AS68RC Input Drum

This is a remanufactured K1 input shaft drum for the Aisin six-speed that Ram calls the AS68RC, Isuzu calls the A465 and Mitsubishi Fuso calls the AS6. The shaft and drum come as one piece, and the assembly stands 11-5/8 inches tall. Shops looking for this part usually have an Isuzu NPR, a Fuso FE or FG, or a Ram 3500-5500 cab and chassis that pulls away weak or will not take 1st through 4th, and a teardown that found a heat-damaged drum or a chewed-up shaft.

What the K1 input drum does in the AS68RC

The turbine shaft drives straight into this drum. The K1 clutch pack sits inside it, and K1 is applied in 1st, 2nd, 3rd and 4th, so it carries the load every time a loaded box truck or flatbed starts from a stop. Apply oil for K1 reaches the drum through sealing rings on the shaft that run inside the stator support, which is why the condition of the shaft journals matters as much as the drum shell. Transmission Digest points out a related problem on this family: if the stator shaft spins in the pump cover, the oil passages misalign and K1 oil leaks across into the K2 and converter clutch circuits. The result is a dragging K2 and an overheated converter clutch, and a pack that burns again shortly after the rebuild.

Symptoms that point to the K1 drum

• No 1st through 4th, while 5th and reverse still work
• A slipping or flaring launch that gets worse as the fluid warms up
• Ratio error codes such as P0731 that come back after clearing
• Burned K1 frictions or a cracked, blued drum found at teardown
• Grooved sealing-ring lands on the input shaft, or a pack that will not hold air

How to confirm it before you buy

Pull codes from the transmission controller, check fluid level and smell, and write down which gears are missing. If 1st through 4th are gone and the upper gears pull, K1 or its feed circuit is the suspect. Our gear ratio code diagnosis guide explains how to read P0731-type codes, and the Aisin slipping under load guide covers pressure and fluid checks. Before you blame the drum, do the cooler-line check Transmission Digest describes. Disconnect the return line, and if fluid comes out of the case fitting instead of the line, the stator shaft has turned in the pump and a new drum alone will not last.

Fitment

The source listing for this drum is tagged for the Isuzu and Mitsubishi versions of the unit. It describes the drum as the 1-2-3-4 clutch drum on the input shaft, 11-5/8 inches tall. Transmission Digest notes the Isuzu and Mitsubishi units differ slightly from the Ram version. Ram owners should compare their old drum against the photo, measure overall height and count the shaft splines and sealing-ring grooves. If you are not sure, send us the truck year and VIN or a photo of your old part before ordering. If you would rather have a used drum that already has a six-friction K1 pack installed, see the loaded 2007-up K1 drum.

Install notes

• Replace the K1 frictions, steels and piston seals while the drum is out. The AS68RC master rebuild kit covers clutches, seals and sealing rings.
• Fit new sealing rings on the shaft, check their fit in the stator support bore, and air-check K1 before closing the case.
• Set K1 clearance with the snap ring and measure it. On the successor AS69RC, FCA traced lost lower gears to a K1 snap ring that worked loose, so seat the ring fully.
• Inspect the pump stator shaft splines before reuse.
• Flush the cooler and lines, install a new filter and pan gasket, and fill with the fluid your truck specifies. Ram units take ATF ASRC or an approved equivalent such as Mobil 3309.

Is the AS68RC the same transmission as the Isuzu A465?

Yes, they are the same Aisin six-speed family. Ram sold it as the AS68RC, Isuzu NPR trucks list it as the A465, and Fuso uses AS6. The Isuzu and Mitsubishi units have small differences from the Ram one, so match the old drum before installing.

How tall is this input drum?

The listing measures the shaft and drum assembly at 11-5/8 inches tall. Measure your old part the same way to confirm it matches.

Which gears quit if the K1 drum fails?

K1 is applied in 1st through 4th. A failed drum, a leaking shaft seal ring or a loose snap ring usually takes out those gears, while 5th and reverse still work.

What should I replace with the drum?

Replace the K1 frictions and steels, piston seals and shaft sealing rings, plus the filter. Check the pump stator shaft as well, because a turning stator shaft cross-leaks K1 oil and will burn the new clutches.

Does this drum come with clutches in it?

It is sold as the remanufactured drum and shaft assembly. Plan on installing a new K1 clutch pack and seals from a rebuild kit.

• Gear Ratio Codes P0730 Diagnosis
• Aisin Transmission Slipping Under Load
• Aisin Overheating Prevention
• How to Flush a Transmission Cooler After Failure