[Kermy87]

Are there any main differences between the diffs sj40/sj50 apart from ratios, have just picked up a couple of Zuke”s and side by side comparison they look interchangeable, being a narrow rack or am i dreaming

[Gwagensteve]

You’ll need to clarify what you mean by “diff”
The completed axle assemblies will interchange with the appropriate yoke fitted to the driveshaft and some messing with u bolts and spring plates.

The front and rear axleshafts will interchange.

Front knuckles will interchange along with front brakes assuming it’s a disc brake SJ40.

The housings, diff centre and ring and pinion gears are unique between each model and do not interchange. Sj40 is considerably smaller.