Have an old 80” trials car with a hybrid of S2 and S3 running gear.
Engine, axels are S3 but the gearbox is S2.

The box is needing a refresh/overhaul and I feel changing to a S3 box would be a better move for the car. It’s jammed in low range and the shift is awful between gears with trying to find first a good guess at times.

With it being a S3 engine, the S3 box should, ( should being the key word ) be a straight swap with minimal faffing about with pipe work etc.

Am I correct in thinking or believing it’s far more simple than reality.

As gathered, I’m not worried about originality on the car as it’s lost it’s original running gear before I was born.

Moving to a 3 box is good as it is said to be stronger. It will fit, the main problem is the clutch slave operation. 2 has it on the drivers side in an upright position, 3 in a horizontal position on the near side. So pipe work will need modifying. It is possible to put the 2 clutch bell housing on a 3 box. Which way you go may depend on your present set up.
Having once shoehorned a Range Rover V8 and gearbox into an old 80 inch trailer I know these jobs can be shall we say sporting

I always heard that the S3 box is weaker- from experience i have had more s3 boxes fail or develop major problems than the S2.

Is your 80" still using pedal through floor arrangement or later footwell pedal arrangement.

The weak point in the 2 box is the lay shaft. In the 3 syncro first and second gear said to be not as strong as the 2's . Both late 2a and 3 gearbox's use the same bearings.

It’s on a later pedal assembly, either a 2 or 3 assembly.

The box that’s in needs work and tbh, I can’t be bothered getting it fixed, it’s beyond my ability to fix and it’s expensive to get refurbished.

So trying to get a good box and swap in.
Given it’s a 2.25 in an 80”, I think a S3 box will be fine.