I have an 89 wrangler with a 6 cyl. Runs good but on highway when I shift to 5 th gear it starts to loose speed ?
The clutch is slipping, most likely.
Very well could be a compression issue with the engine. I had the same problem with my 87 wrangler. Mainly had issues on the highway, especially going up hills.
Search Jeep Wrangler Questions
Jeep Wrangler Experts