Spring over. shackle conversion. Help! (1 Viewer)

Joined
Apr 2, 2014
Messages
474
Yes it is 1⁰ positive castor and 8⁰ upwards on the pinion flange. Tranny is a sm420

Since you have power steering you would be doing yourself a favor by increasing your castor angle to between 4-7*.

It doesn't matter as much for the front drive shaft but your pinion flange is already aiming a little higher than you would want for a single cardan drive shaft.

Fortunately for you this is directionally correct. If you roll your axle back 4* by removal and re-installation of your spring perches you solve both problems at once.

Most people hurt their pinion angle when they add more castor but in your case you have room to spare.

What is the angle of your transfer case's front drive flange?

One thing I can recommend is that you can temporarily install some 4* spring perch wedges (thick side towards the rear) and bring the truck to an alignment shop and see how it measures up. Once they align it you can tell if you like the road feel as well.

After this you can take what you learned and do a more permanent solution i.e cut off the spring perches and weld new ones on in the desired location.

Hope this helps,

Mike
 
Joined
Nov 19, 2012
Messages
26
Location
Oroville, CA
Ok my take on that is get the springs and shackle hangers on and set. Then reposition the spring perches to add more positive caster. From what I remember the tcase flange was around 3⁰ up ill have to recheck it.
 
Joined
Apr 2, 2014
Messages
474
OK so i just want to help a little bit but I don't want to scare you off. This might seem like a lot but I'm going to give you my 0.02$ anyways:

I'm not sure what you plan to have your ride height set up at, but for best road manners you may choose to put your shackle through the frame to bring the truck down further.

Here's how I did mine:
1592613807071.png



It is important for you to determine what you want your final ride height to be before making finalizing your front end geometry. One fot he reasons for this is that depending on your axles location on the spring it will either rotate forward or backwards during the suspensions travel.

If your axle is directly in the center of the spring it will not rotate however.

Once you get your ride height (with the vehicle loaded as it would be during normal driving) you can start to make these changes.

Another thing that is often overlooked is the front axle skew. The front axle skew has an influence on the cross-camber and also the cross-caster. The cross castor you don't have to worry about as much (most vehicles of this vintage rang ~0.2-0.5* additional castor on the passenger side to account for road crown) but the crass camber is important.

If your axle is in good shape the cross camber will be 0*. Now if you axle is skewed in the vehicle (IE front spring hanger is further forward on one side of the other) than what happens is you gain camber on one side, and lose it on the other side. An example would be an axle that is setup to have 0.5* of positive camber (bottom of the tire inboard of the top) such as many vehicles of the era were working with could have 0.0* on one side and 1.0* on the opposite side if the axle was skewed in the chassis. This is due to the steering axis inclination. On most live axle vehicles the steering axis inclination is between 9-15*. I believe most of this era Toyota axle is around 9.5* SAI.

Now I don't want to scare you off but if you really want to get that puppy dialed in you can take a few steps here before you get it all set in stone and make your life easier down the road.

If it were me i would do the following:

Get a Firestone lifetime alignment

Get the ride height of the truck figured out (with the weight on it).

Finish welding the front drivers side spring mount (since you don't have much room to move it around with the steering box).

Get the passenger side partially welded in a location that you cam best determine is the closest to square with the drivers side. Try to weld it in a place where you can cut the welds later without too much fuss. In the past I have used the front spring mount on the rear axle as a reference for this.

Try to get your spring perches heavily tacked up with 5-7* of castor angle at ride height.

Get it to an alignment shop somehow. (I'm not gonna tell you how)

Look at the sheets and see what your Camber/Castor is once the set the toe.

If your castor is between 5-7* finish welding the spring perches on the axle.

If your camber is close to +0.5* on both sides weld the passenger side front perch up.

Now one more thing that is commonly overlooked- The thrust angle. This can be influenced if your front axle is not centered in the vehicle left to right.

Now everything that I said above is assuming your frame is straight and your rear axle is in the original position.

Your front and rear axles can also be skewed if there is a large difference in ride height or spring length from side to side.



If you show me the printout I can help you get it dialed in.

Hope that's not too much,

Mike
 
Joined
Apr 2, 2014
Messages
474
One more thing (you're probably sick of me now) is this:

You want to follow this rule for a standard drive shaft:

1592615685920.png


For a double cardan however this is what you want:
1592615736013.png


I assume you have the standard drive shaft.



Mike
 
Joined
Nov 19, 2012
Messages
26
Location
Oroville, CA
OK so i just want to help a little bit but I don't want to scare you off. This might seem like a lot but I'm going to give you my 0.02$ anyways:

I'm not sure what you plan to have your ride height set up at, but for best road manners you may choose to put your shackle through the frame to bring the truck down further.

Here's how I did mine:
View attachment 2345304


It is important for you to determine what you want your final ride height to be before making finalizing your front end geometry. One fot he reasons for this is that depending on your axles location on the spring it will either rotate forward or backwards during the suspensions travel.

If your axle is directly in the center of the spring it will not rotate however.

Once you get your ride height (with the vehicle loaded as it would be during normal driving) you can start to make these changes.

Another thing that is often overlooked is the front axle skew. The front axle skew has an influence on the cross-camber and also the cross-caster. The cross castor you don't have to worry about as much (most vehicles of this vintage rang ~0.2-0.5* additional castor on the passenger side to account for road crown) but the crass camber is important.

If your axle is in good shape the cross camber will be 0*. Now if you axle is skewed in the vehicle (IE front spring hanger is further forward on one side of the other) than what happens is you gain camber on one side, and lose it on the other side. An example would be an axle that is setup to have 0.5* of positive camber (bottom of the tire inboard of the top) such as many vehicles of the era were working with could have 0.0* on one side and 1.0* on the opposite side if the axle was skewed in the chassis. This is due to the steering axis inclination. On most live axle vehicles the steering axis inclination is between 9-15*. I believe most of this era Toyota axle is around 9.5* SAI.

Now I don't want to scare you off but if you really want to get that puppy dialed in you can take a few steps here before you get it all set in stone and make your life easier down the road.

If it were me i would do the following:

Get a Firestone lifetime alignment

Get the ride height of the truck figured out (with the weight on it).

Finish welding the front drivers side spring mount (since you don't have much room to move it around with the steering box).

Get the passenger side partially welded in a location that you cam best determine is the closest to square with the drivers side. Try to weld it in a place where you can cut the welds later without too much fuss. In the past I have used the front spring mount on the rear axle as a reference for this.

Try to get your spring perches heavily tacked up with 5-7* of castor angle at ride height.

Get it to an alignment shop somehow. (I'm not gonna tell you how)

Look at the sheets and see what your Camber/Castor is once the set the toe.

If your castor is between 5-7* finish welding the spring perches on the axle.

If your camber is close to +0.5* on both sides weld the passenger side front perch up.

Now one more thing that is commonly overlooked- The thrust angle. This can be influenced if your front axle is not centered in the vehicle left to right.

Now everything that I said above is assuming your frame is straight and your rear axle is in the original position.

Your front and rear axles can also be skewed if there is a large difference in ride height or spring length from side to side.



If you show me the printout I can help you get it dialed in.

Hope that's not too much,

Mike
Wow I think that was a little more than 2 cents But very through I appreciate it. It not so much scaring me off I just want a done RIGHT finished product. Looks like I have my work cut out for me... I like the shackle set up you have there. Do you know by chance the length on center is?
 
Joined
Apr 2, 2014
Messages
474
OK just for you:

Looks like 5 3/8"
1592617297004.png


And rear 7.0":
1592617330427.png



I originally had shackles like yours in the front through the frame. The allow for a lot more droop because they rack and swivel independently (the sides of the shackle aren't fixed to each other) but the holes quickly get rounded and "wallowed" out and the whole setup gets really loose causing the front end to wander around a bit. Good for the RTI ramp, bad for over the road characteristics and longevity.

I found these shackles at a land cruiser bone yard, I'm not really sure where they came from. The are ridged and much better for my application.

Mike
 
Joined
Nov 19, 2012
Messages
26
Location
Oroville, CA
Ok guys so i was finally able to get everything mocked up and to a alignment shop and here are the measurements

Left front
-1.7⁰ camber
+1.2⁰ caster
0.12⁰ toe

Right front
+0.2⁰ camber
+2.2⁰ caster
0.09⁰ toe

Front
21⁰ total toe
0.02⁰ steer ahead

Left rear
-0.9⁰ camber
-0.15⁰ toe

Right rear
-0.3⁰ camber
0.41⁰ toe

Rear
0.26⁰ toe
-0.28 thrust angle

I still have room to cut perches and increase castor angle and make the pinion angle better. I have not messed with the rear at all its still factory. Any feed back is greatly appreciated. Thanks.
 
Joined
Nov 19, 2012
Messages
26
Location
Oroville, CA
OK just for you:

Looks like 5 3/8"
View attachment 2345373

And rear 7.0":
View attachment 2345374


I originally had shackles like yours in the front through the frame. The allow for a lot more droop because they rack and swivel independently (the sides of the shackle aren't fixed to each other) but the holes quickly get rounded and "wallowed" out and the whole setup gets really loose causing the front end to wander around a bit. Good for the RTI ramp, bad for over the road characteristics and longevity.

I found these shackles at a land cruiser bone yard, I'm not really sure where they came from. The are ridged and much better for my application.

Mike

I'm thinking just cut and weld new perches and achieve a few more degrees on the caster angle.

15989191342377878378919677145083.jpg


15989191517423657882564497503143.jpg


15989194755153393701602061310598.jpg
 
Joined
Apr 2, 2014
Messages
474
Ok so let's start with the front camber.

There are a bunch of variables here so I will tell you what I can with what I know.

The front camber results are not good. How confident are you in the health of the front trunnion bearings and pins? If they are worn or the pins are bent typically the camber will read negative as we see here. This is due to the loading on the axle when the vehicle is at rest.

If that is not the issue then we have a bigger problem going on. Either the cut and turn was done out of alignment (which is commonly the case) or the axle may be bent. Live axle Toyota's of this vintage typically are set up to run ~+0.5 to +1.0* of front camber. This helps with steering effort and to account for road crown.

Now if the axle was skewed left or right it would show in the cross camber. Example being if one side reads +1.8* and the other side reads 0* you could re-align the front axle and end up in the middle if you did it correctly. Not the case here unfortunately.

Now the front caster... The cross caster is typically more like 0.5*, but here we see 1.0*. Typically you run ~0.5* more caster on the side if the truck nearest the shoulder. In north america that means the passenger side should be 0.5* more than the driver. This is to keep the truck from pulling to the right with road crown. This to me however is not a big deal having an additional 0.5* over target on the pass side. If it were mine I would roll the axle back 4* and shoot for ~5* and ~6* of caster on the front end (turn it so the pinion flange gets closer to the ground).

Now depending on the location of the bend, or the manner that the axle is "tweaked" from the cut and turn adding additional caster will either help or hurt your case. This is because as you roll the steering axis rearward the camber turns into toe, which in turn will be adjusted out by the alignment shop.

Now finally the thrust angle- The location side to side of the front and rear axles will have an influence on thrust angle as well as the angle of the rear axle in the chassis its self.

So in a nutshell- Inspect your front axle trunnions and pins and add 4* more front caster. and see what we get.

Hope that makes sense!

Mike
 
Joined
Jun 8, 2008
Messages
1,074
Location
San Diego
The major ripping happened at the back side of the front brackets. I seem to recall cracks forming on one of the rear shackle hangers. This was roughly 20 years ago with the forward facing brackets.
Not great news for me! ..but good to have the info. Thank you.
 

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