Spring over or under

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Jun 6, 2022
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Keene, NH
I have disassembled and removed the body of my 1972 / 1977 FJ40. The frame is rust free and I have painted it. It came with a spring over lift. I think I would prefer a 2" spring lift. Has anyone converted a spring over back to the original spring under. I believe the SOL has lifted it about 6" and seems top heavy.
Any suggestions would be appreciated.

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EWheeler

4 Cruisers, No Garage !
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Menifee, CA
I have disassembled and removed the body of my 1972 / 1977 FJ40. The frame is rust free and I have painted it. It came with a spring over lift. I think I would prefer a 2" spring lift. Has anyone converted a spring over back to the original spring under. I believe the SOL has lifted it about 6" and seems top heavy.
Any suggestions would be appreciated.

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While I don't disagree with the physics that raising a vehicles center of gravity will make it easier to roll, I would not use it as a basis of decision for setting up the truck how you want. The decision of spring over or spring under lift should be made based on intended use of the truck and required clearances, and also the desired stance or look. There is a difference between lifting a vehicle properly and doing it improperly which should be the basis of the discussion. Decide the look/height of the truck you want, and then figure out how do to it right.

I have three FJ40s that are spring over lifted, and none feel "top heavy".
 

pbgbottle

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Yep i always choose SOA myself softest riding suspension setup out there it can be done lower than 6 inches also. Need pics of Front axle to see what has been done. Might be easier to trade your front housing for another stock one if yours has been modified.might be cheaper to keep the SOA also, we need to see what they did with the steering as well
 
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EWheeler

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Yep i always choose SOA myself softest riding suspension setup out there it can be done lower than 6 inches also. Need pics of Front axle to see what has been done. Might be easier to trade your front housing for another stock one of yours has been modified.might be cheaper to keep it also need to see what they did with the steering.
My SOA '71 on 37's rides sooo much better than my 2" lifted SUA 40 on 35's. Tons of variables to consider though. Do you think an SOA truck with original stock springs rides better than the same truck SUA on the same stock springs? I am curious if there is something about the physics of an SOA setup that is "softer" than the SUA setup. In theory, your shackle angles are the same, sprung weight is the same, you are forced to get longer shocks so I guess maybe new shocks may make it seem "softer"? When you go SOA, you are usually installing larger tires likely with a greater sidewall height to wheel diameter ratio, so maybe some "softness" is gained from the compliance of the tires versus the non-lifted setup? Larger diameter tires also roll over bumps easier, I think this plays a pretty big role that many overlook. I learned this going from 33" to 36" tires on my sand car setup, it was amazing how much of the small chatter/chop was removed from the feel in the chassis when increasing tire diameter with no other changes to the suspension.
 
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Location
Keene, NH
So far the vote is in that Spring over is the way to stay. That's great as I still have the paint stripping on the body over and under. There was a question on any steering modifications. All my books show the steering column attaching to the gear box through a coupling or a U- joint. Mine goes straight into the gear box.

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Cherry Valley, NY
The steering set up is from the '72 which also had a 3 on the tree shifter. The later style box has much stouter guts so I changed my '70 to the later steering set up and moved the shifter to the floor using parts out of a '73. Real easy to change.
 

pb4ugo

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spay-lay-wi-theepi, Ohio
I think the steering modifications mentioned was in relation to steering geometry. Has the spring perches been moved to get a good driveshaft angle and the frt end cut and turned to get a proper caster angle. I'm just guessing though.
 

pbgbottle

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My SOA '71 on 37's rides sooo much better than my 2" lifted SUA 40 on 35's. Tons of variables to consider though. Do you think an SOA truck with original stock springs rides better than the same truck SUA on the same stock springs? I am curious if there is something about the physics of an SOA setup that is "softer" than the SUA setup. In theory, your shackle angles are the same, sprung weight is the same, you are forced to get longer shocks so I guess maybe new shocks may make it seem "softer"? When you go SOA, you are usually installing larger tires likely with a greater sidewall height to wheel diameter ratio, so maybe some "softness" is gained from the compliance of the tires versus the non-lifted setup? Larger diameter tires also roll over bumps easier, I think this plays a pretty big role that many overlook. I learned this going from 33" to 36" tires on my sand car setup, it was amazing how much of the small chatter/chop was removed from the feel in the chassis when increasing tire diameter with no other changes to the suspension.
ALl great logic i wasmostly refer to SOA vs lift springs, I prefer the stock soft springs in SOA vs lift springs in SUA. A stock riding machine is pretty sweet also. The big tires for me probably are softer as I run my swampers at 10 PSI on the street and 6psi in the bush my Toyo open country run 20psi on the street so they are squishy. Lol.
 

pbgbottle

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Not so much the steering box but would like a pic of your steering arms ,the actual axle housing ,we need to see how it was setup. IF nothing major was done it may be easy to drop back to spring under.
Also did they perform a shackle reversal ?
 

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