1975 FJ40 Suspension Help

Joined
Oct 14, 2021
Messages
1
Location
Escondido, CA
Hello! I am new to the forum. Just wanted to introduce myself and see if anyone would be able to provide any help with my suspension. I inherited my Dad's 1975 FJ40. Her name is Midori. The FJ is in pretty good shape. I used to work on it with him, but never touched the suspension before. Please see the pictures below for the current setup.

It has a shackle reversal kit installed, some old Dick Cepek shocks, and what I believe to be is Rancho 43033 leaf springs that aren't in the best shape. The rear shackle is about double the length of the front one.

This thing rides like a dump truck. I'd like to soften the suspension a bit and keep around the same lift or maybe a little less to make sure it fits in a standard garage door opening.

I just replaced the 15 year old BFG KO 35s with some new Pro Comp Steel Wheels and 33in Cooper Discoverer STT Pros.

Now I want to tackle the suspension. Since it has a shackle reversal kit, do I need to buy a kit that is 2.5in in the front and 4in in the back? Or do I buy the 2.5in kit all around and get a longer rear shackle? If that's the case, what size shackles would I need to level this out? I've been looking at the Skyjacker Monotube kit and the OME kit. Also trying to figure out which shackles to buy on Man A Fre. Not sure which route to go.

I am new to the FJ game and just looking to get this relatively comfortable to drive on the weekends on the coast and light trails. Any help would greatly be appreciated.

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Thanks,
Daniel
 

Downey

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5,323
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Brea, Calif.
You are about to get a lot of opinions, I won't comment on spring/shackle choice, but I will tell you to get the softest "rear" shocks money can buy. Guys put the same stiffness of shock front and rear, yet they have a heavy engine front, empty bed rear. Then what happens is the rear end bounces up into the air on every bump you hit. That's why famous desert racer Ivan Stewart said "I hope my rear bumper drags every inch of the Baja 1,000.
 
Joined
Mar 3, 2012
Messages
593
Location
Indiana
Never dealt with shackle reversal myself, but I do believe a set of 4” rear springs will level you out. New bushings as well, for the front maybe also, but I would keep your front springs to save $. I have conventional 4” lift and Bilstein 5100’s, topless and doorless, and I’m quite pleased with my ride, especially on bigger bumps at 40mph on country roads. I believe the shocks are 85% of your ride quality. Load range C tires with 27 psi help as well.
 

Dizzy

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Feb 5, 2018
Messages
2,305
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Santa Fe, New Mexico
Ranchos have like four and five, rear and front, leaves per pack?

The first question that I'd be asking is, how much, if any, has the shackle reversal affected the the axle's caster? Determining the need for wedges/shims that go under your spring perch could be a factor in determining how to level this out. What is the angle on the pinion flange?
 
Joined
Jun 7, 2016
Messages
667
Location
Connecticut
You are about to get a lot of opinions, I won't comment on spring/shackle choice, but I will tell you to get the softest "rear" shocks money can buy. Guys put the same stiffness of shock front and rear, yet they have a heavy engine front, empty bed rear. Then what happens is the rear end bounces up into the air on every bump you hit. That's why famous desert racer Ivan Stewart said "I hope my rear bumper drags every inch of the Baja 1,000.
I followed this advice on my recent lift (skyjackers) and could not be happier with the ride. Softer is better in the rear. Bilsteins 5100s up front and some soft KYB (made in Japan) shocks in the back. Part numbers in my thread, I believe they are spec'ed as T100 shocks. FWIW, the 4" shocks I removed were almost the same as the rear shocks from my 2016 Silverado, so with the right ID bushing that should open up a lot of options.

I also lubed my springs so the leaves could move independently as designed before installing them.
 

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