I have a project 79’ F150 4x4 with an extra leaf in the back and no stock lift block (Leaf springs sit directly on axle). The truck came this way and I liked the height so I kept it the same.

Trying to figure out which shocks to go with. I ordered the stock shock length, before I realized the block was missing. The measurement between shock mounting points sitting is ~21.5 inch. I lifted the rear with the axle hanging and they measured around 23.5 fully extended. This is no weight on the frame, only the rear tank is installed now. The shocks I have are 22.625 extended and 13.75 compressed.

Would these shocks work or should I be concerned about the inch short on the full travel out? I’m worried if I go with something a bit longer that my compressed height will be an issue, which I can’t really confirm without weight in the back. I already have these shocks and can’t return so I was leaning towards giving them a shot unless it’s a terrible idea.

Appreciate the help!

 

It’s pretty normal for shocks to not reach full travel of the suspension.

 

I removed my 3" rear blocks (factory) there over the axle / under the spring stack ... and my '77 4x4 has 4 main leaves plus the one thicker overload under them ... and it now has a 1" block there over the axle / under the spring stack. I had Monroe Gas Magnums on it, but I was worried it might totally compress the rear shocks then since I do occasionally load it and a full compression might damage the shock mounts before the bump stops caught it. I used Monroe #3911 new rear shocks as they were specified for a 4x2 truck.
I can't shake it ......... Lowering rear only idea - Ford Truck Enthusiasts Forums (ford-trucks.com)

34911 for 2x4 extended 19.750" compressed 12.375" travel 7.375"

34901 for 4x4 extended 22.625" compressed 13.750" travel 8.875"

The 34911 are 2-7/8" shorter extended and 5/8" shorter compressed than the 34901 that I had on it. They mount exactly the same. I forget the figures now, but I did measure my lower shock mount to upper shock mount on the truck and that 5/8" shorter compressed length is enough that they will not bottom out. It was gonna be close to bottoming under full compression if I left the longer 4x4 shocks on it. Extension didn't worry me but compression under a load could overwhelm the mounts I think. If you're never going to carry heavy, there is a good chance you're maybe OK. It may be that someone in the past rearched or otherwise changed your springs and eliminated any blocks? 21.5" sounds like a lot without blocks, would seem to extend my 2x4 shocks full just sitting?. The factory blocks on these trucks had "wings" to limit compression of suspension as the "wings" contacted the bump stops instead of the axle tube doing it.

Now that was with my 1977. With my 2007, I lowered it 2" in back by removing the 2" factory blocks and using new bolts, I kept it's 4x4 shocks in place as measuring told me I was maybe OK, and I don't carry heavy in it anyway. I lowered the front too, to maintain rake.

 

Thanks tbear. I know you helped me on another question asking about blocks and you suggested the same 2x4 shock. I was going to go with that as you suggested but when I measured I was surprised that the 4x4 would be almost fully extended when installed as it sits now, just the frame and gas tank weight. And thinking I would have to add weight to the back just to get the 2x4 installed sounded odd. So I was second guessing myself and thinking, like you said, that someone could have rearched and/or the extra leaf is raising the height.

How do you measure the compressed length needed accurately? Measuring the travel of the axle to the bump stop and using that to measure up from the lower mounting point, and retake the measurement to the upper?

Appreciate the help as always. You have a wealth of knowledge for these suspensions. I’m sure I’ll come-a-calln when I get around to the front too! haha

 

On the truck, I measure from the center of the top hole, which on these is a big round hole in a plate, to the center of the lower end bolt holes. I can estimate how much to take away for compressed suspension to the bump stops.

• Of course, if the axle is going straight up to the bump stop, the lower shock mount is going in the same direction, but the shock top is ahead of the axle. One way of guesstimating, is to measure the bump stop distance to contact point.
• Let us say it's 4".
• Then I take one tape, adjust and lock it so the 4" mark is even with the lower bolt hole, stand the tape so it's beside the bolt hole at 4", and pointed near to straight up as the axle will move knowing that the leaves will flatten, which will counter some of the angle generated by the spring mounting. It works out pretty close.
• Then I use a second tape to measure from the center of the top shock mount big hole, to the "0" end of the first tape still standing.
• In the example, 4" travel, likely the shock is only gonna compress nearer to 3".due to it's skewed angle.of travel.

The shocks, I used published figures. At the lower eye end, the maker will use the same hole center the bolt goes through. At the top end they use the point between the bushings where they hug the big round hole. Typically, I do not compress the rubber as it's not needed. I just tighten the top nut on the stem until the bushings are snug enough they don't spin easily. Usually, I'll add a jamb nut or a stamped steel jamb nut from the install kit.