FJ40 shackle reversal...WHY!?!?!

[chicago]

I was planning on doing a SR on my 40 build because it seems that most will do this when they SOA a 40....however, Im not sure as to WHY I should. Is the only main advantage to get spring clear at the front?

Pros and cons of doing this procedure please!
Ive gotta cut off and re locate the hangers anyway, so either way its not a big deal. Just wondering the philosophy behind this mod.

Thanks,

Keith

 

[Downey]

I agree with Lil'John that shackle reversals get alot of credit they don't really deserve. The main drawbacks I see are:
(1) They are an immovable object that hangs down another 1.5" lower than the original shackles
(2) With the front axle travel now rearward during bottoming, you run the risk of totally collapsing the front slip yoke and cracking the transfer-case. This happened two times to the same guy!!!

 

[LAMBCRUSHER]

Do a search- enough to shake a stick at. I am still on the fence. My first 55 got SR (first is op word here), my second one might not, and my first might get-modified. It will be nice to has 2 rigs w the only diff being their front suspension disciplines-good comparison...

 

[General Sherman]

This is entirely dependent on what suspension your running. For any truck with lift springs (springs with any amount of arch in them at ride height) you can count on the SR giving a better ride.

Pro- Better ride. On a SR arched springs the axle travel's up and back when contacting obstacles in the roadway. Stock, the axle travels up and forward. In other words, with the shackles in the front, bumps in the road feel harsher. This is what most are speaking of when they say it handles better. The handling does not drastically change one way or another. Same bumpsteer, springrate, and vehicle weight etc. If its done with stock (IE: flat springs) all bets are off. A spring over will ride the same SR or not on stock springs that are flat. I have never felt a difference.

Biggest Con- Drive shaft. You will need a longer slip in the drive shaft. These are generally expensive and imo are a must. If you try and use the stock slip you will either find it coming apart constantly or bottoming out on the case. Either way its not good.

For off road use, Toyota had it right. I prefer the shackle in the front. It requires less slip in the shaft and some argue that because the axle travels up and forward as it meets an obstacle, the traction is better. The axle movement actually pushes the tire forward applying more pressure to the tread where its needed.

For driving down the road, the SR wins out.

 

[chicago]

Thanks for the input gents.
Its a SO configuration with Fj60 springs that have arch to them, so they are NOT flat.
I know about the extended slip shaft that will be required. Was thinking about the marlin or TG "build your own drive shaft" extended length slips.
Im not really understanding though, HOW would the SR provide better handling on the road? Does this same principal apply to FJ60's? When I built my 62 I kept it in stock configuration and it handled pretty well except for a PS pull which I believe was my OWN fault when doing the CnT. I was off from one side to the other.
How likely are you to hit the shackles? For me...this would be the most compelling reason to do it. To keep that from happening. On the 60 series, the shackles are protected a bit more so I never had an issue with that, but on a 40 I can definitely see that being more of an issue!

 

[Tapage]

(1) They are an immovable object that hangs down another 1.5" lower than the original shackles

not if you locate the fix point up to the frame ..

(2) With the front axle travel now rearward during bottoming, you run the risk of totally collapsing the front slip yoke and cracking the transfer-case. This happened two times to the same guy!!!

easy job taking care of your frond DS lenght .. with a long spline you should solve and improove it.

 

[Mace]

With bigger tires the "bashing" of shackles really never becomes an issue. That is the only reason to do a SR.

SR does not magically make your truck handle better.

 

[chicago]

Ive actaully been looking at some pics of 40s wheeling and that had sort of swung my decision. With the frame horns hangin out front as much as they do, those shackle are REALLY vulnerable out there. Im gonna go with the SR. Like I said, it wasnt an issue on the 62, but this is a different animal.

Thanks for the input on this gents.

 

[chicago]

With bigger tires the "bashing" of shackles really never becomes an issue. That is the only reason to do a SR.

SR does not magically make your truck handle better.

The biggest Ill be going on the tires is 37''...Im thinking that will be an issue with stock set up.
Ill have 35's to begin with.

 

[mookie]

With bigger tires the "bashing" of shackles really never becomes an issue. That is the only reason to do a SR.

SR does not magically make your truck handle better.

i respectfully disagree with the first part of your statement sir.....my front shackles have have been the only thing that stopped me a couple of times in the past including in the middle of little sluice last year and i was running flipped rear 60 springs with 40" tires

i completely agree with your second statement, i did a shackle reversal on my fj55 last year and i couldn't really tell any difference on the road handling wise

 

[Slowerthanu]

Screw that, I don't run shackles, I just weld the springs to the frame!

Actually, I run a SR, sunk into the frame on my FJ40 and no shackle reversal on my FJ62. I cannot tell a difference.

 

[dr_dobro]

SR not good for 12+ shoe size !
I was going to install one I have, but change my mind ! TC is worth more than a pair of shackles IMO !

 

[chicago]

Personally, I'd choose to do a through the frame shackle conversion up front before I did a shackle reversal.

As mentioned, my 40 go a SR. Before the SR, I did Fordyce in bone stock form. I wrecked one of the shackles(big time S shape)

When I downed my FJ40 for some "serious" work, I removed the SR and converted it to a through the frame shackle as I mentioned above. The method I used was:

1. Mount the spring hangers where I wanted
2. Install springs
3. Put a 1" block between the frame and leaf spring on the shackle end
4. Install axle and lower full weight onto springs.
5. Mock up shackle for approximately 45 degree angle
6. Mark frame side for shackle tube, drill, and install shackle tube

The end result was maybe 2" of shackle exposed that was ramped. It flexed amazingly with the 45 degree shackle even with stock FJ40 springs.

In chicago's case, I'd probably do the SR but reluctantly.

So youre saying that you had run the front shackle off the frame horn through the frame to take it up higher?
Not a bad idea...
What did you do about the power steering box (assuming that its set up like a 40)?
I dont think that would work for me without a LOT of fab considering Ill be out boarding the springs 1.5 in on each side.
Even in the aft. pin hole, Ill just have to run the hanger under the frame for this reason.

 

[Fast Eddy]

I dont think that would work for me without a LOT of fab considering Ill be out boarding the springs 1.5 in on each side.

The Saginaw conversion is yet another motivation to do a SR.

The way I measure the SOA C&T fj60 housing I have (supposedly Proffitts), it's only outboarded about 7/8" more than stock on each side. Anyone have an fj60 around they could measure from the outside of the front springs?

Assuming a SR, how are you going to deal with the shackles at the rear of the front springs? One side of the shackle is square in the middle of the frame rail.

I've got the idea to build a custom pair of shackles that are wider than usual, pass through the frame like I want, but the outboard side of the frame shackle tube sticks out 7/8" further with appropriate bracing and the shackle would look like this (Pat. Pend.). There is a bit of torque, but not so much I'm worried about it. It's well less than the torque in the normal flex of the springs under articulation. As long as the shackles are overbuilt as I intend, I believe it will work. Going down the road one end of one spring is only supporting about 500 lbs; maybe double that in a hard corner.

What do you think?

 

[chicago]

The Saginaw conversion is yet another motivation to do a SR.

The way I measure the SOA C&T fj60 housing I have (supposedly Proffitts), it's only outboarded about 7/8" more than stock on each side. Anyone have an fj60 around they could measure from the outside of the front springs?

Assuming a SR, how are you going to deal with the shackles at the rear of the front springs? One side of the shackle is square in the middle of the frame rail.

I've got the idea to build a custom pair of shackles that are wider than usual, pass through the frame like I want, but the outboard side of the frame shackle tube sticks out 7/8" further with appropriate bracing and the shackle would look like this (Pat. Pend.). There is a bit of torque, but not so much I'm worried about it. It's well less than the torque in the normal flex of the springs under articulation. As long as the shackles are overbuilt as I intend, I believe it will work. Going down the road one end of one spring is only supporting about 500 lbs; maybe double that in a hard corner.

What do you think?

View attachment 448581

Ed,
I think that would work IF the dimension is actually 7/8 in off set.
. however, I was of the impression that the spring needed to be out boarded 1.5 in. I havent started on the front yet, so I guess Ill see when I get there.
Im neck deep into a HG replacement on a 3VZ-E 4 runner...
Do you know off hand the dimensions perch to perch? On the rear I think it was like 40 in or something...
As far as how I plan on doing the outboard...I got the ruff stuff gear, so Its pretty simple with that.

 

[chicago]

Okay...I get what you are saying...
Im a little slow, so I had to go back and re read.
So the shackle is wider than stock to allow for the off set and a "keeper" to keep the spring placed.
The only concern I would have would be, as you mentioned, the added torque to outside of the assembly.
Try it and see how it works.

 

[crwlntoy]

According to my research fj60 front perches are 29 3/8" center to center and fj40 is 27". In the rear fj60 perches are 40 9/16" center to center and fj40 is38 3/16"

 

[chicago]

That is it exactly.



My FJ40 was a regular saginaw conversion. When I went through the frame on the shackle, I converted my PS over to a scout conversion

So... no problem at all with PS at all

Reason number 24 to like a scout conversion over standard saginaw

With the regular saginaw conversion, I think you would be hard pressed to do my idea.

For sure.
Ive got the x member tapped, sleeved and welded and the box mocked up and even recessing the upper ports into the frame, the end of the box is about 3/4 of an inch to the frame end. NO ROOM for me to do that.
Great thinking though on solving that issue. Being able to weld is KEY in this game I have found.

 

[Eric_S]

Assuming a SR, how are you going to deal with the shackles at the rear of the front springs? One side of the shackle is square in the middle of the frame rail.

I've got the idea to build a custom pair of shackles that are wider than usual, pass through the frame like I want, but the outboard side of the frame shackle tube sticks out 7/8" further with appropriate bracing and the shackle would look like this (Pat. Pend.). There is a bit of torque, but not so much I'm worried about it. It's well less than the torque in the normal flex of the springs under articulation. As long as the shackles are overbuilt as I intend, I believe it will work. Going down the road one end of one spring is only supporting about 500 lbs; maybe double that in a hard corner.

What do you think?

Ed,

The problem I see with that shackle setup is when the spring flattens out, you will probably hit the center brace on the bottom of the frame. My shackle setup is offset some since my D60 front has a 27.5" spring spacing. I had to make a spacer for the leaf spring end. I will see if I have a pic somewhere and post it later.

If you are doing a SR with that shackle setup, you will be sitting a mile high if you keep that shackle that long and that vertical.

 

[Fast Eddy]

The problem I see with that shackle setup is when the spring flattens out, you will probably hit the center brace on the bottom of the frame. My shackle setup is offset some since my D60 front has a 27.5" spring spacing. I had to make a spacer for the leaf spring end. I will see if I have a pic somewhere and post it later.

If you are doing a SR with that shackle setup, you will be sitting a mile high if you keep that shackle that long and that vertical.

The center brace is going to be the limit on that end of the travel for sure. It's not going to be a mile high even if I have to give up on SOA and do a 2.5" OME SUA.

The picture as I drew it quickly has the center brace in the center. In reality it will be as close to the spring as I can get it. It's possible to do this without the center brace too, but I want it in there to deal with the torque and to keep it stable at higher speeds. I want to be able to drive to the trailhead.

I've got more geometry calculations to do before I fire up a welder.