I have a 67 short tailshaft ST400 that I'm about to tear down and rebuild to back my Stage 2 TA 455 street build. I have some parts that I've compiled together after reading alot of posts on upgrades to the ST400. I will be using an ST300 torque converter, newer style tailshaft & housing, Trans-Go 400-1&2 shift kit, & a mid 70's valve body. Which sprag do you guys recommend? Thanks
The 34 element is the HD one. https://transmissioncenter.net/shop/4l80e-th400-intermediate-sprag-and-drum-the-34-element-sprag/
Hey guys. What is the benefit of using the st300 torque converter over the 400? I have a spare laying around and can easily put it in my 67 gs400 as it's all apart right now for an engine rebuild. We're going to cruise this car and maybe do a little autox and or drag racing once in a while.
The smaller a converter, the higher the stall is naturally without any internal modifications. I am assuming you are talking about the switch pitch transmissions?
It doesn't affect the transmission, you get higher stall speeds. The ST400 13" converter has stall speeds of approximately 2100/1100. Put the ST300 12" in and it would be more like 2600/1400. This is behind a Buick big block. Jim Weise modifies the 12" ST300 converters to produce more like 3000/1800
Your transaction should already have the smooth intermediate sprag. You shouldn't need to buy a full drum, just the sprag. I don't know what year they went to a roller sprag there, but those require a new drum. Your 67 tran's might even have the non roller sprag in the gear set that holds onto the center support. They went to a roller sprag in this location a few years b4 putting it in the intermediate location. The roller worked better in stk form than the 16 element sprag did but didn't allow upgrades........but I don't feel the roller sprag below the center support works better, but those that have a regular sprag down there were 32 or 36 elements not just 16
The none roller sprays had more of a chance to slip, and flip over. The rollers physically can't flip. I honestly don't know how many rollers are in the roller sprags.....
