NV4500 Transmission Fluid Replacement

How to Change Transmission Fluid in The NV4500

Applicable Models:

1994 - 2005 Dodge Ram 2500, 3500
1992 - 1998 Chevrolet & GMC C/K fullsize trucks

Applicable Engine(s):

5.9L Cummins I-6 turbodiesel
6.5L GM/Detroit V-8 diesel (naturally aspirated & turbocharged variants)

Applicable Transmission(s):

New Venture NV-4500 five speed manual

The venerable NV4500 5 speed manual transmission was manufactured by New Venture Gear, a joint venture between General Motor's Muncie division and Chrysler's New Process Gear. Thus, the NV4500 has been used in various Dodge, Chevrolet, and GMC truck applications through the 2005 model year. The transmission's fibrous synchronizers designate particularly specific fluid specifications - failure to use a suitable gear oil will result in transmission damage. While the transmission does not require frequent service, periodically oil changes may extend the life of the transmission and maintain smooth shift sequences.

NV4500 Transmission Service Parts List

Part Description Part Number(s) Remarks/Notes
Transmission fluid GM 12346191
MOPAR 4637579
Amsoil 75W-90 manual transmission fluid
Transmission fill plug MOPAR 04637849 [2]
PTO cover MOPAR 00556875 [2] [3]
PTO cover gasket Fel-Pro 55379

[1] See additional transmission fluid below.
[2] Compatible with Dodge and GM versions of the NV4500.
[3] Gasket optional, may be sealed with RTV silicon only.

NV4500 Transmission Fluid Spec

The NV4500 manual transmission is highly sensitive to its fluid type as it uses special carbon fiber synchronizers. The original fluid spec is Castrol Syntorq synthetic 75W-90 GL-4 manual transmission fluid. Castrol's fluid is difficult, if not impossible to locate (it may be discontinued), but both General Motors and Chrysler continue to sell the formulation under their own brands. The GM part number is 12346191 and the Chrysler/MOPAR part number is 4637579. Amsoil 75W-90 manual transmission fluid is a popular, economical alternative to the relatively expensive OEM oils. Do NOT confuse Castrol Syntrax and Syntorq, and do not assume that any manual transmission fluid of the same viscosity will suffice; fluid must meet the original Castrol, GM, or Chrysler specification.

The Dodge and General Motors versions of the New Venture NV4500 are slightly different, with the Dodge unit marketed as a heavy duty "NV4500HD". For all intents and purposes, the operation of the transmissions remains the same, as are the service procedures. However, for the sake of following OEM recommendations, we would recommend obtaining GM fluid for a GM NV4500 application and MOPAR fluid for a Dodge application; or reduce the impact on your budget and go with Amsoil's alternative.

The Dodge NV4500HD commonly suffers from a loss of 5th gear, where it becomes physically impossible for a driver to put the transmission into overdrive - this problem is extremely rare if at all existent in GM applications. The cause of such failures has been attributed to frequent lugging of the engine; high load, low speed situations. Towing in 5th gear at 1,000 rpm, for example, should be avoided in order to prevent such occurrences. Proper transmission service will not prevent, alleviate, or eliminate such failures as driving behavior alone is to blame.

NV4500 Fluid Change Procedures

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NV4500 drain and fill plug location

• Place the transmission in gear and set the parking brake.

• The NV4500 has PTO provisions on both the driver and passenger sides, while the fill plug is located on the passenger side.

PTO bolt removed, transmission draining

• Place a suitable container below the transmission to collect the fluid. Remove the bottom bolt from the PTO cover with a 9/16" socket; allow fluid to drain completely.

• You may drain the fluid via this single PTO cover bolt, or you can remove the entire PTO cover. We choose to remove the entire cover, which allows us to soak up fluid in the sump of the transmission that will not drain through the PTO bolt hole, as well as give us the opportunity to inspect for metal particles or debris. If you choose not to remove the cover, you can simply replace the PTO cover bolt and fill the transmission with fluid after it drains, skipping several of the following steps.

NV4500 PTO cover removed

• With the cover removed, soak up any remaining oil that has settled in the sump of the transmission using a lint free rag.

• Thoroughly clean the mounting surface of any sealant, then spray a lint free rag with a solvent (brake cleaner, carb cleaner, etc) and wipe the surface clean of any oil. Do not spray solvent directly onto the surface. Do not allow any debris to enter the transmission.

PTO cover sealant

• Thoroughly clean the PTO cover of any sealant, oil, dirt, and debris.

• Apply a continuous bead of oil resistant RTV silicon along the perimeter of the PTO cover (~ 1/4" wide will suffice).

• Reinstall the PTO cover; torque bolts in a cross pattern to 30 ft-lbs. Allow sealant to cure per manufacturers specifications before continuing (24 hours is common if a cure time is not listed).

NV4500 transmission fill plug/port

• Remove the transmission fluid fill plug using a 3/8" Allen wrench/socket.

• Add transmission fluid until it reaches the fill hole level - when fluid begins to spill out of the fill port, the transmission is full. Most auto parts stores sell a convenient adapter that turns an ordinary oil quart container into a fluid pump. Reinstall the transmission fill plug when full. See fluid information above; only use a suitable fluid as discussed above or transmission damage will occur.

• Drive vehicle, allowing transmission to reach operating temperature and check for leaks.