LJ7x/KZJ7x rear axle caster correction?

[GTSSportCoupe]

Is this something that is done?

Since my recent taller lift, I've noticed the coil spring perches in the rear of my LJ78 are not parallel causing springs to bow a bit. I also noticed my bushings in the rear radius arms are due for replacement. Wondering if I should install caster correction bushings instead of regular ones? I think the front style bushings will fit in the back.... This should also correct the pinion flange to driveshaft angle?

Has anyone done this? Advantages/Disadvantages?

 

[oldblue]

You may correct the spring perches, but the pinion angle will be made greater, hence the CV's will be running at different angles which may cause vibrations

 

[GTSSportCoupe]

You may correct the spring perches, but the pinion angle will be made greater, hence the CV's will be running at different angles which may cause vibrations

When you say CV's, do you mean the u-joints in the rear drive shaft?

This is what I want to go for if I understand correctly. Installing caster correction bushings into the rear arms will give me this. Currently the pinion angle is wrong (pointing up).

 

[oldblue]

I stand corrected, the picture explains it all, same angle in each U Joints, all good.

 

[GTSSportCoupe]

I stand corrected, the picture explains it all, same angle in each U Joints, all good.

I find it strange that no one does this when they substantially lift their coiled 70 series. Or at least a google search does not yield any information or mention of this....

I also noticed the rear bushings are solid. Toyota does make some OEM bushings with holes in them for more flex for the 80 series. At the very least I think I'll replace with the relief type. (picture below) Should help the rear of my truck flex easier.

I did take measurements of the LJ78 rear bushings (at axle end of radius arm), and they are 60mm diameter, 40mm wide (press in part), and 50mm wide (bolt part). Same dimensions as the front arm bushings for many models (80 series included).

 

[GTSSportCoupe]

OK, so I'm still torn on if I should try caster correction bushings or just use regular ones. I did find a couple good pics of OEM Toyota ones. The ones without holes are the correct part number for the LJ7x/KZJ7x rear arms. The ones with holes will fit as well, but are the part number for the 80 series front arms. Clearly the 80 series bushings will allow more articulation, so would be more desirable in that sense.

Anyone out there with a LJ7x/KZJ7x should really be checking their rear bushings. Almost guaranteed they need replacement. I can't believe how worn mine are and I did not even know it.

 

[oldblue]

Info from my KZJ71 Workshop manual,

Note , holes are aligned horizontally.

 

[GTSSportCoupe]

Info from my KZJ71 Workshop manual,
View attachment 2495841
Note , holes are aligned horizontally.

That's very interesting. Now I'll have to think about that for a bit....not sure why they would do that.

 

[GTSSportCoupe]

Info from my KZJ71 Workshop manual,
View attachment 2495841
Note , holes are aligned horizontally.

I'm beginning to realize torque from power delivery to the rear axle will constantly be twisting the bushings up/down. Likely it would cause a sloppy feeling and wear out the bushings faster..... Meaning caster correction bushings would likely get ruined pretty quick? And even putting the oem bushing holes up/down would probably be a bad thing. Now 80 series are awd, so the same thing would happen to the front axle on that. I'm going to look at the 80 manual to see how they orient the holes on that model.

 

[GTSSportCoupe]

Well, I decided I'm going to try the caster bushings; especially as I have a set on hand. Will let you guys know how it goes.

Worst case I just have to yank them again at some point and put in factory ones I guess.

I've realized that the power torque on the rear axle shouldn't wear out the bushings any worse than the impact of braking does on the front bushings. Or power deliver to the front axle in an 80 series would for example...

 

[GTSSportCoupe]

Installed the caster bushings in the back and seems to have worked out really well. They won't last as long as the factory originals, but feel good for now. Corrected my pinion angle to what I think is a much better angle. And the rear articulates even better now. I used Dobinsons bushings, but forgot to take a picture after pressing them into the arms....sorry.

 

[GTSSportCoupe]

Went up in the hills with my kids on the weekend to find some snow to play in. I get to play in the cruiser, they get to play on sleds in the snow, haha. We're all happy.

Anyhow, the back articulates so easily now I limited out my shocks a few times (over extended). Gave a little thump/bang sound that I have not heard before. Can shocks (OME or Dobinsons) handle that sort of thing, or should I look at ways to limit the axle movement? I could put on limiting straps, longer shocks, more resistant bushings, or ???

When the truck sits level and unloaded, the 'long travel' dobinsons are 7cm from full extension (out of 20cm possible travel).... I admit I have not messed with this stuff enough yet to know if I should be looking for even longer travel shocks?

Anyhow, little pic from that trip:

 

[Tsvigo]

you can prevent the coils from droping out by switching to a shorter shocks, or else install a strap with the coil spring retainer.
i have read somewhere about the coil spring retainer here, i just dont remember the thread that it was in.