Suspension Upgrade – Coil Over Leaf

Coil over leaf installation

Coil over leaf installation

It’s no secret that the leaf spring setup in the 70 series cops criticism from so called real 4wd’s that come with coil springs standard. I will admit that it doesn’t respond in some conditions but coil springs also have their problems.

While the longer leaf springs introduced in the 78 series deliver a softer ride than the previous 75 series, they were still pretty firm when unloaded. Loaded up – it’s a different story. On camping trips it’s like driving a different car as the extra weight enables the leaves to flex. All of a sudden your firm daily drive becomes soft and comfortable.

The downside here is that it always cost you in clearance. In mine it used to be a couple of inches in clearance as the top leaves sat down on the lower ones. I didn’t change the original setup for 10 years as there was no reason to although it was slowly sitting lower and lower (loaded and unloaded).

It was my first large trip with our kids in 2012 when my springs finally didn’t perform appropriately. We went for 4 weeks up and down the east coast – it was our first remote camping trip with our kids. They were 4 and 2 at the time. When I loaded the car up I’d never seen it sitting so low. The shackles on the rear were stretched back further than I’d seen them before. And we were just heading off for a 4 week trip. Overall it went well.

Particularly through the high country in Victoria, I was dragging the tow bar over rocks as we ventured across creeks filled with boulders and up the side of steep, rough hills. When we returned we unpacked the car. Normally as you pull heavy items out you’d hear the creek from the leaf springs as they slide back up into position. But not this time. They pretty much stayed down.

So I started looking for options to upgrade. I was really disappointed when I did this. None of the major 4WD accessory shops had what I would deem suitable solution. Everyone wanted to increase the capacity of the leaves but I knew this would mean a harsher ride when unloaded and less flex when 4WDing. They also wanted to lift the vehicle 50mm above the standard height. Let’s face it, Troopy’s have pretty good clearance from standard and I didn’t want to do anything that might impact reliability drive train wise. So I went on the hunt for a better alternative. Something that would improve the ride (around town and off road), carry weight better, be reliable and most importantly – affordable.

I looked into Air Bags, but the Air Bag Man said if I wanted it for 4WDing that it wasn’t a practical solution. Great for towing etc but useless where flex is required. His words, not mine. I wasn’t convinced that replacing with large springs was the answer either. I went to a couple of 4WD shows and saw all different kinds of setups (I.e. SAX etc) but they were expensive.  I wasn’t convinced they were going to make the difference. Everyone was happy to take my money though!

So I Googled, and Googled some more. I came across a single forum blog that talked about a coil over leaf concept. Intrigued, I continued to research this option and feedback on it. I didn’t find a lot. I was concerned that this meant one of two things.
  1. Not many people were doing it
  2. Or, If they were they weren’t complaining about it
I found two people that do this in Australia (there could be more).
  1. Fred’s 4WD Conversions.
  2. Another company in Vic – having trouble finding on the web now.
NOTE: There appears to be a lot more written about this in forums now. But when I was browsing through them there was a lot of misleading information and personal opinion vs. fact.

NOTE: I believe Fred from Fred’s 4WD conversions sold his business. I believe it is now run by On Track Diesel Repairs.

After discussing the solution with them I went ahead and did it (The conversation with the VIC guy convinced me – Fred wasn’t one for conversations). The VIC guy also recommended that I get it installed (welded) vs. using the bolt on kits that are available. He supplied both but said the welded solution to the diff housing performs better than the one that sits on top with U-bolts (Again – their words not mine).

I also went and inspected the process being done on Qld Ambulance vehicles (70 series utes) by Fred that we’re having GVM upgrades in Brendale, Qld. I spoke to Fred about it causing issues with the chassis due to the load point moving. He indicated that the Troopy’s are braced at the point of mounting (see photo below) and that after close to 30 years he’s never had a single failure. More importantly, he was doing the upgrades on vehicles getting GVM upgrades that were working well above the weight I would be throwing on my car – although maybe not the off road conditions.

As I don’t live in VIC, my installation was done by Fred from Fred’s 4WD Conversions. It was done on my driveway at home in a couple of hours.

He basically welds a coil Spring mount on the back of your rear diff housing and another in the middle of your rear chassis arch. He modifies the brake lines so they are out of the coil spring path and then adds the coil spring. Depending on the weight you carry he had a range of spring options available – he recommended the lightest option for me (650 Kg). I followed his advice.

He would have fitted the other options but mentioned it would impact the unweighted ride, level of comfort and shackle position when unloaded. He said that you want to keep some angle on the shackles to avoid them bending up the wrong way on the return. I’ve experienced this on my old G60 a few times. Easy to fix but an inconvenience.

Because heavier springs were slightly longer and wouldn’t sit as much unweighted, it would be more prone to shackle reversing. The front springs were done at the same time with new shocks all round (supplied by Fred).

So was it better. It was like a different car. It handles better on the road, takes bumps and corrugations better and moves more freely than before. I gained four inches (due to sag on originals) and now the top of my tyre is in line with the top of the chassis rail. Fred indicated that he prefers to set the car up so it aligns this way (it has the right shackle angle).
View of shackle angle after 4 years

View of shackle angle after 4 years

How about when it’s loaded. The best part is that when loaded up the same as before, I’m only giving up approx. 10mm. This means that when I’m in the rough sections the springs can compress a lot further before hitting the bump stops and bouncing the body.

Also, I believe that the friction from the leaf springs actually help to control the coil spring action under heavy work loads and assists the shock absorber control the coil spring – best of both worlds. This modification was done in 2012, and after 4 years it’s still going well and no problems to report.

What do you get;
  • Rear
    • 2 King coil springs (special to Fred – has code written on spring for replacement which is why I didn’t spray over the springs when I had the body rust proofed again)
    • 2 shock absorbers
    • 4 brackets (4 coil Spring mounts)
    • Adjust brake lines from coil Spring path
    • No changes made to original leaf setup
  • Front
    • 2 King coil springs
    • 2 shock absorbers
  • Steering
    • 1 new steering dampener
Pictures of the rear installation. Front is standard replace. This installation cost me around $2,200 including modification registration with Queensland Transport (all done by Fred). Other points to consider / Final thoughts
  • Don’t replace your old springs.

In conversation with both suppliers, they recommended not to do any work to the existing sagging leaf springs. If you have new leaf springs that are holding the vehicle up obviously they are restricting the coils from carrying the load and doing the work. If you’ve already bought new leaf springs then this solution will still work, but you’ve compromised the benefits the conversion will provide. The new coils supplied will pull the leaf springs back up into position – as can be seen on my car.

  • Greasable shackles.

While Fred was installing my setup, he mentioned that adding high quality  greasable shackles to the rear leaf springs can improve their movement and make the ride feel even softer. I haven’t done this as I prefer the genuine pressed in bushes vs. the aftermarket slide in ones from a reliability point of view (personal opinion)

  • Two spring sets

You can buy two sets of springs for the rear. You could buy a lighter set for day to day and if you really carry a heavy load when heading away, buy a second set for that task. The rear springs are easy to take out and only cost about $200 each. Replacing the springs can also be done a lot cheaper than replacing the whole leaf assembly setup which is approximately $1200 just for the rear and a lot more complicated to replace.

  • Rear only or front and rear

Both suppliers recommended doing the front and back springs at the same time with shocks to get the best results. When I discussed just doing the rear Fred basically refused to do the job. He mentioned that when the rear is firm and the front isn’t changed, that the vehicle doesn’t handle well. I must admit that although the front looked ok, it had also sagged a good 50mm.

I hope this helps you. If you are considering something similar and wanting to speak with someone who’s done it or feel the difference please reach out.

This is an independent view of this suspension solution. I am in no way associated with any organisation mentioned here and I don’t receive any payments from them.

2 thoughts on “Suspension Upgrade – Coil Over Leaf

  1. Tod Maclean

    Interesting read. Have had my troops since 1990. Always had a sagging problem ( mostly passenger side up front but all sag. The passenger side front mostly because of steel bull bar PTO winch which is mounted about 5 inches to the pas side of centre and steel cable on it. Duel batteries on the same side. I have had the springs reset about 3 times over the years. Finally added the airbags at home myself. ( the air bag man rear and firestone upfront ) it has fixed the problem, It is nicer to drive loaded and a bit uncomfortable when empty. Still trying to find the right PSI for empty but I only drive it 6 km to and from work so it doesn’t cause me much trouble. Hope this adds to your page. Tod

    • ChickoChicko

      Hi Tod,
      Thanks for your comment. I have to agree with your thoughts – if it wasn’t for the advice from the air bag sales man himself I would have gone down that route. Just wondering if you go 4WDing, does your suspension still flex with the air bags in?

      I’m also keen to understand your PTO winch setup? What’s involved in getting that installed?

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