We think the engine is shot. Possibly a bad piston or rings.
Are parts availble to do a rebuild? Might do a compression test to see.
It does run but has a miss and is low on power. Are replacement engine availble or maybe a repower with kubota engine?
I have rebuilt 3 of those engines, using 0.5mm oversize pistons. A few years
ago, they were a bit over $100/hole for the piston/ring set from JD. If
you have a broken piston, I have some spares if you don't need oversize.
I am about to do a JD4300.
Forget about a new engine from JD, unless you find a 3TNE84RJ in old
stock at a dealer somewhere. I looked for one when I started my first
955 rebuild and I found a dealer who had one....for $5300!
As for replacing the engine with a non-JD, that is a very doable project,
since the 955 has a full frame and no bell housing betw the engine and
tranny. Only a bare drive shaft with no clutch. I considered subbing one
of my bad engines with a gas Honda engine I happen to have. Also, the
955 has its hyd implement pump on the back end, rather than on the engine.