FJ 60 information

[dieselcruiserhead]

It largely depends on your finances. For example if you go to 4.10 axle gear and/or a locker you will need to remove your front axle shafts at which point I think it is a very good idea to replace your birfields as they do break and *are* the weak link on a 60, period. But if leaving it stock with the stock gearing just bring a spare.

I never broke one until just a few years ago. It is amazing what I got away with because I've seen them pop on nothing before. Google search Longfields, worth their weight in gold according to me, for any part time 4WD vehicle.

 

[ntsqd]

dude, SOA's have spring wrap problems that result, typically, in a broken pinion shaft if left alone. The oft stated 'cure' is some sort of traction bar. The problem with these is that they put the main leaf in a bind and substantially decrease the fatigue life of the spring. I know there are lots of folks who say it's a non-issue and that it works fine. No doubt one or more will post here about that.

They haven't completely done their homework.

There is no way that the common traction bar design(s) used have a travel path that is close to the path that the axle housing would naturally take if the traction aid were not there. It simply can't happen. Due to the bending of the main leaf the arc of the axle housing travel path is not a constant radius, but all of the traction bar designs are a constant radius because they are a constant length. The only reason that they work at all is because of compliance in the main leaf and in the front spring eye bushings. The bar alternately bends and stretches the front portion of the main leaf beyond what the norm would be were the traction aid not there.

Those with a shackle that supposedly cure this overlook the fact that instead of binding the main leaf they force a change in the pinion angle through the range of travel while there would be only a small pinion to non-existent pinion angle change if the bar were not there. That means that the main leaf is being forced by the traction aid into a varying 'S' curve through the travel range, which increases the fatigue of the main leaf.


So sure they work, but for how long? Eventually one or both main leaves will prematurely fail from fatigue. That's a gamble that I'll not take or advise becaus ethere is no way to predict when it will happen. For those who have trailer queens and do rocks it's not as big of a deal. For those who get way out there in the boonies it is a very big deal.

I see only two reasonable solutions, and neither is very appealing. Either put a shackle at both ends of the spring and use the traction bar to locate the housing and define it's travel path; or put a floating cage around the axle housing that is attached to the spring and use the traction bar to locate and define it's travel path.

 

[dieselcruiserhead]

Or just add several leafs which I think you should do anyway, solves all problems and negates a lot of the problems most experience with SOAs at least related to the suspension itself...

 

[cruiseroutfit]

Tom, as usual you are right on the money with regards to traction bar issues. Its been debated since SOA's started happening (the PO of my company started doing them in the early 90's ) and its like not going to go away anytime soon. Many companies have built what they consider to be the end all design for a traction bar but as noted they all have a trade off which in most cases is the stresses added to the front half of the rear main leaf. There was a local Cruiser shop (DJ's Traction Systems) that had a design for a traction bar that was a bit different in this regards, sadly it never took off and he closed his doors several years back (I bought the majority of his Cruiser inventory but not the traction bar stuff). I'll try and dig up some pics of the system he designed and marketed for Cruisers. SL Cruiserheads and several ExPo'ers will remember his setup, some might even have pics of it installed?

This leaves you with two options. Run the traction bar rightfully knowing it could cause issues down the road, but banking on the good track record that may Cruiser owners have had, with little issues. I know that doesn't sit well with some, and take it for face value, but I have customers with traction bar equipped SOA's that literally have hundreds of thousands of miles on them, cross-country, Moab's hardest trails and years of daily driving. You'll find this situation repeated with many users, not to say a spring failure (or more commonly a traction bar failure in my experience) won't happen.

Option two is to not run a traction bar and let your springs suffer the consequence. Its no mystery that stock'esque light rate springs will "S" out in a hurry, that or they crack most often right at the u-bolt plate. However, I have had extremely good luck with using beefier springs, often with thick overload leafs on the bottom of the pack in conjunction with an SOA. Its no secret that we often use modified OME leaf packs on our SOA's and have done so on 40's, 45's and quite a few local 60's and 62's and even a 70 Series that a local owns. Now on your typical lightweight build 'rockcrawler' build, these springs will leave you lacking flex and ride quality versus say a stock flat spring... however on heavy rigs with big winch bumpers, tire carriers, tools, drawers, battery systems, etc, they have proven to be a very good option. For example I run them on my FJ40, (actually using OME 60 springs on the rear and OME 40 springs on the front) and have no notable axle wrap issues and the springs have held up nicely over plenty of on and off road use. Do I lose travel due to this, sure, but I have nice heavy springs that don't sag when I severely load the back of my rig, put the tongue heavy trailer on back and hit the road. Its not an options I suggest to the average LC SOA customer, in fact unless they really have a heavy rig, its likely going to leave them less than satisfied with the ride and flex. Add to the equation a rig that's more likely to be used between a mix of difficult trails and long distance driving with an above average payload and your sitting pretty nicely.

Its important to note that Land Cruiser axle wrap issues are not exclusive to SOA applications in fact I have customer running traction bar setups on SUA setups too. They are just far more common in SOA applications due to the fact that stock, low spring rate and "soft" springs are most commonly used in SOA applications for the added flex, ride and parts availability and that common thick/overload equipped lift springs are just too tall for an SOA. LC's with custom low spring rate SUA lift springs (such as custom Alcan springs) can have similar issues with wrap. This is mitigated with SUA lift springs often by having far more leaves and a thicker overload/anti-wrap leaf on the bottom of the pack. Right back to my note about using thicker/overload equipped packs on an SOA and I think you can have a reliable SOA setup with no issues.

Likewise the actual failure point of axle wrap can be somewhat mitigated too. I use CV driveshafts front and rear on SOA builds whenever possible. This allows use to nearly point the pinion at the t-case (we address all oiling and caster issues accordingly). With a ~0* pinion angle relative to the driveline, a bit of wrap will not cause the same issues as say a 5 or 10* angle, the pinion simply won't bind as soon. That bind equates to a broken pinion.

A couple of local SOA Cruisers we've setup using modified OME packs:

(in this pic my FJ40 was SOA using stock springs modified with OME parts, its now got modified OME packs resulting in a near identical setup with a bit of added height as my payload has continued to increase )

(Brown 60 was SOA'd on OME springs not long after this pic was taken)

Now when I said "the simplicity and reliability of a quality SUA suspension lift is hard to beat when you compare the $1500 OME price tag to a $3000 SOA price tag." I really do mean it. Its easy for a 'complete' SOA setup to reach into the $5k+ range by the time we address all the aspect of the build. 35's lead to 4.88's, R&P changes lead to lockers, lockers lead to upgraded shafts, upgrade shafts lead to complete axle overhauls. One could hit the $10k mark by dropping off their Cruiser for an SOA by the time the last domino lands. Do I feel comfortable sending the customer on a 50k mile trip into South American and back when done, you bet... but if the customer needs dictate a 33" tire and payload, I'll talk him out of the SOA as quickly as possible. Johnathan is right on the money, for a typical 'overland' build, the SUA suspension fits the bill. $1500 and a set of new rubber and your done... seriously, your done. Spend that extra budget on other important aspects of your build, some of which could be debatedly more important than even a lift alone, such as a winch or on-board air? Different strokes for different folks.

Hope I'm not rambling

 

[cruiseroutfit]

Doh, all this talk on SOA 60's and I didn't even post a pic.

The same brown 60 as shown above, now on SOA with OME springs:

 

[the dude]

The axle rap associated with a SOA suspension is not limited to just Cruisers that have a spring over. It would be on all vehicles that have a SOA suspension set up.

That's most, if not all pick ups I believe?? Are you concerned about those rigs suspensions as well? I think they deal with it by adding very heavy springs.

I went with the shackle up front on my traction bar AND heavy springs. No issues yet with broken leafs.

This brings up a good point though. The OEM leafs on ANY Land Cruiser are hitting 20 years old as a minimum, and in reality should be looked at closely for fatigue and wear, with the easiest solution being replacement.

It's funny, I would have picked the only issue with a SOA cruiser is the bump steer up front at highway speeds on rougher roads and big tires. I just don't think the geometry lends itself to a great design for steering. Often "fixed" with hydro assist.

 

[Jonathan Hanson]

The SOAs that really make me cringe are the large American trucks with six-inch lift blocks between the spring and axle.

Dude, I'm not sure what you mean by "lots" of broken birfields, and I'm no expert myself; I merely pay a lot of attention to working Land Cruisers and Land Rovers whenever I'm in Africa, and I talk to every builder of specialty safari vehicles I find. I've personally seen one broken birfield there, and not one of the builders I've talked to includes birfield upgrades in his work. Most give me blank looks when I ask. This leads me to believe the problem is much less common there than here, where we're more likely to stress drivetrain components with big tires and extremely difficult 4WD trails tackled for sport rather than necessity.

I know we all agree that a stock birfield behind 31 or 32-inch tires is significantly less likely to break than a stock birfield behind 35 or 37-inch tires. Thus my point about modifying for overland travel rather than rock crawling.

 

[ntsqd]

Bump steer is curable with the right selection of parts and possibly some custom fabrication. Probably will take some thinking and might not be cheap. I'll bet that it's a factor in Kurt's estimates. I'm going through that right now in converting my Mini to cross-over steering with less than 4" of lift. The parts are out there for 4" or more. I'm not willing to go that high.

The stock Mini rear springs, at least those that came on my '84 Xcab, have an anti-wrap feature built-in from Toyota. The overloads have a strap behind the axle that crosses over the top of the main leaf. The spring can only wrap a short distance at ride height before that strap turns the O/L into a traction aid of sorts. In going to the GM 63's I seriously debated whether I would need to keep that feature or not. So far I have not felt the need to add that feature back into the rear suspension.

Many years ago a friend partly built and prepped a mid 70's Chevy 4x4 truck for desert racing. He had National build the front leaf springs such that the leaf tips at the front were nearly stacked on top of each other, but were spread out over a long distance at the rear of the springs. That made the front part of the springs act more as leading arms and less as springs. The OE SOA springs under the rear of my '91 Suburban are arranged similarly though not as extreme.

 

[the dude]

I agree with the huge blocks on the NA trucks... Our auto insurer is going to allow a 6" lift block but not SOA conversion of any kind. It makes no sense.

I actually had to phone my old man to ask him, he always likes to get calls from me asking him about Africa. So he thanks you for pushing our discussion that way. He figures he has seen 4 or 5 broken birfs over there in the ten years or so that he has been involved or traveling. The most recent one being last winter on a troopy. He said that he has seen the odd inner axle broke as well.

In all, I completely agree with you, not a huge number, but for the cost of less then a new set of tires, I still think it's a good investment.

 

[rmcnabb]

Fantastic replies, thanks.

When I was in Kenya, I asked the guys there how they go about getting service for their diesel Land Cruisers so far away from any civilization. He said they're all passable diesel shade tree mechanics and could keep a diesel going. I said I really meant the drive train - axles, diffs, steering, etc. He (as said above) gave me a blank stare, and said "That stuff doesn't really break." And these trucks saw an insane amount of hard use. I was amazed that vehicles could live and work every day on those "roads". Max lift on those truck was probably 3", max tire height probably 33's. One guy had 36's on a silly truck he built with yellow zebra stripes, but it was the only truck of its kind that I saw over there, ever.