Navara D40 rear suspension.

Submitted: Tuesday, Mar 29, 2016 at 17:04
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My D40 has a saggy rear end. It hasn't got that much weight on it. Fridge, outboard and a camper trailer ball weight 220kg. It's done 65 k and on third struts and second set of leaves with an extra leaf added. My question is do I replace leaves again, go with airbags or helpers. I have done research on airbags and have checked out the cracked chassis problem and it seems air bags don't cause this but overloading or severe use. Looking for some feedback before I throw another grand at it. Thanks.
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Reply By: Bob Y. - Qld - Tuesday, Mar 29, 2016 at 17:23

Tuesday, Mar 29, 2016 at 17:23
"Not much weight on it"

What about the canopy and boat, Kirk? They are going to add some too.

Try airbags at your peril, I'd suggest. Talk to Dobinsons in Rockhampton, and get a set of constant duty spring packs, say 300-400kg. Might ride a bit rough empty, but should do the job loaded.

Bob

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Follow Up By: Member - Kirk L - Tuesday, Mar 29, 2016 at 17:45

Tuesday, Mar 29, 2016 at 17:45
Yeah forgot the boat mate lol. I can lift that myself and the canopy weighs less than the well body that came off it. No not a lot of weight really but thanks for info.
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Follow Up By: Frank P (NSW) - Tuesday, Mar 29, 2016 at 18:11

Tuesday, Mar 29, 2016 at 18:11
Kirk,

I agree with Bob Y.

I had a similar problem with my 2014 Dual Cab BT50, Kirk. Took the tub off, put an alloy canopy on. Total weight change about 50kg, I'm told.

Fitted out the canopy with slide, drawers, battery, water tank and there's another 240kg, so 290 constant load empty. First trip with OEM springs, moderate camping load (no boat) and 160kg on the hitch and it dragged its bum.

I don't like bags for leaf-sprung utes, so opted for a Lovells spring upgrade.

It's firm when empty but comfortable loaded.

I reckon that or something similar is what you should do.

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Follow Up By: Member - Kirk L - Tuesday, Mar 29, 2016 at 18:30

Tuesday, Mar 29, 2016 at 18:30
I had some big doubts with air bags. I spoke to unnamed company at caravan show and they showed me results of independent testing that said air bags did not cause chassis failures. I still had doubts from what I had heard in the field. I think I know I won't go that way. Good set of springs rated to my load I think. It has got a 2 inch lift apparently. Feels really light on front end which I am attributing to the sag in the arse.
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Follow Up By: 9900Eagle - Tuesday, Mar 29, 2016 at 21:23

Tuesday, Mar 29, 2016 at 21:23
Take Bob Y's advise and fit a set of Dobinson load rated sprigs or another brand like Kings or Ultimate for your application. Do the sums and put your vehicle on a weigh bridge, then add the tow ball weight. Most utes have a spring rating to get buyers to buy them with the lovely ride unloaded. That is fine until you actually load them.

I have 300kg plus springs on my ute and have no problems with sag. Around 200kg tow ball weight and the back loaded with canopy, roller draws, fridge slide, Trailblazer fridge, 120 deep cycle battery, solar panels and all the gear in the draws. I can go on and on. over 3 years sag is around 10 to 15 mm which is not bad at all considering this vehicle travels loaded all the time, also the ride is very good.

Air bags don't cut it for me. The vehicle was never designed to have weight placed on the chassis at that point. They are not like truck airbags that are designed to work entirely differently.

My advise is to just replace the springs with a known quality product.
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Follow Up By: GREG T11 - Tuesday, Mar 29, 2016 at 21:55

Tuesday, Mar 29, 2016 at 21:55
It is a no brainer if that is your constant load give or take. A good suspension upgrade is the cheapest thing you will actually get satisfaction from. It is when you are trying to mix and match so to speak, that brings the compromise part into it.
A lot of people here run a dedicated touring vehicle that is built specifically to run at a certain load lucky buggers. Then there are the rest of us that have to compromise.
As someone said, they are built to ride comfortable to a degree for a market segment that on the whole will never load them like a ute of old.on a daily basis..
I ton or 1170 kg is a myth unless you place at least half it on your bonnet .
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Follow Up By: Member - Kirk L - Wednesday, Mar 30, 2016 at 14:40

Wednesday, Mar 30, 2016 at 14:40
Yep springs it is. Was very weary of air bags but some say they are great and some say don't. I have upgraded springs with a 2"' lift now but just bleep springs and they don't do the job. Thanks for good advice people. Cheers.
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Follow Up By: Bob Y. - Qld - Thursday, Mar 31, 2016 at 20:27

Thursday, Mar 31, 2016 at 20:27
Worthwhile perusing the Kings Springs website, Kirk, and seeing what they have available for your model. A bit of a search will bring up a surprising number of options for most vehicles, especially popular models. Kings make springs for TJM, Fulcrum Suspension and probably a few other outlets.

Some time back I had the suspension rebuilt in my Falcon. Was able to check Kings options and ask for what has proved to be a good choice.

Bob



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Reply By: carl h2 - Tuesday, Mar 29, 2016 at 17:57

Tuesday, Mar 29, 2016 at 17:57
Hi Kirk mate of mine had the same problem with his ford ranger does a bit of 4wd and tows a horse float put Air bags on it sits level and has had no problems in the last 2 years TJM fitted them.
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Reply By: 671 - Tuesday, Mar 29, 2016 at 21:39

Tuesday, Mar 29, 2016 at 21:39
I have done research on airbags and have checked out the cracked chassis problem and it seems air bags don't cause this but overloading or severe use.
---------------------------------------

Kirk

This is what causes bent chassis. donkeyIt is not so much overloading but incorrect loading that does it. The problem is too much weight too far back behind the axle.


In these photos of carts lifting donkeys, you could put all the heavy springs and air bags that you can find between the carts and their axles and the back will still go down and the front will still go up.

If you replaced the donkeys with a Clydesdale horse, the horse would most likely remain on the ground. If you then pulled the cart over rough ground with it bouncing up and down, all of the heavy material behind the axle may eventually snap the cart in half at the axle. This is what happens to car chassis.

This is where so many car owners come unstuck. They think lifting a sagging rear end with an aftermarket product is all they have to do and their problems are over. Unfortunately the excess material down the back is still there and the chassis is still at risk.

The only solution is move some of the material forward or take it out of the car.

In your case what you have in the back of the car combined with that ball weight so far back behind the axle is the reason your suspension is sagging. If it was placed directly above the axle, the leverage effect would be eliminated and the car would be sitting up a little higher.

There is nothing wrong with the original suspension when the car is loaded correctly. When fully loaded the springs are supposed to be flat with the front eye of the spring down to the same height of the axle or lower This will then result in some degree of rear wheel steering in corners which increases stability.

The second last and last post with the small photo in this link roll steer covers it briefly.


This link explains it in more detail roll steer drawings It is on semi trailing arm suspension. Read the first section and look at the three drawings. Just about all cars are set up like the centre drawing, leaf springs included.
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Follow Up By: Member - Kirk L - Wednesday, Mar 30, 2016 at 17:47

Wednesday, Mar 30, 2016 at 17:47
Thanks mate. Yeah I do put all the heavy stuff as far forward as I can and balance left to right. Common sense really I guess. Even forward it is still over the axle and not really putting much load on the front. It's not easy but the springs I have are not the best even tho I got them beefed up. I will go with a good set of springs I can rate as best as I can to the situation. I'm pretty mechanically minded (diesel fitter) and understand what you are saying about the cantelever effect. The navshave a lot of overhang rear wards as they try to make the rear cab larger. Anyway I will get some better springs and that will make it better than it is.
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Follow Up By: Whirlwinder - Wednesday, Mar 30, 2016 at 17:52

Wednesday, Mar 30, 2016 at 17:52
I like your explanation of the problem.
My post below is saying just the same thing. Broken chassis do happen and Murphy's law always is in force.
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Reply By: Whirlwinder - Wednesday, Mar 30, 2016 at 16:58

Wednesday, Mar 30, 2016 at 16:58
Kirk,
You will continue to have the problem while ever the load is so far behind the rear axle! It is the same with all the dualcab utes.
If you put heavier springs or airbags on it you will just stiffen the chassis from the front spring mount back but there is still all that down force BEHIND the axle. That down force behind the axle makes the chassis act like a see-saw and the corresponding weight comes off the front until the chassis bends. Simple physics stuff.
The correct way and I believe the only way to fix this is to put the rear axle under the load by having the chassis lengthened by about 500-600 mm. I know it sounds a bit extreme and expensive but I have been through this exact problem with a semi goverment Ford Ranger which was loaded just under it's GVM. It was a dog to drive! I drove a similar ute that had been lenghtened and the difference was amazing. All the jerking (as the chassis flexed uncontrolabely) was gone, the front wheels felt like they were actually on the ground and the rear springs could easily carry the weight because the front wheels were now doing their share.
From memory the cost to lenghten the chassis was about $6500 which included the engineering certificate.
You will lose a bit of ramp over clearance but not much.
As you are out and about on your daily driving keep an eye out for dual cab utes of any brand and you will see loaded ones that look a bit "bent" but maybe not as much as the one below.
A good example of the correct set up is the Landcruiser dual cab ute/trayback. The axle is under the tray, not right at the front of the tray.
Anyway, best of luck with what ever you do.
Ian

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Follow Up By: 671 - Wednesday, Mar 30, 2016 at 19:36

Wednesday, Mar 30, 2016 at 19:36
"A good example of the correct set up is the Landcruiser dual cab ute/trayback"

----------------------------

They look better but they are still not unbreakable.

You have most likely seen this magazine story.bent utes I have a copy of the magazine that story was published in. It contains a couple of photos that were omitted from the copy they posted on the net. One was a very new looking grey dual cab Cruiser with a badly bent chassis. The tray had a canvas canopy so I don't know what was in it. About half a metre of the draw bar of a trailer was also visible.

Whatever was in the back plus the draw bar weight was too much for the end of the chassis.

The tow ball weight may be the main culprit in many of these cases. It can be well under the maximum specified weight but if the car manufacturer says a WDH must be used for any weight over a certain amount and the ball weight is exceeding it, that will definitely overstress the chassis.

The handbook for my car says a WDH must be used for any ball weight above 90 kg. The maximum is 180kg.

If Nissan says the same thing then Kirk's 220 kg could be far too much unless he is already using a WDH.

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Follow Up By: Whirlwinder - Wednesday, Mar 30, 2016 at 19:59

Wednesday, Mar 30, 2016 at 19:59
Yes 671, you are absolutely correct. The Landcruiser design can still be broken by overloading or bad loading but the concept is still the right one.
How many trucks, and I mean trucks not 4wds, do you see with the rear axle largely in front of the load?
The answer to the whole problem lies in putting the axle under the load.
Ian
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Follow Up By: 671 - Wednesday, Mar 30, 2016 at 23:10

Wednesday, Mar 30, 2016 at 23:10
Whirlwinder
I can't remember ever seeing a truck like that but plenty of 4wds are like it.
My 03 Hilux single cab 4x4 has the axle slightly forward of the centre of its Toyota aluminium tray. It looks wrong but if you load it correctly it works.

The first thing I noticed when I bought it was the tyre pressures listed in the handbook were the same at the front regardless of load. The rear varied depending on load. This would suggest that a correctly distributed full load should not increase the weight on the front suspension.

This is most likely part of the reason for the slightly forward position of the rear axle. The rest would be connected with weight distribution, suspension geometry, tyre size pressure and slip angles etc etc. There is always a lot more to the design of a car than meets the eye.

During the nine years that I have owned it, it has been everywhere from coastal mountain tracks to the Gunbarrell Highway but always around 200 kgs under GVM. On one occasion though on a short sealed road trip, it was loaded to the maximum capacity of both axles. It went over a weighbridge at its destination. There were two people in the cabin and the load consisted of hundreds of small metal items. This made it easy to evenly distribute the load.

The car looked level from side on. There was definitely no sign of the rear sagging.

All of these utes are fine when they can be fully loaded in that manner but few people can distribute their load like that. Unfortunately if you want to take one to its maximum capacity you have to be that exact.

This is not the fault of the car manufacturer. They can't make one that is adjustable to suit every owner. If it won't carry all of your gear without the rear end sagging then the only solution is to remove some of it or buy a bigger car.
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Reply By: Nomadic Navara - Wednesday, Mar 30, 2016 at 23:08

Wednesday, Mar 30, 2016 at 23:08
Before adding air bags, read this article.


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Follow Up By: Member - Kirk L - Thursday, Mar 31, 2016 at 10:22

Thursday, Mar 31, 2016 at 10:22
Thanks Peter. Pretty much common sense to those with half a brain really. Not rocket science but basic physics. I didn't realise it was such a huge problem tho. Funny how so many vehicles of all makes built that are built so close to the wire and not with too much extra strength to allow for what we do with and to our vehicles. Maybe we need to drive unimogs or hummers. I guess a lot of it is to do with how we drive in some of the places we go. Respect the gear and it will respect you. Thanks all for information.
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Follow Up By: 671 - Thursday, Mar 31, 2016 at 20:11

Thursday, Mar 31, 2016 at 20:11
"I didn't realise it was such a huge problem tho"
-------------------
Unfortunately it is a huge problem but from my observations on the net and while driving in the Outback, is seems to be confined to tourists. They are the ones who take half their house with them on every holiday or camping trip.

If local people out there were constantly bending their chassis while just going about their usual daily routine, the car manufacturers would have done something about it decades ago.

One more point that I forgot to mention is the load in the seats. All of those utes have been designed to carry large people. That means a fully loaded dual cab should have the weight of five football player size people in the cabin. It is no use designing them to carry no more than the weight of five people half that size.

I read somewhere that Toyota works on 85 kg per person plus 15 kg each for clothing, briefcases, hand bags and all the other things that people put in the front with them. That means if you want to load a Hilux dual cab up to the max, you need 500 kg in the cabin before you start loading the back. If you can't get that much in the front then you can't take it up to maximum load without overloading the rear end
.
When you do set one up with 500 kg in the front you will have 300 in the back seats. The rear axle is not all that far back behind the seats and the springs usually extend forward up under them. That could be another reason why the axles are placed in that position.
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Reply By: 9900Eagle - Thursday, Mar 31, 2016 at 20:24

Thursday, Mar 31, 2016 at 20:24
No matter what anyone says about who loads what where and by how much, air bags put point loading on the chassis in a place that was never designed for it.



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Reply By: Swaggie - Saturday, Apr 09, 2016 at 14:03

Saturday, Apr 09, 2016 at 14:03
I have a a Hilux 2004 SR5, I've added a lot of accessories including full length Black Widow Drawers, Kaymar Rear Bar, ARB canopy plus a 6x4 loweline roofrack. I've just updated with Tough Dog Suspension. Leaves are 500kg constant with Adjustable Shocks with 9 settings with about a 700% range according to Tough Dog from 1~9...

Well I couldn't be more happier so far, had them on for 5 months. I had it fitted all around...


Cheers..
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Reply By: Member - Iggy - Thursday, May 12, 2016 at 17:00

Thursday, May 12, 2016 at 17:00
G'day. I have a 2006 D40 on which I had suspension upgraded in 2012 by Outback Suspension...unfortunately located at Factory 2/43 Vinter Ave, Croydon VIC 3136 [03] 9723 3809.

I went to them on the recommendation of my next door neighbour...an ex-truckie/truck mechanic. He had his first 4x4 done around 12 years ago & with much trepidation handed over a large slab of money. When he came to replace his 4x4, he booked the brand new replacement in for an upgrade before pick up, something which he has done with each replacement vehicle ever since.

Essentially what happens is:
1. rear bump stop cut off the axle & welded to the frame rail above the axle facing downwards.
2. a set of King Springs [made to Outback Suspenion specs...I believe they are what he calls '100 lb' springs] set over the rear axle aligned with the relocated bump stop.
3. front springs replaced with a 30/40mm lift King Springs
4. Koni 80 series shock absorbers fitted all round.

The cost was around $2200 but did not include replacing the shocks but did include some front end suspension parts which were damaged as a result of a previous suspension upgrade attempt. I already had Koni 90 series shocks fitted.

The first trip after fitment was from Maffra to Alice Springs via Binns Track; Binns Track to Katherine then to Kalkarindji [Wave Hill], Townsville, Rockhampton, Longreach, Winton, Blackall, Camerons Corner, Broken Hill, Mildura then home.

On the Alice Springs to Katherine via Binns Track leg, the couple with whom I was travelling rolled & wrote off their Tvan. I was already quite loaded but took a 6 foot x 4 foot x 1 foot bag of clothes [for the community op shop at Kalkarindji] from them as they needed to salvage stuff from the van. I can only assume I was 'near' [I suspect over] GVM but the Navara did not sag at the rear & handled flawlessly.

May be worth a phone call to get more details.

Regards
Ian
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Follow Up By: Member - Kirk L - Thursday, May 12, 2016 at 17:35

Thursday, May 12, 2016 at 17:35
I have a couple of days ago purchased a set of old man emu springs and shocks for rear but at this point they are still in the back of my truck at macakay Nissan as the engine shit itself 2 days ago at 72000km. They are still pulling head off (10 hrs labour) to asses. Oil in water and water in oil. Done a lot of research today and sounds like these 2.5 engines are a good boat anchor! Have heard a few instances of cracked blocks!!! There will likely be a lot of politics and I may even return springs and get rid of said piece of rubbish vehicle. See other thread for updates.
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