Transmission starting to slip on and off

[98FordLove]

So I just noticed this weekend that my auto trans is starting to slip when going from 1st gear to 2nd gear. It only happens when the trans is fully hot and been running for awhile. It doesn't slip all the time, just on occasion and it's very random. I do notice it tends to slip more if I am light on the acceleration. But if I'm noticeably heavier on the gas, it won't slip. This makes no sense, I would have thought that harder acceleration would cause the slip to show more.

I checked the ATF and it's dark red and smelt like hot rubber. I guess you could say it was a strong smell but not nessecarily a burnt smell. The ATF level was quite a bit over the max line, I'd say by half a quart. But I've been driving it with this ATF level for the last 3 years when the ATF was last changed and no issues until now.

1) Should I change the ATF and see if it helps?
2) It says on the dipstick to use Mercron. I'm 99% certain the ATF in my trans now is not Mercron. It's just standard Prestone's Universal American car ATF that comes in a yellow bottle.
3) Is there an issue of me keeping the trans in 2nd gear and then manually shift into D as I accelrate? Then shift back to 2nd gear when stopped. Or will this damage the trans? This way I can avoid the 1st-2nd shift.

What would be the next step?

Thanks

 

[wollimann]

It only happens when the trans is fully hot and been running for awhile.

If you have a transmission oil cooler (not the one inside the radiator) check if it works,
maybe the transmission oil gets too hot.

MerconV oil is recommended, i would give it a chance.
But you don't want to mix up different oil manufacturer, the old oil inside the torque converter
did not came out with only one oil change.

If there is an big issue, then you should get DTC's.

Maybe there is a light pressure issue, could caused by worn servo pistons.
The valve body could leak by blown seals or loosened valve body bolts.
The solenoids must have a tight fit, looking for broken/loose brakets.

Manually shifting into 2nd gear and back to D should not cause any issue.

 

[C420sailor]

Burnt smell isn’t good.

You can try changing the fluid. It may make it worse.

Generally a 2-3 flare is caused by a separator plate gasket leak…not sure about 1-2. How many miles on the tranny?

If she’s high mileage, it’s likely about rebuild time.