Understanding our Two-piece Drive Shafts

I'm having troubles understanding our two-piece drive shaft angles. I'm documenting the stock angles in an effort to work out any problems I may have with mods in the future, suspension additions and lifting the truck. I'm reasonably well versed in one-piece drive shafts, with and without double cardon joints, as I have run both of those configurations in another vehicle. This two piece has me scratching my head as to why the particular angles?

I've watched a few videos and read some tech documents to no avail. I'm just not understanding the angles and how the two shafts relate to one another.

Spicer has a drive shaft configure app, with no explanation of why the angles? The app seems to be designed to measure U-joint operating angles, so no one exceeds their design limitations.
Driveline Operating Angle Calculator | Spicer Parts

Vehicle is an 4x4 Access Cab, Long Bed, Off Road. I believe the running gear length is the same for the much more prolific Double Cab, Short Bed trucks.

On very level ground, all angles are stated as "angled down" towards the rear of the vehicle as that was the only principle I garnered from the videos and tech documents:

Starting at the transfer case the flange is angled down 3.1 degrees
The first short section of drive shaft is angled down 5.8 degrees
The body mount for the Center Carrier Bearing is angled down 5.9 degrees
The second longer section of drive shaft is angled down 4.7 degrees
The pinion flange is angled down 5.1 degrees.

Sorry, no drawing capabilities.

There is also an ~2-degree pinion angle wedge between the rear springs and the axel perch angling the pinon, without this wedge the pinon angle would be ~7 degrees down. The thick part of the wedge is towards the rear, and the thin part is toward the front of the vehicle.

Measurements were taken with:

iGaging Digital Angle Cube Guage Bluetooth Bevel/Level/Protractor Magnetic Panes Lighted XL LCD

iGaging Digital Angle Cube Guage Bluetooth Bevel/Level/Protractor Magnetic Panes Lighted XL LCD: Amazon.com: Tools & Home Improvement

It is a stock vehicle with no rear suspension work. Only weight in the rear is a shell (~200lbs) and maybe another 100lbs of miscellaneous. ~300lbs total.

Any help with the theory of two-piece shafts? In an easy-to-understand language.

Future additions will be a crawl box which will shorten the first short rear drive shaft by ~9". Plus, some sort of suspension and lift after that.

I plan on shortening the short drive shaft when I do the crawl box and possibly going to a one-piece drive shaft with the suspension work or lift. Those plans may change.

My only thought is that somehow the carrier bearing is acting as a double cardon as the rear shaft is basically straight into the pinion. As it would be in a one-piece shaft application using a double cardon out of the transfer case.

I have searched here on TW and found no discussion of this topic. If there are any good threads, please direct me to them.

Awaiting GREAT information!

 

The front half of the driveshaft is considered an extension of the transfer case. It is not an exact extension of the transfer case based on the fact that it is angled a bit down from the transfer case, but that is for various reasons such as lubrication of u-joints and tweaking the rear half angles.

The rear half is treated like a standard 2 joint shaft. Angles mostly parallel.

When you do the crawl box, you will probably want to do a 1 piece driveshaft. The reason being the drivetrain is angled down already, and you will be eating up that 9” of the front half, making the front half really short and throwing its angles off. The angles will be off because the angle of the drivetrain will put the transfer case flange closer to the ground than it is currently, which will tweak the angle of the front half and then correspondingly throw off the rear half as well.

 

The stock driveshaft is two-piece because it would otherwise have too long of an unsupported span and approach its critical speed. This is why shorter-wheelbase models like the 4Runner and FJ can get away with a one-piece driveshaft, and without a double cardan joint. With a crawl box, you would probably be able to get away with a one-piece shaft as well.

 

I found this forum post helpful. The screenshots in that post are from this website, which I would recommend reading:

https://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml

After installing new leaf springs with 3" of lift I checked to see how parallel the transfer case flange angle was to the pinion flange angle. Using an angle finder I zeroed it on the transfer case, then found the pinion flange to be 0.5 degrees off. Closer to zero is ideal. If the angle was 1 or 2 degrees I would have used a shim between the rear axle and leaf spring to get it closer to zero. Sometimes further adjustment of the carrier bearing is needed, usually by adding small washers between the frame. I had no vibrations at hwy speeds so I did not adjust my carrier bearing.

 

You guys sure think a lot about shaft angles!

 

I feel like your baseline is flawed because they are against an imaginary level plane when the truck could be sitting differently on the suspension and that would impact your angles. Should you measure of of something more constant to the vehicle like off of the frame? Then regardless if the vehicle is pitched nose down or ass down a little your angles should be consistent. Or am I missing something?

 

OK, I am still not feeling confident in my understanding of two-piece drive shaft angles - still studying. So, I would like some more easily understood instructions.

What I can comment upon at this time is the expected use of a one or two-piece drive shaft after the installation of the crawl box. And before any suspension/lift work, which will be the very last major modification I will perform on this truck. All modifications will be done and the truck weighed for consideration of suspension work - it will become more than a bit heavier.

Tom Woods custom drive shafts no longer makes a one-piece rear drive shaft for any Tacoma - he has had too many customer problems:
Toyota Tacoma Rear Drive Shaft – Tom Wood's Custom Drive Shafts

Even the company Tom Woods references on the above page:
TOYOTA 2005 &↑ TACOMA 4X4 UPGRADE ONE PIECE CONVERSION – KNOXVILLE DRIVELINE
Refrains from making any expectations of eliminating vibrations. For this particular Aluminum shaft, the thickness is only 1/8" - I would dent that on my first run in the rocks.

This makes me suspicious of my own ability if these people cannot make a one-piece reliably work.

Sequence of work is to install the crawl box, have the existing front lengthened, the first section of the rear shortened and try to use the existing two piece. One as an exercise in gaining experience with the design and setup of a two-piece and to avoid some expense. I've already talked, nonspecifically to a local drive line shop who did some work on another vehicle. They, in our very short talk were of the opinion to use a one piece. Like @BLtheP and @3JOH22A the use of a two-piece shaft with too short of a first section was a concern of theirs.

The time between installing the crawl box and the suspension/lift work could be several years between. Also, I may go to a shackle flip or shackle reversal for the final work - this would most likely involve also moving the rear axle rearward trying to maximize departure angle. These trucks have a big ass. I am trying to minimize the amount of rework on the rear shaft(s).

If it helps I am not opposed to milling wedges to put at the Center Carrier bearing to drop it and/or to change the angle. This will clearly be an experiment. But to experiment I must understand and what I am seeing in the original Toyota factory angles I am not yet clear if they did it correctly to learn from or if I should use some other examples.

@th3clara I will read through your input a bit later - I just wanted to get to the first two commenters.

@GTGallop My understanding is the baseline has to be from the very front of the driven flange - in this case the engine, transmission and transfer case are inline. The first angle can be taken off the engine crank shaft pully, which is the same as the transfer case flange.

See this video: 5:20-15:45 - Rear suspension will change of course with torque applied and suspension movement. For me most suspension movement will come from going over obstacles moving slowly.
How to do drive angles 1 piece & 2 piece shafts /w POI markers for quick access / Mustangs & others

 

The factory did it correctly, but that’s for stock trucks. I am almost certain adding a crawl box by itself will screw it all up because of what it will do to the front half. Granted this is on a very modified truck but @Supr4Lo did the Ecocrawler on his which is something like 6.5”, so that’s how much he modified the front half of the shaft by. He had vibes he couldn’t solve. With a 9” crawl box that will be even worse.

I can’t speak in absolutes because the angles are somewhat difficult to measure on this truck due to tight spaces when the driveshafts are installed, but I know that they also installed different rear axle housings on DCLB trucks. My assumption is the perches welded at a different angle to account for the rear half of the driveshaft being longer. So as far as stock is concerned, it only takes a little bit of difference in truck for them to start implementing different parts and solutions to make things work.

Wedges are always an option to dial things in, but they can’t solve all problems. If your front half of the driveshaft gets tweak to angle upwards going from front to rear, no amount of shim will fix that because the u-joint angles will simply be too steep. You’d definitely need to lower the carrier bearing to begin to address the problem and even that might not be enough to fix the other angles.

 

I'm not sure I can agree with this... Mine vibrated pretty bad when it was completely stock (and there are numerous posts from others on here complaining about their stock trucks vibrating too).

Honestly I think it's a bit of a crap-shoot with these things... There are many here who have had success with reducing vibrations by lowering the CB (myself included), and then there are others who said that that made it worse. I suspect the only good way to attack this is to just do the mods you want to do, and then deal with the driveshaft angles afterward (play with different CB heights, and different degree axle wedge shims) until you get something acceptable.


I'm at ~4" lift and for me I was able to get it *almost* as good as it was factory (which is to say it still sucks) with the CB dropped down ¾" and the pinion adjusted up 3½°. There might still be a bit more room for improvement, but I'd need to get a wider assortment of wedge shims, and for right now the vibes aren't real bad (mostly noticeable only at speeds less than 10-12mph only while under heavy load / going up a very steep road or driveway... Occasionally I can also hear/feel a very slight vibe while coasting in gear around 55 mph, but again, it's not so much as to cause a passenger to ask: "what is that?").

 

While I know there are plenty of people complaining about vibes on stock trucks, I don’t think that is anywhere close to the norm and I would suspect the vast majority have 0 issues whatsoever. They definitely got mine perfect, I am at stock height and I had 5.29 gears that I took up to 100 mph a few times with stock tires. That is over 6,000 driveshaft rpm and it was still smooth as silk. Crapshoot may be the correct way to describe it, but I think the vast majority are perfectly fine. No telling why those that aren’t, aren’t.

Regardless of whether or not I’m right on the factory getting it right, the principles of a 2 piece driveshaft still apply and keeping it ideal with lift and especially mods like crawl boxes is going to get very finicky. I don’t think you can get it right with a crawl box and a 2 piece shaft. Especially when adding in lift. Considering there aren’t very many confidence inspiring 1 piece driveshaft options either, I’d be hesitant to do any mods like that because I’d be too concerned about not being able to get it right in the end. I want to install a full time FJ transfer case, but I’m hesitant to because I’m concerned the 1” of driveshaft modification will screw up what is currently a good thing.

 

I don't see why one couldn't move the CB back a little bit if more front-half length needs to be kept (you'd just need to fab up a bracket to hold it in its new position on the crossmember). But you are correct about the finickiness of these things. Raising/lowering the transmission (t-case) is yet another option one can do.

A crawl box is potentially in my future as well. I know the Tom Woods one-piece shaft wasn't solving everyone's issue, but with the crawl box reducing the span length between the t-case & axle, I think a one-piece would be a lot more workable in this case.