G56 Transmission Bearing and Seal Rebuild Kit BK474

If your Ram 2500 or 3500 with the Cummins and the six-speed manual has started to whine with road speed, growl on decel, or drip gear oil from the bellhousing or tailhousing, the bearings and seals in the G56 are the usual cause. This kit replaces BK474 and carries the bearings, races and seals that have to be renewed any time the G56 case is split: the tapered roller bearings for the input, mainshaft and countershaft, their races, needle bearings, the input and output shaft seals, and the case gaskets. It fits the G56 behind the 5.9L and 6.7L Cummins in 2005-2018 Ram 2500 and 3500 trucks.

What the bearing kit does in a G56

The G56 is a Mercedes-Benz designed heavy-duty six-speed with an aluminum two-piece case and an integral bellhousing. The input shaft, mainshaft and cluster (countershaft) ride on tapered roller bearings, and those bearings set where the gears sit relative to each other. When a bearing wears, the shaft gains endplay, the gears stop meshing on the center of the teeth, and noise starts. The Turbo Diesel Register's G56 rebuild write-up singles out the front input shaft bearing as the one most prone to failure, and notes that nearly every G56 that comes in for a rebuild has large input shaft endplay. Because aluminum expands with heat much faster than iron, heavy towing in a hot floor tunnel makes that endplay worse. New bearings and races put the shafts back where they belong before worn bearings take the gears and case with them.

Symptoms of worn G56 bearings and seals

• A whine that rises and falls with road speed in every gear, with the clutch in or out
• A growl or rumble on deceleration, or a noise that gets louder as the gearbox warms up on a long tow
• Gear oil at the bottom of the bellhousing (input seal) or at the tailhousing and driveshaft yoke (output seal)
• Fine metal glitter on the drain plug magnet
• Noise that changes when you press the clutch at a stop, which points at the input bearing and pilot area

How to confirm before you buy

Separate gearbox noise from clutch and dual-mass flywheel noise first: a rattle at idle that goes away with the clutch pedal down is usually the flywheel, while a whine tied to road speed is in the gearbox. Drain the oil and look at the plug; bronze flakes point at synchros, steel glitter at bearings. If the truck grinds going into a gear, plan for synchros as well, because this kit does not include them. Our guide to manual transmission repair costs helps you decide between a rebuild and a replacement unit.

Fitment

This kit is listed for the G56 six-speed manual in 2005-2018 Ram 2500 and 3500 trucks with the 5.9L and 6.7L Cummins, and it replaces BK474. It does not fit the NV5600 used in earlier Cummins trucks. The G56 input shaft changed during production (an early two-groove and a later three-groove version tied to the overdrive ratio change), so compare the new input bearing against the old one before you press anything. If you are not sure which version you have, send us the year and VIN. More manual gearbox parts are in our rebuild kits collection.

Install notes

• Clean the case and every part thoroughly. A manual gearbox has no filter, so any grit left behind circulates through the new bearings.
• Press bearings on with a driver on the inner race and races into the case with a driver on the outer edge, never through the rollers.
• Set input and countershaft endplay with the shim pack before closing the case halves. Worn and stretched cases often need more shim than the factory piece.
• Inspect the welded shift forks and the gear tooth contact pattern while the unit is apart.
• Factory fill was ATF+4, and there is long-running debate about whether a heavier lubricant holds up better under heavy towing. Check the fill level at the plug, because many units were found low. A G56 PTO cooler cover adds capacity on 2005-2010 trucks.
• While the shifter is out, a G56 short-throw shifter is an easy upgrade.

Replace the pilot bearing whenever the clutch is out, and order synchros separately if any gear grinds.

Which trucks does this kit fit?

The G56 six-speed manual in 2005-2018 Ram 2500 and 3500 with the 5.9L or 6.7L Cummins. It replaces BK474. It does not fit the NV5600.

Does the kit include synchronizer rings?

No. It covers bearings, races, needle bearings, shaft seals and gaskets. If the truck grinds going into a gear, order synchros separately.

What noise means the bearings are bad?

A whine that follows road speed in every gear, a growl on deceleration, or noise that gets worse as the gearbox heats up on a long tow. The front input bearing is the one that fails most often.

What fluid goes in a G56?

Ram listed Mopar ATF+4 as the factory fill. Many rebuilders prefer a heavier manual transmission lubricant for heavy towing. Whatever you use, fill to the bottom of the fill plug hole.

Do I need special tools?

A press, bearing pullers, bearing and seal drivers, and a way to measure endplay so you can choose the correct shims before closing the case.

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