This weekend I plan on installing lowering hangers, lowering shackles, and cutting approximately 1 coil off of the front springs.

I was initially worried about the negative camber in the front, but after searching the web, YouTube, and looking at the positive camber I already have in the truck, it should actually make the camber fairly neutral.

I've got a pretty good understanding of how to do each modification, but from what I've read, driveshaft length is also something to consider, specifically how much yoke travel I can accommodate, as well pinion angle.

Pinion angle can be fixed by adding shims under the leaf springs specific to the amount of angle gained/lost after being lowered.

Is there a way I can test the amount of possible travel that the driveshaft currently has, so that I either know I'm good to go, OR that I'll need to have the driveshaft shortened prior to actually lowering it? Is there a good rule of thumb that I should go by?

 

When I lowered the rear of my 4wd, which has a two piece rear shaft, I first compressed the slip joint and placed a mark next to the larger piece showing me max travel, then I installed it with the lower rear, put a zip tie snugly to act like a "tale tell" on a tachometer. It let me know how far the slip joint compressed just runing around the yard before taking it on the road, and then I took it for some drives on back roads gradually going faster through dips ... and soonI knew I was very near the point of maximum push in and after that, the arc of the axle will pull it back.

In your case, if I had the one slip joint at the transmission, I'd undo the rear U-joint and push the drive shaft forward until it stopped, mark it with my sharpie, the do the lowering and put my zip tie on the slip joint to tell me ... if I was concerned.

 

How much drop you going for? You can always find a MDT truck shop or a frame repair shop and see if they know how to bend the beams if the camber needs adjusting. They're the only places i know of that might be local and still know how to do it.

Before lowering it, remove the driveshaft and measure from the trans output to the rear axle yoke. Do all your lowering, then re-measure at the same spots and have the D-shaft modified that amount. I've seen trannys split in half when a D-shaft gets shoved into it, so it's not something I'd take a chance on.

 

The typical shackle/hanger rear drop is between 3-4 inches. Cutting a coil usually results in between 2-3 inches. Nothing super drastic.

So if I'm reading you right, there is no option but to remove the amount the amount of yoke that is subsequently pushed into the transmission output after lowering.

Let's say before lowering, have approximately 3 total inches of travel before bottoming out and after lowering I have 2. This being a street truck and not intended for heavy hauling or off-roading, would the two inches of travel still fall within acceptable tolerances? I've read for some classic cars 3/4 - 1 inch of space before bottoming out is sufficient.

I'll get it cut if absolutely necessary, but hoping to get clarity on the absolute part.

 

You've got way too much slip yoke showing now! The answer after lowering normally is to have the drive shaft shortened but you will need to measure from "U" jonit to joint. The worn part on your yoke is the travel. I guess you could saw off part of the slip yoke but you may have the wrong one. Need to insure it wont bottom out of course.

 

Cutting the front of the yoke does nothing to shorten the transmission tail shaft or it's housing ... and that is a lot of yoke showing there now (but I have never looked at one under a Dent F100 or 150 2wd with 1 pc rear driveshaft) ... why I said test travel by hand first with rear U-joint unhooked. I'd say that unpainted, wear evidenced part, just shows how far in it went at some point with the truck at current height ... unless the yoke is from a different vehicle. Of course, if you lower the truck, you also reduce suspension travel so while the yoke might ride further into the transmission, it ain't likely to move a lot more.

If it'll be OK at "frame bumpers on axle" bottomed out under a ton+ load now, then it should be OK if you just put longer shackles that poke up into the bed and let it ride permanently on those same frame bump stops.

I was cautious because by removing my 3" OEM blocks, I was also removing the "wings" on them that hit those same bump stops on a 4wd which would allow my axle to travel 3" higher. I did swap to shorter 2wd spec rear shocks too.

I know it would at first seem like lowering always shoves the driveshaft front yoke forward, but the axle is "swinging" on the rear leaf springs that are anchored at the front to hangers that do not move unlike shackles, the front of the spring under load will flatten some, and with the arc, will at some point of travel swing the axle rearwards.

 

I unbolted the rear of the driveshaft and pushed as far as it would go into the trans and it bottomed out at the base of the yoke. The approximate amount of that travel is 2.25".

 

Swallowed the whole thing huh? Likely you're good to go then. At this point, I'd do my lowering, then put the rear U-joint back in place. Once it's all together, I'd still put a zip tie on the yoke next to the transmission to act as a "tale tell" as the transmission will push it back on the yoke at maximum engagement reached.

 

Sounds like a plan! Thanks a ton. I'll take measurements and before/after photos and post 'em here.

 

While planning this out and looking online at how others have done it, I came across an interesting problem with the upper bolt on the rear shackle. The bolt head faces inside, toward the bed, and is too long to pull out once the nut is removed:



I don't want to cut the bolt as some others have, and it isn't seized so this is what I'm thinking:

1. Remove leaf spring from front hanger
2. Loosen u-bolts on axle
3. Remove lower bolt from rear hanger
4. Shift leaf spring until clearance, remove upper bolt from hanger

Is my thinking somewhat sound or will I likely run into an issue with this approach?

 

So I went in the garage, thought about my plan, and decided that I'm probably over complicating things.

I unbolted the lower rear shackle and WHAM!!! spring under load hits the bottom of the bed. Well now I can get the upper bolt out fairly easy, so I do.

I then install the new shackle, and use a combination of a bottle jack between the u-bolts and the frame, and a crow bar to pry the leaf spring back enough to slide the bolt through.

Now on to cutting/drilling out the rivets on the front hanger.

 

Before:




After:




Getting the rivets out of the hanger were the largest challenge. Ended up cutting the rivet heads off after cutting an X and trying to air chisel them failed to work. Then proceeded to hammer on them with an air hammer combined with a 3lb sledge and punch for what seemed like a total of about 6 hours spread across 2 days. Finally got them in and bolted up but the leaf springs no longer lined up with the holes. A combination of a jack under the axle and a bottle jack between the leaf spring and the frame straightened out the leaf spring enough to pull it into alignment with a stout screwdriver.

The fronts were fairly easy, just a lot of rusted bolts. The top of the shock complete broke off when unbolting it, which prompted a trip to Advance for a pair of Monroe Gas-Matic front shocks since they most matched the dimensions of the DJM drop shocks (and I needed them asap). They work pretty well so far. Other than that, I cut off 1.5 coils off of each of the front coils. I'm sure the new shocks are adding a bit to the ride height (maybe not). Overall not as drastic a drop as I was thinking, but when I upgrade the wheels/tires to a Torq II they'll likely tuck a little nicer.

 

I hate to sound ignorant, but why would lowering the truck a small amount require(potentially) the driveshaft to be shortened?

I have has plenty of lowered vehicles and have never heard of this issue...none o fthem were old trucks however either. LOL

 

It depends on the track of the rear axle in relation to the transmission. Some set ups, lowering the rear down on the axle will shorten the distance from axle to transmission. On others it will only do so a little bit before stretching the distance. It depends on if the axle goes straight up, or swings in an arc towards the rear, or even in some rare cases, moves forward under compression. It is worthy of some attention.

 

I will have to pay attention when I gett of my butt and install my stuff that has been in my garage for 4 months LOL Thanks for the info