Death Wobbles in HZJ75 ute

Battle Truck 75
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Death Wobbles in HZJ75 ute

Unread post by Battle Truck 75 » July 7th, 2011, 11:21 pm

G'day Guys,
Just wondering if anyone might have experienced the death wobbles in their 75 series and been able to cure it?

Bit of background.
I have been going through a bit of a trial and error exercise over the past 12 months when I decided that the harsh ride and limited flex of my utes suspension which comprised of some extra heavy duty King Springs (8 leaf) in the front and I suspect some sort of aftermarket rear leaf packs fitted with 160mm pin to pin extended shackles was all I could handle after owning it for 15 years.

In theory I figured one of the better ways to achieve my objective of a softer ride (only has alloy tray and alloy front bar and rarely used to carry heavy loads) and more flex was to opt for a longer (overall along the arc) springs. I then proceeded to fit up a factory set of Toyota 78 series rears to the back and my original 75 series rears to the front. These were fitted up with my original 160mm pin to pin extended shackles. They however could only be fitted up once I had the springs reset to bring each eye closer together as I did not want to butcher the vehicle by relocating hanger mounts.

While it did not take me long to realise this combination does not work, as the springs would not carry any load and essentially were flattening out resulting in the shackles up against the towbar at the rear and bullbar at the front. It did however take me considerable time to figure out exactly why this was occurring no thanks to what I would have previously considered three separate reputable and well know suspension specialists in Brisbane. The suspension at both ends were in and out many times with alternative people attempting to improve on the previous persons reset, using different load bearing springs which were also reset to come into play earlier and the inclusion of extra leaves at each end to try and support the springs and prevent them from collapsing. All of this proved to be in vein and a complete waste of time and money.

It was eventually discovered that spring lengths, shackle lengths and the distance between the fixed hanger points on a vehicles chassis all need to be the correct lengths to prohibit the spring when under load from elongating past the point permissible by the shackle subsequently resulting in the spring 'locking out' Wanting to keep the long springs and not wanting to relocate the hangers, the only option was to build some super long shackles 300mm pin to pin in the rear and 270mm pin to pin in the front. This proved to be the solution to the springs collapsing and I was able to go down to five leaf + single load bearing in the rear and a 6 leaf pack in the front (did have 9 leaves in front at one stage!)

While I agree that these are pretty serious shackles they were engineered to compensate for there extended length, gusseted and braced. This combination essentially achieved what I intended, which can be seen from the forklift flex photos which I will post shortly.

This was until I attempted to travel down the road resulting in some serious death wobbles. Which at this stage are still undiagnosed. Even though I had 10 and 11 degree caster wedges on the right and left sides respectively as recommended by the front end specialist, new Rancho XL9000 shocks, new bushes, new tie rod ends, new wheel and new swivel hub bearings approx 10000km ago which still feel tight a serious shake develops particularly when a bump in the road is hit at anything over 50km/h.

Vehicle has just gone in for a wheel alignment which shows the caster at LH +2.78 and RH +2.51 degrees and toe and camber are all within normal limits.

Power steering box does not appear to have excessive play. Possible contributors that could be causing the issue include my 35in MT Claws which have about 60% tread. Death Wobbles have not been so regular since the second balance of these tyres and an expert tire and wheel inspection. While I believe the tyres are not helping my cause I do not believe they are the underlying problem but are rather exposing another issue. Same with my steering dampener which is still the original pee shooter. While I suspect there are better dampeners out there this one still feels good throughout its stroke. Before the fun and games with the suspension I was getting around with no dampener, no problems. The other potential issue which is likely not helping my cause is the excessive angle of my drag link. This is causing bump steer which again I think is not the main reason for the death wobbles but may be amplifying an issue. I am thinking of fitting a 60 series pitman arm (greater drop) to assist with this problem. Just wondering if anyone has also done this to help with bump steer in a 75?
As a last resort I have accepted that the long shackles in the front must be creating to much leverage particularly when considering the front half length of the 75 rear spring being used up front. For this reason I have had the front springs out again cut down to around the length of a 60 series rear and my old 160mm shackles have gone back in. This has also resulted in me having do the same to the 78 rears. But guess what still got the death wobbles even though its been lowered (still approx 4 inch of spring lift) and old shackles are back on - I could nearly cry. There was a bit of play in the left hand wheel bearing which we tightened up last weekend. I am thinking its time to go digging deeper in the front end. Even though the front end was reco about 10 000km ago which has been mainly done on tar I'm aware that swivel hubs could be a potential culprit. Just wondering if anyone knows what these should be shimmed to or what preload should be applied as standard and if anyone knows of anything else (U bolts and everything is tight getting good at installing and removing suspension components) that might be causing this predominantly Nissan problem before I start ripping my front axles out for another rebuild???
Thanks

STOIE
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Re: Death Wobbles in HZJ75 ute

Unread post by STOIE » July 8th, 2011, 8:55 am

I would just spend the ~$600 and buy a new set of springs for the front and back, that are std lengths.
Remove the silly 300mm shackles and fit stock ones...

The problem, as you have stated is simple... you have springs that are too long!
You have tried to overcome the physics of this by extending the shackle, which is the wrong way, you would need to move the hanger.
What you are experiencing is a result of over-sized shackles that are forward facing the the front, this means sideways movement of the axle is magnified through the spring, this is then transferred back to your shackle then back to the shackle hanger.
The length of the shackles in this case causes the problem because of simple physics.


I will see if I can make a rough diagram...

Sorry about the excess white space, anyway, basically what I'm showing would be the shackle and spring arrangement from birds eye view... the red line displays the movement, side to side of the shackle/spring opposed to the hanger. The longer shackles also provide the springs with more leverage to have a wider arc. Basically, as you can see, the longer the shackle the more it magnifies the vibrations...
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99' HZJ79 (GT28-68, Canvas Canopy, ~33 MT-117, Recaro, PTO)
86' Hilux 4x4 ExtraCab (2.2 4Y 5spd, Extractors, Webber)
05' Yamaha YZ450F (Tit-Pipe, Rekluse CoreEXP, Cycra Busters)
03' Yamaha WR450F (Staintune, FMF)
96' Honda RVF400 (Full Tyga RCV211, Full Tyga CF-Ex, Tyga Rears)

dogbox
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Re: Death Wobbles in HZJ75 ute

Unread post by dogbox » July 8th, 2011, 8:06 pm

what rims are you using have them checked for being true steel rims can be a problem as they are pressed not machined
have you had a wheel balance the type that has "fingers" not the center locater
an have you had the wheels finish balanced on the veichle
spent lot of dollar an still had the shimmies bad an the only thing that fixed it was to have the wheels balanced on the veichle

Battle Truck 75
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Re: Death Wobbles in HZJ75 ute

Unread post by Battle Truck 75 » July 8th, 2011, 9:46 pm

G'day
Thanks for the replies and suggestions.

If I could go into a shop and purchase a set of springs that would provide the kind of ride and flex I'm chasing I would have done so along time ago. However all products available off the shelf are just going to put me back where I started. This trial and error process however is pushing me to the limits and on many occasions I have thought about scrapping the lot and starting again.

As mentioned in the original post I have gone back to my original shackles which are still longer than standard 160mm pin to pin and have had the main and wrap leaves cut down to suit due to the issues with the extra mechanical leverage you described in you post. However this still has not solved my death wobbles.

The wheels fitted to the 35in Claws are an alloy 6 spoke 15 x 8. These have not given me any dramas in the past and have had a thorough look over by a wheel and tyre expert. I do believe that the tyres in particular are not doing me any favours however at this stage I think they are exposing an issue which may be rectified with a new set of rubber but really this is only masking an underlying issue. Worse come to worse though I will have to try a new set of tyres.

Since the second balance I do believe there has been an improvement. I was with the balancer when this happened resulting in approx 25g coming off the outside and 15g off the inside. The balance machine however was the centre type. I was not aware that any other designs existed or that you could do an on car balance. Can you please confirm if you are aware of anyone in Brisbane which has the ability to do these sort of balances.

I have found out today that factory caster for these utes was +2.5 (+-0.75) which makes my specs on the money. I also have found out today that the front swivel hubs on there own with TRE disconnected should swing with 10 -15lb of torque. I will be checking this tomorrow as at this stage I think this may be where my problem exists? However its hard to beleive there is a problem in the front end considering it was only rebuilt approx 10 000km ago however in saying that it has experienced a few very violent wobbles which potentially could have done some damage or loosened something originally when the longer shackles and full length 75 rears were in the front?

Keep the ideas coming

Thanks
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enragedcruiser
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Re: Death Wobbles in HZJ75 ute

Unread post by enragedcruiser » July 9th, 2011, 9:19 am

Dude u could use them shakles as a step ladder... to big who eva advised u to do that has no idea about how things work bigger is not allways beter

STOIE
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Re: Death Wobbles in HZJ75 ute

Unread post by STOIE » July 9th, 2011, 9:55 am

Battle Truck 75 wrote: As mentioned in the original post I have gone back to my original shackles which are still longer than standard 160mm pin to pin and have had the main and wrap leaves cut down to suit due to the issues with the extra mechanical leverage you described in you post. However this still has not solved my death wobbles.
Sorry mate, didn't realize you had done that...

Love the stacks by the way :P
99' HZJ79 (GT28-68, Canvas Canopy, ~33 MT-117, Recaro, PTO)
86' Hilux 4x4 ExtraCab (2.2 4Y 5spd, Extractors, Webber)
05' Yamaha YZ450F (Tit-Pipe, Rekluse CoreEXP, Cycra Busters)
03' Yamaha WR450F (Staintune, FMF)
96' Honda RVF400 (Full Tyga RCV211, Full Tyga CF-Ex, Tyga Rears)

dogbox
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Re: Death Wobbles in HZJ75 ute

Unread post by dogbox » July 9th, 2011, 7:03 pm

i get my tyres done at a truck an bus aglinmet bussiness but they must be balanced off veichile first then they do a finnish balance on the veichle which is basically just minor adjustment of the weights an it works for me

Battle Truck 75
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Re: Death Wobbles in HZJ75 ute

Unread post by Battle Truck 75 » July 9th, 2011, 9:08 pm

enragedcruiser wrote:Dude u could use them shakles as a step ladder... to big who eva advised u to do that has no idea about how things work bigger is not allways beter
Agree bigger is not always better. But considering the length of a 78 series rear pack this is the shackle length required when not wanting to relocate hangers. Shackle length is all proportional to spring length along the arc and the fixed distance between the hanger points as I have discovered the hard way. There is nothing wrong with longer shackles if you also increase the overall length of your spring, however there is limited benefit from increasing the shackle length when running standard length springs between standard hanger points. In the rear it worked a treat however issues are created in the front end resulting from increased leverage and sideways flex from excessively longer shackles and impacts driveability.

The photos were taken with a full length 75 series rear packs in the front
(load bearing spring removed but 9 leaves in total) bolted up to my original extended shackles (160mm pin to pin) and full length 78 series rears in the back with 300mm pin to pin shackles. Was getting around for a couple of months like this no worries and no death wobbles. Until a trip to Moreton Island resulted in the front springs deciding to collapse resulting in the front hangers leaning over up against the bullbar.

It was after this trip that it was decided to fabricate the correct length shackle to accommodate the 75 rears up front. This shackle was approx 270mm pin to pin which allowed me to drop back to a 6 leaf pack. However from then on it developed the death wobbles even though now my original shackles (160mm pin to pin) are back on and the main and wrap leaf have been cut down to approx the length of a 60 series rear.

After more work on the ute today involving refitting the cut down 78 series rears and original shackles to level the rear up with the front, it still felt sketchy no death wobbles but on the verge. Also removed the drag link from the pitman arm to see if there was any fee play or something suss with the power steering box. We discovered that there was a pooth tenth of play which we have eliminated through the adjustment bolt on top of the box. While this has stiffened up the steering which does add confidence when driving it, the ute was still on the verge of the shakes.

After a couple of test runs today I am tending towards the tyres being the culprits. There is a definite shake around 75km/h even on a smooth even section of road. This can be driven through and once at approx 80km/h the shake disappears, whoever as you get of the gas and slow down at around 75 - 80km/h it becomes a little sketchy again until more speed is taken off. This to me seems like a balance problem, as opposed to the inital death wobbles with the long shackles which seemed to eventuate at speeds over 50km/h when a bump in the road was hit which made me think something in the front end was not right. We rotated the tyres front to back and agree that the tread pattern on the rears which are now on the front have more consistent wear and less peaks and troughs in the tread pattern. Another test drive has shown that the shakes are almost gone and has instilled alot more confidence when driving my ute. Initially I thought the tyres were exposing another underlying issue however seeing that the front end has been rebuilt new bearings all round only 10k ago and I have just put brand new bushes, Rancho Shocks, TREs and caster wedges in the front which from the wheel alignment print out show everything within spec I am thinking my 35in Mickey Thompson Claws could actually be the cause. I suppose it would not matter how tight and well maintained your front end is if your tyres and wheels have an issue this is going to show in any vehicle. Just wondering what others think ?

Thanks

Gunsmoke
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Re: Death Wobbles in HZJ75 ute

Unread post by Gunsmoke » July 12th, 2011, 12:03 am

Wow that much flex in a ute is insane. Tyres may contribute but I dont like long shackles on the front. They give too much diff rotation and too much stress is placed on mechanical components when fitting large degree castor wedges.
Take the easy less expensive safe way...2 in lift, standard shackles , std 75 series springs and 12R33s....otherwise get a 78/79 series with coils and mod that.
Just my opinion.....leave the death wobbles to Nissans.

maddog_75
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Re: Death Wobbles in HZJ75 ute

Unread post by maddog_75 » July 12th, 2011, 12:21 am

its the tyres... i've had a few set of older tyres/rims balanced and got the wobbles. i bought a 2nd hand of near new tyres on semi old rims and problem solved :)

also check your bushings, though i've ran the car with blown bushings and it didnt cause wobbles lol

Battle Truck 75
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Re: Death Wobbles in HZJ75 ute

Unread post by Battle Truck 75 » July 12th, 2011, 9:56 pm

Gunsmoke wrote:Wow that much flex in a ute is insane. Tyres may contribute but I dont like long shackles on the front. They give too much diff rotation and too much stress is placed on mechanical components when fitting large degree castor wedges.
Take the easy less expensive safe way...2 in lift, standard shackles , std 75 series springs and 12R33s....otherwise get a 78/79 series with coils and mod that.
Just my opinion.....leave the death wobbles to Nissans.
Thanks Gunsmoke. The intention when this trial and error exercise started was to improve the flex and ride quality over the original 2in lift which the ute started with. Have had lots of comments that I should have done a coil conversion, put a pair of 80 series diffs under it or better still put the cab on an 80 series chassis. Thing is I wanted to keep the design essentially the way Toyota released the 75 and thats leafs all round, plus I don't have the time, money or expertise to really start moding the ute to the extent of a coil conversion. Really if I wanted a coil cab ute I would go and by a Nissan. But I'm a 70 series man and for better or worse thats why I will probably be buried with my ute. Definitely agree it was not doing me any favours when I had the long shackles in the front with the full length 75 rears with 6 leafs. Because they are so much longer than the original 75 fronts particularly the front half of the spring to the shackle end (which is the rear half when in the back) it created a situation where the rear half of the spring was much steeper than the front half. Even though I had 3 caster wedges stacked up on each other on each side (LH = 4,4,3 degrees and RH = 4,3,3 degrees) I believe that when I hit a bump in the road and the spring compressed further flattening the front half of the spring and rotating the axle forward not doing me any favours in the handling department and was most likely a contributor to the death wobbles.

However I believe there is a compromise which is why I have had the main and wrap leaves cut down from the full length 79 rears and 75 rears and my original shackles (160mm pin to pin ) have been returned. The photos taken with my ute flexed up were with these shorter shackles in the front but my long 300mm pin to pins in the rear. Still I reckon most would agree not bad for a full leaf sprung ute.

Like others have suggested I reckon you are onto something with the tyres being the contributors since the leaves and shackles have been shorten. I rotated the fronts (which are quite uneven and have significant peaks and troughs in the tread pattern) back to the rear which so far feels like it has sorted the problem. I am booked in tomorrow to balance these rears up which are now on the front which will hopefully result in problem solved and a 75 series which is designed as Toyota intended but flexes and rides a whole lot better.
Will keep you posted
cheers

ferral errol
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Re: Death Wobbles in HZJ75 ute

Unread post by ferral errol » July 13th, 2011, 9:29 pm

Your not fooling anyone hideing those huge shackles behind the rm williams mudflaps :truck: :D

spud79
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Re: Death Wobbles in HZJ75 ute

Unread post by spud79 » July 21st, 2011, 4:50 pm

hi mate,my 79 has a mad wobble,shake at around 70-80k's.sort of fixed it yesty,it was the tailshaft half hangin off.tightened it back up and she's brand new again,sort of....not really,but it is better!have a look at yours maybe?check all the bolts on the flanges both ends ,and the uni's too.hope you find the prob. spud.

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Re: Death Wobbles in HZJ75 ute

Unread post by emma.louise.purdie@gmail.com » October 12th, 2011, 11:59 am

Hi guys,

I have the same problem, but I havent put crazy long springs on my rig.. just really heavy ones.
My mechanic is dumbfounded.
Bearings, fine.
King pins, fine.
Swivel hubs, fine.
Bushes, fine.
Buggered if I can work it out...
Could it be caster?
we are about to replace the whole suspension kit, from bushes to dampner and back again, to eliminate it as a cause.
its scary how bad it gets, the whole cab shakes and you just about have to stop to get it to stop.
It is running a 5L holden v8 thats been built for low down torque, double valve sprung, fat cams, bored, the whole shemozzle.. she is a great ute, besides the death wobbles.
everything is new, except the suspension, and my tyres are pretty average, but I am pretty damn sure the tyres are only exhibiting patterns of wear from the mechanical issues further up the chain. New ones are on the list of to buy items though....
help!

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Re: Death Wobbles in HZJ75 ute

Unread post by maddogrc » October 14th, 2011, 12:05 am

where are you at? i might be able to take a look and swap over to a good set of tyres to check if it wobbles or not

after a few sets of tyres i found a new set fixed it

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