Hot Rods 54 Chevy truck pinion angle opinion

Hi, I'm doing a resto on a 54 chevy 5 window truck and looking for some help with the pinion angle. I have a T-5 S10 tranny going behind the 235 stovebolt with a camaro 10 bolt rear end. The engine and tranny are out of the truck so I can't check what the pinion angle is on that end. I'm trying to weld in a triangulated 4 bar rear suspension setup and wondering if anyone here has already done this and knows what the pinion angle should be to best match up to the t-5 tranny. I have read that 3 degrees down is a good spot and can be adjusted with the 4 bar links. I'm paranoid with that setting as I measured the torque tube before I removed the old rear end and it was pointing to the sky at 5 degrees. I should also mention that I'm lowering the rear end to about 4~6 inches below the frame rails depending on bag or shock setup (not notching the frame).

 

It would be best if you could mock in the engine/trans and rearend at intended ride height. and then figure out where you need to be.
The engine will end up around 3 degrees nose high.
I would guess the pinion may end up needing to be around 1 degree nose down. BUT that is only a guess.

 

...this has been discussed many times,...after your engine/trans is mounted, set the pinion angle with the weight of the truck on it's springs,..if your trans angles down 3 *, angle the pinion up 3*...or close, a degree or 2 off wont hurt anything.

 

Torque tube driveshaft angles and open driveshaft angles have nothing whatsoever to do with each other.

Get the transmission cross member instilled, and put in the transmission in. Set the chassis up level, at ride height, tires on the ground. Measure the angle of the output shaft. This should be roughly 3º sloping downward toward the rear. Record that exact angle.

Get the rear axle centered in the chassis, squared to the center line of the frame. make sure that the wheels are aligned with the wheel openings.

Prop the pinion shout UP TOWARD THE FRONT at the angle that you recorded on the transmission output shaft.

Set all of your links at the middle of thread travel, and set the jam nuts. Put the tabs/brackets on them.

Then you can tack weld them on. Take the links back off. Push out the spacers that are in the bushings, or find a stack of washers that are the same height. Put the the bolts and those spacers/washers back in the bolt holes. That will keep the tabs/brackets aligned during final welding.

Weld them up slowly, in segments, so as to not warp the axle housing.

Transmission output shaft points down toward the rear. Pinion points up toward the front. The angles should match at ride height.



A pinion does not get set nose down, except for in an incredibly high torque race application (600+lb-ft.), with suspension elements that can be distorted, like leaf springs.

 

Good info, note that a line drawn through the trans output shaft and a line drawn through the pinion should be parallel.

 

Bingo.

 

Gimpsy, you're exactly right. I have an exception with my Model A chassis due to the engine height and I would change even more with a Z'd chassis. This is not in argument.
On my Model A, I had to reset my pinion angle to have the pinion down that smidgen to accomplish complimentary angles thru the u-joints. In a two u-joint shaft, the rule is the u-joint angles need to be equal or within 1 degree of each other. If you have 2 degrees in the front u-joint angle, you can range from 1 to 3 degrees thru the rear u-joint. The rules don't state that the angles will always be in the same attitude. \ _ / situation. If altitudes of parts differ enough, you can't always get the engine/trans centerline parallel with the pinion centerline. In a lot of cases you can, so it's the easiest way to apply the degree rules.
I know this complicates the question of the thread starter. In the science of proper installation of driveshafts many rules apply and some can be swayed on a little.
I have seen a specialty 18 wheeler auxiliary transmission in a new truck being delivered blow out bearing and guts because of improper angles of the entire powertrain, and guided the technicians on how to correct it. The early warning that was ignored in Texas at the beginning of the delivery was an odd gear noise the driver didn't recognize. When the truck was going thru Ohio, it splattered. Obviously, this was an extreme exception, but the point is an angle induced vibration will even chatter out the centers of the clutches in an automatic transmission.
Too much food for thought. Even include a junk driveshaft while mocking up the parts to accomplish what Gimpsy and I are talking about. I would sure be glad to answer question for guidance as I'm sure Gimpsy would too. We have a fair amount of experience between us.

 

My engine and transmission in my Falcon are set to 0º, so is the pinion.

That sounds like it should not be, but the pinion is 1-3/8" above the output shaft. The driveshaft runs uphill to the back.

I have only hit the transmission case on the ground a few times.

I am always happy to answer questions. If we don't share this, it dies with us.

 

I was to abstain from this one, but I guess I don't know any better. LOL
First, let me say , I'm sure you've built many cars over the years, and I'm not going to disagree with what you've shown in the diagrams here.
But let's look at another scenario, okay?
Let's look at the second diagram .
The O/P has installed his T 5 crossmember and mount per OEM right? That being engine slightly down in back, to promote oil drain back, but with the carb flange level.
Now, he said he wants to lower the rear and substantial amount.
So, let's move the rear end straight up , 4 inches.
Now , three degrees off the trans goes away, and so does the three at the pinion.
So, now we're at 0-0 .No working angle at U-joints. We're always told you can't do that. They won't grease, and will wear. Oh, and now it vibrates a little. Not bad , but noticeable at certain speeds.
What are we going to do fix this situation?
Not looking for a debate here. Just asking.

 

"""Now , three degrees off the trans goes away, and so does the three at the pinion."""

you are confused as to what is going on here. you could move the rear axle 2 feet up and it would not effect the angle at the trans.

 

My personal car is set up 0º-0º.

U-joints not greasing at 0º-0º assumes that the output shaft and pinion are on the same y and z planes (up/down, and side/side), and that the suspension does not move.

In that hypothetical instance, there would be no working angle, and u-joint life would indeed be shortened.

These angles described in the diagram, and in my instructions reference the ground (gravity actually, so they technically converge on the center of the Earth, but that is so far away that it does not matter).

While my personal car is set up 0º-0º, the output shaft and pinion are both on different y and z planes.

The pinion is to the passenger's side, and above the output shaft.

It has seen 100, with zero vibrations. That is as fast as it can go.

The actual angles that matter are not the ones that reference the ground. Those are just shorthand.

The only angles that matter are the working angles of the two joints, in a 2-joint shaft. Those must be complimentary. Up/down, or down/up, they must be equal and opposite, and within reason.

Harsher working angles will shorten u-joint life, and there will be vibration that cannot be cancelled out by those angles. This is not something that most hot rodders will need to be concerned with. Only the guys with 4x4's with big tires and short shafts will have to compensate for

 

Mark, this is where your mockup plan comes to play.
In that situation, I would prefer to put a little bit of pinion down in play with the line of thinking like Gimpsy stated about drag cars, the pinion wants to rise with takeoff and acceleration. And to get more technical, an overhead measurement of the angles to see if pinion offset is enough to help with the victim vehicle.
The goal is to have equal or complimentary angles thru both u-joints. So a person has to be flexible in thinking of which ways he can apply that goal. It could include to raise the front of the engine too, or lower the rear of the transmission. I have used caster shims or changed axle seats on trucks to accomplish the needed rules that apply.
I'm not going to start on two piece or multiple shafts due to further complications, but I have helped design and correct many, to include being involve with the suspension manufacturer that supplied the bus manufacturer with the problem child 4 shaft bus that was sent to me by the local dealer.

 

The beginning of my solution is going under the assumption that the engine/transmission and pinion are in line with each other from an overhead view. Not all applications are that simple.
Throw in some beer math......
.240" of change at an angle at 1 foot distance compared to it's baseline is 1 degree of change.
When you're making corrections on a complete vehicle, you have to use this in your mind's eye and calculations to achieve correction accomplishments.

 

He is running a 4-link. The only movement outside of suspension cycling will be bushing deflection.

I highly doubt that will be more that 1º, or at worst 2º, both of which would be well within acceptable range to leave uncompensated.

 

And then you hear people say "It ain't that damn complicated", but sometimes it is.
I did this every day for 25 years, in the shop, under the vehicle, and guiding others over the phone.
We've pretty well covered the bases.

 

So confused , I need a diagram for that one.

 

Gimp, Only 4 links I know about are for racing. LOL
I assume there's some engineering in those diagonal 4 bar set ups.
I don't know first hand , so I won't state that. My example was more hypothetical, when I said straight up.
The change would depend on how close together the horizontal planes were, to start with, right?
No dimension given.

 

Oh no. Can't do that . We were told never down ;-)
More on this after dinner.

 

More beer math with beer...
Assuming centered or parallel overhead view of engine/trans to pinion centerlines.
Engine/trans at 3 degrees nose up to 1 degree nose up on the driveshaft equals 4 degrees of change.
Driveshaft angle 1 degree nose up to 2 degrees nose down pinion equals 3 degrees.
Angle comparison from front to rear are 4 degrees in the front, 3 degrees in the rear. That complies with the rule of the angles need to be equal or within one degree of each other in a two u-joint shaft.
To get to the science of this with non-complimentary angles, you have to skew them less than you think to induce a vibration.
When I've had the opportunity to use the display unit Dana Spicer owns to display this, I also throw in out of phase, which means the yokes don't line up in a vertical plane if looked at it that way, and at super-speedway speeds, it will make a difference on how a car feels, Bonneville too.
With a machine that has a low speed electric motor with a "sprocket" to put a card in the bicycles spokes to, angle adjustment....a small driveshaft between that has parts modified that are for display only to allow for out of phase and a "sprocket", to a driven end with another "sprocket" and angle change capability.
With this instructional tool is used, as you change angles and display how the drive and driven react to angle changes in RPM changes at the driven end. If the angles are complimentary, the card sounds the same at both ends. If you make drastic changes to angle and phasing, you can make the noise of the card cycle like cyclic noises in the vehicle that has a problem.
One example of cyclic would to apply the simple way I explain.
If you only look at one plane of change and apply, take the motor at 1000 RPM input thru the u-joint that has .5 degrees angle thru it. Needles in the cap rotate so the u-joint lives. The driveshaft spins at a cyclic speed dependent on how much angle goes thru that first u-joint. The cyclic rotation speeds up and slows down twice thru each revolution. Go thru the second u-joint that has a complimentary angle in any direction, the driven end rotates at the same speed as the drive end. This is why we call angles complimentary. Let's call it 1000 RPM in, 950/1050 thru the shaft, 1000 RPM at the driven end.
Skew the angle of the driven end and throw in out of phase, you develop a new scenario. The driven end still spins at the same rate. The driveshaft cyclic depends on angle thru the driven end angle. The more problematic non-complimentary driven end u-joint angle throw in a new problem because the pinion has now developed a cyclic rotation cycle that's not the same as the driveshaft, and not a steady speed like the drive end. The card in the sprocket displays it to your fellow mechanics. Let's call it 1000 in to 950/1050 thru to 900/1100 cyclic driven.
What this does is to cause a vibration back and forth thru the shaft as the u-joint angles fight each other. Take the RPM up, and the vibration increases square on RPM doubled. Dadarummm rummm rummm, to Drummm, Drummm, Drummm.. Like a welded crooked, slightly bent, slightly bent and twisted driveshaft, but different.
A vibration of this nature will cause bearings and gears to howl, automatic transmission clutches to have teeth hogged out in a back-and-forth fashion, unneeded noise in a vehicle. I would venture to state that a vibration like this caused undue engine bearing wear in the proper instances.
Some vehicles use out of phase to induce a vibration to cancel another vibration, i.e. first gen Camaros and Firebirds.
I know this is longwinded, but this is one step of the science that is applied to make what we think is simple to get down the road. It Ain't That Damn Complicated...Bullshit. I'm just going by what I know and use and could teach it at the shop or manufacturer tech service level.

 

Thank you Patrick.

I think we might have killed off the original poster.

I need to just preemptively post those videos that explain this, every time driveshaft angle issues come up.

Your description is dead-on.

 

Like this, yo:

 

transmission 3 degrees down, pinion angle 3 degrees up. your numbers may vary.

I bought a car with the motor and trans set close enough, but the pinion was 4 degrees DOWN. to be honest with you after I fixed it I didn't notice any difference. I bet my U-Joints did though.

 

I think we lost him at 5 degrees of the torque tube.

 

Angle description is one area that I like to keep relative to the way I look at a vehicle sitting in front of me and how I describe the angle attitude.
The vehicle front is the nose. Is the nose higher that the rear? Nose up.
Is the front of the pinion or driveshaft front lower than the rear in a centerline thru it? Nose down. Mistake if an engine or transmission that's not built to deal with oil drain and fuel source.
It's also like rotation direction of the engine. If you're looking at the nose of the crank, most turn clockwise and you relate to all other rotations of parts turned by the engine by looking at the headlights from the front of a vehicle. This goes with sales and usage of power take-off equipment et.al. that doesn't generally apply to what we do here.

 

Do we have a tech library here? I had been away long enough that I don't remember and if so, don't remember how to find it.....

 

Basically the point I was getting at earlier. On this subject, down doesn't necessarily mean negative pinion angle.
To me, it just means opposite of up.
A couple of weeks ago , Mr Thomas, with the 50 Chevy , SBC, T350 conversion, found himself confused by all the up/down descriptions. This was after having a rod shop install spring pads @ 1 deg. UP, so he was told.
His trans mount was somewhat low, in relation to his pinion. He ended up with two similar U-joint angles, rather than opposing angles.
Anyway after a few phone calls, we got it fixed. He shimmed the pinion down some ( not necessarily negative ), and then I suggested spacing the trans mount up a bit.
He must have got it close, because his vibration problem went almost completely away.
So yes, the subject is complex, but the set up isn't that way, so much, as long as everybody is on the same page with the descriptions.

 

How do the rules change when my rod's front u-joint is a double carden front constant velocity joint?


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Wow! that is a whole bunch of information for me to chew on. Now I'm more confused than I was before sending this in. I appreciate all the knowledge being sent my way. To summarize my situation, I believe I need to get my engine finished first, set it back in the frame with tranny attached and do some calculations before I weld in the rear 4 link. The drawing and video helped more than anything.
Thanks everyone. I was really hoping for that one guy to have the same setup and vehicle as me to give me his pinion angle.

 

If I'm not mistaken on a double carden cv shaft you want the pinion pointed at the transmission output. There's a lot of guys on here that know way more than me but that's how it's done on 4x4's with short shafts and steep angles

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The question of if the front u-joint is a double cardan and a single rear, like a OT Bronco.
Basic setup is get all the parts in, suspension height set shaft in.
Then using an angle finder or eyeball engineering, first point the pinion directly at the driveshaft, then kick the pinion down a couple of degrees to put some angle thru the rear u-joint.
But with having said that, a double cardan CV joint doesn't like to run with little angle going thru it. I would venture that they really like at least 7 degrees angle thru them to make the parts function correctly.
Part of this I learned from 4WD trucks, part from a customer's '49 Buick Roadmaster convertible that was on the cover of Street Scene, and a '37 Buick convertible old custom that graced the cover of another magazine. I had to help my customers overcome some of the problems we took out and built in by using a two piece driveshaft with double cardan u-joints. Kind of like an S10 Extreme truck driveshaft.