GaryalpUSA

Hi I just rebuilt my nephews 95 Z 4l60E. My first auto trans after many manuals. Did not think it was too difficult with all the help on line and a good shop manual. I have one question that maybe someone here will have the answer to. We used the rebuild kit from Monster transmission. It included a box that had a variety of springs and drills to drill the seperator plate and replace springs in different areas. It was labeled as a shift kit. The larger stiffer spring that went into the 1,2 accumulator is so stiff it wont allow the piston to remain on the lip in the housing. It pushes the piston to the bottom of the housing as opposed to sitting about a quarter of an inch from the bottom, where the O ring on the piston catches on the housing lip with the stock spring. I can mount the accumulator with the piston sitting on the seperator plate but Im pretty sure that is not the way it is supposed to go. Will it work like that or should I just put the old spring back in for a stock shift? Thanks GA

mrvedit

The 700R4 and perhaps early 4L60(E) had the 1-2 spring between the separator plate and the piston. Later 4L60E have two springs UNDER the piston and none between the separator plate and piston. (The Transgo HD2 shift kit has one on each side.)

I would not do anything that would allow the piston o-ring to hit a lip! Therefore, if you still have the two stock springs under the piston, I would go with that. (Perhaps the early 4L60/700R4 had a different housing without that lip)

If the shift isn't firm enough, you can easily change the 1-2 setup later. I don't know what your kit recommends, but drilling the 1-2 feed hole to .093 will firm up the shift anyway. If needed, stiffer springs are available to firm things up a bit.

During operation, the space between the separator plate and the piston is filled with pressurized fluid (pressure is controlled by the accumulator valve in the valve body). When the trans shifts into 2nd and starts to apply the band, the apply fluid goes to the other side of the piston and pushes it toward the separator plate. When the piston stops moving, the band applies fully. The piston will stop moving when it either hits the separator plate, bottoms out any spring above it; or doesn't move much if the spring above it is too stiff, in which case the shift is very abrupt.

GaryalpUSA

Thank you for an excellent instructional reply. Maybe I misspoke when I said "a lip" in the housing. When I took the housing off originally the piston was about a quarter to half an inch inside the bore. I used air pressure to pop the piston out of the housing. That is why I assumed there is a Lip or a tightening of the bore that held the piston at that position. My accumulator had one spring behind the piston. When I push the piston into the housing after changing to the new spring and o ring provided in the shift kit I can feel where the piston catches in the bore where it was when I took it off. The new spring will not allow it to stay at that position and pushes the piston out to the bottom of the housing.

From your reply I see that having the piston sitting on the plate will cause a very abrupt shift. Does that also affect at which rpm the shift will happen? Im sure my 18 year old nephew wont mind a little chirp of the tires when it shifts, however having it shift at too high a rpm, in auto, will become annoying after a while. We are using an 1800-2200 stall converter with a LT1 cammed for about 325 lbs of torque. GA

GaryalpUSA

I called Monster transmission and spoke with their tech. He said to put the piston in first and then the spring. The spring will be sitting on the plate. Of course I forgot to ask him if I should turn the piston over so the spring is in the seat. Another phonecall.........