[68WarDog]

I have a T400 transmission with a standard valve body. The transmission shifts from 1st to 2nd irregardless if I'm still holding the shifter in first. I tried disconnecting the mechanical modulator ( don't use a vacuum modulator), no affect. Short of installing a manual valve body, is there anything I can do to get the transmission to hold off the 1st to 2nd shift?.

[25stevem]

Yes, the install of a shift kit I believe will allow you the option to make the 1st to 2nd shift whenever you want

[Skip Fix]

Controlled by the governs. Can also change weights and springs to dial it in. B&M has a kit.

[68WarDog]

Steve we installed a BM shift kit along with new Kevlar clutches and 34 sprag elements during the refresh. The kit did firm up the shift but the shift points were unaffected.
Skip the governor modification sounds interesting, and will bring it up with the shop. I have one of Jake's Performance forward manual valve body on hand, but looking for alternatives to full manual vb.

[Cliff R]

You do NOT need a manual valve body.

You can set the TH400 up for full manual control/retain the auto upshift function and stop the automatic 1-2 upshift even if the selector is in "L" by grinding down the last land of the 1-2 shift valve and blocking the corresponding exhaust hole in the valve body.

You can also purchase the Transgo 1 & 2 shift kit to accomplish the same thing. It comes with a modified 1-2 shift valve and drive in plug for the VB. This is covered in my TH400 book on pages 124-125.

You can also find procedure/pics of this modification on some of the Forums as well.

I prefer to use the Transgo kit here as it also improves shift performance and double feeds the direct clutch pack w/o having to take the transmission apart.........Cliff

[Half-Inch Stud]

I think the modified valves supplied in shift kits may fit most but not all TH400 VBs. Those 1-2 valve sizes have some variation across 65-70 VBs.

if you really junking for holding Manual 1st to high rpms, then grind the valve shown that is found in the factory Valvebody. No need to take the whole diameter off when a couple flats will do.

[68WarDog]

Originally Posted by Cliff R

You do NOT need a manual valve body.

You can set the TH400 up for full manual control/retain the auto upshift function and stop the automatic 1-2 upshift even if the selector is in "L" by grinding down the last land of the 1-2 shift valve and blocking the corresponding exhaust hole in the valve body.

You can also purchase the Transgo 1 & 2 shift kit to accomplish the same thing. It comes with a modified 1-2 shift valve and drive in plug for the VB. This is covered in my TH400 book on pages 124-125.

You can also find procedure/pics of this modification on some of the Forums as well.

I prefer to use the Transgo kit here as it also improves shift performance and double feeds the direct clutch pack w/o having to take the transmission apart.........Cliff

Thanks Cliff,

[Cliff R]

You are most welcome. It's mentioned in my book but be aware that after this modification the transmission will still retain it's automatic function as before. The difference is that now it will shift into and stay in either 1st or 2nd gear at any speed. So if you inadvertently shift to low gear at 100 mph it's going to be ugly!.......

[sdbob]

Back in the late 60s I tried PHR article modifications to m40. Then a Winters Trans kit. Then I used Trans go. I will use them anytime. Very nice install and as Cliff said. It works.