Jeep J20 stock height

[Cecil14]

They sound like stock rear leafs. Extreme wear like that is not uncommon, the stock leafs on these are usually ~40 years old. They were usually built for ride quality as well, and not longevity, so long term wear wasn't really considered.

If it were me, I would ditch that block. I'm not a fan of blocks in general, but a block that tall is just asking for trouble. Do you need a lift? How much do you actually want? A new high quality kit might be a good option for you.


aa

[eldudderino]

They sound like stock rear leafs. Extreme wear like that is not uncommon, the stock leafs on these are usually ~40 years old. They were usually built for ride quality as well, and not longevity, so long term wear wasn't really considered.

If it were me, I would ditch that block. I'm not a fan of blocks in general, but a block that tall is just asking for trouble. Do you need a lift? How much do you actually want? A new high quality kit might be a good option for you.


aa

I think it needs a lift. I want to keep the 35s. I am thinking about a 4inch spring and a 2 inch spacer in the back. From what I have read the ride quality of 6in is awful and the thing already makes you almost pee blood hahaha. Who makes springs for these? I am having a hard time finding rear leafs.

[Cecil14]

You should be able to get 35s under a J-truck pretty easily with a good 4" lift. What year is your truck? There were some changes around the '74-'76 time frame. The biggest problem you're likely to encounter when looking for a lift is keeping the payload capacity of a J-20. I've never seen lift springs for the heavier trucks, just J-10s. They're the same physical dimensions, so you can bolt a long bed J-10 spring on your J-20.

If you want to maintain your J-20 carrying/towing capacity, you'll have to have custom springs made. Alcan is one extremely highly rated spring maker, but they're not cheap. I had a quote done for some pretty basic replacement springs from them and was at about $1250 for all four corners.

To the 6" springs...yes, those are going to be horrible. To make a lift spring, they have to make the spring physically longer, but still fit between the same two mounting points. This gives the spring its "lift." When you arch the spring that much more, though, it doesn't flex nearly as well. That is partially due to the static arch being that much higher, as well as being limited by shackle length.

Personally, I think 4" is probably the biggest leaf spring lift I would ever go with. If I wanted more than that, I'd be looking at a link/coil conversion or airbags.

Give us a few more details about your truck, and what your intended goals are, and we can start throwing out better options for you.


aa

[eldudderino]

You should be able to get 35s under a J-truck pretty easily with a good 4" lift. What year is your truck? There were some changes around the '74-'76 time frame. The biggest problem you're likely to encounter when looking for a lift is keeping the payload capacity of a J-20. I've never seen lift springs for the heavier trucks, just J-10s. They're the same physical dimensions, so you can bolt a long bed J-10 spring on your J-20.

If you want to maintain your J-20 carrying/towing capacity, you'll have to have custom springs made. Alcan is one extremely highly rated spring maker, but they're not cheap. I had a quote done for some pretty basic replacement springs from them and was at about $1250 for all four corners.

To the 6" springs...yes, those are going to be horrible. To make a lift spring, they have to make the spring physically longer, but still fit between the same two mounting points. This gives the spring its "lift." When you arch the spring that much more, though, it doesn't flex nearly as well. That is partially due to the static arch being that much higher, as well as being limited by shackle length.

Personally, I think 4" is probably the biggest leaf spring lift I would ever go with. If I wanted more than that, I'd be looking at a link/coil conversion or airbags.

Give us a few more details about your truck, and what your intended goals are, and we can start throwing out better options for you.


aa

Well I bought it a little over a month ago. It is a 1984 J20 with a flat bed. The main reason I would like to keep the 35s is because well they are there and the look of the big rubber in the wheel well. The ground clearance is also cool even though maybe not needed. I bought it because it was a good price and my family and I are jeep junkies so it is just a fun truck. Also I drive a 2dr JK so I wanted something that I could use to hall and tow things. (Like a 1963 CJ6 i have been thinking about) It has 3.90s in the rear ends just checked a couple days ago. The 360 was rebuilt 30k miles ago with an edelbrock performance package. It has a MSD distributor and ummm its reliable. The springs are not exactly the most important thing I am just making a list of things for later down the road. First thing first is to paint the under side before winter because illinois is brutal. No rust holes in frame the only holes are the cab corners..not bad. It has been a really cool truck thats for sure.

[threepiece]

Stock front (after '74 or so) is spring under, this was done to accommodate moving the spring hangers from the side of the frame to under the frame.




aa

To expand on this: I believe the front spring relocatin was done to accommodate the introduction of the Dana 44 open knuckle axle in 1974. With the springs placed outboard of the frame they would certainly interfere with the tires because the open knuckle offered more turning angle (less turning radius). With the springs in a lower position under the frame they had little choice but to move the axle on top to keep from too much lift.

[tgreese]

Well I bought it a little over a month ago. It is a 1984 J20 with a flat bed. ...

Look on RockAuto -they list Dayton springs for these trucks. These are also available from spring shops elsewhere on the net, not necessarily under the Dayton name. I was thinking primarily as a replacement for the rears - these are not lift springs, and would return the truck to stock height if you installed them all around and without the blocks.

If your fronts have some arch, you could try removing one or a few of the shorter leaves. You'll need clips and a new spring center bolt to build the new pack, and you're supposed to replace the u-bolts after each use.

My feeling is you're pretty close to ok for 35s at stock ride height. Tire clearance is quite good for these trucks, and you'll have zero issues at tthe rear with a flat bed. A bit of judicious trimming at the front could also help. I would try some factory height rears with say 2" blocks, and less arch in the front.

[eldudderino]

Look on RockAuto -they list Dayton springs for these trucks. These are also available from spring shops elsewhere on the net, not necessarily under the Dayton name. I was thinking primarily as a replacement for the rears - these are not lift springs, and would return the truck to stock height if you installed them all around and without the blocks.

If your fronts have some arch, you could try removing one or a few of the shorter leaves. You'll need clips and a new
spring center bolt to build the new pack, and you're
supposed to replace the u-bolts after each use.

My feeling is you're pretty close to ok for 35s at stock ride height. Tire clearance is quite good for these trucks, and you'll have zero issues at tthe rear with a flat bed. A bit of judicious trimming at the front could also help. I would try some factory height rears with say 2" blocks, and less arch in the front.

So the rear springs I have now are 4 leafs. So would the Dayton 5 leafs have more load capacity anyway?

[tgreese]

So the rear springs I have now are 4 leafs. So would the Dayton 5 leafs have more load capacity anyway?

Maybe. Depends on what the GVWR is of your truck. I recall it's given in the VIN if you decode it.

There is a part book at www.oljeep.com that covers your year. It may give you information about the number of leaves and the how that fits with the GVWR.

[joe]

No telling how after market springs are built? For OEM as mentioned depends on the GVWR. The heavier GVWR set ups run fewer but heavier leafs. The more but smaller leafs on the lower GVWR rigs is for ride comfort.