Decided to Be More Off-road Serious with the FJ40 (1 Viewer)

[NikP]

I've had my FJ40 for 12-14 years and then I retired to Colorado a couple years ago. I started spending more time off-road bouncing around on 2-inch lift springs. A stable but rough ride. My F40 is unique in that it has to do double duty as my snow plow in the winter. (I'm too frugal to by special purpose vehicle).

It all started with a trip to Moab with some friends. I had never been on anything more serious than a Colorado pass trail. I'm not sure I'm into serious crawling but I did enjoy the more serious trails.

Time to 4-link the rear and link the front. I started this build last year and thought I begin to capture my learning experience for others.

List of things in focus for this build:

• 4-link the rear
• link the front - you'll see I changed directions on this during the build.
• Coilovers
• Lockers Front/Rear
• Gearing?

My start is a TBI 350 small block adapted to stock Toyota 4-speed transmission and transfer.

 

[NikP]

Let's dive right in to the build. I didn't get pictures of the tear down or some of the mock-up (Oh-well). I started with the rear suspension. (lesson on that later). After lots of laying under the vehicle with a measuring tape, I decided I can tuck 8-inch coilovers under the rear. I wanted to try to fit within the contraints of not cutting holes in the floor or carving out fenders to get extreme travel. I figured 8-inches was a good compromise.

To make them fit without an extreme ride-height for the body, I fabbed a drop bracket which allowed the bottom coilover bolt to be below the axle but not too low to cause a drag hazard. I ended up just barely below the axle tube. I boxed in the bottom of the bracket to become somewhat of skid plate.

Yeah, I probably went overboard with the truss as it could be smaller, but I had the 1/4 inch plate laying around... I inserted the tubing for looks and a bit of a stabilizer.

 

[NikP]

Lesson #1: You buy cheap, you buy it twice!

Well technically, I haven't bought it twice but those who follow; be ware.

I'm a bit frugal since I'm retired and income is non-existent. Fox and King coilovers seemed a bit expensive and ORI's were way out there. In my Internet searching, I found a rather economical coilover by FOA. I ordered them as their lead-time was quoted as a couple weeks. I also did some Internet reading about dual spring rates and what people are running. I was a novice. So I just ordered what others were running.

 

[archie73]

I’m listening.. I’m debating the same route- affordable linked suspension. I’d ideally like more wheelbase, but I’m not going for a comp cut, so that means a stretch. I’m torn….

 

[Firemedic831]

I’m listening.. I’m debating the same route- affordable linked suspension. I’d ideally like more wheelbase, but I’m not going for a comp cut, so that means a stretch. I’m torn….

I didnt want to comp cut mine as well. i pushed it back 4 inches

 

[NikP]

I’m listening.. I’m debating the same route- affordable linked suspension. I’d ideally like more wheelbase, but I’m not going for a comp cut, so that means a stretch. I’m torn….

I was the same. I wanted to get more wheelbase but not cut up the body. I think I was able to easily get 3-4 inches and maintain everything. The rear axle at stock sits forward in the wheel well so there's a couple inches there. The front can sneak a couple inches also with no problem.

 

[NikP]

Lesson #2: Reviews mean something.

So my FOA coilovers and springs became a nightmare. First off, the tophat for the coil stripped out from simple adjustments even with no weight not the shock. I raised the warranty flag and they shipped a replacement right away. I tried to get help with determining spring rates and got no response. Multiple calls with no answers, multiple emails with no answers. I finally found one of their dealers who stepped in to help although I bought nothing from him. www.davesoffroadsupply.com.

The better business bureau give FOA shocks a D+ rating. I know why. Their customer service is none existent and if you by chance get someone on the phone they act like you're wasting their time.

Anyway, Dave at Daves Off Road Supply was super helpful and pointed me to here for insights to calculate spring rates: Coilover Spring Rate Calculator (Dual Rate Spring Calculator) - https://www.crawlpedia.com/spring_rate_calculator.htm

For reference, here's my calculations:

10 inch free height spring.
Measured height with when installed as a single spring with weight of the vehicle: 7.125”

(10-7.125) * 250 spring rate = 712.5 corner weight

Desired ride height = 4 inch (which is exactly half the travel of the 8 inch coil-over)

8 inch coil-over - 4” = 4 inch desired squat

712/4 = 178.25 lbs/in

With a dual rate setup double this

178.25*2 = 356 lbs.

Then split the difference, so it looks like I require a 325 secondary and 375 primary coils. Springs don't come in this range so I ended up at 300 and 400.

 

[NikP]

Lesson #3: When forums suggest there's a problem with a design, they're probably right even if there's no science presented to support it.

The rear went relatively easy until it had to be redone. With the rear mocked up, the front is full of all sorts of challenges. Real estate mainly. I thought at first I'd avoid all the real estate issues by installing radius arms. I saw a number of radius arm setups and thought why not, there's a lot out there. I read also that they tend to bind. I didn't quite understand and thought since I was installing Barnes 4x4 Enduro joints they would have enough movement to avoid binding. I studied all the prevailing ways and decided I to try and have upper radius arms on both sides for strength and redundancy. And it seemed to tuck nicely up under the frame at full bump.

Next step, let's articulate to see how everything fits. Oops... it binds. I could get about 3-inch of articulation with this design and it would bind up. What's next? I could remove one radius arm and it seemed to be good. Or should I re-think the radius arm idea?

 

[NikP]

Lesson #4: Plan for re-doing things.

With much time lying on my back under the vehicle. I decided I didn't like the idea of one radius arm. With the Enduro joint movement, the radius arm seemed to flop to one side when articulating which changed pinion angles when it moved. I also started reading that most radius arms run rubber bushings in the front. This eliminates the flop of the arm and the rubber bushing is the key to helping with the bind as it provides more movement.

Scrap the radius arms!

It's tight under there. No room inside the frame rails for upper link mounts. I have center drop manifolds and I route the passenger exhaust to the drivers side to avoid the front/rear driveshaft and transfer case on the passenger side. Can I get 4-links? Probably not without much work and redoing the driver exhaust manifold and piping.

Good news though, the passenger had a bit of an opening for an upper link mount. You'll notice, I mounted it so the bolt can insert vertically. I did the geometry calculations and with the misalignment movement of the Enduro joint I'll have 2-3 of extra range so articulation can work with the joint installed this way. If I had more travel, then I'd have to install the other way, which requires more engineering.

Also notice, I had to make a 15-degree bend in the upper link to clear exhaust at full droop. Not an issue since bending link doesn't change the path the links travel.

 

[NikP]

Lesson #5: When linking, do the front first.

With the change to a 3-link, it requires the upper link to attach on top of the differential which takes more room. To get more room, I'll had to set the ride height up a couple inches. I was trying to avoid an exaggerated ride-height, but it looks like I'm not going to be too bad.

The problem this presented was the rear sat too low now. I could try to make up the 2-inches or so with the coilover adjustment ring but I didn't like that idea. So, let's re-do the rear coilover mounts to level it out. Originally, I welded upper link mount to the stock tube where the shocks mounted. I ended up cutting that out and replaced it with rectangular tubing. I need to get some pictures of that.

 

[NikP]

Lesson 6: Things take longer than expected.

Once I did some work with the actual vehicle to determine spring rates, I sent the springs back to FOA since they have an exchange program. (Or they really didn't). My goal was to beat the winter snow and have everything wrapped up so I could mount my snow plow for the winter.

I sent the springs in and hoped for a relatively short turn around time. I even sent a pre-paid shipping label so all they had to do was drop new springs in a box and slap the label on.

Weeks went by. No response to emails. No answer when I called. Then after about 30-days, they said they sent them, but didn't provide shipping info and my shipping label still showed inactive. Were there lying? After 45-days and multiple attempts to get a status... nothing. All I wanted was the springs sent out for the ones I returned. How hard can this be?

60-days in... nothing. Time to file a Better Business Bureau complaint like everyone else and challenge the credit card charges. Finally, got a response. They said they shipped them... again no shipping info and my label not activated. Many of the BBB complaints say things got "lost in shipping".

Meanwhile, it's snowing. Time to plow. But how with no coilovers? Replace the coilovers with a piece of round tubing. Rough ride but at least aI can move the snow.

I finally gave up and ordered Eibach springs from Summit Racing. (Remember that buy cheap, buy twice lesson?). Now I've spent it twice.


It took months to finally get a refund from FOA on the original springs.

 

[Firemedic831]

Are you running a Radius arm on the Drivers side and frame mounted upper link on the passenger ?

 

[Firemedic831]

Also it looks like your tie rod is going to hit the pan hard frame mount. make sure you turn the wheels back and forth as the tie rod gets closer when the wheel is turned .

 

[NikP]

Are you running a Radius arm on the Drivers side and frame mounted upper link on the passenger ?

No, I ended up scrapping the radius arms altogether and went for a 3-link with the upper link on the passenger side.

Also it looks like your tie rod is going to hit the pan hard frame mount. make sure you turn the wheels back and forth as the tie rod gets closer when the wheel is turned .

I've got clearance and nothing hits when steering and when articulated. I'm actually going to re-do things and install a high-steer so I can minimize any bump steer.

Here's where I stand currently in pictures. Close clearances but everything clears.

 

[NikP]

Lesson #7: Know when to ask for advice

Now that I'm on the road. It's really twitchy especially in the corners. I'm afraid to drive it on mountains roads above 40mph. I'm going back to lesson #4 to re-do things but need some advice.

I believe my twitchy ride is rear roll-steer. Is 8 degree rear oversteer a lot? I think it probably is. I'd like comments on how to solve it based on the link calculator results. I'd like to triangulate the lower links for the rear but it all comes together where the transfer case resides. No room. I'm afraid that I'd have to stick a cross member below the transfercase. This will create a very low spot mid-vehicle. My frame is at 21-22 inches off the ground and the transfer case drops down below the frame by 2.5 inches.

I'd appreciate advice.

 

[NikP]

It looks like the simple way to vastly improve the rear roll steer is to raise the lower link on the rear axle and drop it a bit at the frame. Is it really that easy?

Does this all revolve around a nearly horizontal lower link?

 

[peesalot]

Have you cycled it to see if the suspension over articulates the steering ?

 

[NikP]

Have you cycled it to see if the suspension over articulates the steering ?

I'm not sure what that means. I've never heard of suspension over articulating the steering. If that means roll steer then yes, that's what I'm trying to solve (hence the high roll axis angle). If it means something else, then educate us.

 

[White Stripe]

Lesson #7: Know when to ask for advice

Now that I'm on the road. It's really twitchy especially in the corners. I'm afraid to drive it on mountains roads above 40mph. I'm going back to lesson #4 to re-do things but need some advice.

I believe my twitchy ride is rear roll-steer. Is 8 degree rear oversteer a lot? I think it probably is. I'd like comments on how to solve it based on the link calculator results. I'd like to triangulate the lower links for the rear but it all comes together where the transfer case resides. No room. I'm afraid that I'd have to stick a cross member below the transfercase. This will create a very low spot mid-vehicle. My frame is at 21-22 inches off the ground and the transfer case drops down below the frame by 2.5 inches.

I'd appreciate advice.

View attachment 3301514

View attachment 3301515

Have you tried adjusting your caster?

 

[NikP]

I'm running the front axle at about the same angle it was before I linked. That's close to the stock setting. My twitchiness comes from the rear and it's obvious when you drive it.