A341E Shift Kit 1985

If the A341E in your 1990-1997 Lexus LS400, SC300, SC400 or early GS300 has gone lazy between gears, smells burnt after a rebuild, or slips the converter clutch once it is hot, this is the kit transmission shops reach for. It is the TransGo 340-HD2 Reprogramming Kit with Gear Command, part number 340-HD2, written for 1985-and-later A340, A341, A343 and AW4 series transmissions. The listing year of 1985 is where the kit's coverage starts, not the only year it fits.

What the 340-HD2 shift kit does in an A341E

The A341E is the heavy-duty, high-torque member of the Aisin four-speed rear-drive family, and its shifts are set by hydraulics in the valve body, not just by the computer. The computer picks the gear; the accumulators, feed orifices and pressure regulator decide how long the clutch takes to lock. A stock calibration is soft by design, and with age the slip time grows. The 340-HD2 recalibrates those three things together, so each clutch applies quicker and with more holding pressure. TransGo describes the result as short, firm shifts that extend clutch life, aimed at hot rods and work trucks.

Two extra pieces make this kit more than springs. A USA-made hardened steel TCC relay boost valve and bushing drops in where the soft aluminum factory parts wear and leak lockup pressure. And a hardened steel 1-2 shift valve with ball, pin and rivet is supplied as an optional low hold, which keeps the transmission in first gear when the lever is in manual low.

Symptoms this kit addresses

• Soft, slow upshifts that feel like the engine flares before the next gear catches
• Burnt clutch plates and dark, smelly fluid, especially after towing or hard driving
• A rebuilt unit that wears out its new frictions quickly
• Converter clutch slip or shudder and high fluid temperature at cruise; on OBD-II vehicles a TCC performance code such as P0741 can follow
• No true first-gear hold in manual low on long downgrades

How to confirm it before you order

A shift kit corrects pressure and timing, so rule out the electrical side first. Pull any stored codes, check the fluid level and condition, and confirm the shift solenoids click and read correctly. A unit that misses whole gears or starts in third usually has a solenoid problem, and the A341E shift solenoid kit is the better first buy. If the fluid is black and full of friction material, the clutches are already gone and the kit belongs inside a rebuild, not in place of one.

Fitment

TransGo lists the 340-HD2 for 1985-on A340, A341, A343 and AW4 transmissions, which covers the A341E (also called the AW40 or 30-41LE). In North America that means the first- and second-generation Lexus LS400, the 1992-1997 SC300 and SC400 and the 1993-1997 GS300; it was also used in home-market Toyota Crown, Celsior, Chaser and Mark II models. One honest caveat matters for Lexus owners: TransGo states the TCC relay boost valve fits type two, three and four valve bodies except some Lexus models. Compare the boost valve bushing in your valve body to the kit part before you replace it; if it does not match, leave the original in place and install the rest of the kit. If you are unsure which unit you have, read the tag on the transmission case or send us your year and VIN. Browse every A340-family part in our Aisin transmission collection.

Install notes

• The kit can be installed with the transmission in the vehicle; the valve body comes out from below after the pan and filter.
• Have new valve body gaskets that match your exact unit on hand before you start. TransGo's instructions warn there are 17 different gaskets across this family and identify four valve body types, so identify yours first.
• Follow the TransGo instructions in order: some accumulator springs and spacers are swapped, some orifices are drilled with the supplied bits, and the pressure regulator and cut back valve springs are changed.
• Lay the removed parts out in order on a clean bench. Mixing up check balls or accumulator springs is the most common install mistake.
• Refill with the ATF your vehicle specifies, check level hot, and road test before you put the tools away.
• During a full rebuild, pair the kit with an A341E overhaul kit with frictions and steels; if your valve body bores are worn beyond a kit, a replacement A341E valve body is the cleaner fix.

Will this kit fit my 1990-1997 Lexus LS400?

The LS400 of that era uses the A341E, and TransGo lists the 340-HD2 for 1985-on A341 units. The one exception is the TCC relay boost valve, which TransGo says does not fit some Lexus valve bodies, so compare it to your original before swapping that piece.

Does the kit make shifts harsh?

It makes them shorter and firmer, not violent. The goal is less clutch slip time, which is what burns plates. It is a common choice for work trucks and modified cars that see more torque than stock.

Can I install it without removing the transmission?

Yes. TransGo states the kit can be installed with the transmission in the vehicle. You drop the pan, remove the valve body, make the changes, and reinstall.

Do I have to use the low hold 1-2 shift valve?

No. The hardened 1-2 shift valve is optional. Install it if you want the transmission to stay in first with the lever in manual low, for example on steep downgrades or off-road.

Will a shift kit fix a transmission that is already slipping?

Not if the clutches are worn out. A shift kit protects good clutches. If the unit slips in gear or the fluid is full of debris, rebuild it with new frictions and steels and install the kit at the same time.