Shop All Transmission Parts →
"No 2nd" on a Turbo 400 gets used for three different complaints, and they have nothing in common under the pan. Pin down which one you have before you order parts.
- Never upshifts. It stays in 1st until you lift. That is a shift command problem: governor, 1-2 shift valve, or pressure.
- Flares on the 1-2 shift. Rpm jumps like neutral, then it catches in 2nd or goes straight to 3rd. That is the 2nd gear apply side not holding.
- Goes 1st to 3rd. Same family as the flare. 2nd is commanded but does nothing, and the next thing that holds is 3rd.
How 2nd Gear Works in a TH400
In Drive 2nd, the intermediate clutch applies and holds the outer race of the intermediate sprag, and the sprag in turn holds the sun gear through the direct drum. The forward clutch stays on from 1st. In 3rd the direct clutch applies and the sprag simply overruns.
Now the useful part. In manual 2 the front band also applies and clamps the direct drum directly. That bypasses the sprag entirely. So:
- Manual 2 holds 2nd, Drive does not: the band is doing the work the sprag or intermediate clutch should be doing. The fault is the intermediate sprag or the intermediate clutch.
- Neither Drive nor manual 2 holds 2nd: look for a pressure loss to both, starting with the center support and the intermediate clutch feed, and check the front band and servo too.
- It will not shift out of 1st in Drive: go to the governor section below.
Step 1: Fluid, Modulator, and Pressure
- Fluid level and condition. Check it hot and running. A burnt intermediate pack leaves dark fluid and friction material in the pan.
- Vacuum modulator. A ruptured modulator diaphragm drinks fluid (look for white exhaust and wet vacuum line) and throws line pressure and shift points off. Pull the vacuum line and check for ATF.
- Line pressure. A gauge on the case port in Drive and manual 2 tells you whether the problem is general low pressure or something specific to 2nd. See our line pressure test guide for hookup.
The Intermediate Sprag
The sprag is the most common hard cause of a TH400 that flares or skips 2nd in Drive but holds in manual 2. Sprags wear the elements and races, and a worn sprag freewheels in both directions.
- Worn or broken sprag elements. Individual elements roll over, the cage breaks, or the races get pitted. Replace the TH400 intermediate sprag and inspect the inner race on the direct drum hub.
- Installed backwards. This is the classic freshly rebuilt TH400 that has no 2nd. The sprag has a correct direction. Before the unit goes back together, hold the assembly and confirm the sprag locks and freewheels in the directions the manual calls for.
- Worn outer race. The outer race gets brinelled where the elements load. A new sprag in a pitted race slips again quickly.
The Intermediate Clutch and Center Support
The intermediate clutch piston is housed in the center support, and its oil comes up from the case through the support. If this side is leaking, 2nd in Drive will flare and 3rd may also feel soft because the direct clutch feed runs through the same center support.
- Intermediate piston seals. Hard, rolled, or cut seals are common on high-mileage units. Always new on reassembly.
- Burnt intermediate clutch pack. Check frictions and steels, and measure clearance on assembly. Our clutch clearance guide covers the method.
- Center support bolt. The support is bolted up from the case. A loose or improperly torqued bolt lets the support move and the intermediate feed leak. Check it any time the pan is off.
- Center support sealing rings and bushings. Worn rings leak direct clutch oil; a worn support or loose support fit leaks intermediate oil. Inspect the ring grooves for steps.
- Case snap ring and support fit. On high-power builds the center support can move enough to damage the case. A billet case saver is cheap insurance on a performance build.
Stuck in 1st: Governor and 1-2 Shift Valve
If the TH400 simply never upshifts, the apply components are probably fine. The shift is never being made.
- Governor. The governor sits behind a cover on the side of the case and is driven by the output shaft. A stuck governor valve, stuck weights, or a stripped governor gear means no governor pressure and no upshift at any speed. Pull the cover and check that the valve moves freely and the gear teeth are intact.
- 1-2 shift valve. A varnished or worn 1-2 shift valve in the valve body will not move against its spring. Clean it, check the bore, or replace the TH400 valve body.
- Detent downshift solenoid or switch. If the kickdown switch or detent circuit is stuck on, the unit acts as if you are at wide open throttle all the time and holds each gear to high rpm. It will still shift, just very late.
Symptom to Cause Table
| Symptom | Most Likely Cause | Next Check |
|---|---|---|
| Flares on 1-2 in Drive, manual 2 holds | Intermediate sprag worn or backwards | Teardown, inspect sprag and races |
| Flares in Drive and manual 2, 3rd soft too | Center support leak, intermediate seals, support bolt | Air check intermediate and direct |
| Goes 1st to 3rd | Intermediate clutch or sprag not holding | Manual 2 road test |
| Never upshifts from 1st | Governor, governor gear, 1-2 shift valve | Pull governor cover |
| Shifts very late every time | Detent circuit stuck on, modulator | Unplug detent, check modulator |
| Just rebuilt, no 2nd | Sprag installed backwards | Check sprag direction on teardown |
Parts and Cost
| Repair | Parts Needed | Parts Cost Range |
|---|---|---|
| Modulator | Vacuum modulator | Roughly $20 to $50 |
| Governor service | Governor or gear, cover gasket | Roughly $30 to $120 |
| Intermediate sprag | Sprag plus overhaul kit | Roughly $120 to $250 |
| Intermediate clutch rebuild | Master rebuild kit | Roughly $150 to $350 |
| Valve body | Remanufactured or performance valve body | Roughly $150 to $400 |
Our opinion: the manual 2 test is free and saves a lot of guessing. If it points at the sprag or center support, the unit is coming out anyway, so rebuild the whole thing with a Banner rebuild kit or, for a truck or performance build, a heavier master kit and a TH400 shift kit to shorten slip time on the 1-2 shift.
Shop the Part
Intermediate sprags, center supports, clutch packs, governors and complete rebuild kits for the Turbo 400 at our sister store, CoreTransmissionParts.com.
Shop TH400 Parts →FAQ
Why does my TH400 skip 2nd gear and go straight to 3rd?
Second gear in Drive depends on the intermediate clutch and the intermediate sprag. If the sprag is worn or the intermediate clutch leaks, 2nd never takes hold and the next thing that works is 3rd. Drive it in manual 2: if 2nd holds there, the front band is covering for a bad sprag or intermediate clutch.
Can a TH400 intermediate sprag be installed backwards?
Yes, and it is a common cause of no 2nd gear right after a rebuild. The sprag must lock in one direction and freewheel in the other. Check its rotation against the service manual before closing the unit up.
Why will my Turbo 400 not shift out of 1st?
A TH400 that never upshifts usually has no governor pressure or a stuck 1-2 shift valve. Pull the governor cover and check for a stuck valve or stripped gear, then look at the valve body.
Can I fix TH400 no 2nd without pulling the transmission?
Sometimes. Governor, modulator, valve body and center support bolt problems can be handled in the car. A worn intermediate sprag or burnt intermediate clutch means pulling the transmission and tearing it down.