FJ40 rear shock travel (1 Viewer)

[spdracr58]

So I have a 1974 FJ40 and purchased some new shocks. I installed them this weekend and I think that the rear shocks are too compressed. The shocks I purchased were the Bilstein 5125's. The front are model 33-185606 with a compressed length of 14 and extended 22.5. The rear are 33-185552 with a compressed length of 15.9 and an extended length of 25.9 (so 10" of travel). They are compressed to about 19". So the question that I have is, Is the shock to compressed. The alternate would be to put the same ones from the front to the rear.
The ones that I pulled off were some Rancho 5000 and they had the same travel range. I can post a photo if that is helpful

 

[White Stripe]

Flexible out without shocks and then take measurements of what length shocks u need.

 

[B y r o n]

It might help to know if you rig is stock or modified in any way that changes the ride height.

 

[Downey]

White Stripe is right, remove shocks, jack rig until axles are in full droop, measure, then use shocks slightly longer than your extended length (so that you will not stretch them to their ragged edge). Then if you are able to fully bottom-out the shocks, get taller snubbers (bump stops) to protect the shocks on full compression.

 

[tlc762]

You may have the wrong rear shocks... Remember the lower shock mount moved to the bottom of the leaf spring plate from above the rear spring on the axle in 75. Did you order the early to 74 or 75 and later part number?

 

[spdracr58]

i ordered for a 74 with a 4" lift. I asked my father-in-law that I purchased the rig from and he said it is a 4-6" lift.

 

[roadstr6]

Remove shocks and drive crossways across a deep ditch. Stop and take pin-to-pin measurements of the compressed side and the extended side. Order shocks based on giving an extra 1-1.5 inches both ways.

 

[KingAir Driver]

Did you install with the boots on? When I flexed my suspension and measured and ordered, then when installed the boots made it appear too compressed. Pics would help, I think my sitting distance was 19" with a 2.5 shackle lift.

 

[spdracr58]

I will post a photo. I think going through the travel that i actually have the correct ones on there.

 

[spdracr58]

Photos of the rear shocks. This is as it sits unloaded.

 

[spdracr58]

Its about 4" of travel to bottom out shocks.

 

[Downey]

Your SOA required a longer shock. Along with a longer shock came a taller shock oil can. Your compression travel now puts that tall oil can up into the upper shock mount (taller oil can than the amount of travel built into the shock shaft). This is the normal Baja race truck problem (more travel than the length of shock allows), that is why you see ultra long shocks with the top mounting well up inside the bed on these race trucks. You need a shock with long enough travel to handle your full amount of travel/droop/extension, then if you don't raise the upper shock mount, you have to use taller snubbers (bump stops) to prevent the top of the oil can from bottoming out on your upper shock mount. Does this make sense??

 

[Rock40]

I'd be curious to see if your SOA actually has that much up-travel. Like others have said, said, you're going to have to take the shocks off and cycle the suspension to know for sure. When my 40 was SOA, it had more down travel but every truck is different. And please remove those squished up shock boots....

 

[Downey]

Totally agree on removing the shock boots. Boots have top breather holes, otherwise they would blow up like a balloon every time the shock compresses. Problem is the breather holes allow water to enter, where it is trapped. The trapped water than rust the shock shafts, then the rust moving through the oil seal wipes out the oil seal, then shocks leak oil (plus are a rusty mess).

 

[atazman]

I think you might be surprised on how little the rear shocks compress. I have the SOA with Alcan springs and my rear shocks compress only about 1 inch. Anxious to hear how much yours actually compress.

 

[65swb45]

Just extend the bump stops so they hit before the shock bottoms out and you'll be ok...on that end. Because SOAs like to unload in a hurry, you may have to install limiter straps to protect them on the downstroke...unless you want to get into custom shock mounting like @Downey .

I learned a lot about shock geometry from @wngrog as well.

 

[spdracr58]

thanks for the all the responses. I will take off those boots. I have been sick the last two weeks. But I will take the shocks off and articulate and measure soon as well.