Where is My Rear Lift Coming From?

Does your Mitsubishi L300 make a strange noise? Need wheel alignment specs?
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cosmo727
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Where is My Rear Lift Coming From?

Postby cosmo727 » Wed May 09, 2018 1:31 pm

Hello Delica Fans

A recent thread about ride hide and rear leaf springs has got me thinking about my ride height again.

I think my rear end is sitting too high. I don't see any extended shackles so I'm thinking it may be after market leaf springs. Because the rear end is so high I had to compensate with the front end to make her level. I have the tapered spacers up front and the torsion bars cranked.

I would prefer to lower it a bit overall because I believe it may be stressing the driveline components.

Attached are some pictures of my ride height and rear leaf springs. Also attached is a picture of the shackle in the lift kit offered for sale on Delica.ca.

Any thoughts would be greatly appreciated!
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Growlerbearnz
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Where is My Rear Lift Coming From?

Postby Growlerbearnz » Wed May 09, 2018 1:42 pm

That looks like a re-arched stock rear spring. The lowest leaf, the short thick one, is normally flat, and barely touches the leaves above it. It's designed so that the top leaves do most of the work, but the flat leaf (the "overload" leaf) helps when the van's heavily loaded. Since your overload leaf is now touching the rest of the spring pack all the time, I imagine your ride is a little harsh.

Here's a disassembled spring so you can compare:
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Maybe just replacing that lower overload leaf with a stock one would fix it? It would allow the re-arched upper leaves to relax, lowering your ride height a bit, and softening your ride.

You've also got an axle wedge in there- below the lowest leaf there's a wedge shaped spacer block (you can see how the top plate with the bump stop doesn't sit flat against the metal case). The wedge re-angles the axle to correct the driveshaft angles after fitting goofy springs.
Nothing says "poor workmanship" more than wrinkles in the duct tape.

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cosmo727
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Where is My Rear Lift Coming From?

Postby cosmo727 » Wed May 09, 2018 3:22 pm

Thanks for the reply Growlerbearnz !

Yes you are right, my ride is bone charring!! Looks like I have a new mission to find stock lower leaf springs which are flat. By going that route do you think that I will still have a higher lift than stock but lower than now? Also should I leave in the wedge? I guess the other option is to go with OEM springs and the shackles offered on delica.ca.

...or is it possible to flatten the lower leaf???

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Growlerbearnz
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Where is My Rear Lift Coming From?

Postby Growlerbearnz » Wed May 09, 2018 8:29 pm

If you just replace the overload leaf, I imagine you'll still sit a little higher than stock, but not by much. It depends how the re-arch was done. As a test you could just remove the overload leaf temporarily and see how it sits. (Since the overload leaf doesn't do anything when the van's unloaded). Don't drive with that leaf removed, of course, as the spring pack will be loose in its mounts.

Whether to leave the wedge in or not (or swap it for a slimmer one) depends on your driveshaft angles once you've fixed the springs. Here's a good page all about driveline angles: http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml
That said, I doubt lowering the rear a little would be all that bad. You could certainly drive for a while with the wrong angles, it's just hard on the universal joint bearings.

A shop that re-arches springs should be able to de-arch that lower leaf. Alternatively, find a set of stock springs, disassemble them (and your springs) and mix-and-match leaves to build a spring pack that's the height you want. Use the stock top (fourth) and overload (first) leaves, and swap out the second (or second and third) leaves for re-arched leaves until you reach the height you want.
Nothing says "poor workmanship" more than wrinkles in the duct tape.

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cosmo727
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Where is My Rear Lift Coming From?

Postby cosmo727 » Sun May 13, 2018 7:10 am

Thanks again Growlerbearnz!!

Definitely some interesting reading. I am planning on visiting a couple of suspension and spring shops whenever I manage to have some free time. At least now I have a better understanding of my rear suspension.

Always something to tinker with to make these vans just right.

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cosmo727
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Where is My Rear Lift Coming From?

Postby cosmo727 » Sun May 13, 2018 10:37 am

Here's something interesting.

I had a bit of time at work to grab the digital inclinometer and this is what I measured.

86° on the transfer case flange (4° from vertical)
78° on the pinion flange (12° from vertical)

That's a difference of 8° with the shim installed !! From what I understand, both angles should be about the same. I would think that with a difference this large there would be a noticeable vibration. Does the perfect angle have more to do with wear on the U-joints and oiling within the diff?

Is it possible that these L300's can tolerate a higher angle?
Even with a typical extended shackle for rear lift I haven't seen any mention of shims being installed to keep the angle within a degree.

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Growlerbearnz
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Where is My Rear Lift Coming From?

Postby Growlerbearnz » Sun May 13, 2018 2:58 pm

You want the operating angles to be the same- the angle of the flanges relative to the driveshaft. What's your driveshaft angle?

If your driveshaft is at 8° (82° from vertical) your operating angles will be equal: 4° positive at the top, 4° negative on the bottom.

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Here's another, slightly longer article on driveline angles, and Bill describes this kind of driveshaft geometry as "broken back" alignment: http://www.pirate4x4.com/tech/billavist ... ndex2.html

With the short rear driveshaft it's tricky to get the angles correct when doing a lift, and a broken back setup is probably easier. When I had my add-a-leafs installed I had to lower the rear of the transfer case and shim the axle the axle to get the angles to work; that lead to the gearbox blowing oil out the breather. If I hadn't replaced the add-a-leaf with adjustable air shocks, a broken back setup was probably my next step.

For me the main disadvantage of a broken back setup was that the pinion wouldn't get as much oil as it should, and I wasn't willing to risk it since I've already turned one differential into glitter.

Our front driveshaft is in "broken back" configuration from the factory.

Vibration: yup, it'll vibrate if the angles are wrong. I forget, is yours an automatic or a manual? The automatics have a 2-piece driveshaft with a sliding spline, if your angles are out by 2° the splined section will make a truly horrifying noise when you're coasting (it goes away under acceleration or deceleration). On a manual it's harder to tell, but on my van there was an extra noisy rumble from the rear, and the whole van went from feeling fairly smooth and pleasant, to feeling like an agricultural old bus at speed. Oh and it flung all the grease out of the CV joints like I've never seen before.
Nothing says "poor workmanship" more than wrinkles in the duct tape.


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