busta9876

iTrader: (3)

I've rebuilt a lot of TH400 and learned a few things that can be done to get tire chirping shifts 1-2, 2-3. I was wondering if anyone has applied these things toward the 4L80E. I am in the process of building a 80E for my 89 Caprice that has a 5.3L vortec, and soon to get a single turbo, 8-10 PSI. I purchased a 10" converter from Edge Racing Converters (with lockup), should stall fairly high.. I bought a TCI Super Pro rebuild kit, includes their Trans-Scat valve body modifications. (I may got with a Trans-Go kit however)

Anyways. Here are a few of the things I am considering trying out. Wondering if those with the experience would chime in with any ideas or suggestions. Thanks -Brendan.


1. Intermediate clutch. Removed the cushion plate from on top of the piston, and replace with an extra steel plate. (my ASTG does not show a cushion plate on this clutch, my core is a 2001 model) GM Service Manual indicates to measure piston travel with 80psi, with a dial indicator on the piston. This means you will measure the total travel (including squishing the cushion plate) I have removed the cushion, so my measurement with a feeler gauge under the snapring should be close. I get .045" clearance. GM specs .040 to .107.

2. Forward Clutch. removed the cushion plate, however NOT a shifting clutch, this will cause a slightly more firm engagement to drive. I added an extra steel plate in the MIDDLE of the clutch stack, to give it an extra heat sink. clearance is at about .070. GM specs piston travel of .050 to .172

3. Direct Clutch. removed cushion plate, added extra steel plate in the MIDDLE of the stack, clearance is at .055. GM specs piston travel of .050 to .172

I also LEFT OUT the MIDDLE seal that installs on the direct drum with the lip facing upward. There are two fluid chambers for the direct clutch when assembled. Both chambers are filled in Reverse for increased torque capacity, however when shifted into 3rd, only 1 chamber is filled. You can more then double the clamping force by removing that middle seal. In order for this to work, you have to install a 1/8 pipe plug in the REVERSE oil circuit that feeds the center support. The hole in the case is already correct size, I used a 1/8 pipe tap to thread it, then installed a hex drive 1/8 plug into the port. This prevents oil from back feeding into the low/rev band apply circuit when shifted into 3rd gear. (This modification is the SAME thing done by a shift kit for a TH350, that use the 3 steel plates to make a fluid transfer.)

I also used the return springs from a TH400 forward clutch drum. The springs are 2 coils longer. This should help prevent centrifugal apply of the direct clutch when in 1st gear.

Orifice in separator plate for direct is enlarged, to get more oil in (increased area to fill now)


Well that's as far as I have got on the rebuild, TCI sent me the wrong Intermediate band for my year trans. I've got the 1.25" wide band, vs the 1" wide band on 99 and older. Different length band apply pins were used for each. I'm up for suggestions in the Overdrive section. My kit come with standard paper frictions for the 4th clutch, and high energy for the Overrun. I may buy a friction plate kit to upgrade these a bit more...although I doubt i'll need WOT 3-4 shifts...