Isuzu Trooper Owners Club UK™

[Smudger096]

Hi all, I have a 93 bighorn auto that engages all 4 gears, but is running 3100rpm at 62mph, the switch behind the gear selector does nothing when pressed, any ideas please?

[Google]

[placebouk]

When was last time you did a full ATF flush? Believe in total is 8ltrs to flush the entire system.
If you just drop sump you only replacing approx 3 ltr?

Your oil shud be red/pink and smell sweet!
If is browning or smells burnt it needs a change.

Since you mention rev and speed i would rule out speed sensors in the box playing up.
Other areas to check could be temp sensors believe there is 2 for auto, been while since i looked at my truck or had a play. But the OD system is reliant on temp aswell.

After this i would suggest checking wiring harness too the box, runs passenger near firewall, down under truck and then along truck and into the box itself to the solenoids internally in the box but also splita off to the inhibitor switch on the drivers side the box and a few other sensors which i forget what  are.

Make sure all wires are in good condition, actually feel along the entire length of the wires

When i did mine i had to repair 5 weak points/breakages in wiring that was degrading from age.

Last stop would be to strip the inhibitor/neutral start switch off the box and carefully, open it up and clean it, regresse it with dielectric grease and put it back on. They get twitchy when full gunk.