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How to: Bighorn Automatic Transmission Pan Gasket Replacemen

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How to: Bighorn Automatic Transmission Pan Gasket Replacemen

Postby arthurdent » Thu Oct 20, 2022 4:18 am

My transmission leaked all over my drive way this summer - hope this helps!

To change the pan gasket (and the oil filter while you're down there)...

Tools:
    Ratchet set
    Putty knife (thin metal blade)
    Rubber mallet
    Plastic spoon
    Razor blade
    Steel wool
    Wooden toothpick
    Brake cleaner
    Drain pan

Parts:
    Pan gasket (1989 Jeep Cherokee part)
    Drain plug and gasket (1989 Jeep Cherokee part)
    ATF

Steps:

This is actually pretty easy to do. It just takes patience.

    1. Check the ATF level. Start the car and verify the level is between Min and Max. If it's too low, you'll have to add more when it comes to refill. If it's too high, less.

    2. Place the drain pan under the transmission pan, and remove the drain plug. I drained about 5L of ATF.

    3. Once the pan is mostly drained, place the plug back in. It will drip for days, you'll get the rest later.

    4. Remove all 19 bolts holding the pan in place. If your pan is siliconed on, it will hold itself up. If you have an actual gasket in place, you can skip right to step 10.

    5. Gently - try to find a spot where your putty knife will slide between the pan and the transmission. Be careful not to slide it in too far. There are wires and solenoids in there you don't want to damage. If the knife only goes in a few millimeters, it hasn't gone in far enough. It should slide in about half an inch.

    6. Once you've found a spot for the knife to slide in, gently tap it with the mallet to get it to travel along the edge of the pan. The objective here is to break the silicon bond between the pan and the transmission. I physically could only reach two side of the pan, So I broke the bond on those two side, then wedged in two putty knives, and broke the bond on the other sides by leverage.

    7. Be careful not to scratch the surface of the transmission that the pan mates to. It's aluminum so putty knives can scratch it. you can try using plastic putty knives but I'm not sure how well these will do.

    8. To clean the pan, I removed the bulk of the silicon with a razor blade. I found that using the edge of a plastic spoon worked pretty well to remove the residue. It takes patience, but it's effective. Once you've got most of it off, clean off the rest with some fine steel wool. Also clean out the remaining ATF that leaked into it, and look to see what kind of residue you have in there.

    9. Clean the mating surface on the transmission. Same process as in step 8.

    10. Degrease the surfaces with brake cleaner, then don't touch them ;-)

    11. Replace the oil strainer

    12. Clean the surface to which the new strainer mates with a clean rag. Torque the strainer bolts to 10N.m (i.e., not much)

    13. The the FelPro rubber gasket does not require any sort of glue or sealer. It was also pretty rigid so I didn't have any issues with the gasket not holding in place while I put the pan back on. The gasket holds the screws in place, so you can actually place all the screws into the pan and gasket before you get back under the car to screw the pan back in place.

    14. Screw the pan back in place. Torque to 8N.m.

    15. Replace the drain plug and plug gasket.

    16. Refill with as much ATF as you removed, or less if the level was too high in step 1.

    17. Start the car, and see where the level drops to. Add as required.

    18. If the gasket starts to leak, tighten the gasket where ever it's dripping.

    19. All done!
arthurdent
Isuzu Baby
 
Posts: 13
Joined: Thu Oct 20, 2022 4:06 am
Age: 28
Country: Canada
City: Canada
Vehicle: 1992 Bighorn (4JG2T), AW30-40 Automatic

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