88 mercury cougar slips in fourth and fifth gear what could cause this?

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)

More than likely it's not the linkage. Sounds like the fourth to fifth synchronizer is very badly worn, which will cause the shifter to "pop out" of fifth gear.

theirs an adjustment that mounts to the tranny it could have slipped out of adjustment

The fourth gear, or over drive gear is burning out transmisson is in need of overhaul or replacement.

This is being caused by the seals in the transmission worn out and the heat is causing them to become to plyable thus losing pressure, an overhual is needed

Check ATF fluid level. Top up if neccessary.

first gear clutch plates or bands probably worn need rebuilt will just get worst

you may have a sticky valve in the transmission try adding lucas transmission stop slip

check the oil lever in the transmisson assuming it's automatic, if the fluid level is fine then with it in gear running and the brake on look to see if the drive shaft is turning, if it is then you have a prboblem with the drive shavft depending on engine size and wheather it's front or rear wheel drive. if it's not turning then you have a transmisson problem. If this is helpful please rate.

The clutch on the cougar is hydraulic and is self adjusting the closest thing to do is bleeding the clutch to make sure there is no air in the line that can cause the clutch to not fully engage. if the clutch is slipping you more than likely are going to have to replace it. however if the car is off and you can't go through all the gear your shifter cables may need adjusting. Btw, whatever you do not use ATF in your MTX75 tranny!!!! its bad you need to be on ford honey its about 15.00 a qt or the next best thing is royal purple. any questions feel free to contact me [email protected]