I see a lot trouble in the replacement of the older Airstream Marvle 2500 lb jack. The problum seems to be that the old jack has an outside dia. of 1.9in and the replacements all seem to have a dia. of 2.125 to 2.375. The newer jack will fit in the top hole but not the lower hole. Many are grinding the lower hole out fit the newer jack. While this works to mount the jack you wind up loosing the use of the wheel and the extision leg that came with the Airstream.
Attwood does make a 2 in od tube jack they are only raited at 1000 lb or 1500
lb, and most boat dealers cary these in top wind and frount wind. I feel that the lighter weight cap concerns me.
So what to do?
It seems that the major proublums with the old jack is that the jack scerw has stripped, you wind and jack bobs up and down.
I rebuilt the old jack.
Simple go to Lowes or Tractor Supply or Home Depot and buy a 5000 lb top wind Bull Dog jack. To take the jacks appart grind off the swedged end of the pin that holds the handle to the top of the jack and drive it out. Now take the inner tube out with the jack scerw. Set inner tube in a vice or good chopsaw and cut it off square [this is vary important that this cut is square] aproximitly 1/2 in down [on the new jack make sure that the scerw is all the way to the top out as far as it will go so it does not get damaged]. Now gind the new center plug [or nut] so it will fit in the old inner tube [make sure to keep it round and centerd I use a lathe]. When it fits in the old inner tube stick it in aproximitly 1/2 way and weld it in [veary important keep it square] and grind it off to the od of the old tube. Install the tube back in old outter tube using lotts grease on the inside of the tube and the scerw. Reinstall the handle with a 1/4 grade 8 fine thred bolt and lock nut.
Injoy anouther 40 to 50 years of happy jacking.