Ahc torsion bar and rear springs (1 Viewer)

[hokievet]

I have read on this for a while now but still am not clear on what will work best.

2002 lx470. Currently stock. I am wanting to go through and replace most all bushings as they are worn out and while doing so am wanting to also make some changes. System all works as it should. No issues. I just want to make some upgrades.

1. Front Ironman bumper with winch
2. White knuckle sliders
3. Rear dissent bumper with tire swing arm
4. Auxiliary 40gal tank in rear spare location
5. Rear adjustable upper and lower arms (in case I ever do get rid of ahc figured I might as well)
6. New upper and lower control arms (easier to replace than deal with the bushings and ball joints)

My plan is as follows:

1. Replace Rear springs with kings Ktrs-79
2. Front torsion bars with Ironman ones
3. Replace all ahc bushings

Question:

1. Will changing out the torsion bars create an issue for me? I want to retain the ahc but by adding all the extra weight I grew concerned that the stock torsion bars would be insufficient


Thank you all in advance

 

[GTV]

#1- Get Techstream up and running if you haven’t already. It is a must have, especially with AHC.

Techstream will allow you to read and correct your hydraulic pressures as you add weight and/or sensor lift.

If you get to a point that you have re-indexed and adjusted your torsion bars, there is no more adjustment threads left and your front pressures are still too high, then yes, you should upgrade your bars. Aftermarket bars will be much too heavy to use with AHC, if anything use stock TB’s from a standard LC suspension.

 

[JunkCrzr89]

1. Will changing out the torsion bars create an issue for me? I want to retain the ahc but by adding all the extra weight I grew concerned that the stock torsion bars would be insufficient

Yes, a major issue. Don’t install the Ironman TBs.

 

[riffman12]

Yes, a major issue. Don’t install the Ironman TBs.

Why? Because they're too stiff for the AHC? It sounds like he has quite a lot of extra weight

The AHC system works in tandem with the springs and torsion bars, so it's all about finding the right balance of springs/t bars to get to optimal AHC pressures with the weight you have.

For reference, I have an ARB front bumper, a roof tent, and a simple drawer setup in the back. With that setup I have the King springs and cranked my front bars and it got me into a good range of AHC pressures.

It sounds like you have a good amount more weight than I do with sliders AND a rear swingout. I'd almost consider getting OEM Toyota non-AHC land cruiser springs. But it' a bit of trial and error to see what gets your pressures in spec.

 

[hokievet]

If I were to reuse the stock ones…

I removed them to do lower control arms and to clean up the underside and was planning to install new ones.

Now that they are out, would I index them 5 splines just as if I was installing any aftermarket ones?

 

[GTV]

Why? Because they're too stiff for the AHC?

Yes.

But it' a bit of trial and error to see what gets your pressures in spec.

Correct. Every build is different, there isn't a one size fits all solution.

 

[GTV]

If I were to reuse the stock ones…

I removed them to do lower control arms and to clean up the underside and was planning to install new ones.

Now that they are out, would I index them 5 splines just as if I was installing any aftermarket ones?

I left just a couple threads holding the adjusting bolt in and re-indexed them as far as it would let me.

 

[hokievet]

I left just a couple threads holding the adjusting bolt in and re-indexed them as far as it would let me.

Ok. So doesn’t matter if it’s 4 or 7. Just shove it back in there. So get the front bolted in loosely and then get the back in place.

 

[OregonLC]

Your build is a lot of weight for the 100 series AHC to handle. You're likely going to be over GVWR when fully deployed with water, camp gear, pax, etc. While the Ironman spring rates work well in a heavy build, as others have said they're not really a good match with AHC. Doubtful the AHC would be contributing at all to load height and would likely be overwhelmed by the damping needs. You'd be over-sprung and under-dampened.

If you're really set on retaining AHC, you might want to try Land Cruiser bars/springs. Those might be a good intermediate match. If that's not enough then OME would be the next increment. Ultimately, though, I think you'd be happier with replacing the AHC system entirely. You've got a nice build planned, probably worth it to go all-in if funds allow.

If you retain the LX springs you'll need to be mindful that adjusting the torsion bars to get the truck to sit properly in the driveway does nothing to change the spring rate. Re-indexing and torquing them down still results in and under-sprung front end that will bottom out easily on impacts.

I see that you're also looking for rear links. For that I would suggest the Ironman as they use OE style rubber in the joints at both ends. The 2000 I built had Metal Tech rear links. Those had spherical bearings ('Jonny Joints') on one end. Those tighten up the handling and flex with less friction but contribute a lot to NVH being transmitted into the cabin. Stick with rubber. Ironman also has an adjustable panhard rod which will center the rear axle of a lifted truck laterally (though it can't fix the altered geometry).

HTH.

 

[JunkCrzr89]

So far @GTV is the only one providing useful info. The AHC can handle the weight with some minor adjustments. Ask @suprarx7nut and @kreiten, the latter of which ran the Rubicon in a fully armored LX470 with AHC.

 

[Tres Toys]

I just got through replacing the rear springs on our LX470 with a pair of used rear ones off our 80 Series yesterday. I only have maybe 250-300 lbs of gear in the back. The 80 series springs just brought the rear AHC pressure back within spec. I am even consider adding some spacers to bring the pressures down a little further. All the armor along with the large tank for your rig may require something beyond the KTRS-79 springs or adding some spring spacers to get pressures within spec. You might consider checking with the folks at SLEE to see what they recommend for springs in your application as I believe they have done a fair number of builds with AHC. Best of luck

 

[suprarx7nut]

I have read on this for a while now but still am not clear on what will work best.

2002 lx470. Currently stock. I am wanting to go through and replace most all bushings as they are worn out and while doing so am wanting to also make some changes. System all works as it should. No issues. I just want to make some upgrades.

1. Front Ironman bumper with winch
2. White knuckle sliders
3. Rear dissent bumper with tire swing arm
4. Auxiliary 40gal tank in rear spare location
5. Rear adjustable upper and lower arms (in case I ever do get rid of ahc figured I might as well)
6. New upper and lower control arms (easier to replace than deal with the bushings and ball joints)

My plan is as follows:

1. Replace Rear springs with kings Ktrs-79
2. Front torsion bars with Ironman ones
3. Replace all ahc bushings

Question:

1. Will changing out the torsion bars create an issue for me? I want to retain the ahc but by adding all the extra weight I grew concerned that the stock torsion bars would be insufficient


Thank you all in advance

I like the concept of adding minimal weight where possible. IE Aluminum armor vs steel. You've got a lot of $$ in that list. Might as well ditch the steel Ironman for an aluminum bumper that weighs far less and has much better clearance. If you do that, I bet you'll find the stock AHC torsion bars to be all you need. Life is much simpler that way.

Ironman torsion bars are a terrible idea for AHC, IMO. That would be waaaaaaaay too much spring rate unless you plan on storing a Geo Metro on your hood.

Replacing all the bushings is a great idea. When people switch from AHC to conventional and they say it "feels better" often they're just feeling new rubber. It makes a huge difference.

Get the King springs, minimize weight up front, use Techstream to inform your AHC decisions.