Can anyone tell me what the stock unloaded distance is between the top of the rear leaf spring at the point where the axle u-bolts are and the bottom of the frame on a '92 D250?

I'm installing air bags on mine and it says that the kit is designed to be installed with the truck unloaded but I don't really want to have to remove the topper and tool box and auxiliary fuel tank to find out what height to install it at. My concern is that if I don't pre-load the bags enough, they might get damaged if the axle drops down and hangs off the shocks.

Thanks in advance.

 

Not sure on the measurement, but you could always juack the truck up by the frame to allow the axle full droop. Then at least you'd have a 'worst case scenario' measurement. Then, measure where it sits presently and get the difference. If it's, say, 6'' and the bags are only good for, say, 4'' of travel, then you'll know you need to cheat the mounting 2'' up to compensate. Anyhoo, here's your bump

 

I'm with Toyota boy.

 

Jack it up till it sits level & install the kit in that position.

 

Good stuff, Dave, good stuff.... (in my best Stewie Griffen voice)

 

Just for the record, here is what I found. My truck, with it's current load, was sitting with the springs basically straight (no arch) and in that position, I still had 2" from the axle to the bump-stop and 6.75" from the spring to a bracket on the frame (reference point). I then let the suspension on one side drop to full droop w/o a wheel on it. My distance from the axle to the bump-stop increased to 6-5/8" and the distance from the spring to the reference point increased to 12-1/8".

I chose to mount the top bracket using the front bolt that mounts the shock absorber crossmember for one of the mounting holes. With no air in the shocks and the weight back on the wheels, the air bags are slightly overcompressed but any air in them (5 psi minimum according to the instructions) should keep them at a safe level. They can overextend more than I am comfortable with so I will have to be careful until I can fabricate a limit strap but the instructions do say "Once the air helper springs are installed, it is recommended that the vehicle not be lifted by the frame, as over-extension may occur, resulting in damage to the air helper springs. However, should it become necessary to raise the vehicle by the frame, deflate both air helper springs completely.".

I need to go search and see what Jim Lane came up with for his.