I have a RV on F450 chassis when we cross some bumps or try to enter ramps the tail will drag. The front also sits low in comparison. I need to find some lift kits I guess of about 2 inches for the front and rear, just dont know if there are any out there for these vehicles. I dont know if the lift blocks from the F series are the same?
it has been recommended to just get some longer shackles to help PU the rear end. Fairly long overhang is the problem not the springs etc.
Well, no this is not true at all! Shackles--for those of us from the'60's when raising a car's rear end to look cool---do nothing to improve a thing related to weak springs. In fact any change in static or ride height affected by longer shackles tends to return to the sagging height eventually.
The tail dragging thing only over bumps directly speaks to sagging or weak springs. Effectively that longer tail adds weight to the rear springs, perhaps almost too much they can't overcome it. I wonder if this doesn't also contribute to such springs wearing out sooner than expected?
The dragging on entry ramps is certainly about the overhang which suggests to me the static ride height is a bit low when driving on the typical city streets. A lot of parking lots etc aren't really designed or built to accommodate RV chassis where the body extends so far behind the rear axle.
I'd suggest making sure the rear springs are sized for your load and length first. After that it might simply be a matter of avoiding or more carefully (slowly) entering and exiting some ramps.
Just curious OP have you yet had this RV chassis to a known good local spring shop?
Just some incite on your plan, you've obviously not looked under your van to see whats on it, the actual geometry of your suspension system, the shackle swings above the mount, you can drop it easy, get an extended shackle, but raise it, that is an entirely different job, can be done, many 4x4 guys do it, but intensive, and requires the use of many special tools. I have lifted many vehicles, have owned 4x4's for years, had to jack them up, and those shackles you are talking about, they are garbage, put a strain on the bushings until the body shifts side to side, floating on them, the springs going from left to right, creating a driving hazard, the factory don't use them for good reason.
Get an add-a-leaf, requires cutting off the U-bolts, be sure to buy another heavy set, those long ones at parts stores are not the same diameter as the factory set, they are not heavy enough, need some heavy duty jack stands and pressure treated 4x4's to make cribbing to set the jack stands on to get it high enough, the springs droop down and need to be off of the axle that rests under them.
Your first order should be to get underneath and see how the leaf springs look.
Do they have a negative arch? (bowing up)
OE springs arch down, the axle is lower that the shackles.
Few years ago, I had the rear leafs go on a cube van, took it to a spring shop, and they added 2 leafs on each side, took care of the sagging rear end, took care of the body roll, which was really bad on the open highway (rocking side to side and couldn't keep the front end on the ground for steering) with a load in back.
Problem was this way, was rock hard ride with the added leafs, and $530 cost.
The 14ft cube van I'm driving now, the OE leafs were not made for that I haul, and I op'ed out to go the Timbren route this time, and love them.
Picked up the rear end, stopped any and all body roll, and took about an hour to install them (myself) and cost, under $300 for the E350 kit (6000 lb kit)
Plus, when I get a 1200# load skidded in the box, the rear end does not drop at all.
Great way to salvage the OE springs. As long as your springs are not broke.
Then you have no choice but to go with new rear leafs.