What part number is the best one? The one with the special thick plate. Street and strip with original shift position and no trans brake, etc.
The advantage of the dual feed is that it feeds the clutches from both sides, which lengthens the life of the clutches and allows for faster and safer shifts. At least, that is what I remember.
The direct drum has 2 separate chambers separated by a seal. The smaller of the 2 chambers is used for 3rd gear, the larger chamber is used in reverse. If you remove the piston seal that separates the 2 chambers, then the entire piston surface is used to apply the clutches, basically tripling the clamping force. Unfortunately, simply omitting the seal won’t accomplish this. You need to block a feed hole in the reverse hydraulic circuit. During an overhaul, this is easily accomplished by using a 3/8 freeze plug, or brazing a hole closed in the spacer plate. TransGo uses a stacked spacer plate, the plate that goes to the case blocks off the feed hole, the middle plate has channels to direct fluid to both chambers in the drum, the plate that goes against the valve body seals the special channels. The advantage to the TransGo kit is it doesn’t require transmission removal to dual feed. The disadvantage, the stacked plate kinda limits the volume of oil that can be used to dual feed. If the trans is being overhauled, save the 80 bucks Go to AutoZone and get a Dorman 555-003 freeze plug, drive it into the round case hole next to the center support bolt. Omit the seal in the direct drum, omit the 2nd sealing ring from the center support, drill the stock spacer plate as per the TransGo or B&M instructions, and you have the same benefit. The 2004R, 400, 350, and 4L80 all use the direct drum with 2 chambers. All of the trans can be dual fed using basically the same methods. I have asked many times, many very knowledgeable people, nobody can explain why GM felt the need for the added complexity of the dual circuit direct drum. Seems to me it’s a lot of added machining and hydraulic waste. To the best of my knowledge, no other transmissions makers do this.
Just received my TransGo 400 PRO kit. It has that special 3 layer dual feed seperator plate (not just one thin metal plate). And it will allow fully automatic shifts in drive.
Because I didn't know if the 1-2 kit included the 3 layered seperator. This Pro kit has extra internal small parts I'm not going to use. So does the 1-2 kit for sure have a 3 layered seperator plate?
That may be good news for many members of v8buick here. TransGo 1-2 shift kit!!! Just specify TH400 or TH350, etc
