Best shift kit for a TH400? - ClassicOldsmobile.com

Best shift kit for a TH400?

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Old November 14th, 2017, 06:45 AM
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Best shift kit for a TH400?

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.
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Old November 14th, 2017, 11:02 PM
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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.
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Old November 15th, 2017, 05:21 AM
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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.
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Old November 15th, 2017, 10:46 AM
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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
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Old November 15th, 2017, 04:13 PM
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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.
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Old November 15th, 2017, 05:05 PM
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Transgo

Transgo in every T350 or T400 I have ever had built.
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Old November 15th, 2017, 07:43 PM
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in my dads shop years ago transgo was thee only one we used.
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Old November 15th, 2017, 08:20 PM
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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.

Last edited by droldsmorland; November 15th, 2017 at 08:25 PM.
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