so, because the trans is very close to the floor right now and in order to achieve the driveshaft at the downward angle to the rearend I would have to jack the rearend of the car up like we did back in the `70's. I don't wanna do that, I was too young to realize how stupid that looked back then :grin:

 

If the tranny is 0, and the pinion is 0, it is "parallel" and has no pinion angle,.

Asuming the engine/trans is now 0 degrees. the pinion reading, if other than 0, will be a + or - reading. The pinion should be showing parallel or an angle that gradually angles down toward the trans line, not away from it. Under power the pinion line will rise.
This means your pinion angle should now be 0 (parallel), or - 1 downward, or -2 downward to stay in the range we are discussing.
For a cruiser/daily driver, your pinion could go 0, (perfectly parallel with the 0 on the tranny), or -1 down from parallel. Probably right on for your car. You said you have a 1.8 angle. If it is down, you're good enough. If it is up, change it.

My 67 GS was -4 down on the tranny, sloping toward the rear. My pinion was -3 down sloping toward the front (from the factory). I had 7 degrees below parallel!
It is now -4 at the tranny, sloping down toward the rear. My pinion is now pointing upward toward the front at +2, which is 2 degrees below parallel (+4). It has been said that some GS Buicks have picked up .20 ET and 2 MPH in the 1/4 mile with this pinion setting by freeing up the drive shaft.

Now after all this has been said, you will notice I ignored the angle of the drive shaft & the stance of the car, (low rider, or jacked up for off road, or high/low in the ass , etc.). That is where the IC stuff comes into play for drag racing. After the racers get the stance and IC where they want it, they reset the pinion angle and hammer down.

 

Ok, so I'm not much of an artist but this should give you an idea where I am at with it, and the angle in the drawing is exaggerated for the sake of illustration because 1.8 degrees isn't much so it looks almost straight on the car. I can't get the transmission any higher in the back and I can't, or don't want to, change the height of the rearend. I'm feeling like a bit of an idiot because I still don't think I'll getting it yet, hence the picture. I'd really like to lower the back of the transmission because I have a lot of shims under it but this is the only way I can get the trans centerline and the pinion lined up perfectly with each other. And, as you can also see in the drawing, there's no way I can get the driveshaft to angle downward toward the rearend. I was under the impression that both angles on the u-joints should be the same but now I am wondering if that's not as critical as I thought it to be as long as they are opposite each other. I'm chasing a vibration and even though I'm not certain this is the cause, I also don't want to rule anything out before I go buy a new transmisison. So, what should I do next? And I really appreciate the help on this.

 

The drawing appears to show the centerlines of the transmition and the pinion to be parallel. That would be zero pinion angle. The pinion angle is neither "up" or "down" if it is parallel with the tranny angle.
The drive shaft angles are of no concern.
It is also common for the pinion centerline to be sloping upward above the transmition. And the transmition centerline slopes downward under the pinion centerline, just as your drawing shows.
It is also typical to shorten the upper arms (if adjustable) to bring the pinion line down two degrees from parallel for performance use, or about 1 degree for cruising, although parallel is not bad for cruising.
If you think about it, the bushings in the control arms get squeezed a little under full throttle, and brings a lowered pinion line back up to parallel for a better flow of power for racing at full throttle.
I cannot see where you got the 1.8 degrees you have. If it is the angle of the drive shaft, you have no problem with shaft angles. Only the transmition and pinion angle relationship is of any concern.
The only differance in a drawing of my angles and the drawing you have , is that my upper line (from the pinion) tapers closer to the transmition as it goes toward the front of the car because I tilted the differential slightly (2 degrees nose down). Theoretically, my lines are parallel at full throttle because as the wheels drive the car, the differential reacts by pulling the pinion nose upward (the differential tries to roll backward as the wheels turn foreward. I want them parallel for maximum power to the ground while racing.
To change angles at the tailshaft of the transmition, it takes a pile of shims for a tiny change. I think you can take them out. Recheck the angles and see what you have. Let me know.

 

Ok, I took all the spacers out of the trans mount and it only dropped the back of the trans .05 degrees. Not much. I think I am finally getting what you are telling me, although old habits die hard and it's really hard not to consider the driveshaft angle compared to the trans and rearend. I'll work on that So, the back of my trans is now 3.5 degrees down from actual level but for the sake of simplicity I zero'd the level on the engine/trans centerline and re-set the pinion for 2 degrees down. How am I doing? :grin:

 

Normal trans to pinion angle is Negative 4 degrees. Remember your relationship is NOT to the ground or anyother part of the car. It is the u-joint from the trans yoke in comparison to the u-joint cup in the pinion saddle. It is the one subtracted from the other to get what your angle will be.


Check the internet on this subject...MAny race chassis shops have laid out the pictures and the how to:

http://www.carcraft.com/howto/91758/index.html

http://www.drivetrain.com/parts_catalog/drivetrain/driveline_angles_and_phasing_problems.html

 

Ok, I've finally got a grip on this. For whatever reason I was under the assumption that under power the pinion had to raise up to be in line with the driveshaft and since my driveshaft angled up toward the rearend that was not going to be possible. Now I can see that it only needs to rise to be in line with the transmission, or driveline angle. I was also confusing some of the terminology and was associating "driveline angle" with driveshaft angle ou: Thanks for all your help everyone, and Gary, I hope you didn't get a few gray hairs trying to get me to understand this :grin: I'll raise my pinion back up to be in line the the transmission for street driving and when I go to the track I'll set it for 2 degrees down.

 

With poly bushings, -2 should be fine. Heim joints could be less.
A stickshift car needs at least -4 or more depending on the stiffness of the control arm setup.

I run -2 because I have two heim joints, two rubber joints and four poly joints as well as bulletproof control arms.

Another factor to consider is the torque output of the engine. More power will call for a little more tweakin on the pinion angle.

Leaf springs often require as much as -7, -8!

 

Uppers are poly bushings and lowers are stock rubber. Engine torque is 438ft.lbs at the flywheel. Sounds like I should go maybe 3 degrees for racing?

 

Two should be fine.
It is hard to guess what amount the chassis and axle will move under power, but you will cover more miles at cruise than under full throttle. You don't want to over work the ujoints or get vibration at 70 MPH.
If your a degree off under power, It should not be a problem. You just want to be sure you don't stress the drive train cruising for many miles.
High powered cars (that cruise on a trailer), and some leaf spring cars, need 4 to 7 degrees for racing.

I leave mine at -2 at all times and street cruise all I want, or race. Feels smooth and never see any wear at all on the u-joints.

Be sure you have BRACES that tie the front bolts togther on the upper and lower rear control arms or you may have some dangerous flexing going on with the cross panel the upper arms bolt onto. DON'T LEAVE HOME WITHOUT'EM.www.v8buick.com/showthread.php?t=73629

 

Well, I already have a vibration but I'm 99% sure it's in the transmission, I just don't to leave out any possibilities in that other 1%. And, I already have the braces. That's one of the first things I did when I removed the original 300 cu.in. engine.

 

Vibrations I've seen:
Worn out thermal fan clutch. fan wobbled crazy
Gear Venders housing rubbing drivehaft tunnel
Broken motor mount or trans mount.
Wrong vibration damper (364 eng) on the nose of a 401 engne that I bought.
Driveshaft threw off a weight
Rear u-joint u-bolt overtightened, squeezed the needle bearings and cap.
Twisted axle
Excessive pinion angle
Control arm bushing, the hole wallered out and the bushing and it's shell FELL out when I removed the control arm.
Control arm bushing rubber disintegrating.
Replacement flywheel off balance from factory flywheel
Can't think of anymore tonight. Someone may add to this.

 

I'm pretty sure I've got all those bases covered. For starters, the vibration isn't engine related because it starts around 55mph and I can get it up to or above that speed and slip it into neutral and let the engine idle down but the vibration continues. I had a new driveshaft built ($340), and later wondered how good his work was and took it to a different place and had it checked. I had a new rear bushing installed in the trans, I've replaced the entire rearend and put all new bushings in the control arms. Stock rubber lowers, in fact, the lower control arms are the boxed GM pieces that were NOS. Poly in the aftermarket adjustable uppers. Pinion angle is where it needs to be for cruising. Trans mount was new 3 years ago, and even though it looked good I recently replaced it with a new Energy Suspensions urethane mount. Motor mounts are 3 years old. Maybe also worth mentioning is the problem persisted even after a rearend swap but the mph at which it started changed due to gear ratio change. With the 3.36 gears it started at 65mph, with the 3.73's it started at 60mph, and I later switched to 4.10's and now it starts at 55mph.

This vibration is getting worse now, but all along all I could do is feel it. Lately I've had some noise coming from the trans area. I can't really descibe it but it's not a sound that should be coming from an automatic transmission. In addition, the noise doesn't wait until 55mph to begin, it's pretty much all there all the time. The trans was used when I put it in and it had been in a Turbo T that was running 11.30's so I know it has been abused. I have put 7,300 miles on it myself now and made 97 passes down the dragstrip. The most puzzling part about it all is that the trans still shifts and works perfectly but it's getting to the point where I'm afraid to drive it out of town anymore. I was hoping it would live long enough until I get the 455 ready to go in later this year, then get a new one and put it all in together.

I have a TH350 here that is good, or at least useable, and I am tempted to put that in just to confirm that the problem is in the transmission, mainly because I have never had an automatic transmssion act like this and am having a hard time facing the fact that that's the problem.