NV4500 Transmission FAQs: Specs, Gear Ratios, Problems & Solutions

Last Production NV4500 Specifications*:

The NV4500 series transmissions have undergone many minor and major design changes since 1992. The minor changes, while important for durability and shifting ease, are not easily identifiable to the layman trying to determine the features of a particular transmission. The following list shows the major changes we have identified. To precisely identify a particular transmission by part number, get the numbers off the build tag on the left PTO cover and the decals on top of the top cover.

For Dodge:

• The light duty 1" 19 spline input shaft used in 1992-93 was changed to 1 1/8" 10 spline in 1994.
• 1992-93 models had a coarse thread shift stub. This was replaced by a square stub that accepted a press on shift lever for 1994-1997. A metric threaded shift stub was introduced for 1998.
• 1992-1996 had an interlock mechanism built into the 1-2 syncro to prevent high speed downshifts into 1st or second gear. This feature was dropped during the 1996 model year.
• In 1997, New Venture changed the design of reverse gear from a dual plane to a single plane. The reverse gear ratio was changed from 5.61:1 to 5.04:1.
• For 1998, the shift tower and shift handle were redesigned. 2WD models no longer had a speedometer drive (the speedo works off the rear axle). 4x4 tailshaft housings were changed to eliminate mountings for the transfer case shift lever. Also, with HD models, the mainshaft nut was redesigned late in 1998. This change first showed up on transmissions with an AD suffix on the Dodge part number (ex: 52108131AD).

For GM:

• 1992-1994 transmissions had a wider gear ratio with 1st gear being 6.34-1. Starting in 1995, the 1st gear ratio was changed to 5.61-1.
• 1992-1998 models did not have a synchronized reverse gear. A synchronized reverse was introduced for the 1999 model year.
• 1992-93 models had an interlock mechanism built into the 1-2 syncro to prevent high speed downshifts into 1st or second gear. This feature was dropped for 1994 according to our GM parts book, however we have found them on some 1994 transmissions.
• 1992-1995 transmissions had a bellhousing bolt pattern unique to GM. For 1996 and newer transmissions, GM uses the Dodge bolt pattern.
• In 1997, New Venture changed the design of reverse gear from a dual plane to a single plane. The reverse gear ratio was changed from 5.61:1 to 5.04:1.

"Losing" fifth gear can happen to any stock NV4500, but it is most commonly experienced with 1994-1998 Dodge turbo-diesel trucks used for heavy trailer towing and/or equipped with enhanced horsepower Cummins engines. The problem is less frequent on 1999 and newer Dodge turbo-diesel trucks with the revised factory 5th gear nut. While the nut is often blamed, the part failing is really the factory mainshaft.

For more information on fifth gear failures and cures, go to Tech Article

There can be many causes of this phenomena with the most common being wrong or degraded lubricant. NV4500 series transmissions were specifically designed for use with Castrol Syntorq LT® GL4 rated synthetic gear lubricant. Most other gear lubricants will damage the carbon fiber surfaces on the synchronizer rings.

Another problem related to shifting difficulty is failure of the pilot bearing. The stock pilot bearings used by Dodge and GM are needle bearings. Over time, these bearings have a tendency to run out of lubricant and disintegrate. This allows the front of the input shaft and clutch disc to "float" about. Erratic clutch performance and misalignment of the internal transmission components result. This combination often causes shifting problems.

New and newly rebuilt NV4500 transmissions may shift hard until the synchronizers wear in. At the other end of the spectrum, well used, high mileage transmissions with worn bearings and/or thrustwashers may shift hard or pop out of gear due to excessive mainshaft endplay.

Rebuilt transmissions with brass synchronizer rings often are hard to shift. Sometimes, changing the oil may help, however, in most cases you either have to install genuine New Venture rings or live with it.

A clutch that does not fully disengage will make it hard or impossible to shift the transmission, particularly into first and reverse. Installing a new clutch usually is the trigger for this problem, but the clutch itself is almost never the culprit. A new clutch will require pretty close to the full travel of the clutch pedal to disengage. Sometimes it is as simple as removing an extra floor mat that the pedal bottoms against. Any internal wear in the hydraulic system or external wear in the under dash components, clutch fork, and/or fork pivot ball can cause inadequate disengagement. The solution is to replace or repair the guilty parts.

Castrol Syntorq LT® was a low-temperature rated, 75w85w GL4 synthetic oil formulated specifically for the New Venture NV4500 5 speed manual transmission used in Dodge and GM light trucks. Syntorq LT® was also used by many import car manufacturers with various other manual transmissions. It was not an extreme pressure rated lubricant so it is not suitable for use in the hypoid gear axles found in almost all light trucks. Castrol discontinued Syntorq LT® a few years after NV4500 production ended in 2006. Our Redline QU90020 75w85w GL4 Manual Transmission Oil specifically meets the GM 12346190, Chrysler/Dodge MS-9070, 4637579 and 4874459 specifications. In operation, QU90020 equals or exceeds the performance of the original Castrol LT® oil for New Venture NV4500 5 speed manual transmissions.

It is relatively easy to increase the power output of late model Diesel engines. While the NV4500 is a pretty good transmission, it is not capable of taking extreme increases in horsepower on a sustained basis without sacrificing longevity.

The factory torque rating for NV4500HD transmissions is 460 ft/lbs. (About 235 hp). The design does seem to be capable of up to 600 ft/lbs with little loss of durability. However, as the horsepower and torque increases beyond 275hp/600ft-lbs torque, the size of the bearings, synchronizers, gears, and splines are no longer adequate. Rarely does a NV4500 fail catastrophically even at double the factory ratings, but the fact is most grossly overloaded 4500's will not last even 100,000 miles without a rebuild.

Yes, we can eliminate typical fifth gear failures with our Torque King® mainshaft and gear sets, and yes, we can even supply larger input shafts, but there is no practical way to increase the capacity of the other components. Except for competition pulling, stock input shaft breakage with the NV4500 is extremely rare. Mainshaft breakage is even rarer.

When subjected to repeated overloads, accelerated bearing and synchronizer wear will occur. The NV4500 is a 195 pound transmission designed for stock vehicles up to 1 ton and 19,000 lbs Gross Combined Vehicle Weight. If your engine horsepower or towed loads are typical of medium and heavy duty trucks, you should, as a minimum, consider retrofitting a 6 speed transmission such as the 365 pound NV5600. Better yet, would be to buy a 2 ton truck made to take the power/loads you require.