[tanshi]

We have a wide track sierra that has been RUF'd and narrow tracked with EFS rear lifted springs. both front and rear mounts were moved to fit the springs, and the shackle angle is around standard with standard length shackles.

We have noticed previously and again on the weekend that it often refuses to push one wheel up onto a rock or step, instead trying to push into the rock, or push the rock along instead. This results in the it just sitting there and wheel spinning. its on 33s and simply will not drive up some things that my LJ on the same tyre just cruises up without even knowing they are there.

IN the process of testing this we noticed that the spring sometimes prefers to compress horizontally curving the spring near the rear hanger and pulling/rotating the front shackles backward rather than compressing upwards and flexing up into the wheel arch. The diff pushes physically backward toward the firewall rather than trying to climb up onto the object.

I thought I would post this up here to get a few peoples opinions on why this is doing what its doing. We have our suspicions but wanted some input on other things it could be.

[JrZook]

Can you really compare the weight distribution (as well as lack of weight) combined with the slightly shorter WB of the LJ to the sierra? What's this particular sierra compare to other sierras? I wonder if a track rod on the front end would help this.

[tanshi]

i have never seen any other sierra do it.

we were out with another sierra and it didnt have an issue. And AAron's sierra is RUffed in a similar way but also doesnt do it.

Its not like we are talking about climbing 4 feet high rocks or anything like that.

Just pushing up maybe a rock 2 feet high...

[JrZook]

Odd.. Almost sounds like that wheel had no drive.

[tanshi]

happens both wheels,

its one of the main things about Dads car that stops it being Extremely!!!! capable.

It even used to do it when the front diff was locked

[31zook]

Is your LJ locked and the Sierra wasn't?

Only reason I could think of...

[tanshi]

nope.

Im LSD'ed rear, The other LJ out with us is completely unlocked.

We have wondered whether its a by product of the auto gearbox but ruled that out when we saw the spring flexing backward rather than upward.

[Gwagensteve]

I don't think this is unusual at all.

The trolley tug does exactly what you are describing, and as far as we can tell, it's because of the amount of spring lift it's running. For some reason the tug sits higher than pretty much all the other RUF cars I've been involved with, in fact, here's a photo of it in the process of doing it:



I think it's more a case of the car driving over the top of the springs, and that's easier to do if the axle is further away from the car.

The tug always ran about 2.5" to the bumpstops - more than was typical for our stuff.

Another factor might be that those springs are now wrecked. If the springs are showing a preference for bending up near the chassis mount, they're probably bent there, it's just not visible when the car is loading them. This will just make the problem worse. Again, this was the problem with the tug.

Steve.

[tanshi]

Hmm. might have to try a different set up springs then.

[zukmeista]

I think it must be the amount of arch in the springs, my EFS springs do it too.

[Jazzor]

Got any pics of the spring? even it just sitting flat in your shed?, that doesn't sound great :S.

[nick_bj40]

sounds to me the shakle angle is too steep and the spring has no guidence on which way to go so its trying to invert the shakle

if the shakle mount was further back it would allow the spring to flex upwards like the axle wants it to do not downwards like its trying to do whilst the axle is pushing up making the spring flex where it can (which is usually at the rear about 5-6inch from the rear spring mount resulting in broken/bent springs) while steve has a good point as you can see in the photos the shakle is 'pointing backwards' while some positive angle is to be expected with droop excessive angle is working against the spring resulting in the axle trying to push up and the shakle reacting fast enough for a smooth action as to expected. it is essential to get the spring and shakle "working" in conjunction with one another

[tanshi]

I might redrill the shackles shorter to improove the shackle angle and test it.

[tanshi]

well the front springs were well the truly rooted. swapped them out for new ones.

it still does it unlocked now. but onces the front is locked it is heaps better.

i think we need to take some rate out of the front springs though as it now doesnt flex to the bump stops.

[3cyl]

Even looking from back here at my keyboard I can see the springs are wrapping. Tell him to buy a coily... Oh and he should sell me that old thing cheap.

[3cyl]

Though you'd think it'd wrap less with the front locker off. What's it do with the hubs unlocked in the same gear?

[tanshi]

spins one less wheel.

[zooky08]

My old sierra did the same thing on ome springs. Springs bends just infront of the rear spring mount

[3cyl]

Maybe that's the problem when you try to use the same component for bendy travel AND axle location. I think my fronts might do it mildly and I've seen my rears wrapped in some Ripley pics.