Jeep Wrangler Sport, 4.0L, 5-speed NV3500 transmission

A friend has a Jeep Wrangler Sport, 4.0L, with a 5-speed transmission? It currently has the stock NV3500 and he was told it’s going bad. He said he has heard mixed reviews on that model and some Jeep forums call for an upgrade instead of having that one rebuilt.

He is seeking advice on an upgrade. Could he replace the NV3500 with another bolt in available trans (with as minimal mods as possible) ?

I don't know the year or the exact issue but am awaiting an answer. I thought there might be allot to be learned asking here. Thanks in advance

If it's a Jeep it's a 3550.
There's info on Wikipedia.

Here's the Novak Gear writeup.
https://www.novak-adapt.com/knowledge/transmissions/manual/nv3550/
Novak is big in the 4WD world and they don't seem to think the 3550 is so bad. The only transmissions they talk about for swaps are granny low 4 speeds from fullsize pickups or larger. This is for the rock-crawling crowd. Giving up the overdrive gear for a Jeep driven on hard surfaced roads would be a mistake, IMHO.

Remember the three most dangerous words, "I have heard."

R.