98 s10. It wont stay in fourth gear. It always shifts back to third

Make sure the shifter cable is correctly adjusted.

https://www.kiaownersclub.co.uk/threads/kia-sportage-auto-gear-shift.54702/

This forum may help you.

Which transmission does yours have 4T65-E or 4T80-E ?

4T80-E
No Fourth Gear

Checks

Causes

1-2 Shift Solenoid Valve
?€¢
Inoperative
?€¢
Debris
?€¢
Pinched wires

3-4 Shift Valve Bore Plug

Misassembled

4th Band

Burned, slipping, missing

4th Servo Cover

Cracked

4th Servo Pin

Broken, seized

4th Servo Piston

Damaged

4th Servo Seals

Rolled, cut or damaged
4T65-E
Slipping or No Fourth Gear
Slipping or No Fourth Gear Checks
Cause

DEFINITION: A large engine RPM increase is noted in fourth gear, Drive range, with little or no vehicle forward speed increase. First, second, and third gear operation are normal. Shifts into fourth gear are soft or do not occur. Fourth gear ratio is 0.705:1.

Automatic Transmission Fluid Level
Low fluid level

Transmission Main Line Pressure
Low transmission main line pressure

Oil Filter Assembly
• The oil filter assembly (100) is missing, plugged, or damaged.
• The oil filter seal assembly (101) is missing or is damaged.

Control Valve Body Assembly
• The 3-4 shift valve (362) or the 4-3 manual downshift valve (360) is stuck or binding.
• Debris is found in the passages of the control valve body (301) or of the control valve body spacer plate and gasket assembly (396)

Case Cover Assembly
Distortion or damage occurs at the manual valve (404) or at the case cover (401), causing PRN oil leak.

Driven Sprocket Support Assembly
A plugged third clutch oil passage in the driven sprocket support assembly (609)

Fourth Clutch Assembly
• The clutch plates (500-502) are worn, damaged, or misassembled.
• A missing or not seated fourth clutch spring retaining ring (601)
• A damaged spring assembly (602) or piston (603)
• Worn or damaged fourth clutch piston seals (604, 605)

Third Clutch Sprag Assembly
• The sprag (720) was misassembled or backwards on the inner race (661).
• A damaged third clutch sprag assembly (653, 661, 719-721)

If this is a clutch then you need to look into the shift actuator is what I believe it is called. It is a located on your clutch pedal. If this is an automatic it still could be something similar to that.

bad synchros.

you may try reving engine alittle higher try shifting to fourth if that works your third gear sincroniser is shot

you need a new cluch thats why.

this problem is a common failure associated with your shift solenoinds inside your tranny. of course a shop is not gonna tell you this because by the time you wanna get it repaired it is usually too late and have already cause damage to your clutch pack and internal parts, thats the main reason why a shop wont mess with just replacing your shift solenoid (aka valve bodie)

the trans computer has seen a problem possible a bad sensor, or an internal problem, and puts it into a safe mode, or limp home mode , it wont shift , it will stay in 3rd gear, this way this reduces the possibility of further damage trans damage, when you turn the ignition off and back on it resets the tcm, my advice is to take it to your local dealer, they can diag your trans as they know the product, i dont advise pep boys, or discount auto parts.

The Dog clip for the fourth gear is gone ...needs replacing...tranny overhauls required.

inside the hood there are two clips holding the shiftting cable you may have lost them. you may want to check the driveshafts because one of them might have poped out.