4L80E vs A340: Differences and Which One to Choose

The GM 4L80E and the Toyota/Aisin A340 are both longitudinal, rear-wheel-drive, four-speed automatics with a lock-up converter and electronic control. On paper they look like direct competitors. In practice they never shared a vehicle, they were designed around wildly different torque loads, and the only people who genuinely choose between them are engine swappers picking a transmission for a project.

So this comparison works on two levels: identifying which one you are working on, and - for the swap crowd - understanding which one belongs behind your engine.

The short answer

The 4L80E is a heavy-duty truck transmission descended from the TH400, built for 3/4-ton and 1-ton GM pickups and vans, rated for 440 lb-ft of engine torque. The A340 family is a mid-size Toyota unit that ran behind six-cylinder and early V8 Toyota and Lexus engines in 4Runners, Tacomas, Tundras, Land Cruisers, Supras and LS400s, with a torque capacity roughly a third of the GM unit's.

If you are building a heavy tow rig or putting real power through it, the 4L80E is the transmission. If you are keeping a Toyota truck or a Lexus on the road, the A340 is the transmission, and there is no reason to swap away from it.

Architecture and origin

The 4L80E, per Novak Conversions, is "the advanced progeny of the legendary TurboHydramatic TH400 automatic transmission, and is based heavily on the 400 in both parts and strength." GM took the TH400, added an overdrive gear, a lock-up torque converter and electronic controls, and released it in 1991. Sonnax makes the same point from the parts side: the 4L80E and higher-torque 4L85E share gear ratios with the 3-speed TH400 and add the 4th gear overdrive.

The A340 is an Aisin design. Per gearboxlist, the A340E was produced in Japan from 1984 through 2018 - a 34-year production run - and the family includes the A340H and A340F all-wheel-drive and four-wheel-drive variants. The letters follow Toyota's convention: E denotes the two-wheel-drive electronically controlled version and F the four-wheel-drive version, with the A343 designation appearing on longer-input-shaft V8 and Land Cruiser applications.

Both are longitudinal RWD units with a separate bellhousing arrangement dictated by their engine families. The 4L80E, Novak notes, has "an integrated bellhousing with only the Chevrolet 90 degree engine bolt pattern being available" - there is no removable bellhousing option. The A340 is likewise cast for Toyota bolt patterns, and the practical differences between A340 variants come down to the torque converter, the bellhousing and the input/output shafts.

Gearing side by side

The 4L80E ratios come from Diesel Hub; the A340E ratios from gearboxlist.

The A340 runs a deeper first gear (2.804 versus 2.482) and a taller overdrive (0.705 versus 0.750). That combination gives a wider overall spread - more launch multiplication down low and lower cruise RPM up top - which suits a smaller-displacement engine that needs the gearing to do more of the work. The 4L80E's tighter spread is a TH400 inheritance: a big-torque engine does not need a 2.8 first gear to move a truck.

Strength, size and rating

• 4L80E torque: Diesel Hub lists 440 lb-ft of engine torque for the 4L80E and 460 lb-ft for the 4L85E. Novak gives 440 ft-lbs maximum input torque, 885 ft-lbs maximum output torque, and GVWR capacity up to 8,000 lbs for the 4L80 or 16,500 lbs for the 4L85. Gearstar gives the same 440/460 input and 885 ft-lbs output figures.
• A340 torque: gearboxlist lists a maximum torque capacity of up to 300 Nm - roughly 221 lb-ft - and engine displacement supported up to 3.5 liters.

That is the single most important number on this page. 440 lb-ft against roughly 221 lb-ft. The A340 is a well-built, long-lived unit, but it was designed around Toyota six-cylinder and small V8 torque, not diesel-truck torque.

Size follows. Novak lists the 4L80E at 26-1/4 inches long and 254 lbs dry, with a 310 mm torque converter and a 32-spline output shaft in both 2WD and 4WD applications. Diesel Hub lists it at 236 lbs dry / 260 lbs with fluid in a die-cast aluminum case, on DEXRON VI, with roughly 13.5 quarts total capacity. The A340 is a physically smaller unit; gearboxlist specifies Toyota ATF Type T-IV and gives a capacity figure of 8.3 liters, with oil and filter service recommended every 75,000 km.

Applications - how to tell which one you have

4L80E: Diesel Hub lists 1991-1999 GMC Sierra / Chevrolet Silverado 1500/2500/3500 and Suburban, plus 1996-2002 GMC Savana / Chevrolet Express, with the 4L85E running behind the Duramax in the vans through 2005. Gearstar puts the family's production from 1991 through 2009 and later, with the 4L85E arriving in 2002. Novak notes it is used almost exclusively in trucks and heavy applications, with some rear-drive luxury cars.

A340: gearboxlist says it was installed on 20-plus vehicle models including the Toyota 4Runner, Supra, Tundra, Tacoma and Crown, and the Lexus LS400, SC300 and SC400. The A340F and A343F show up in four-wheel-drive Land Cruisers, Prados, Hiluxes and the Lexus LX450.

If the truck is a GM 2500/3500 or a full-size van, it is a 4L80E. If it is a Toyota or Lexus with a longitudinal engine and a four-speed automatic from 1984 onward, it is an A340 variant.

Identifying your A340 before you buy parts

This is the part most people get wrong, because "A340" is a family, not a part number. Sonnax's Toyota A340E/F identification guide splits the '00-later V6 and V8 units by valve body casting:

• Type 3 - casting ID #8935 - V8 applications, EPC-style throttle control only
• Type 4 - casting ID #8938 - V6 or V8 applications, EPC or cable-style throttle control

Earlier units are Type 1, identified by the 8931 (or 8930) casting code. Sonnax's parts listings make the distinction concrete: the boost valve kits 97855-23K and 97855-30K fit Type 1 with 8931 casting, and are split further by whether the large spool measures .566" or .546" in diameter. The oversized pressure regulator valve kit 97855-24K replaces the 3-spool PR valve in units with three or fewer solenoids, Type 1 only, while the Type 3 and 4 pressure regulator kits split by whether the small EPC spool is .353" or .426" in diameter.

The lesson: measure or identify the casting before ordering valve body parts for an A340. There is no universal A340 valve body kit.

What breaks on each

On the A340, gearboxlist describes the wear pattern directly: dirty oil causes bushing wear and pressure loss, and clutch failures progress sequentially - the forward package first, then the 2nd brake, then Low/Reverse. It puts the expected lifespan at roughly 350,000 km with proper maintenance, which is a genuinely long life for a four-speed automatic.

Sonnax's A340 parts list reads like a symptom index for the same root cause: the boost valve kits cure delayed engagement, low line rise, low or high line pressure in reverse, erratic line pressure, soft upshifts and repeated clutch failure. The oversized pressure regulator valve kits cure low or high line pressure, poor shift quality, low lube oil flow and burnt clutches. The lockup relay valve kits cure no lockup, overheated converter, overheated fluid and low cooler flow. The A340-LATE-ZIP Zip Kit for '00-later V6 and V8 Type 3 and 4 units targets burnt clutches, delayed engagement, inadequate lubrication, low pressure, slips and flares, soft shifts and TCC codes.

In other words: on an A340, low line pressure from valve body bore wear is what burns the clutches. The clutches are the casualty, not the cause.

The 4L80E fails more like the truck box it is - heat, clutch and band wear under sustained load, and electronic control faults on units that have been working for decades.

The fix - which parts you actually order

For an A340 with soft shifts, delayed engagement or burnt clutches: address the pressure circuit and replace the friction material. The A340 friction clutch kit for 85-up units covers the friction plates that go in when the packs come apart. If the complaint is converter-related - shudder, no lockup, RPM fluctuation - the A340E TCC lock-up solenoid kit for 2000-2015 is the part that controls apply.

For a 4L80E going through a freshen-up or a tow-season rebuild: the unit comes apart as a whole, and a 4L80E master rebuild kit with gaskets puts the frictions, steels, gaskets and seals in one box. Browse the rebuild kit collection for the rest of the family.

Replace while you are in there

• All soft parts. Gaskets, seals, sealing rings and O-rings. Already in a master kit - use them.
• Filter and pan gasket. On the A340, gearboxlist ties bushing wear and pressure loss directly to dirty oil, so the filter is not optional.
• Bushings. On the A340 specifically. If the fluid was dirty long enough to cost you pressure, the bushings are already worn.
• Valve body pressure circuit. On the A340, replacing clutches without addressing a worn boost valve or pressure regulator bore is how the same unit comes back burnt.
• Bands. If the unit was slipping, the band material is glazed whether it looks it or not.
• The torque converter. Debris from a failed pack ends up inside it. A flushed converter is not a clean converter.
• Cooler and lines. Flush or replace. Sonnax's A340 lockup relay kits list low cooler flow and overheated fluid as symptoms for a reason - heat is what kills both of these units.

Cost, effort, and which one to choose

An A340 valve body repair is the least invasive job here: the pressure circuit parts are small, and correcting a worn bore is far cheaper than replacing the clutches it burns. A full A340 clutch job means pulling the transmission - a smaller, lighter unit than the GM box, but still a driveline-out operation.

A 4L80E rebuild is the heaviest job on this page: a 254-lb unit out of the vehicle, full teardown, and a converter. The labor of removal and installation is identical whether you replace one clutch pack or everything, which is the standing argument for doing the complete job once it is on the bench.

Which to choose, if you actually have a choice:

• Heavy towing, a big-block or LS, or any build over about 400 lb-ft: the 4L80E. 440 lb-ft input rating, 885 ft-lbs output, 8,000 lbs GVWR, and TH400 hard parts underneath. Nothing in the A340 family competes at that level.
• A Toyota or Lexus that already has one: keep the A340. It is rated for what the engine makes, parts support is deep, and gearboxlist's 350,000 km lifespan figure is real if the fluid gets changed.
• A Toyota truck with a GM engine swap: this is the only case where the comparison is a live decision, and the 4L80E usually wins on capacity while the A340 wins on packaging - Novak notes the 4L80E's 26-1/4 inch length rules it out of short-wheelbase chassis entirely.

Frequently Asked Questions

Is the A340 stronger than the 4L80E?

No. gearboxlist lists the A340E's maximum torque capacity at up to 300 Nm, roughly 221 lb-ft, with engine displacement supported up to 3.5 liters. Diesel Hub lists the 4L80E at 440 lb-ft of engine torque and the 4L85E at 460 lb-ft, and Novak adds 885 ft-lbs maximum output torque and up to 8,000 lbs GVWR. The 4L80E is in a different weight class.

What is the difference between an A340E, A340F and A343F?

The suffix follows Toyota's drive convention - E for two-wheel drive, F for four-wheel drive - and gearboxlist describes the A340H and A340F as the all-wheel-drive modifications of the A340E. The practical differences between them are the input and output shafts, the torque converter and the bellhousing, not the core gearset. The A343 designation appears on longer V8 and Land Cruiser applications. For valve body parts, Sonnax's identification guide is the authority: identify the casting code before you order.

Can you put a 4L80E behind a Toyota engine?

Only with an adapter. Novak states the 4L80E has an integrated bellhousing with only the Chevrolet 90-degree engine bolt pattern available and no removable bellhousing option, so any non-GM engine requires an adapter plate. Length is the other constraint - Novak lists the unit at 26-1/4 inches and specifically rules it out of short-wheelbase chassis on packaging grounds.

Sources

• Diesel Hub - GM 4L80E, 4L85E Transmission Specs & Ratios
• Novak Conversions - The Novak Guide to the GM 4L80E Automatic Transmission
• Gearstar Performance Transmissions - Ultimate Guide to the 4L80E Transmission
• gearboxlist - Toyota A340E: specifications, gear ratios, oil
• Sonnax - Toyota A340E/F Identification Guide
• Sonnax - GM 4L80E Performance Transmission Upgrades

Related reading: 4L60E vs A340: Differences and Which One to Choose, Toyota A340E/A340F Delayed Engagement and Burnt Clutches, and TH400 vs 4L80E: Which One for Your Build.