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Do-It-Yourself Projects
Guide to Transmission and Axle Service
By Jim Smart/autoMedia.com
Printable version
Degree of DifficultyModerate
Moderate
Estimated Time180 minutes
180 minutes
Seals should be gingerly installed with a seal driver coupled with gentle blows because some seals have a lip retention spring. Hit the seal too hard and you will dislodge the spring. Good preventative medicine is to heavily pack the seal with wheel bearing grease to where the spring doesn’t go anywhere. Inspect inside the axle tube to ascertain spring integrity. If you can see the spring lying inside the tube, the seal has lost its spring.
Use a Seal Driver to Install the Seal
When axles are removed for seal and bearing replacement, inspect axle to bearing mating surfaces. Surfaces should be dressed as shown.
Dress the Axle
Axle installation should be handled carefully and with wheel bearing grease on both axle and seal. Elevate the axle to where it doesn’t touch the seal during installation.
Elevate the Axle so it Does Not Touch the Seal During Installation
C-clip installation should be performed with great caution ensuring the axles are seated and secured properly. Of course this applies only to C-clip axle packages.
Installing C-Clips if Applicable
One mistake we see made time and time again is the use of too much sealer. Remember, gaskets are the primary seal. Sealer is there only to fill in any imperfections, so use it sparingly – a super thin bead works. If you’re using a composite silicone/steel gasket, you won’t need sealer at all.
Use Sealant Sparingly
Locking differentials should always get a friction modifier to ensure good clutch engagement as required.
Additive Friction Modifier
Mix it in with your manufacturer’s specified gear lube.
Mix Friction Modifier with Gear Lube
When you drain transmission fluid, examine the color. You want to see pink/red in color. If the fluidis brown to black it is burned with clutch and band material. Once fluid becomes dark, the damage is done. Fresh fluid may buy you time, but not much time. Burned fluid loaded with friction material damages seals and hurts line pressure.
Drain the Transmission Fluid
In this pan is clean fluid, however; check the sump and magnet. There’s ferrous metal and friction material in the sump and both can be damaging to seals and bushings.
Check the Transmission Fluid Color
The filter is removed and disposed of. A new filter and o-ring seal will be installed and the transmission is allowed to drain.
Remove and Dispose of the Filter
Automatic transmissions have been computer controlled since the early 1990s. Solenoids and microprocessors do the work cables and vacuum modulators used to do. Rarely does this solenoid ever have to be replaced.
Rarely Does this Solenoide Need Replacing
This computer-controlled Automatic Overdrive has two solenoids aside from the pressure control solenoid. One controls upshift while the other controls torque converter lock-up in overdrive.  
Automatic Overdrive with Solenoids
Here’s everything needed to service Ford’s 4R70W, including a filter, EPC solenoid, bulkhead connector, and wiring harness. Because this particular 4R70W has more than 230,000 miles, we’re changing out electronic components.
Components Required for Servicing a Ford's 4R70W
Once the filter has been installed, the pan is next using a silicone/steel composition pan gasket. Though the aftermarket sells cork gaskets, go with the OEM composite gasket. The OEM gasket does not leak.
Install the Filter then the Pan
Check to see if your torque converter has a drain plug. If it does, drain the fluid until it is down to the last dribble. Secure the plug using a thin film of sealant on the threads for leak prevention.
Drain the Torque Converter Fluid
Service the transmission with the manufacturer’s recommended fluid type. There are also universal fluid types. However, play it safe and never change fluid type. Changing fluid type tends to shock seals, leading to transmission failure.
Add Transmission Fluid
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