I did the DJM 3/4 drop on my 68. I have the completed truck box back from the paint shop and the rest of the truck is still there. I remember someone here saying the DJM rear shackle will hit on the box crossmember so the crossmember will need some cutting. Since I don't have the truck here to set the box onto to check can someone confirm this for me? Any idea how much needs to be trimmed. I see the factory indent in the crossmember for the stock shackle clearance so I know where they line up. Anyone have pictures of the way they did it? Or has anyone had a clearance problem or not?

 

F or M100? Styleside?
Just looked at my '67 f100 Styleside and to me it's so close that I would wait to see if there is actually a problem. I do see a slight change in the vertical height of the crossmember but it's well outboard of the shackle travel envelope.
maybe your truck is different.
I hadn't heard of this before but I'll be waiting for others input.

 

F100 styleside. I removed the spring assist set up at the rear shackle, whatever the proper name for it is, when I put the longer DJM shackle on.

 

Doesn't removal of the Flex-o-matic set up require different (longer) leaf springs?

 

Nope. Used my original springs. I checked my notes and prior to the mod my original shackle sat 7/8" above the frame. After the flex-o was removed and the drop shackle installed it was 2" above the frame. So it's up just over an inch. What I didn't check before and after is how much it moved fore or aft, if any. There's also a second set of holes on the new shackle an inch shorter. In the picture I'd only done the shackle. I wonder if the spring is too long, if anything?

 

I thought the flex-o-matic springs were longer from the pin to the back eye, mine are about 31-32" where regular springs are about 28". Here is link where someone did lowering shackles and where they trimmed https://www.ford-trucks.com/forums/1...c-springs.html. Uni Moe, you started that thread..

 

So your pickup looks like a short wheel base.
OK your spring eyes look WAY well behind the shackle box pins. I'm pretty sure the crossmember will totally interfere. Also when the weight of the bed gets on the frame it will get worse. Loaded even worse. Could have a bad result if a heavy bump lengthened those springs out even more. You need shorter springs.
I just looked at my NON Flexomatic spring shackles and they are actually forward of the box pins by almost an inch. This is what you want. I think you need the NON Flexo springs. And perhaps that way you won't have to cut the X-member.

 

Okay, my truck WAS a long wheelbase truck with Flexomatic springs. I've shortened it. I looked in the NPD catalogue. They measure springs from one eye to the axle bolt plus the other eye to the axle bolt. Long wheel base with flexo are 24 + 32. Short wheel base without flexo are 24 + 28. A full 4" shorter on one half, I'm assuming the rear shackle half. That explains a lot.

 

.... Hmm.. i thought non-FOMs were longer. Well, at least yer aware of the issue.

 

So now you may need to confirm the distance from the axle centerline to the rear shackle hanger pin ON A SHORT wheel base. Make your truck the same if it isn't already. Then use the SWB non-FOM springs and you're GTG
Looks like you just need the shorter springs to me but best to make sure of the geometry since you shortened your frame.

 

32" from leaf pin to back shackle eye is correct and what my SWB flex-o springs measure out at too. I agree with 67 StylesLide, If you use the regular leaf springs you shouldn't need to trim anything by using a longer shackle, providing your wheelbase is exactly the same as a regular SWB truck.

 

I thought I remembered ND Bill posting in the past the with or without Flex-O-Matic suspension the springs are the same length. So I just looked. This is true. Believe it or not Ford lists 3 sets of rear springs for 66/71 F100 4X2's. Between those years there are a few part number changes but always listed the same. By check load rating. 950#,1250#, or 1650#. Not even SWB or LWB! Strictly by those check load ratings.

 

Check out these, flex-o's and regular springs are different length.
https://www.ford-trucks.com/forums/8...x-o-matic.html
https://www.ford-trucks.com/forums/1...-backside.html

 

My pictures are in this thread. If there's anything else you need, let me know!

 

Thanks 68Murc. That's the thread I was looking for!


So here's what I conclude:
If you do a DJM rear drop kit and you have the Flexo-o-matic springs you have two choices. Either keep your original springs and notch out your box crossmember to allow clearance for the DJM rear shackle after Flexo parts removed,
OR
Spend money on standard (non-flexo) springs which are 4" shorter and don't notch your crossmember.


I priced a pair of springs, same spec (24 + 28, 4/1 leafs, 950lb) from three places shipped to N.Dakota:
NPD $439.80
SD Truck Springs $404.36
General Spring $350.98