Auto Transmission 2000 Rodeo

possible dirty transmission oil
could be a problem wire to the servo/solenoid

code p 1870 refers to AT---component slipping===causes mechanical fault
this could be a band or clutch problem and could possibly be a matter of adjustment , fluid change or filter clean
I would take it to an accredited auto transmission specialist( only-no local mechanic ), have them do a proper diagnosis and quote and ask will a fluid change and adjustment when the pan is off fix the problem
if could be a band piston seal failure or low oil pressure from a failing pressure regulator
cannot suggest repair costs until you know exactly is wrong and that will be determined when the pan is off and the internals can be inspected

manual or auto
bet automatic.

alldata.com has this.

but really you don't need to read that.
cable off trans.end.
set the transmission to say, drive. position at the t actual trans manual shift lever on side of trans. (the PRNDL switch may be here)
count the detent clicks., (easy huh?) to drive PRND bingo there.
then attach the cable and get it to the Drive marker in the cab console.
the lock it all down.
the test all gears. park and neutral , in drive way, not on road yet.
if all ok, hit the road.

Change trans fluid, just did mine and it runs like brand new with 117k miles

you have apparently drain the transmission fluid out of the trans pan. check your oil level to see if it is overfilled, this would be a good indication especially if you didn't have to refill the oil with at least 5 quarts.

I would change the trans flter, trans fluid, and have the linkage on the trans adjusted.

more than likely it would be your torque converter and not your trans
but you could have the overall dreaded problem that your second gear has grinded its self down and thats why you cant get second gear
no vacumes for the 94 straight mechanical and electrical if there was a vacume you would have found it when you dropped the pan it isnt hard to see around the whole trans cause it would be located next to the speedo with a rubber hose 1/4 thick

There is no dipstick on your auto trans. Checking it is a real PITA The trans pan has 2 plugs in it. The one on the very bottom is the drain. The one in the corner, up higher in a recess is the check/fill plug. To check, the engine must be warm and running, tranny in P. Remove the plug and fluid should dribble out. If it doesn't it's low, fill until it dribbles out, while engine is running. Obviously the truck must be on a lift or up on jackstands.

We had the same problem with a 2002 Rodeo. The transmission must be replaced. But keep in mind the Powertrain Warranty (yes this does cover the transmission) on 2000-2003 Rodeo's is 10yr/120,000 miles. Call 800-255-6727 with your vin# and they will verify. Good luck!

There are two drain plugs on the bottom of the pan. remove the lower one to drain the trans fluid. To refill, use a pump and pump the fluid into the upper drain plug until it seeps out and re-install the plug, similar to refilling a manual trans.
Once this is done, Start the vehicle and run it for about 3 minutes, shifting through all gears (do not drive vehicle Remove the upper drain plug and let any excess fluid drain out. Done. This is as per Mitchell OnDemand.