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Thread: How to change gear oil in a manual transmission/axle

  1. #1
    Vulture of The Western World Eric's Avatar
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    How to change gear oil in a manual transmission/axle

    If you can change your own engine oil/filter, you've got the basic skills needed to change the gear lube in a manual transmission or axle/transfer case (4WD vehicles). Many people neglect doing this important service, which is a shame because it really is an easy job.

    Here's how:

    * Determine the type and quantity of lube you will need - as well as any additive (in the case of some limited-slip axles). This information should be available in your owner's manual, but if not, it's a good time to buy a more comprehensive service/repair manual (available at auto parts stores such as NAPA, Pep Boys, etc.) Or you can ask the counter person to look it up for you. Or find out by asking at the dealership (for your make of vehicle) service counter. Just be sure - 100 percent sure - that you get the right type of lube before you begin. And, get an extra container to have on hand for top-offs.

    * Most lube comes in quart/pint bottles which have a screw-top cap with a nipple end piece that you cut open to pour/squeeze out the fluid. Here's a helpful tip. Buy about 2 feet of clear plastic tube in a diameter that fits the nipple - plus a small hose clamp. You'll understand why in a minute... .

    * Warm up the vehicle by driving it for about 15 minutes or so.

    * Using a hydraulic jack, raise the vehicle enough to give you easy access to the underside/transmission/axle, etc. Support with jack stands.

    * Most manual transmissions (and front axles/transfer cases on 4WD vehicles) have a drain plug and a fill plug; the drain plug should be located toward the bottom of the case; the fill plug on the side. Rear axles may have a drain plug, or a rear cover that has to be removed in order to drain the fluid. Check to see whether a gasket is necessary if so.

    * Place a catch pan underneath the drain plug and first remove the fill plug. You may need to use a loosener such as Liquid Wrench, PB40 or equivalent to get the plugs out. Some plugs are of the recessed type and a 1/2 inch socket extender fits perfectly. If you need additional leverage, use a pry bar (a hollow jack handle works well).

    * Allow the old lube to drain completely; the drain plug may have a magnetized tip with small metal filings sticking to it. Clean the plug thoroughly.

    * Reinstall the drain plug, being careful not to overtighten it. "Just snug" is usually tight enough. Check your shop manual to see whether a sealer/thread locker is recommended and if so, use that on the threads before installation.

    * Now, install a length of that clear plastic hose appropriate to your vehicle/situation (each car will have more or less room to work with) and secure with the hose clamp.

    * Crawl back underneath the vehicle; slip the other end of the clear hose into the fill hole. Position the lube container as far above or near the fill hole's level as possible and squeeze in as much lube as you can. When you can't get any more in, pull the hose out, being careful not to spill, and crawl back out from underneath the car. Refill the container with lube and repeat the process until the case is full - which is usually indicated when lube is just barely trickling out of the fill hole. Be sure not to over-fill the case.

    * Reinstall the fill plug, crawl back out from underneath, lower the car.

    You're done!

  2. #2
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    Quote Originally Posted by Eric View Post
    If you can change your own engine oil/filter, you've got the basic skills needed to change the gear lube in a manual transmission or axle/transfer case (4WD vehicles). Many people neglect doing this important service, which is a shame because it really is an easy job.

    Here's how:

    * Determine the type and quantity of lube you will need - as well as any additive (in the case of some limited-slip axles). This information should be available in your owner's manual, but if not, it's a good time to buy a more comprehensive service/repair manual (available at auto parts stores such as NAPA, Pep Boys, etc.) Or you can ask the counter person to look it up for you. Or find out by asking at the dealership (for your make of vehicle) service counter. Just be sure - 100 percent sure - that you get the right type of lube before you begin. And, get an extra container to have on hand for top-offs.

    * Most lube comes in quart/pint bottles which have a screw-top cap with a nipple end piece that you cut open to pour/squeeze out the fluid. Here's a helpful tip. Buy about 2 feet of clear plastic tube in a diameter that fits the nipple - plus a small hose clamp. You'll understand why in a minute... .

    * Warm up the vehicle by driving it for about 15 minutes or so.

    * Using a hydraulic jack, raise the vehicle enough to give you easy access to the underside/transmission/axle, etc. Support with jack stands.

    * Most manual transmissions (and front axles/transfer cases on 4WD vehicles) have a drain plug and a fill plug; the drain plug should be located toward the bottom of the case; the fill plug on the side. Rear axles may have a drain plug, or a rear cover that has to be removed in order to drain the fluid. Check to see whether a gasket is necessary if so.

    * Place a catch pan underneath the drain plug and first remove the fill plug. You may need to use a loosener such as Liquid Wrench, PB40 or equivalent to get the plugs out. Some plugs are of the recessed type and a 1/2 inch socket extender fits perfectly. If you need additional leverage, use a pry bar (a hollow jack handle works well).

    * Allow the old lube to drain completely; the drain plug may have a magnetized tip with small metal filings sticking to it. Clean the plug thoroughly.

    * Reinstall the drain plug, being careful not to overtighten it. "Just snug" is usually tight enough. Check your shop manual to see whether a sealer/thread locker is recommended and if so, use that on the threads before installation.

    * Now, install a length of that clear plastic hose appropriate to your vehicle/situation (each car will have more or less room to work with) and secure with the hose clamp.

    * Crawl back underneath the vehicle; slip the other end of the clear hose into the fill hole. Position the lube container as far above or near the fill hole's level as possible and squeeze in as much lube as you can. When you can't get any more in, pull the hose out, being careful not to spill, and crawl back out from underneath the car. Refill the container with lube and repeat the process until the case is full - which is usually indicated when lube is just barely trickling out of the fill hole. Be sure not to over-fill the case.

    * Reinstall the fill plug, crawl back out from underneath, lower the car.

    You're done!
    You reminded me that I need to do this on the Saturn. It has been quite a while since I've changed it.

  3. #3
    Vulture of The Western World Eric's Avatar
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    Quote Originally Posted by swamprat View Post
    You reminded me that I need to do this on the Saturn. It has been quite a while since I've changed it.
    I do mine every 30,000 miles - and while that may be slight overkill, all my vehicles also run "as new." I am uber-anal about maintenance!

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