olds 307 and 403

I assume the Transgo kit is best? I plan on picking up a junkyard short tail trans, I assume they came factory in the 2 door 70S with a 455? I will also only run auxiliary cooler only and probably a Hughes 2500 stall converter.

matt69olds

TransGo is probably the best, they are they only kit to include parts to dual feed the direct clutch. For some reason GM decided to split the direct clutch into 2 separate chambers, o e for 3rd gear, the other for reverse. With some cheap mods you can use both chambers and basically triple the clamping force. You can do it yourself with a 50 cent freeze plug, or just the TransGo kit.

olds 307 and 403

Thanks, yes more clamping force is better, need a trans that has a hope in hell with higher torque. I would love a 4L80E but there are so many mods necessary and about $600 to $800 more for a used trans. I know a junkyard that has a few BOP TH400 short tail trans and I know someone who might have a factory drive shaft near by for a 70 Cutlass with a TH400.

matt69olds

If your reasonably comfortable with transmission work it's pretty easy to make a good 400 better. Get replacement valve body gaskets, a pump gasket and o-ring, and pan gasket and filter. There are lots of YouTube video that explain the process. For about half the cost of the transgo kit you could have a mch better trans and will have the opportunity to inspect the trans to make sure it's in good shape

TripDeuces

I second Transgo but have also had success with TCI kits and B&M. I have a full manual TH400 and it clamps like mad. I love the harsh shifts but it's an acquired taste so know your limitations.

oldsmobiledave

Transgo in every T350 or T400 I have ever had built.

cherokeepeople

in my dads shop years ago transgo was thee only one we used.

droldsmorland

TransGo is the ONLY kit that dual feeds without doing the internal mods. So it is the only kit you can install for dual feeding with a trans in the car.
They do so by using a sandwiched separator plate assembly. It is a patented deal that has 3 plates riveted together, the center one performing the same function as all the TH350 kits "transfer plate" but it is a little more complex due to the nature of the TH400's fluid passages in the worm casting area. The TCI and B&M kits are almost the same less the patented separator plate.

Careful with the "cheap mods" such as turning the 2-3 accumulator piston upside down on the TH400, grind off the 3 tabs, and then re-install with no spring. NO movement, NO accumulation, KILLER hard shifts, and broken parts...Ask how I know...The same thing can be accomplished on a TH350 with a 3/8" nut on top of the piston...Not suggested as well!

There's more to it for killer hard shifts without self-destructing such as governor mods and correct modulator etc... so do your homework. Make sure the trans is fresh. I never install a kit without going through the trans. Why would one increase line pressures on well-used seals, steels n frictions? Its a recipe for a burnt trans. You will find the weak link in the rest of the driveline too...lol...Always flush the lines and cooler. Consider an aux cooler as well.