Help with driveshaft angles: photograph your driveshaft please?

Growlerbearnz

Growlerbearnz

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Could y'all help me out here and take a photo of your rear driveshaft, including differential nose and gearbox flange? From as side on as possible, like this:


PXL_20210307_000221195.jpg
My rear axle has been modified a few times as I've installed/uninstalled various "upgrades" and now I've forgotten what the driveline angles on a standard 4WD L300 look like.

I'm beginning to suspect the differential nose should be much higher, so the driveshaft is running in "broken back" configuration:


download-2.jpg

Thanks!
 
That's great, thanks! (Though more photos from other vans would still be welcome).

...and it looks pretty conclusive to me: I done messed up my driveline angles.

088F1282-867F-44EF-9666-E05B11A78BA5.jpg

I know what I'm doing tomorrow. *sigh*.
 
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Growlerbearnz said:
That's great, thanks! (Though more photos from other vans would still be welcome).

...and it looks pretty conclusive to me: I done messed up my driveline angles.



I know what I'm doing tomorrow. *sigh*.
Click to expand...
Mine's stock and also non-parallel; although nearly straight leaving the gearbox. Unless your suspension is nearly maxed out in the pic of yours I might be concerned as well.

IMG_20210307_092530955.jpg
 
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Upon reviewing all these photos, @Growlerbearnz, your drive shaft is oriented 90 degrees (rotationally speaking) from all the other’s. Does the differential rotate (up and down) on the axel as the drive shaft turns? If you rotate the driveshaft a quarter turn does that affect the alignment of things?
It’s -11C today and I am loathe to lie on the ice and play with mine to find out. :p
 
You're all awesome, thanks so much!

sk66 said:
Unless your suspension is nearly maxed out in the pic of yours I might be concerned as well.
Click to expand...
I found the culprit: when I fitted the add-a-leafs a few years back they changed the arch of the leaf springs, and I had to add some angle shims/wedges to tilt the diff back down.
It seems that when I got bored with the leafs I forgot to remove the shims. D'oh!


deskinthewoods said:
Does the differential rotate (up and down) on the axel as the drive shaft turns?
Click to expand...
LOL! Bloody hell, I hope not! (No, it doesn't. The wonky alignment is giving me some vibration, but not *that* much.)


mikldom said:
Un modded. Wore Out Torsion Bars Cranked. Monroe Air Shocks at about 20psi. 235/75/15 AT Tires.
Click to expand...
Those angles look good @mikldom but your driveshaft is out of phase (says the man who can't install an axle properly).
The drive lugs should be aligned like this:

DriveshaftAlignment.png

Your driveshaft is a two piece unit, the centre section is splined. It's been separated and reinstalled incorrectly at some stage.
If you remove the four nuts on the transfer case flange (they're usually the easiest/cleanest) you can remove the front half of the driveshaft, rotate it until it's aligned, and reinstall it. Super easy.

Caution: There's an odd number of splines, so there's only one way it goes together aligned perfectly. If you put it together (almost) 180 degrees out it'll be close, but not quite right.

An out of phase driveshaft will vibrate and will eat U-joint, diff, and transfer case bearings. Worst case is a failed U-joint leading to a flailing around driveshaft which punctures the fuel tank. It's a quick and easy fix so I strongly recommend you sort it out ASAP.


Thanks again, everyone!
 
Thanks for the info. I have had mine for over 3 years. While I have done a lot to the van I don't think I pulled the drives shaft for any reason. I have removed and reinstalled drive shafts and replaced ujoints on other vehicles tho. I will do as you suggest real soon. Funny... the van is smooth as butter with no vibrations anywhere. I do not want any bearings to go bad so it is on my list asap.
 
mikldom said:
the van is smooth as butter with no vibrations anywhere...
Click to expand...
Your driveline is nice and straight, those U-joints are operating through very little angle so yeah, it's probably quite smooth. I'd still fix it though, failed U-joints can be very exciting. In a "thank god I have the brown upholstery" kind of way:

39149883_251471032147853_2166076260776673280_n.jpg

...though maybe mark the driveshaft before disassembly, just in case you want to put it back the way it is now.
 
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When I did a lift on my '86 SE L300 many years ago, I recall seeing that the maximum difference between input and output angles should be less than 3 degrees before phase velocity differences were a problem and things became lively.

Mine were greater than 3 degrees after fitting the Ironman leaf springs and a 200m test drive was more than enough to convince me that more work was required :)
 
...and after doing a bunch of measuring and trigonometry I'm surprised at how much the U-joint operating angles change with only a small change in ride height (even without some moron installing a 4 degree shim under their axle.)

On my van, standard height and angle come out at 2.3 degrees on the diff, 3 degrees on the transmission. Under load the diff joint will tilt and lift up, which brings the angles closer to 2.5 degrees even. Lovely.

Raise it by just one inch and the angles become 1.3 and 5.6 degrees. (My messed-up angles are 7 and 10 degrees, not good at all.)

Still, exploding U-joints aren't all *that* common, so they're clearly tough enough to handle some abuse.
 
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All fixed! And as usual I might have overthought it just a little.

PXL_20210309_031704349.jpg

So I removed the wedges, and the U-joint angles were much better: 1° at the diff, 5° at the front (was 7° and 10°).

...but still not perfect, because the back of my van is slightly lifted thanks to the air shocks. And just to complicate things, the axle and differential pinion will twist up under drive as the springs react to the torque. But how much does it twist? This is where I might have overthought it just a bit: all I need to do is apply upwards force to the diff nose to simulate 250Nm of engine torque operating through a 4.875 diff ratio... Math ensued, and I used a bottle jack with pressure gauge to apply 350kg to the front of the diff.

Long story short: the diff rotates about 0.8° when loaded with 250Nm of torque from the engine. (Edit/clarification) I want the driveshaft to be perfectly aligned most of the time not just when fully loaded, so I set the diff to 0.5° (a total guess) before adjusting the transmission height to find the ideal alignment. It turns out, due to the way the angles change as the transmission drops and/or the diff rises, the ideal alignment happens when the diff end operating angle is 0.8° less than the transmission at rest. Suspicious that this is the same number as the total diff rotation under load, but it's either coincidence or I just don't have the smarts to recognise why these numbers are the same.

I removed the transmission mounts and used a jack to raise and lower the back of the transmission until the angles were perfect: it only needed to be 8mm lower. I achieved this by slotting all the transmission crossmember and mount bolt holes by about 3mm each. It's subtle, but it adds up.

PXL_20210309_031556644.jpgPXL_20210309_031613851.jpg

Result?

Zero the gauge so all angles are relative to the driveshaft...

PXL_20210309_031159454.jpg

Transmission 3.85°

PXL_20210309_031435004.jpg

Diff pinion 3.06°

PXL_20210309_031328087.jpg

That'll do.
 
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Growlerbearnz said:
All fixed! And as usual I might have overthought it just a little.

View attachment 10839

So I removed the wedges, and the U-joint angles were much better: 1° at the diff, 5° at the front (was 7° and 10°).

...but still not perfect, because the back of my van is slightly lifted thanks to the air shocks. And just to complicate things, the axle and differential pinion will twist up under drive as the springs react to the torque. But how much does it twist? This is where I might have overthought it just a bit: all I need to do is apply upwards force to the diff nose to simulate 250Nm of engine torque operating through a 4.875 diff ratio... Math ensued, and I used a bottle jack with pressure gauge to apply 350kg to the front of the diff.

Long story short: the diff rotates about 0.8° when loaded with 250Nm of torque from the engine, so I want my rear U-joint operating angle to be about 0.8° less than the front one, so they'll be equal when heavily loaded.

I removed the transmission mounts and used a jack to raise and lower the back of the transmission until the angles were perfect: it only needed to be 8mm lower. I achieved this by slotting all the transmission crossmember and mount bolt holes by about 3mm each. It's subtle, but it adds up.

View attachment 10840View attachment 10841

Result?

Zero the gauge so all angles are relative to the driveshaft...

View attachment 10842

Transmission 3.85°

View attachment 10844

Diff pinion 3.06° (raising to 3.8° under load)

View attachment 10846

That'll do.
Click to expand...
I wondered if the Nissan bushing substitution for the OEM ones was going to affect the gearbox angle when I did mine as the OEM ones had an offset to the inners whereas the Nissan ones had a central fixing. Probably should go back and check this now.
 
Growlerbearnz said:
...and after doing a bunch of measuring and trigonometry I'm surprised at how much the U-joint operating angles change with only a small change in ride height (even without some moron installing a 4 degree shim under their axle.)
Click to expand...
With such a short prop shaft it doesn't take much...
Growlerbearnz said:
Long story short: the diff rotates about 0.8° when loaded with 250Nm of torque from the engine, so I want my rear U-joint operating angle to be about 0.8° less than the front one, so they'll be equal when heavily loaded.
Click to expand...
Except that the front angle changes (decreases) at the same time. But, as long as the installed angles are within 1*30' of each other there's nothing to worry about (other than exceeding mechanical limits).
 
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