Pinion Angle

[edwardb]

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

Maybe there's some variation I'm not aware of (certainly very possible!) but that doesn't sound right. My DART block along with the Energy Suspension mounts took considerably more than that to get the mounts to sit flat on the block.

Something just isn't right here. You're doing a pretty typical installation. Doesn't make sense you should have to raise the TKO more than 3/4 - 1 inch. Something else is going on.

[karlos]

Yep, something's out of sorts. Assuming you can find it and then get the engine roughly level, all your angles will come in. Some new numbers based on the now known driveshaft angle.




Three scenarios are shown. Left: current situation (angles unacceptable); middle: how the numbers would look with a level engine (angles marginal but acceptable); right: numbers with pinion rise under power accounted for (angles look great).

I think this shows pretty clearly it's the engine/trans angle that needs to be addressed. If you can get it close to zero degrees with a shim thickness in the neighborhood of 1" you'll be all set.

[BB767]

Yep, something's out of sorts. Assuming you can find it and then get the engine roughly level, all your angles will come in. Some new numbers based on the now known driveshaft angle.




Three scenarios are shown. Left: current situation (angles unacceptable); middle: how the numbers would look with a level engine (angles marginal but acceptable); right: numbers with pinion rise under power accounted for (angles look great).

I think this shows pretty clearly it's the engine/trans angle that needs to be addressed. If you can get it close to zero degrees with a shim thickness in the neighborhood of 1" you'll be all set.

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? As previously stated I have already shimmed it up one inch to where it is now at 4.5 degrees!

It seems to me if the "banana" bar and shock mounts were relocated only a slight amount on the axle everything would be good. All I need is 3 degrees up on the pinion and I think I would be within limits. (Trans down 4.5, pinion up 1.5 equals 3 degree difference in the acceptable direction)

[karlos]

The angle calculator is your friend. Link is provided in post #2. Use it to consider various hypotheticals so that you have an idea of what you're trying to achieve before you start modifying the car. If I understand correctly, I believe you're proposing changing the slope on the differential from its current 1.5 degrees upward to 1.5 degrees downward (a total change of 3 degrees). If you plug those numbers into the calculator you'll see that the pinion angle still ends up being a factor of 2 too high (assuming a driveshaft angle of 2 degrees and a differential angle of 1.5 degrees, pinion angle ends up being 2 degrees).

Just to be clear, no one is suggesting that you raise the back of the transmission 3 inches. If you need something like 3 inches in order to get the engine approximately level, then there's another issue at play here. Need to find what that is first and then move on to setting up the driveline.

[BB767]

Can some of you tell me what your pinion angle is? I am talking about the pinion shaft itself coming out of the rear axle housing. Is it pointed down or up in relation to the frame of the car?

Stepping back a moment; almost all vehicles have the engine/transmission mounted at some angle down towards the rear of the vehicle, although I will agree some may be exactly level, that's just the way it is. Therefor, most vehicles have the pinion shaft pointing slightly up, or again, some may be level, again, that is just what is most common. But none that I have ever seen have been mounted pointing down!

So, are all yours different? Do your pinions point down towards the ground in the front? Mine does and I do not think that is normal. But if you all have the same thing going on, then I guess I am wrong. I would just like to establish this fact before moving on to raising the transmission.

[karlos]

Look at Kleiner's post (#6). You want about 2 degrees nose down relative to the transmission output shaft. You're currently at 1.5 degrees nose down on the pinion. But your transmission is at 4.5 degrees the opposite direction. So the angles add. 1.5 + 4.5 = 6 degree operating angle. No good. But if your engine were roughly level, you'd be 1.5 degrees nose down relative to the trans output shaft. Perfect.

[karlos]

Is that dark semicircle in your photo a shadow or a gap?

[edwardb]

Can some of you tell me what your pinion angle is? I am talking about the pinion shaft itself coming out of the rear axle housing. Is it pointed down or up in relation to the frame of the car?

Stepping back a moment; almost all vehicles have the engine/transmission mounted at some angle down towards the rear of the vehicle, although I will agree some may be exactly level, that's just the way it is. Therefor, most vehicles have the pinion shaft pointing slightly up, or again, some may be level, again, that is just what is most common. But none that I have ever seen have been mounted pointing down!

So, are all yours different? Do your pinions point down towards the ground in the front? Mine does and I do not think that is normal. But if you all have the same thing going on, then I guess I am wrong. I would just like to establish this fact before moving on to raising the transmission.

Each of my four builds (including the newest one on the lift right now) have the diff pointed up toward the front. With the engine/trans typically pointing down in the 1-2 degree range (that's what mine have been), that equals an acceptable pinion angle.

[Joee]

Look at Kleiner's post (#6). You want about 2 degrees nose down relative to the transmission output shaft. You're currently at 1.5 degrees nose down on the pinion. But your transmission is at 4.5 degrees the opposite direction. So the angles add. 1.5 + 4.5 = 6 degree operating angle. No good. But if your engine were roughly level, you'd be 1.5 degrees nose down relative to the trans output shaft. Perfect.

Right, BB767 you have to have an assembly problem your rear sounds fine. Most of us only need to fine tune the rear and done. This thread is way too much going on. Is there a builder /owner in your area to stop by and look at your car. Experienced eyes can usually spot a problem immediately.

[BB767]

Is that dark semicircle in your photo a shadow or a gap?

Hi Karlos, I went out and inspected it closely, there is no gap, the mounts sit square and flush on the frame pad.

[BB767]

Each of my four builds (including the newest one on the lift right now) have the diff pointed up toward the front. With the engine/trans typically pointing down in the 1-2 degree range (that's what mine have been), that equals an acceptable pinion angle.

Thanks Edward. I feel if my pinion were pointed up, (as yours is) or even level, the problem would be easy to solve. I just do not understand why my pinion is pointed down with no adjustment left. My trans angle may be excessive compared to most but I view the main problem as the pinion angle, if that were more like yours there would not be a problem.

But on the other end;
Do you have any builds with the tunnel still open? I would like to know the clearance between the transmission and the frame. There is a silver cover plate on the top of my TKO600 just in front of the shift lever. I have 2 inches from it to the bottom of the frame cross member. Also, the gap between the transmission tail shaft and the frame cross member (underneath). Mine is currently 1 inch.

[BB767]

Right, BB767 you have to have an assembly problem your rear sounds fine. Most of us only need to fine tune the rear and done. This thread is way too much going on. Is there a builder /owner in your area to stop by and look at your car. Experienced eyes can usually spot a problem immediately.

Joee, can you tell me the angle of your pinion shaft? Is it currently pointed up or down in relation to the frame?

[Joee]

I have a stock 91 302 block, stock Ford motor mounts, T5 trans. My rear is down about 2 deg from trans out put shaft just like Jeff's picture. My transmission mount sits on A frame with a washer as a spacer.

[edwardb]

Do you have any builds with the tunnel still open? I would like to know the clearance between the transmission and the frame. There is a silver cover plate on the top of my TKO600 just in front of the shift lever. I have 2 inches from it to the bottom of the frame cross member. Also, the gap between the transmission tail shaft and the frame cross member (underneath). Mine is currently 1 inch.

The completed Roadster sitting in the garage right now (#8674) wouldn't be particularly easy to measure. It's a Coyote with TKO and IRS. So probably not applicable to yours. But dug through some pictures and found this picture of Mk4 Roadster #7750 with a DART 347 and TKO600. It's a 5-link solid axle. Still not the same as yours, but a little similar. Trans spacer is 3/4-inch.

[BB767]

The completed Roadster sitting in the garage right now (#8674) wouldn't be particularly easy to measure. It's a Coyote with TKO and IRS. So probably not applicable to yours. But dug through some pictures and found this picture of Mk4 Roadster #7750 with a DART 347 and TKO600. It's a 5-link solid axle. Still not the same as yours, but a little similar. Trans spacer is 3/4-inch.

Exactly what I am looking at. Can you estimate the distance between that crossbar and the silver cover plate below it?

[BB767]

I have a stock 91 302 block, stock Ford motor mounts, T5 trans. My rear is down about 2 deg from trans out put shaft just like Jeff's picture. My transmission mount sits on A frame with a washer as a spacer.

To help narrow down the problem, can you tell me what the angle of the rear end is in relation to the frame of the car? In the picture it appears level or slightly nose high.

[Joee]

I will tell you later not near car and that pic is 10 yrs old

[edwardb]

Exactly what I am looking at. Can you estimate the distance between that crossbar and the silver cover plate below it?

It's been a few years since that picture was taken and I don't own it any more. I would put it in the 1/2 - 3/4 inch range. The rubber shift boot, as I recall, was right at the bottom of the crossbar. Hope that helps.

[CraigS]

BB767 a couple of questions. Is your trans a-frame on top of the tab on the main frame or under it? I know it's not much difference, maybe 3/8 inch, but could be helpful raising the trans w/o using a thicker shim. Can you get some pics of your rear axle including the banana bracket? I wonder if there is a chance it is clocked incorrectly relative to the pinion. I think you alluded that it is the FFR supplied axle assembly w/ the bracket welded, but there could always be a mistake there.

[rich grsc]

What tranny mount are you using? Take a picture of your mount and the A-frame.

[BB767]

IMG_0390.JPGIMG_0399.JPGIMG_0400.JPGIMG_0402.JPG

Couple of requests for photos.
390 shows A frame looking aft. It is mounted on top of the bracket with shims installed.

[BB767]

IMG_0406.JPGIMG_0404A.JPGIMG_0405A.JPG

404 shows that air cleaner and injection body almost level with the frame

[BB767]

BB767 a couple of questions. Is your trans a-frame on top of the tab on the main frame or under it? I know it's not much difference, maybe 3/8 inch, but could be helpful raising the trans w/o using a thicker shim. Can you get some pics of your rear axle including the banana bracket? I wonder if there is a chance it is clocked incorrectly relative to the pinion. I think you alluded that it is the FFR supplied axle assembly w/ the bracket welded, but there could always be a mistake there.

My feeling exactly, is this clocked incorrectly? I'll try and get photos of that that are clear.

[BB767]

BB767 a couple of questions. Is your trans a-frame on top of the tab on the main frame or under it? I know it's not much difference, maybe 3/8 inch, but could be helpful raising the trans w/o using a thicker shim. Can you get some pics of your rear axle including the banana bracket? I wonder if there is a chance it is clocked incorrectly relative to the pinion. I think you alluded that it is the FFR supplied axle assembly w/ the bracket welded, but there could always be a mistake there.

Can you tell anything odd from the pictures?
IMG_0407.JPGIMG_0409.JPGIMG_0410.JPGIMG_0411.JPG

[karlos]

Not sure how much difference it makes, but it doesn't appear the shim is in the correct location.




Picture's kinda dark, but it looks like you've got a stack of 3 washers that add up to maybe 3/8" or so? That would explain the tail-down trans angle. Shim's not thick enough, plus at that location vs. under the trans mount the shim is less effective in producing an angle change. Suggest you try removing those washers, set the A-frame back down on the chassis tab, take the bolts out of the transmission mount, and then raise the back of the trans until you have a 3/4"-1" gap between the transmission and the transmission mount. Then recheck the engine/trans angle. Guessing you'll be much closer to zero degrees. If so, you can put in a new (thicker) shim under the trans, leave the differential where it is, and all driveline angles will be close to the desired values.

[BB767]

Not sure how much difference it makes, but it doesn't appear the shim is in the correct location.




Picture's kinda dark, but it looks like you've got a stack of 3 washers that add up to maybe 3/8" or so? That would explain the tail-down trans angle. Shim's not thick enough, plus at that location vs. under the trans mount the shim is less effective in producing an angle change. Suggest you try removing those washers, set the A-frame back down on the chassis tab, take the bolts out of the transmission mount, and then raise the back of the trans until you have a 3/4"-1" gap between the transmission and the transmission mount. Then recheck the engine/trans angle. Guessing you'll be much closer to zero degrees. If so, you can put in a new (thicker) shim under the trans, leave the differential where it is, and all driveline angles will be close to the desired values.

OK, I'll take a look at that tomorrow.

[johnnybgoode]

Here's how I adjusted mine if it's of any help. Very similar to Jeff's diagram in post#6. I made up a couple of 3/4" spacers out of some 1" AL thick wall round tubing stock on the lath. Jacked up the transmission and bolted them up under the transmission mount with longer 2" grade 8 bolts and lock washers. I reset the pinion angle to 1.8*. The crank pulley measures 87.5* (or 2.5* downward angle) and the pinion flange is 89.3* (or 0.7* upward angle) which gives me the 2* differential that is required (your pinion flange should be close to 90*). If you have a digital level with a relative angle setting you can zero the level to the crank pulley and the reading you get on the pinion flange will be the number you want, mine's 1.8*. As I remember the 3/4" spacer got me about 1.5 to 2* less downward angle on the motor/trans. Before the spacer it measured 86*. Hope this helps. Good Luck. Scott

[BB767]

Drive Train Angles.png

OK, I went out this morning and raised the transmission until it almost touches the frame above it. It requires a shim thickness of 1 and 7/8 inches. It is now pointing down 1.5 degrees just like most of yours. Take a look at my depiction of the current angles and see what you think I should do now.Original Position.png

[NAZ]

Can't comment on the spacial position of the engine and trans but using Jeff's negative 2-degree static setting, rotate the pinion up until the angle is ~2-deg less than the output shaft. That would make the pinion shaft pointing down at 0.5-deg if your trans output shaft is pointing down 1.5-deg. Then check your driveshaft angle. The pinion angle has to be measured at ride height.

If the rear end won't rotate because of shock clearance then use the method I detailed earlier to get clearance.

When you are taking the engine / trans angle is the chassis level with the world, at ride height, or ???

[karlos]

Is the driveshaft really at 22.7 degrees? That's about 10 times what I would expect to see (mine ended up right at 2 degrees). Something's really, really wrong. Starting to wonder about the accuracy of your angle measurements. Did you say you're using an app on your phone? Do you have another way to try to confirm the numbers? Something like this, maybe (only $5 at Harbor Freight): https://www.harborfreight.com/dial-g...der-34214.html

[BB767]

Can't comment on the spacial position of the engine and trans but using Jeff's negative 2-degree static setting, rotate the pinion up until the angle is ~2-deg less than the output shaft. That would make the pinion shaft pointing down at 0.5-deg if your trans output shaft is pointing down 1.5-deg. Then check your driveshaft angle. The pinion angle has to be measured at ride height.

If the rear end won't rotate because of shock clearance then use the method I detailed earlier to get clearance.

When you are taking the engine / trans angle is the chassis level with the world, at ride height, or ???

I am using the Tremec app on my phone for the measurements. Since I assume that is level with the world (as are the other measurements) I am simply looking at the differences to check limits.

Karlos, I'll go out and double check now.

[Jeff Kleiner]

This = 6 degrees; way too much.



This = 3 degrees; still too much but closer.

The only way to change the relationship is by lowering the front of the engine, raising the rear or lengthening the upper link. I too have been suspicious about your method of measurement and ask once again, what is your ride height in the rear? Show us a photo of the top of the banana bracket and panhard bar brace interface. Doesn't matter in the least whether the chassis is level with the world...for pinion angle we're only interested in two things; the angle of the output shaft and angle of the pinion shaft. I've been building these cars for years using a hardware store angle finder like Karl showed and never had a problem. It's like Jacob the Amish IT guy says "Sometimes the old ways are the best ways" (youtube it ).

Jeff

[BB767]

IMG_0412.JPGIMG_0413.JPG


With transmission raised.

[BB767]

IMG_0409.JPGIMG_0410.JPGIMG_0411.JPG

Best I could get photos of rear axle.

Ride height is 4 3/4 front and rear, give or take 1/4.

I have a couple of angle gauges but most are to big to get into the area. The walls of my house measure "0" on the Tremec measurement app, I don't know what else to say. When remeasuring the driveshaft I come up with 21.9 this time. The measurements may not be 100% precise but they appear to always be within 1 degree. Close enough to get this problem figured out, I can get a more precise measuring device when I am closer to the target numbers and correct positions..

[BB767]

IMG_0377.JPGIMG_0378.JPGIMG_0407.JPGIMG_0408.JPG

More photos showing my clearance issues with the shock mounts and the banana bar. I think your idea of trimming the shock mounts will work but what can I do about the banana bar?

[Jeff Kleiner]

Maybe the camera is playing tricks but when I view your 78435 photo it sure looks like the top of the axle tube is very near even with the top of the 4" chassis tube:

If that's indeed the case the only way I can see this being possible is if the axle is hanging. PLEASE give us some wider shots showing how it sits during your measurements.

Jeff

[Erik W. Treves]

Maybe the camera is playing tricks but when I view your 78435 photo it sure looks like the top of the axle tube is very near even with the top of the 4" chassis tube:

If that's indeed the case the only way I can see this being possible is if the axle is hanging. PLEASE give us some wider shots showing how it sits during your measurements.

Jeff

yeah that looks like full droop to me as well Jeff. Although in one of the pics you can see the jack stands...

the rear shock looks like it's angled pretty good.. don't remember mine be like that.... can you take some pick of the lower control arms and mounting of the brackets... I would expect needing over 1" of tranny spacer.. for sure you need some... the few I have done, I think I am in the 3/4" range

[BB767]

This = 6 degrees; way too much.



This = 3 degrees; still too much but closer.

The only way to change the relationship is by lowering the front of the engine, raising the rear or lengthening the upper link. I too have been suspicious about your method of measurement and ask once again, what is your ride height in the rear? Show us a photo of the top of the banana bracket and panhard bar brace interface. Doesn't matter in the least whether the chassis is level with the world...for pinion angle we're only interested in two things; the angle of the output shaft and angle of the pinion shaft. I've been building these cars for years using a hardware store angle finder like Karl showed and never had a problem. It's like Jacob the Amish IT guy says "Sometimes the old ways are the best ways" (youtube it ).

Jeff

I understand and agree. The front of the engine is not going down without some kind of special motor mounts or major modifications to the frame supports, probably not possible. The rear cannot come up any more as it is almost touching the frame above it now. The only option left is somehow raising the rear pinion angle. This is the basic premise of the whole post and still is. How in the world am I going to get that done? That is the question.

As far as the measurements go, the Tremec app measures level to the earth, period. I assume everyone here understands that. As you said, it makes no difference what the numbers are, what matters is their relationship to each other. Parallel within 1 degree, total difference not to exceed 3 degrees. It's that simple, but again, I cannot figure out how to get there with the restrictions I have on the pinion angle adjustment!

[Jeff Kleiner]

Gotta' head out to the shop and get some work done...I'll check back in later to see if there are any updates.

Jeff

[BB767]

IMG_0414.JPGIMG_0415.JPGIMG_0416.JPG

I know someone said the shock adjustments looked high but as they are, with 4 3/4 ride height, the side pipes only clear the neighborhood speed bumps by one and a half inches. Any lower and I will not be able to leave my driveway!