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Clutch Service. Why?. Automatic transmission clutches are considered ‘wear parts’ which are normally serviced during transmission overhaul. Clutch Assembly. Drum Piston Seals Return Springs. A typical clutch assembly contains the apply piston, piston return springs, and the clutch plates.
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Clutch Service Tom Birch, 6/07
Why? Automatic transmission clutches are considered ‘wear parts’ which are normally serviced during transmission overhaul. Tom Birch, 6/07
Clutch Assembly Drum Piston Seals Return Springs A typical clutch assembly contains the apply piston, piston return springs, and the clutch plates. Snap Ring Lined Discs Pressure Plate Unlined Plates Tom Birch, 6/07
Remove Snap Ring A screwdriver is being used to pry the snap ring out of its groove. Then the pressure plate, clutch discs, and clutch plates can be removed. Tom Birch, 6/07
The Clutch Pack Clutch Pack Tom Birch, 6/07
Clutch Pack A clutch pack is a group of steel (separator) plates and lined friction discs. The old plates and discs are normally replaced with a new clutch pack when the transmission is overhauled. Tom Birch, 6/07
Clutch Packs A transmission might have 5 or 6 clutch packs. Each of them different to suit the requirements for that particular clutch. Tom Birch, 6/07
Piston Return Spring Snap Ring (hidden) Return Springs Piston Clutch Drum Most pistons are returned to the released position by a set of coil springs. These springs must be compressed in order to remove the retaining/snap ring (hidden). Tom Birch, 6/07
Piston Return Spring(s) Coil Spring Belleville Spring Some clutches use a coned Belleville or single coil spring. Tom Birch, 6/07
Spring Compressor Spring Compressor Snap Ring A variety of spring compressors can be used to compress the return springs so the snap ring can be removed. When the compressor is released the springs will extend and the springs and piston can be removed. Tom Birch, 6/07
SC 2 Spring Compressor The piston return spring for case-mounted, holding clutches is compressed in the same manner. There is a variety of spring compressors. Tom Birch, 6/07
SC 3 This bench-mounted spring compressor can easily compress the piston return spring on most clutches, even those that have an input shaft (lower right). Tom Birch, 6/07
Remove the Piston Shop Cloth Clutch Drum Piston Pump Air Nozzle The piston can be removed by applying low pressure air to the hydraulic inlet port. The pump provides easy acess to the hydraulic port. Tom Birch, 6/07
R&R Piston Seals The old inner piston seal is being pulled out of its groove; a new seal ring will be used to replace it. The outer seal is also removed and replaced. Tom Birch, 6/07
Check Ball Tests Check Ball Air Nozzle Clutches that release while spinning contain a check ball in either the drum or piston, and the check ball must hold pressure. It should not leak air through it. The check ball must be free to move off of its seat when pressure is released. Piston Tom Birch, 6/07
Replace Piston Seal Guides The new seals should be lubricated before installing the piston back into the drum. The seals can catch on sharp edges and be damaged. Seal installers guide the seals past these potential problems. Tom Birch, 6/07
RP 2 The thin edge of a lip seal is especially prone to be damaged during piston installation. Most techs use a feeler gauge or shop-made tool to ease the lip past potential damage points. Tom Birch, 6/07
Install Return Spring(s) With the piston back in the drum, the return spring(s) is compressed using the same tool that was used for removal, and the snap ring is replaced. Tom Birch, 6/07
Install Clutch Plates A new clutch pack with the correct number and type of plates is installed into the drum. Note: Be sure to presoak the frictions in ATF before installation. Tom Birch, 6/07
Parts Blowup A blowup illustration shows the proper relationship of the parts in a clutch assembly. Don’t forget to inspect the bushing (yellow) and replace it if necessary. Tom Birch, 6/07
Clutch Clearance The assembled clutch should have the correct clearance between the plates. If specifications are not available, use 0.010 inch (0.5 mm) of clearance for each friction plate. Tom Birch, 6/07
Clutch Piston Travel Air Nozzle Dial Indicator You can watch the amount of piston travel/clutch clearance as you apply and release air pressure. The dial indicator has a long stem that is touching the piston. Note that the clutch pack with snap ring must be installed before making this check. Tom Birch, 6/07
Clutch Clearance, Feeler Gauge Feeler Gauge A feeler gauge can be used to measure the clutch pack clearance. Some clutches use selective snap rings to adjust clearance. Selective Snap Ring Tom Birch, 6/07