Technical Opinions on th350 tailshaft position in 53 bel air

Yes 0 operating angle is bad for u joint life, however they should be within 0.5-1 degree of each other.

 

Probley way wrong as usual...but I do it with a string tied to the u joint clamps with the yoke in the trans... I can tell by looking at it which way to go...up or down, and i do this before the rear pads are welded to the rear end in case I need more rotation...

 

I would say this is spot on , and set the pinion angle to work....

 

Thats the best I can explain it. If you feel that setting a rearend in a position that could allow the u joint to overtravel while under power is acceptable, then follow your thoughts and best of luck to you. In every vehicle, the results are going to reflect the interactions of the components and their locations in that vehicle. What works fine in a 32 Ford powered by a flathead will be different from one powered by a Blown Hemi........but we all have to have a starting point and then work from there.

 

Can you tell me how much extra uni-joint operating angle will be added under braking conditions?

Do you think this should also be a concern when setting up the driveline in a parallel rear leaf spring street-driven car considering the acceleration/braking ratio is fairly equal?

Can spring wrap happen in both opposing directions?

Which do you think exerts the most force, acceleration or braking?

There is a very good reason why recommended practice on street-driven cars is to have the trans shaft and pinion shaft set up parallel at static condition. The 'middle ground' allows range for the pinion nose to move up and down.

Drag cars are a different animal. They live their lives accelerating, so setting pinion angle to offset pinion climb makes sense in that application. But when you try and do this on a street-driven car you sort of end up robbing Peter to pay Paul. Braking has to be part of the formula or you can have problems at the opposite end of the equation. Minimizing spring wrap is a far better option.

 

some times putting a pinion snubber is a must for drag/ hi power cars...

 

Here is a good video showing how much the pinion moves in both directions.

 

Here is some more info on race set ups , starting at the letter G and going down to the photo of the axle that is taken out of the Chrysler Race manual. As for a pinion snubber you would use one on a stick car with leaf springs and have to reinforce the floor pan with a piece of plate as the snubber would beat a hole in it. An automatic car very rarely needed a snubber. http://www.moparts.org/Tech/Archive/axle/8.html

 

No idea. Never heard of street oriented vehicle having a u joint problem while braking. The key here is that the angle of the u joint affects its ability to survive power applications. Under braking there is no power being applied thats sufficient to break a ujoint.............as far as I know.

TaDad found an excellent video and posted it above. Watch the movement closely and you will notice that the pinion starts out in a downward position and ends up in a slightly upward position . Look at the 15 second mark and as the car takes off , the pinion rotates up even tho the acceleration is not severe. Remember also that this is while driving/racing, but the car is moving and the application of power is "mostly" smooth rather than a launch shock. The unknown hp of the vehicle is probably at least 300 since its a racecar. He says he has 6 leaf springs and that doesn't do the job. Compare his set up to those of the 53 Chevy the OP has. Even tho the engine is capable of lots of power, it is not at full power.......its simply accelerating thru a range of hp. At about the 1:22 mark of the video, watch the pinion rise even farther than before due to a hard shift. This person has a camera in place, so they are probably experimenting with their driveshaft angle. If this vehicles pinion started out without the nose down adjustment, the amount of "over center" when he shifted would have been greater. Since I don't see any pinion snubber, the springs and the power of the engine are all thats determining this range of motion. Most driveshafts/u joints in a street driven but stoplight performance orientation are going to suffer trauma at the initial start of hard acceleration. If someone is always gonna granny drive their vehicle, then they don't need to allow for problems. You have to have an acceptable "range of motion" in which the u joint can survive a harder than normal launch and acceleration. You can limit how much it can move upward with a snubber but then you get into other issues. Anyway, this video clearly shows that even mild power application causes the pinion to rise which is the point I was trying to get accross. It seems pretty logical that even more power and harder launch would continue that trajectory until the springs either stop it or the springs begin to wrap up.

Excellent video.............

 

All this arguing yet every oem application I have measured are at the same angle and many of them make far more than 300hp. They must not know anything.

 

What’s interesting is how things are set up and figured out.
When I put a different rear in my ‘59, to save crawling around, etc. I leveled the spring pads, then put the angle finder on the pinion yoke.
It was around 10 degrees difference, don’t recall up/down, etc. so did the same when I used the pads on the rear end I replaced.
I assume it was due to how the leaf springs located things, or Chevrolet had a bad day

 

Generally how I do. Unfortunately in this car stock was a closed drive with pivot perches. So wasn't an option lol

 

I agree, that is an excellent video. It is Russell McDowell in his Group N race car. This car is based in Australia, and races all over the country in a historical class. It has raced regularly at a track very close to where I live. The car is definitely no slouch.

The lap shown in the video is fairly close to what you would see at full race conditions. You say that the application of the power is mostly smooth, but that doesn't mean that he is not putting as much into it as possible without breaking traction. He does actually break traction a few times.

Have a look at the start of the video and you will see that the pinion and driveshaft seem very close to being in a straight line before any power is even applied. I don't know why it is set up like this. He is the racing car owner and I would say he has a lot more experience and knowledge than I do. Maybe he has more than you as well. The flatter pinion shaft starting position makes for a higher final position under load. The thing I find most interesting is the comment he made about definitely fitting 'reaction rods', yet he never says anything about adding more positive pinion angle (lower pinion nose).

Here are his comments on the youtube video site. Take note about the 'braking' part.......

I wanted to prove if I needed to fit traction bar/tramp rods/reaction rods (what ever) to my Falcon XY GTHO Group Nc racecar. The car has original 6 leaf GTHO type rear springs with one anti-tramp leaf on top of the main leaf. I knew there would be a lot of diff housing windup on acceleration (scary when you see it) but didn't think about braking!! You'll notice just as much under deceleration. (also scary) I WILL be fitting reaction rods in the near future!!!

hot429scj

Oh, and one more thing.......... again. Setting up for street driving is a different box of frogs.

 

We have gotten a little off the path here.
In my opinion, @The Chevy Pope will get the best overall results by just following the basic setup with trans shaft and pinion shaft parallel, and keeping the universal joint static operating angles matching and between 1 & 3 degrees.

300 engine horsepower is not going to cause excessive wrapping in the leaf springs........ and if it does, addressing the spring problem would be number 1 priority. Adding an extra 3 degrees of positive static pinion angle in the OP's situation is not the correct option.

 

Forgot I had this link saved. https://www.iedls.com/Power_Train
This is excellent info about driveline setup, even for those that don't think they need it.......

 

That's good stuff right there.

 

And honestly once I have it making 300ish HP after cam and head swap it'll rarely be allowed to produce said 300ish hp

 

Clearly this is your hill to die on.

You set yours up with an extra 3 degrees, and the rest of us will go equal and opposite (parallel), life will go on and we'll all be happy.

 

Adding anything to somehow allow for spring wrap or pinion lift on acceleration is stupid. Why would you induce 3 degrees of angle to the setup for some short period of time like initial launch and then have it off by 3 degrees for 99% of your drive time?
All it accomplishes is to induce vibration when your car is not under hard launch.

 

100% correct.

 

Maybe we should dig Boyd Coddington up and tell him he was wrong too...........

Ok, start out with your pinion angle at zero................ Its not gonna be at zero any more as soon as you apply any torq to it. Its going to be over center immediately. A u joint is capable of withstanding the most torq when it's at zero... so zero isn't where you want to start, its where you want to end up when you apply torq. In real life, you want to be as close to zero as possible because variations in traction and and torq being applied will vary as the vehicle first takes off, and then as it accelerates thru its gears. You induce the initial downward angle so you end up at zero (or close) not only on takeoff, but while driving. If you watched several of the videos posted, they all show the rearend rotating upward..........so if you started at zero, you won't be at zero . Ever notice that many vehicles came from the factory with rubber bump stops to prevent too much suspension movement? Some were even mounted on the pinion. So I have tried to explain the phenomenon of "equal and opposite" reaction when a force is applied. THE key point is that every u joint is strongest and less prone to vibrate when it is in a straight line.......so you have to be cognizant of how you can get the u joint to stay alive when its getting the harshest treatment. Setting it on a slight downward angle does not mean it will cause vibration. If someone does get a vibration, they simply try shimming the rear to a lesser angle to see it it goes away. Then whatever rise the pinion has will be that much more over center under hard acceleration.......unless there is something like a bump stop to prevent it.

Now I've tried to explain this every way possible. Those that want to follow what I suggested are welcome to do so, and those that have different opinions can ignore what I'm saying......I don't really care. The OP asked for opinions and he has mine along with videos and diagrams to illustrate why I believe what I believe. Other than @twenty8, who provided some good things to illustrate his opinion, most all I saw were just unsubstantiated opinions.

 

350/350 combo…used Chassis Eng engine mounts and trans mount kit. The trans mount required a cut out section of original crossmember and welding in a prebent piece that was included. This is the only picture I can find so you will have to zoom in. Trans sits on standard gm rubber mount. Car is a Canadian 51 Pontiac Fleetleader which is essentially a Chevy Fleetline. Hope this helps!

 

Honestly crossmember on yours looks kinda like a prettier version of what I did to mine

 

I’m curious about the actual application as well.
The parallel leaf trucks I’ve messed with has more pinion angle. So Ive always set mine with a little more. Not much.
I’ve seen engine centerlines at 3* and OE rear axles at 5*. Possibly some as much as 7* (if memory is correct)
I’m no angleoligist

 

As far as the ramps. It’s the relationship between the parts. You can still get the actual u-joint angles no matter how it sits.
We built chassis in jigs. At ride height.
That’s how I do mine today. If the car has a 2-3* rake you still get the angles correct regardless of not being level.
0* angles? Built a few with zero on the engine and rear end. It’s the U-joint angle that counts.
I’ve even seen the “0* U-joint angle is bad” theory debated.

 

Ok, a quick update on a possible reason the Falcon GTHO race car in the video has a shallow pinion shaft angle.
This is just something I found and read, but it would seem feasible for a circuit track car to help stop traction loss, especially if the racing class limits the tire width the cars can use (eg: historical classes).

"More pinion angle creates a faster bite but if the track has no bite it will break the tires loose faster. If you run less pinion angle it wont be as fast of a feel for forward bite but it will be more forgiving on a slicker track."

 

Could that have to do with compensating for suspension compression when trucks are fully loaded ?

 

If anyone has a chance to view a book called "Door Slammers the Chassis Book" by Dave Morgan it has an excellent description and how to on setting up a leaf spring pinion angle.
It does give the math on adding the extra degrees and it's effect.
Unfortunately I loaned my book out and never got it back, published in 1990 but as a testament of how good this book is it still commands premium prices IF you can find a used copy.
This book is for hardcore race fans and would be over the heads of most nostalgia street car owners, but it definitely explains the benefits of adding extra degrees.

 

Possibly.
The angles change as you cruise it or load it

unless it IRS.

the 4x4 stuff seems to ignore most of the rules

 

I'm not saying 3 degrees of pinion or driveline angle is wrong, or bad. I'm saying that trans and pinion angles should be the same angles. If that's 3 degrees at each end or 6 degrees at each end, as long as they are parallel, and cancel each other it's great.
But putting the pinion angle down 3 extra degrees is wrong. Again, why would you put the pinion down an extra 3 degrees different from the trans angle to allow for torque under acceleration, or braking, or anything that only happens for a short amount of time, and then have the angles not be perfect for the other 99% of driving? You're simply inducing vibration into the whole setup for nothing.