Floor mount automatic shifter for the GM Turbo 400 with a 12 inch chrome stick, gated lockout, linkage rods, brackets and a 5 inch boot.
Building a hot rod, gasser or truck swap around a Turbo 400 and the column shift is gone, or the old floor shifter is so worn that the lever no longer matches the gear you are in? This floor shifter kit is made for the GM Turbo Hydra-Matic 400 (TH400). It has a 12 inch chrome shift arm with a billet aluminum knob, a lockout gate, the linkage rods and transmission-side brackets, and a 5 inch round black boot with a stainless trim ring. It is a direct floor-mount setup for cars and trucks where you want the stick on the tunnel instead of on the column.
The TH400 is shifted by a manual shaft on the side of the case. Inside, that shaft turns a detent lever that moves the manual valve in the valve body and, in Park, pushes the parking pawl into the output shaft gear. The factory selector has six positions: P, R, N, D, L2 and L1. A floor shifter does nothing more than move that external lever through those six detents, but it has to land each one exactly. If the rod is long or short by a few millimeters, the manual valve sits partly between ranges, which feeds the clutches low pressure and can cause slipping, a late engagement, or a Park that does not fully lock. The lockout gate here keeps the lever from being knocked out of Drive into Neutral, Reverse or Park by accident, which matters on a car that is launched hard.
Harsh or late shifts that do not change with lever position are hydraulic, not linkage; our TH400 harsh shift guide covers the modulator, governor and valve causes.
Disconnect the rod at the transmission and rotate the TH400 selector lever by hand. You should feel six clean detents, fully rearward or forward for Park depending on the installation, and the output shaft should lock in Park. If the detents are crisp on their own, the problem is the shifter or rod, and this kit fixes it. If the selector feels vague by hand, the detent spring or internal linkage needs attention first; see our TH400 valve body testing guide. A late engagement that comes and goes can also be a fluid or pump issue, covered in the TH400 delayed engagement guide.
This kit is listed for the GM Turbo 400 only. It is not tied to a model year because it mounts to the floor and to the TH400 case, so it suits swaps and custom builds as well as original TH400 cars. The gate is meant for a stock-pattern TH400, which reads P-R-N-D-2-1. If your transmission has a reverse-pattern manual valve body such as the reverse-pattern full manual valve body, the gear order will not match the gate, so plan for a shifter built for that pattern. Check tunnel clearance for the 12 inch arm and boot before cutting the floor. Questions on fit? Send us the vehicle and transmission details. All parts for this unit are on our TH400 parts page.
For firmer shifts to go with the new stick, add the TH400 shift improver kit.
| Transmission | GM Turbo 400 (TH400) |
| Mount | Floor |
| Shift arm | 12 in chrome, billet aluminum knob |
| Boot | 5 in round black boot with stainless trim ring |
| Includes | Shifter, linkage rods, brackets, boot |
| Gate | Lockout style |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
It is listed for the GM Turbo 400. The bracket and rod geometry are for the TH400 case, so we do not list it for other transmissions.
The factory TH400 order is P-R-N-D-2-1, and a reverse-pattern valve body changes that order, so the gate stops would not line up with the gears. Use a shifter built for the reverse pattern with that valve body.
No switch is listed in the kit contents. Wire your car's neutral safety and reverse light circuits so the engine only starts in Park or Neutral.
Put the transmission in Neutral at the case lever and the shifter in Neutral, then set the rod length with no preload either way. Check every position with the engine off, and confirm Park locks the output shaft.
The shifter with a 12 inch chrome arm and billet aluminum knob, linkage rods, mounting brackets, and a 5 inch round black boot with a stainless trim ring.
A rod set slightly long or short leaves the manual valve between ranges and lowers clutch apply pressure. Re-check the detents at the case lever before chasing a hydraulic problem.
