Outer Limits 4x4 Board

I have a 1991 Triton 2.5td and the weak link seems to be the gearbox which had a kit in it a couple of years ago & is still a bit noisy in 5th at times.
What I need to know is there any way to overcome this without massive expense?
Can a later gearbox (which one?) fix the problem?
Do I need a different t.case with a later box as well as different drive shafts?

There are some new boxes available aftermarket & I would like to be up to date on this before buying!

Thanks all.

This is a tricky one.
The 2.5 diesel will basically have the 4 cylinder size gearbox and bellhousing either the KM145 or V5M21 gearboxes.
The gearbox you want is the V5MT1 which is from the V6 and is much better.
I believe the t/cases will bolt up to either size gearboxes.
The question is will the V5MT1 bolt up to a 2.5 diesel ??
I have been told the V5MT1 has several different bellhousing sizes to fit the 4 cylinder, 3.0 V6 and 3.5 V6.
The question is finding one and then there could be other changes that are required such as the clutch assembly.
I can't answer your question outright as it would take a bit of research and Mitsu just loved to change things to make life difficult for swaps etc.

Thanks Bitsamissin, will try to find out more.
Standard is the easy way out but maybe not the strongest.