Pinion Angle

[BB767]

For background, I have read most of the info posted here for pinion angle requirements so many times i think I have them memorized!

The problem seems to be my specific rear end mounting. It cannot be set higher than minus 1 degree (down). The transmission output shaft is also at negative 1 degree (down). I know this match is not good and out of limits according to everything I have read. Problem is, the "banana" bar is already set 1/16th inch away from the panhard brace, it cannot be set any further back (thus raising the Pinion angle). In addition, I have already shimmed up the transmission about an inch which is the length of the supplied bolts. I am hesitant to raise it too high and cause other unanticipated problems elsewhere. Will be in contact with FFR but wanted to see if others have had this problem and how they solved it. Thanks.

[karlos]

If using the convention that the slope of the drivetrain is measured going from front to rear, a component slopes downward if it is lower at the rear than the front. A component slopes upward when it is higher at the rear than it is in front. If both your transmission and your differential slope downward as described above, you should be looking at this:




If this is the case, then your pinion angle is zero. Right where you want to be. However, the u-joint operating angles still need to be checked to confirm no more than 3-degrees at either end. You'll need to measure the driveshaft angle in order to check this. Use this handy online calculator once you have your measurements: http://spicerparts.com/calculators/d...gle-calculator

Objective is to get the operating angles at each end to be 3-degrees or less, and the difference between them (the pinion angle) to be 1-degree or less.

This is what the online calculator returns if I plug in your numbers. Note that I had to guess on the driveshaft angle. When I was done messing with my car it measured 2.2-degrees, so I just used that as a placeholder. If these were your final numbers you'd be in pretty good shape. Pinion angle is zero, and the 3-degree max operating angle is only exceeded by 0.2-degrees. Don't forget to compensate for driveline squat that will occur under hard acceleration. You'll probably want some upward slope bias on the differential so that the pinion angle and the operating angles are within spec while under load.

Good luck!

[Gromit]

Getting these angles right is important for so many reasons... Something I would be concerned about is the 1/16th inch clearance on the banana bar to pinion brace. the bushings on the rear end will flex more than 1/16th inch during acceleration and or braking. that would cause these 2 parts to hit. just my $.02
Chris

[GoDadGo]

BB767,

I had the same issue, but mine was self-inflicted, because of the way that I set my engine and transmission which tilts down a couple of degrees toward the rear of the car.

Overview of Driveline:
https://youtu.be/_wnHDNgnNqs

I had two sets shorter lower control arms made, 16 7/8" and 17" which allowed me to get my the pinion to angle spot-on so that my U-Joints could be in phase with my driveline.

This did shorten the wheelbase of the car, which was something I planned to do anyway since everything was custom fit plus I really wanted the rear wheels to be centered in the arches.

Car Without Body On & Shock Move:
https://youtu.be/PCngiKoopkA

Car With 16 7/8" Lowers:
https://youtu.be/IGYtX-3p7xk

In addition, I had my lowers made at Spohn, but they do custom work an also offer adjustables for Factory Five Cars.

Customer Lower Contol Arms:
https://www.spohn.net/shop/Custom-Pa...ed-Length.html

Adjustable Lower Control Arms:
https://www.spohn.net/shop/Factory-F...ot-Joints.html

Good Luck!

Steve

[xlr8or]

Has the banana bar been welded to the rear axle? If not it's easy enough to adjust in more space.

[Jeff Kleiner]

If the top of your banana bracket is that far rearward it tells me that the upper link is adjusted long which makes me suspect that you have the pinion pointed upward (i.e. front high). Once again when we speak of pinion angle we are referring to the pinion shaft relative to the transmission's output shaft. When determining pinion angle the driveshaft does not come into play---you can leave it on the workbench, and in fact if you follow my method method for measurment described below it will be easier if you do just that

Don't get caught up or confused on any thoughts of horizontal. Think of it this way; when looking at the car from the side if you were to project one line from the transmission output forward and another line from the pinion shaft forward with your pinion angle at zero they would be parallel. If you put any angle to the pinion the two lines are not parallel and would get farther apart as they go forward. If the pinion were to be angled UP (relative to the trans) it's line would be above the output line; if it were angled DOWN the pinion line would be below. Below is what we're after.

Clear as mud? Maybe a visual will help. Here is a quick drawing I made when this topic came up again on the other forum a week or so ago:



Doesn't matter whether the rear end is above or below the output centerline; 2 degrees down in relation to the trans output is 2 degrees down either way. Need more? print this image and then rotate the paper so that the line through the engine is pointing up or down left to right...see how the line through the pinion still remains pointing 2 degrees downward in relation to the line through the engine?

My method for ease of measurement:
Set ride height then put the car on jackstands so that the axle is loaded. We don't care if the frame is dead nuts level; we're only going to look at the difference between output shaft & pinion. We know that the crankshaft and trans output shaft are parallel therefore the face of the damper/ crank pulley is perpendicular to the output. We also know that the pinion flange face is perpendicular to the pinion. See where I'm heading? For me it is easier to get a good measurement with the magnetic angle finder by reading vertically on the crank pulley/ damper and pinion flange rather than trying to work with the horizontal shafts themselves. Once you can see the two angles you can then calculate the difference. Generally with these cars we want the pinion down ~1-2 degrees the input is pointing down in relation to the transmission output shaft. Reason being is so that when the axle tries to rotate it's input upward under accelleration the pinion angle becomes less. This rotation is especially more pronounced on a 4 link car using the soft rubber bushings in OEM Mustang arms vs. a 4 link car with poly bushings or a 3 link with polys in the lowers and the solid upper link.

Hope all that helps!

Jeff

[GoDadGo]

This You Joint Phasing Video May Be Of Help Too:

https://youtu.be/Idk3BVDVHq4

My pinion points up because I'm Special, but standard build point down a from what I understand.

[BB767]

Pinion photo 2.jpg

It looks like the ABSOLUTELY NOT diagram if you flip it upside down.

[BB767]

karlos - I am pretty sure I understand what needs to be accomplished. The question is how?
Gromit - I agree, thus I need even MORE clearance than what I have indicated.
GoDad - Yes, I have seen adjustable lower control arms on the market, those do look like a possible option, however i am concerned about wheel location in the well when I am done. And I still may have clearance issues with the shocks and their mount (yes, I have already turned them over).
xir8or - Moser welds them, and there is also the issue of the shock brackets.
Jeff - I am confident I have the measurements correct to within 1 degree for the pinion and within .1 degree for the transmission. See my "depiction" picture post above for clarification.

[GoDadGo]

My car is 2 degrees positive and is my pinion angle set at ZERO to 1 degree for pre-load.

If the "Absolutely Not" picture has your engine on the left and the differential on the right,
then you need to pull the upper link in so that you i can get it in the "Moderate Strain" zone.

U-Joints need to be set up in this manner (Moderate Strain Zone) in order to cycle the needle bearings.

Also, from what I understand the Ford driveline is about a degree or two downward facing so the pinion also needs to be a degree or two downward facing.

Does This Help?

[NAZ]

If your set-up looks like the "Absolutely Not" picture then I think you found the source of your vibration. I also think you would find it easy to adjust out of this issue with adjustable upper and lower control arms. By adjusting both you can rotate the axle to change the pinion angle AND maintain the same wheelbase so that if your axle is centered in your fenders you can keep it in that same location.

[karlos]

The problem with setting the pinion angle without regard to the driveshaft angle is that it can lead to operating angles that will kill a u-joint in short order. Here's an extreme example.




The red centerlines are parallel, and as a result the pinion angle is the ideal zero. But the u-joints would clearly be very unhappy under these conditions.

In one of my previous posts on this topic (is there a more confusing topic in all of roadster-land?) I mentioned that I got looking at the angle of my driveshaft (hope Miller doesn't see that one) a few weeks after my driveline setup had been completed. Driveshaft was at about 5 or 6 degrees and, when viewed outside the context of just the pinion angle, didn't look right. When I did the initial install I was laser-focused on pinion angle and didn't even realize I should be paying attention to anything else. After a little research it became apparent that complete driveline setup needs to consider more than just pinion angle. Although my pinion angle was within spec the operating angles were way in excess of 3-degrees and probably would have led to noise, vibration, and an early death sentence for the u-joints.

Recognizing that pinion angle is really nothing more than the difference between the two operating angles, it would seem to make more sense to dial-in the operating angles first and then simply verify that the difference between them is less than 1-degree. That way all the important parameters come together at the same time.

Just trying to save others from the same slow-learner syndrome I seem to be inflicted with. Not that much fun to invest an hour or two in setting up your driveline only to find out you did it wrong and have to start over.


With regard to the how: does your differential currently slope upward or downward (when moving from the front of the car to the back of the car)? And which way are you unable to move it? Can't move the pinion flange up or down?

[BB767]

GoDad - You might have missed the part where I said to turn the picture upside down, correction is the opposite direction.
NAZ - I think you have the best understanding of the problem and a good solution. Only problem is there is no more clearance between the shocks and their mount, I cannot extend the upper control arm any further (thus rotating the axle) without them rubbing on each other even if the lowers were shortened. (Yes, I have already inverted the shocks for more clearance.)
Carlos - I agree but I do not think that will be a problem for two reasons, one, the driveshaft is so short they would have to be off a lot more to make this a concern and two, any fix will bring the angles you depict closer together (better) than they are now. You are correct and that is exactly what I am looking at, the RELATIVE angle (difference) between the transmission output shaft and the pinion itself.

[BB767]

If using the convention that the slope of the drivetrain is measured going from front to rear, a component slopes downward if it is lower at the rear than the front. A component slopes upward when it is higher at the rear than it is in front. If both your transmission and your differential slope downward as described above, you should be looking at this:




If this is the case, then your pinion angle is zero. Right where you want to be. However, the u-joint operating angles still need to be checked to confirm no more than 3-degrees at either end. You'll need to measure the driveshaft angle in order to check this. Use this handy online calculator once you have your measurements: http://spicerparts.com/calculators/d...gle-calculator

Objective is to get the operating angles at each end to be 3-degrees or less, and the difference between them (the pinion angle) to be 1-degree or less.

This is what the online calculator returns if I plug in your numbers. Note that I had to guess on the driveshaft angle. When I was done messing with my car it measured 2.2-degrees, so I just used that as a placeholder. If these were your final numbers you'd be in pretty good shape. Pinion angle is zero, and the 3-degree max operating angle is only exceeded by 0.2-degrees. Don't forget to compensate for driveline squat that will occur under hard acceleration. You'll probably want some upward slope bias on the differential so that the pinion angle and the operating angles are within spec while under load.

Good luck!

karlos - I read your post more thoroughly. The numbers I initially posted were estimates to illustrate the reverse angle I am concerned about. Using the top diagram you posted maybe you can plug in the actual numbers and see what you get. The engine is angled as depicted 4.5 degrees. For the rear end (pinion), rotate the depicted axle housing counter clockwise until the left end of the red line touches the imaginary ground. Make this angle 1.5 degrees. Now what does the calculator tell you?

[NAZ]

I'm sure there are plenty of ways to deal with shock clearance issues but photos of the clearance issue would help. Bottom line is you have to correct the problem that is causing the out of phase u-joint vibration. That means rotating the pinion angle or the angle of the trans output shaft. With all the builders that have accomplished this I have to think it's just a matter of determining what's different about your build that is making that difficult. If this was a wild modified build I'd suggest you look into a double-cardan u-joint but it's hard to believe that would be necessary.

[BB767]

IMG_0286.JPG

NAZ, I totally agree. I just don't understand why mine is so different (difficult) and was hoping someone else had run into the same problem and found a fix. The photo is an old one as I was concerned about this problem long ago. I discussed it with Dan at FFR and he said not to worry about it as they tend to look that way during the build.

[phileas_fogg]

My build includes the 1988 Thunderbird IRS, so I've got nothing to add but encouragement. Driveline angle, pinion angle, and U-joint phasing are all details you need to get right; good on you for sweating these details. I spent at least a week* dinking around with measurement methodology (so I could get repeatable measurements), various spacers ('cuz you have to torque everything to spec to make sure it's right), and jacking the car off the ground & putting it back down ('cuz you can't install spacers with the car only 4" off the ground). If you're stymied work on something else while your subconscious generates options in the background.

Keep at it & you'll get there!


John

* Yeah, I know; but while I'm not fast, I am slow.

[NAZ]

OK, I've dealt with this one before and it's an easy fix. I used a hole saw to cut a relief in the bracket to add clearance for the shock. I don't recall the size but was just slightly smaller than the I.D. of the bracket where it joins the axle tube.

[Jeff Kleiner]

BB767,
One last question...is the rear axle loaded and at approximate ride height while you're taking measurements and making adjustments?

Jeff

[NAZ]

Guess I should have clarified what I did. Remove the shock from the bracket and measure down from the top edge of that bracket 3/16" to 1/4" and centered. Drill a 1/4" hole here for your hole saw pilot drill. Select a hole saw that's slightly smaller than the I.D. of the bracket (think of the bracket as a channel and measure the inside of the channel). Carefully drill with the hole saw to remove basically half a hole worth of material from the top edge of the shock mount bracket that's welded to the axle tube. Clean up the cut edges and touch-up paint.

Make sure to set the hole saw pilot drill so it does not drill into the axle tube.

When you reinstall the shock you will have more clearance -- should be enough to rotate the axle to adjust the pinion ange.

[Jeff Kleiner]

BB767,
One last question...is the rear axle loaded and springs set at approximate ride height while you're taking measurements and making adjustments? In the photo above it appeasr that the axle is hanging and the amount of threads on the adjuster show a high ride height.

Jeff

[karlos]

Now what does the calculator tell you?

Yeah, really bad...



Max operating angle is 2X too high; pinion angle is 4.5X too high. Question: the engine's at 4.5-degrees downward slope with a 1-inch shim already in place? Doesn't seem right, as my engine measures 0.2-degrees upward slope (essentially level) with a shim thickness of about 7/8". Also, 7/8" raised the transmission so far that the midshifter contacted the 3/4" frame tubes in the transmission tunnel. You sure the motor mounts are seated and everything else is located properly?

A couple observations:

- With a front operating angle in the vicinity of 6 degrees, this probably explains the noise
- At 1.5 degrees nose down, the differential is probably about where it needs to be. It will likely rotate up to about 0 degrees while under power (note that I used 0 degrees in the calculator based on this assumption)
- Looks like you mainly need to get the engine closer to level. If you could reduce the 4.5 degree reading to about a 1.0 degree reading, all angles would be in spec

You didn't indicate what your driveshaft angle is. I'm still guessing 2.2 degrees. The actual value will change things somewhat, so please make the necessary updates. But something seems wonky with your engine/trans angle...

[BB767]

Thanks NAZ, more good options.
Jeff, in that photo I am not sure and the car was light. Now the car is more near finish and the axle is on jack stands (loaded) and the ride height is set, still looks the same as far as shock clearance as that does not change with load (well, maybe a 16th on an inch, but not a noticeable change).
Mr. Fogg, thanks for the encouragement.

[NAZ]

Wow, the engine / trans is angled at 4.5-degrees??? I missed that part earlier.

Typically you may see 2-deg +/- but I don't think I've ever come across one close to 4-deg. So I suggest you start there and determine what it will take to get that engine / trans combo closer to 2-deg or less if possible. Then work on pinion angle and use Jeff's 2-deg down setting to start with. And if you still have shock clearance issues the fix I suggested before should take care of that problem.

[BB767]

Wow, the engine / trans is angled at 4.5-degrees??? I missed that part earlier.

Typically you may see 2-deg +/- but I don't think I've ever come across one close to 4-deg. So I suggest you start there and determine what it will take to get that engine / trans combo closer to 2-deg or less if possible. Then work on pinion angle and use Jeff's 2-deg down setting to start with. And if you still have shock clearance issues the fix I suggested before should take care of that problem.

Just went out and and verified it, 4.5 at the output housing and at the crank pulley.

I can't see messing with the engine mounts. They are stock FFR mounts that fit the 351 block perfectly.

I have already raised the transmission about an inch (the limit of the existing bolts). I am hesitant to jack it up to much for fear of causing other unforeseen problems elsewhere. Any other suggestions for this?

[NAZ]

Well since you're running EFI there's probably nothing to keep you from running that steep angle and adjusting the pinion to match. However, I'll tell you if this was my car I'd have to have something very compelling to keep me from lowering the front of that engine.

[karlos]

Like you, I have a 351 block with a TKO 600 and the FFR-supplied motor mounts. The engine/trans should be roughly level with a shim thickness of only about 3/4". Something's not right if you're 4.5 degrees down with a 1" shim installed.

Is the pin on the motor mount in (not on top of) the chassis bracket hole as shown below?

[BB767]

Yes. The mounts all dropped into the the slots and holes very nice and easy!

[BB767]

It is a Dart block if that makes any difference, it does look different than the one in your picture, at least in that small area.

[karlos]

The photo shows a Coyote, but does a good job of illustrating the pin/hole fitup. Couldn't find a clear shot of my specific motor mount, so the photo is borrowed. I've got a Ford block so not an exact match either. Maybe someone else with a Dart block could chime in with engine position vs. shim thickness?

[BB767]

IMG_0385.JPGIMG_0387.JPGIMG_0388.JPGIMG_0385.JPG

[karlos]

Yes, see post #22 above. Need the driveshaft angle to get accurate numbers but I believe you will be able to get everything within spec if you can get the engine closer to level.

[BB767]

Much lower and my oil pan would be below the frame. The tail shaft of the trans was setting on the crossbar before I added shims. now it is about 1 inch above it. It appears there is plenty of clearance above the transmission to the frame, the frame now is about even with the shift lever bolts.

[BB767]

Yes, see post #22 above. Need the driveshaft angle to get accurate numbers but I believe you will be able to get everything within spec if you can get the engine closer to level.

It is 3.5 down towards the rear.

Even if I could get the engine level, which I doubt is possible, the pinion is still angled down (towards the front) about 1.5 degrees which is still in the NO area.

[NAZ]

I must have missed what the issue was with raising the rear but it sounds like you now have clearance to accomplish raising the trans, if so then that's your mission for today. To help you as you wrestle with this you can download a smart phone app from Tremec (Tremec Tool Box) that will allow you to use your smart phone to take angle measurements and automatically calculate if your drivetrain is "in spec". You can use the app to play "what if" until you get all the angles to play nice. For instance, when you take a reading and the app tells you you're out of spec you can play with the angle of individual components to see how close that gets you to your goal. A nudge here and a nudge there and soon you'll be happy and so will your drivetrain.

[BB767]

Thanks NAZ, that's what I have been using all along, at least the angle measurement part of it.

The issue with raising the trans is it just doesn't seem right to have it jacked way up off the mount (your talking about 3 inches or more). Seem's like a set up for future problems with movement and bolts working loose, what about the torque on those bolts and the mounts?

[phileas_fogg]

You said Dart block. Some folks have reported that there is a fin or protrusion on the block that prevents the motor mount from seating all the way. The solution is to grind the mount (not the block!) and eliminate the interference. Have you checked that?


John

[BB767]

You said Dart block. Some folks have reported that there is a fin or protrusion on the block that prevents the motor mount from seating all the way. The solution is to grind the mount (not the block!) and eliminate the interference. Have you checked that?


John

Yep, had to grind off only about a 32nd of an inch, very small correction and it fit nice and tight.

[GoDadGo]

BB767,

When I was fighting my pinion angle, I made some temporary lower control arms from 2" square tubing.
I drilled some holes at 17" (Stock is 17 5/8") to see if rotating the bottom forward would allow my banana bracket to clear and also to get the pinion angle right.
I also pulled the shocks so that I could use my floor jack to articulate the rear suspension.
Taking this action also required me to move the top of the shock further aft so that they would clear the lower mounts.
I don't know if making a set of test/temporary lower control arms would help you, but it did help me.

Steve

PS: I too have a Moser Rear (Dana 44 / TSD-500) but I think my brackets were welded in the correct location, but I'm not feeling the love on yours.

[BB767]

Thanks Steve, I'll certainly add this idea to the pile of options I am accumulating. I appreciate all the input from everyone as it gives me a well rounded view of the problem and possible solutions!