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