Part 4 Rebuilding the Transmission Main Case: Installing the Front/Intermediate Servo Piston and Lever

Now I'm ready to install the front piston and lever. The band gets installed with the front clutches.

I decided to upgrade this piston to a "no leak" item. The new piston has double seals as well as a rubber seal and bushing on the rod guide. It's all billet material as well. The old one just had a bushing. On the left is the original part. On the right is the upgraded piston. You can see the double seal rings as well as the rubber seal the rod guide for the piston rod. The spring and snap ring are reused. I upgraded the spring earlier when I installed the Transgo shift kit.



The smaller seal is a lapped teflon type. So spread a little assembly lube on the seal area and groove in order to hold it in place. Spread some fresh ATF on the larger metal ring seals. Offset the ring gaps by 180 degrees.



Then lube the bore of the servo with some fresh ATF.



Slide the piston down into the bore. It turned out to not be too hard. I had to coax the two metal rings a little. But, overall, much less effort than the rear piston was.



Place the piston spring onto the piston.



Lube the rod guide seal and bushing with a bit of assembly lube.



Then slide that onto the piston rod, seal facing down.



Make sure the metal sealing ring clears the groove for the snap ring.



Use some sort of c-clamp to compress the assembly a bit. The FSM suggests a valve spring compressor with a special end. I found this clamp to work fine.




Install the associated snap ring.



All tidy!



Now let's install the band lever. I upgraded this part as well. The OEM lever is a 3.8:1 ratio. I opted for a 4.2:1 ratio. Just a bit more holding strength. There is a 5:1 Mopar lever specced for high horsepower Hemi motors. I decided that may be overkill...although it was cheaper than the 4.2 lever.



Spread some assembly lube on the pivot rod.



Install it into its bore through the pump side (externally in the bell housing) just far enough so you can get the lever on.



Here's the orientation of the lever and it's slot in the case. The long end of the lever contacts the piston rod on the servo just installed. (Naturally I have no photo of the lever insalled! You'll see it later.) You can see the pivot rod to the left of the lever in the case.



Spread a little sealant on the pipe cap plug that holds the rod in place. You don't want this leaking after you've got the transmission buttoned up and into place. I used a little hi-temp RTV.



Torque that to 13 foot*pounds.



Here it is all in place and sealed.



Next: rebuilding the rear planetary assemblies. This could be a long one! I may break it up into a couple of posts.