Projects Engine and pinion angle question 39 Ford SBC

Hi Is anyone running a pinion angle of more than 4.5 degrees with a Ford 9 inch? My SBC engine angle is 5 degrees so need to match it with the diff or reduce the engine angle. Thanks for your input.

 

There’s plenty of 4x4 broncos in that range

 

Providing the pinion angle is parallel to the tail shaft angle, there will be no issues.

 

And that’s potentially incredibly incorrect without further info.
If the drive shaft goes up hill to the rear ,,,

 

^True. Carry on.

 

Thanks, so, as I now understand it the pinion and engine angles are the same ie the diff and engine are parallel - they align. But the diff must be positioned relative to the out put shaft so the operating angles are no more than 3 degrees. Is that right?

 

Operating angles not exceeding specs are important for maximum u joint longevity. A little more and they wear out quicker. Way over and they wear even faster. Exceed the max and they quickly self destruct.
Is changing u joint easier than getting the engine angles a bit more user friendly?

 

Thanks everyone. Here's the specs for my chassis. Engine sits on a hurst cradle at front and chassis engineering chassis centre plate mod kit at the trans end. SBC Engine sits at 5 degrees with the chassis at ride height. Drive shaft is 1/2 degree down at the back end to mate with ford 9 inch. So having trouble making the 3 degree limit. Any ideas appreciated?

 

Just so everyone is talking the same lingo...how about posting a few pictures of what you have going on.

Now might be a good time to move/redo engine mounts, trans mounts, axle pads etc. But it's hard to tell without seeing what is going on.

 

The 4x4 guys do very radical angles. If need be they sell different degree shims for the rear to adjust the angle.

 

One wonders what angle the frame sits at to achieve a 5° engine angle ?

 

The best thing you could do is to reduce the angle of the engine/trans.

 

Thanks everyone I'll post some pics and info. In the meantime does anyone have a 39 or 40 with an SBC and not cut the firewall? If so what's your engine angle? Cheers Smart

 

I might get smacked, but I don’t look at engine angle, with the yoke bolted to the tranny I put flat stock on the yoke and angle finder to the flat stock.
I figure that’s a better look at operating angles than a angle finder on the intake.

 

Totally, that is how it is done. No idea why this always comes up as voodoo and is so hard for folks to grasp.

PARALLEL NON INTERSECTING

 

Really,,, the reason is because that pinion being parallel with the output shaft is pointing down. Not up

 

That is the optimal driveline angle ,,?

Tommy

 

Put a trans hump in the floor & raise the trans. Drive shaft down angle increase and rotate the pinion.
I’m guessing the trans to floor relationship is messing the angles up.

 

You can have engine/trans at zero, drive shaft at zero, and pinion at zero -
it be between optimal and just fine if your pinion is located off center of rear housing

 

There is no optimum, always a compromise. Goes back to the reason Ujoints were patented over 100 years ago. This is not rocket surgery

 

No idea WTF you are trying to say

 

Parallel means equal slope same direction
That visual says trans down pinion up while showing the pinion down.
Slopes are read pictured and displayed AND determined left to right always. A positive and negative slope intersect. A down trans and up pinion intersect.

 

look at the the imaginary lines projected off the trans yoke and pinion, they are parallel, non intersecting. This is the best way I have ever heard it described to laymen. My old boss at the hot rod shop used the visual to help customers.









Lots of ways to look at it but if those two lines cross, you will have binding and wear. I think where folks get crossed up is just like the OP, using some arbitrary engine angle and/or carb pad angle. OR trying to inject too much math into it. As @Budget36 said, slap an angle finder on the end of the tranny, same on the pinion, get it down to a low degree number as in under 5 and call it good. Ujoints are there for this reason.

 

Sorry Tman,
I got “Optimal driveline angle “,,from your diagram l
It states it at the top of the diagram .
That’s why I ended my statement with a question mark .

Tommy

 

Are we really doing this again?

 

This is what alot of people don't quite grasp. Coupled with mislabeled diagram's further complicates things.

 

On my hot rod the carb mounting surface being level my transmission output shaft was 3*down. This dictated a 3* up on rearend. Seems simple enough.

 

You don't want the crank center line in perfect alignment with the pinion. The U joint will not move and the rollers in it will get flat spots on them. That's why you want them parallel but at different heights so the U joints move. Or the pinion off sideways to make the U joints move.

 

Looks like sound advice there. Thanks everyone fr your time and replies.

Ok. I get that the two have to be at the same angle and both driveshaft bearings are therefore also the same angle. Which has to be 3 degrees or less. One question though. can the prop shaft be rising toward the back end or does it have to be falling? I am guessing falling angle.

So for my car - The one fixed height is distance from ground to the diff output shaft. This diff shaft must be below the trans output shaft or level with it.
Everything else can be altered.
So, I can either lift the chassis at the back or / and drop the front and thus lower the engine angle, to get my 3 degrees (although this increases the distance between ground and trans output shaft.
Or I can lift up the trans mount thus levelling the engine
or drop the front of the engine to level it.

Is that right?
cheers and thanks

 

Thanks.