I've got a 2000 Ranger with 70,000 miles. When I start driving first thing in the morning (or after the truck has been sitting for a long time), I have to accelerate quite slowly till it shifts into 2nd at around 15 mph. If I accelerate normally it tries to shift but won't engage. In those situations, I let up on the gas, wait about a second or two and then it engages. After that, I'm fine. It's a problem when I'm leaving work and try to pull out onto a semi-busy road!

I feel like I read somewhere that this can happen when there's a transmission cooler. Since I have a transmission cooler, could I possibly fix this issue by slightly overfilling the transmission?

 

Are you the original owner?
Did you install the cooler or is the cooler original to the truck? My 2005 came with a cooler and tow package.
Is the truck used for towing?
Did it come with a hitch? If it did, it may have towed plenty under previous ownership.

Check the fluid level.
Does the fluid smell burned at all?
Infer what you can from wiping the dipstick on a white cloth but remain open to the idea of transmission maintenance.
A 26 MY old transmission, even with your low mileage, wouldn't be hurt by a pan drop and filter change.

A 6-pack of MerconV is what I bought on Amazon for my next service. Look for a sale price.
Since MerconV is fading into the sunset, I had to hit several Walmarts before servicing my friends' Fords
Also, buy a filter which includes the pan gasket.

I included 10 oz. of LubeGard (red bottle) when I refilled mine. The product has improved shifting in several of my vehicles which use mineral based ATF.
MerconV is a mineral based fluid.

Fluid & filter servicing is the cheapest thing you can do first.

 

I'm not the original owner; I'm the second owner. It did come from the factory with the cooler and tow package. The original owner gave me the impression that the truck has never towed (and I haven't towed with it). The fluid looks good and doesn't smell burned, but I'll change the filter and fluid and see if that makes a difference. I'll also add the Lubegard you mentioned.

Thanks for the advice!

 

My 2005 was purchased by a family and used primarily to shuffle their 6 sons to and from college dorms and first apartments.
It surely may have towed, but I don't think it was ever abused in any way. The owner was diligent with oil changes and repairs.
However, there was no gear oil or transmission fluid servicing. My fluid was dark maroon and smelled OK at 50k but it felt good to get half the dirt out.
My original filter looked completely 'debris free', but it's good to know. They do catch weird stuff sometimes.

I got a replacement transmission pan with a drain plug from Dorman.

 

Update: I did what you suggested: Replaced the filter, added 10 oz. of LubeGuard and topped off with Mercon V (about 4-4.5 qts.). Since then, it hasn't missed a shift. Thanks.

 

Glad you found joy.

If I experienced your condition and cure at 70,000 miles, I'd consider doing another drain & fill (leaving your new filter in place) after 1,000 miles of driving.

Why, you ask?
Your fluid was dirty enough to effect shifting as you described. That's bad. It's real good you caught it.

The total system capacity is around 11 quarts By dumping half your fluid, you got rid of half the dirt.
The other half of that "dirty original 11 quarts" stayed in the transmission.
By doing another drain and fill, you'll remove more dirt. You'll get "half of the remaining half of the dirt", or another 25% of the total "original" dirt out of your transmission.
You'll be doing a more thorough job.
Plus, it ain't that hard to do nor is it expensive.

Remember, dirt abrades transmission parts. Don't you want clean, slippery fluids rather than fluids with grit?
Half the dirt which gave you problems is still in the transmission.