TH350 Shift Kit, new and ready to install. Fits the TH350. Ships fast from the USA.
A Turbo 350 with a long, lazy 1-2 and a 2-3 that slides in under throttle is slipping its clutches on every change, and that slip is what wears out the frictions. This new TH350 shift kit is the plate-and-gasket type that goes between the valve body and the case. It fits the GM TH350 used in Chevrolet, GMC, Pontiac, Oldsmobile and Buick cars and light trucks, and the shift gets shorter and firmer without changing the hard parts.
The TH350 is fully hydraulic. Line pressure comes from the pump and pressure regulator and is raised under load by the vacuum modulator. A governor on the output shaft and the modulator decide when each shift happens, and the 1-2 accumulator softens how the intermediate clutch comes on. Inside the valve body, the separator plate is a flat steel plate with small holes that meter oil between the valve body passages and the case. Hole size sets how fast each clutch fills. A shift kit like this one changes those holes. A recalibrated separator plate with matching gaskets lets the intermediate and direct clutches apply faster, so there is less time spent slipping between gears. The kit pictured includes a plated separator plate, valve body and plate gaskets, smaller transfer plates, an O-ring and a cork pan gasket.
These symptoms can also come from other problems. A leaking modulator, a worn 1-2 accumulator bore, a scored intermediate servo bore or a worn boost valve sleeve all lower line pressure and cause slip. A shift kit will not fix them.
Check the fluid level and smell first, then pull the vacuum line at the modulator. Fluid in the line means the diaphragm is leaking. If the transmission slips in a single gear or has no second at all, the problem is mechanical, and our TH350 common problems guide covers the usual causes. For pure shift quality, the TH350 shift quality guide explains how line pressure, the modulator and the accumulator work together. A pressure gauge on the line tap during a road test is the best proof. Our vacuum and pressure gauge kit does that job.
The listing is for the TH350 without a specific year range. The TH350 ran from 1969 through the mid-1980s, and the later TH350C added a lockup converter circuit to the valve body. Separator plates are matched to their valve body, so lay your old plate on top of the one in the photo and check that the outline and bolt holes line up before you start. If you have a TH350C, we also carry the TransGo 350C-1-2 lockup shift kit, which is made for that version. Send us your year, vehicle and the code on the case if you want us to confirm fit. All TH350 parts are on the TH350 parts page.
If you are doing a full rebuild, the TH350 overhaul kit covers the gaskets and seals. A TH350 governor shift point kit lets you raise the shift points along with the firmer shift.
| Fits | TH350 |
| Part type | Shift Kit |
| Condition | New |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
The kit pictured includes a recalibrated separator plate, valve body and plate gaskets, small transfer plates, an O-ring and a cork pan gasket. Compare the photo with your valve body and old plate before you start.
The TH350C valve body has an added lockup circuit, so a plate made for the non-lockup TH350 may not match it. Lay your old separator plate over the one in the photo. For a confirmed lockup fit, the TransGo 350C-1-2 kit is made for the TH350C.
Yes. The separator plate sits under the valve body, which comes out after you drop the pan and filter. Keep track of the check balls and the linkage on the manual valve, and use all new gaskets.
It shortens the shift on a healthy unit but will not repair burned frictions, a leaking modulator or worn accumulator and servo bores. Diagnose those first. If the clutches are worn, install the kit during a rebuild.
Dexron ATF. After a pan drop it takes about 2-1/2 quarts to refill, according to GM's 1976 truck service supplement. Set the final level hot on the dipstick.
