96 Ranger 4.0 4x4 reluctant to overdrive

[GreenRanger9096]

Hey guys, gonna keep this short and sweet.

My truck has 33" tires on it and at high way speeds (55-60 mph) the truck would rather stay in 3rd gear at 3.5-4k RPM rather than shift up into overdrive. Shifts slightly rough (compared to a new car) nothing alarming, 3.73 gears, 128k miles, no transmission service that I know of to date.


Any input on what could cause this? Truck will be going in for Trans. Filter / fluid change tomorrow morning, hopefully that will help. Also noticed the trans is slightly 'over filled' from the last oil change, could this cause the shifting issues?

 

[4x4junkie]

I would guess it's the bigger tires combined with the fact it still has stock axle gears.

Will it shift into OD when going downhill at that speed?
Have you tried putting stock size tires on it to see if then shifts into OD?

 

[hondaxr650]

33s are just too big for the 3.73s. I'm runnin' the same combo and have the same problem. Coming to the slightest uphill grade makes it shift out of overdrive and you almost have to be going downhill to get it to shift back in. I'm going back to smaller tires when mine are worn out since I don't have the time, money or ambition to regear it.