[02XLT150]

Once in while when accelerating(going through all the gears) on the highway, the transmission will skip fourth gear and go right into overdrive. I can turn off overdrive and the truck will stay in third gear, but I can feel that overdrive still kicks in. Is this a computer issue, or is this a sign of transmission failure? I had the fluid changed about a year ago. I am also using custom tunes on the Gryphon. Any advice would be appreciated.

[Power Hungry]

I highly doubt that it's a transmission issue. It's probably more of a shift pattern related concern than anything else. Does this odd shifting occur when the engine is cold? Hot? Moderate acceleration? Hard acceleration? I'd be inclined to think that it is probably just situation where the converter lock strategy might be close to the regular shift which causes the converter to engage at roughly the same time as the shift. It cold also be offsets based on the cold shift strategy.

First thing to check is your tranny fluid. Is it unusually high? Normally you'll be between 160 and 180 under normal driving situation. Again, I doubt you'll find anything unusual but it doesn't hurt to check.

If you can let me know which tune(s) are experiencing the problem and anything you else you can add about when they occur (vehicle speed, throttle, temp), I can look for strategy related issues.

Thanks.

[02XLT150]

Thank you for the reply. I drove to work today which is only like a 5 mile trip and I had the transmission skip 4th gear when I was going about 45 mph with no more than 1/4 throttle. I didn't have the trans temp up on my gryphon, but I know the temps wouldn't have been very high for that short of a trip. I took it for a short drive tonight but it didn't skip any gears. The trans temp only made it up to 143 with a short trip on the highway. I've noticed this skipping problem can happen anytime and I'm pretty sure I'm doing no more than half throttle at max. I only use the custom tune you made for me which is the 89 performance tune. If you need any more information, just let me know.