Outer Limits 4x4 Board

my zook hard top is now sprung over [wat a job it was]it only took 2 days to do but it ius done now any way the rear diff roles a bit wen u give it a bit of stike any help will be apresiated

SHORT T wrote:my zook hard top is now sprung over [wat a job it was]it only took 2 days to do but it ius done now any way the rear diff roles a bit wen u give it a bit of stike any help will be apresiated

You have increased the leverage on the springs by quite a bit, and you may find front does it too, in 4wd of course.
You may find this hard on uni's, too.
You either need stiffer springs, or a track bar, anti wrap bar, torque bar.
There is heaps of pictures on here, and info, try search button up the top 2nd from the left.
If your driveshaft angles are a problem, there is also heaps on that subject, also..

christover

what chris said.

There is a very fine balance between lift height, spring rate, driveshaft angle and axle wrap on a SPOA sierra. (This is part of the reason why no manufacturer ever produced a SPOA SWB car, the other being stability)

Generally, stock sierra springs will be too soft to prevent axle wrap once you go SPOA.

However, most aftermarket springs are for lift and so the driveshaft angles will go out if you add a lift spring with a SPOA. If you roll the diff up to point at the rear output of the transfer, you will have driveline vibration unless a CV joint or double cardan is installed at the transfer end of the driveshaft and you still run the risk of the rear tailshaft binding if the car does start to axlewrap.

Many sierras with SPOA end up with custom packs that are quite flat but relatively stiff. Have a look at the design of the trail tough "bonz eye" springs - these were designed specifically for a spoa.

Contrary to popular belief, it is impossible to build a "perfect" traction/antiwrap bar that will not hinder travel whilst also eliminating axle wrap.
SPOA Sierras tend to wind up and flog out the RHS rear spring even with a working traction bar .

sorry of this seems negative, I am a well known SPOA hater, but there are some worthy challenges to be overcome.

Steve.

Gwagensteve wrote: (This is part of the reason why no manufacturer ever produced a SPOA SWB car, the other being stability)

can i ask how u know this?

Gwagensteve wrote:
Contrary to popular belief, it is impossible to build a "perfect" traction/antiwrap bar that will not hinder travel whilst also eliminating axle wrap.

and this ?

mine was neva limited in anyway

ramped the same with it on and off

is it as much of a problem with extended wheelbase?

mad_landie wrote:is it as much of a problem with extended wheelbase?

yes u will have axel wrap if u have soft springs SOA or SUA no matter what ur wheel base is

not the axle wrap...

driveshaft vibes?

nvm thought it thru a bit more...

Here we go!

Name a SPOA SWB, factory- the shortest I can think of is the 4 runner @ 100" - and there was a reason why they came out of the factory with dead flat springs front and rear, and marginal front dorveshaft angles.

I think there was a european military thing or two with under 100" and SPOA, but not much under 100". These are low powered cars with short shocks too.

Can you think of any reasons why a manufacturer hasn't gone under 100" with a SPOA if it works so well in a SWB?

- IMHO there are too many compromises with a SWB and SPOA for it to be worth the effort to try and get it right, and engineers from manufacturers clearly think to too.

Axle wrap is far worse SPOA than SPUA. Also, because of the higher COG it creates (and correspondingly more dramatic weight transfer), axle wrap manifests itself more dramatically in a SPOA car than in a SPUA.

Interestingly, many desert race hiluxes in the US actually convert to SPUA from SPOA so they can run a soft spring through long travel without unacceptable axle wrap. (So did Fred Williams when he buit clampy recently.... wait for it... to counter axle wrap!)

Additionlly the greater driveline angles associated with SPOA in a SWB sierra will tend to make rear driveline life short even if the axle wrap was the same for both set ups.

Mad Landie - axle wrap will be as bad regardless of WB, but it will be more noticable the shorter the wheelbase (due to the exaggerated weight transfer)

Redzook - Just because It ramps the same with it in or not, doesn't mean it is not influencing the behaviour of the car. Our engineer asked Greg and I to model the behaviour of the rear axle and then work out the acceptable design of the traction bar. We went through every idea we had seen or though of and none of them were acceptable through the full rangle of travel- they all loaded up the springs one way or another or there were other unacceptable compromises. One of the key issues is what happens with the force that is being restrained by the traction bar? Generally, this goes into teh springs and becuase of this, (and the weight transfer) the SPOA SWB cars I have seen have had short rear spring life.

I am sure with the weight of your car, and the leverage of its width, the traction bar will twist the springs enough to ramp acceptably.

Gwagensteve wrote:Here we go!

Name a SPOA SWB, factory- the shortest I can think of is the 4 runner @ 100" - and there was a reason why they came out of the factory with dead flat springs front and rear, and marginal front dorveshaft angles.

I think there was a european military thing or two with under 100" and SPOA, but not much under 100". These are low powered cars with short shocks too.

Can you think of any reasons why a manufacturer hasn't gone under 100" with a SPOA if it works so well in a SWB?

- IMHO there are too many compromises with a SWB and SPOA for it to be worth the effort to try and get it right, and engineers from manufacturers clearly think to too.

Axle wrap is far worse SPOA than SPUA. Also, because of the higher COG it creates (and correspondingly more dramatic weight transfer), axle wrap manifests itself more dramatically in a SPOA car than in a SPUA.

Interestingly, many desert race hiluxes in the US actually convert to SPUA from SPOA so they can run a soft spring through long travel without unacceptable axle wrap. (So did Fred Williams when he buit clampy recently.... wait for it... to counter axle wrap!)

Additionlly the greater driveline angles associated with SPOA in a SWB sierra will tend to make rear driveline life short even if the axle wrap was the same for both set ups.

Mad Landie - axle wrap will be as bad regardless of WB, but it will be more noticable the shorter the wheelbase (due to the exaggerated weight transfer)

Redzook - Just because It ramps the same with it in or not, doesn't mean it is not influencing the behaviour of the car. Our engineer asked Greg and I to model the behaviour of the rear axle and then work out the acceptable design of the traction bar. We went through every idea we had seen or though of and none of them were acceptable through the full rangle of travel- they all loaded up the springs one way or another or there were other unacceptable compromises. One of the key issues is what happens with the force that is being restrained by the traction bar? Generally, this goes into teh springs and becuase of this, (and the weight transfer) the SPOA SWB cars I have seen have had short rear spring life.

I am sure with the weight of your car, and the leverage of its width, the traction bar will twist the springs enough to ramp acceptably.

umm of course there not built like that there designed for road and not hard offroad use
desert racing is complety different
and most are 4 linked in desert racing anyways

next ur gunna be telling me to convert to IFS cos there are hardly any solid axels getting manafactured anymore
so there for it must mean IFS is betta offroad

my rig dosent have leaf springs anyways


edit: it does in the front

my old swb zook ran yjs with 4 leaf fronts and 5 leaf rears i never had a problem with axle wrap and never need a traction bar, also was runnin 32 simexes, plus i had a dc in the rear shaft, also never flogged out any leafsprings.

Sounds like a pretty sound SPOA set up to me - YJ springs have been proved useful for SPOA in much heavier cars than sierras.

I imagine that with the wider spring and 5 leaves they would way harder to wrap than the kind of set up post people SPOA with - 3 and 4 leaf sierra packs.

Steve.

thanks for the help i will try to sort it out over the next few days do u think if the drive shafts are out a few centametres it will vibrate at all im puting spacers in the shafts hopfuly that will help thanks again