How do you repair an Allied 3.5 ton hydraulic floor jack, model /# 45491SUV

=release the valve so no pressure in cylinder.
-clean area around filler hole on both cylinders
-use compressor to blow out area so no contaminants in hydraulic cylinder.
-USE ONLY HYDRAULIC JACK FLUID
-fill cylinders till you can see fluid just below opening
-close valve to activate jack
-bleed cylinders by pumping arm of jack to remove air from cylinders 10-15x.
-replace filler hole plug
-test jack (if doesn't work properly, bleed again

-

possible blown internal seal

A generic replacement will be fine. Princess Auto near me in Canada sells lots of 'wheels'.

https://www.google.com/search?q=automotive+jack+replacement+wheels

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The average mass produced trolley jack capacity 1.5/3.0 tons has been for a few decades an item of generic manufacture - copies of copies that are label engineered and with minor differences in detail to suit different price/value brackets.

Unless a jack is a special type such as low entry, lightweight aluminium, quick lift or an extra high lift long chassis type, the standard types are now available so cheaply it is hardly economic to replace many parts as part of a repair, especially as such parts that tend to be available through the dealer tend to be grossly overpriced. A seal kit where available as a spare part for the jack from the brand dealer is likely to be similarly overpriced.

The most economic method is to buy such seals that are needed from a local hydraulics specialist, of which there is certain to be at least one in every town.

Presume it a hydraulic jack. Most are sealed, some of the more expensive types will have a valve, usually hidden somewhere.
But what you need to look for first is where it is leaking from.
If it has lost fluid chances are one of the seals have blown.

https://www.harborfreight.com/15-ton-aluminum-racing-floor-jack-with-rapid-pump-62160.html


https://manuals.harborfreight.com/manuals/62000-62999/62160.pdf



1 5 Ton Aluminum Racing Floor Jack with Rapid Pump

You really need the car on a lift or tall jack stands to do this. You will need a full set of hand tools, a good hydraulic floor jack, a set of Jack stands (AKA Safety Stands) and a 1.5 Ton bottle jack. Raise the front of the car as high as possible and unbolt the old mounts from the engine and engine cradle, then Carefully using the bottle jack (put a piece of wood on the plunger of the jack to avoid damage to the oil pan) raise the engine off the mounts and remove them, and reverse install new mounts, time about 2-3 hours to do the repair.

hydraulic jack oil. or like me use regular transmission fluid

About every 15 years, they need to be rebuilt

Have to find a hydraulic jack repair shop in your area

2 1/2 ton should be sufficent!