Assuming manual transmission and for an '02 4.0l SOHC engine that would be an M5OD-R1HD transmission, then $2,500 would be highway robbery.
I would change transmission fluid and check what comes out, sounds like you will find alot of metal filings which would indicate it is time for a rebuild or swap.
M5OD-R1 was used in Rangers since late '80's so alot of used ones are around.
You need one out of a 4.0l OHV engine(1990-2000) 4x4 to match your engine bolts.
The R1HD was same trans inside but had an extra bolt hole in the bell housing for use in the 4.0l SOHC engines, it also had lower 1st gear ratio but not that noticeable, so you can use either R1 or R1HD.
You could get a used M5OD-R1HD from a 4.0l SOHC 4x4 as well.
A rebuilt M5R1(common abbreviation) should run $800-$900
But used would be much less and the M5R1 was a good transmission, I would think your problem would be from someone running it low on fluid, and once the wear starts topping up the fluid delays wear but can't stop it once it has started.
So getting a used M5R1 is not a big gamble.
If it is an automatic then it will be a 5R55E and you can also go used from a 4.0l 4x4 for about $600, although used is more of a gamble with automatics.
Rebuilt 5R55E runs about $1,500 but check with local transmission shops(NOT mechanic shops), you could get transmission swapped out by them for about the same price.
The time it takes to remove and reinstall an automatic in a shop is only a few hours.
Mechanics don't usually do the rebuild "in-house" they send it to transmission shop and then up the price for the rebuild part, so go to the source.
I prefer manuals but.................usually either costs the same in the long run, even if well maintained manuals require clutches and when using "shop rates" the "must have" clutch service and the "may have" automatic service come out about the same in cost.
Although when the automatic bill comes due it does seem extreme, lol.
And most DIYers do their own clutch service so..........
Last edited by RonD; 07-26-2015 at 01:52 PM.