Mine only locks in OD, however my tranny shifts into OD and locks MUCH too early. For example, if I try to accelerate at partial throttle from 40mph to 50mph, the tranny will downshift and then almost immediately upshift again to OD and lock.

My first thought when I bought the truck last year was a bad TPS. I hooked up my OBD2 scanner and watched the TPS. Everything seemed to be fine. I'll double check it again with the method on 4x4wire. Thank you for your suggestion.

Does my 98 have different gearing than my old 95LS?

Yes, US Gen 2.5s with 3.5SOHC have 4.2X versus the 4.6X from original Gen IIs (oldest SRs with 4.88s aside).

Common swap is 3.5 sports that came with the 4.90s.

Also, in my past discussions with OldColt and the MT swap, he was advocating that swap first and see how the 4.2s with a 5-spd ran, then regear if still felt the need.

I had mine adjusted. Or was it the "kick down" cable? It responds better without having to mash the pedal in as much

If I swap in 4.90's from a sport, does it mess with the transfer case or gearing in the front? Does it mess with the rear locker?

Tcase wouldn't care. You'd have to do both axles for when in 4WD.

I adjusted my kickdown cable as well to remove the slack out of it and a little more when I bought my '99... I am satisfied with the way it shifts and what not.

No, not the transfer case but yes the gearing in both the front and rear differential will be different. It does not affect the locker.

I received the A/T Mode switch from Brokeback yesterday. It officially does not plug and play with a Gen2.5. There is a 4 pin connector available in the truck, however the A/T Mode button is looking for 5 pins. It actually does plug in but functions exactly like the HOLD button.

Next I will try to trace the wiring for the 5th pin and see if I can add that to the 98 TCU or if I need to use an older TCU.

You guys might think I'm crazy, but my GEN2 in PWR mode was much more pleasurable to drive than it was in ECO mode. My Gen2.5 feels like it is stuck in ECO mode all of the time. I will probably not be able to investigate this issue further until next year though, so it will be awhile before I have another update.

Are you sure its not the terrible 4:22 R&P, that makes the Gen 2.5 feel significantly under powered.

The gears don't help, but my tranny shifts early taking the engine completely out of the power band and then locks the TC before accelerating has completed. It's terrible.