In some ways IH just didn't keep up with JD and Case on their tractors. Particularly in the transmission. The 86 series were good tractors and huge step up from the 66. The only thing lacking was an easy to shift transmission that JD had. When they brought out the 88 series I think that was a "Hail Mary" and a last ditch effort to keep going. The only thing that was better in those tractors was a synchro transmission and hydraulic clutch. But with no TA it didn't give that H or L option in every single gear. Or if those tractors would have had a power shift from 1st to 6th gear (similar to the Case) it would have made those a LOT more desirable tractors. Our 5088 was poorly balanced compared to the 1086. The forward air flow was a joke and did not cool the engine as well as it should have. The doors opened the wrong way and made it more difficult to get in and out.
The Magnums were supposed to be the next IH and not Case IH tractors and when those tractors came out I think they were the best on the market. Good hydraulics, Cummins engines, power shift standard on all models unlike JD, a roomy cab for it's time unlike the coffin cabs of JD at that time, muffler was moved to the side and out of the driver's line of sight.
If IH could have held on another year or so they probably would have made it. I think it was their lack of keeping up with Case and JD tractors and of course the farming crisis of the 80s didn't help them either. They were behind on the tractors but ahead of the game with the combines. One great thing IH did in the 70s and 80s was using the same oil and fuel filters on most of their tractors. Made servicing them very easy.