New Venture NV4500

NV4500 Manual Transmission Specs & Ratios

The New Venture 4500 (NV4500) 5 speed manual transmission is likely one of the most popular manual transmissions offered in the light duty diesel pickup category. Its light weight, short case length, and relatively high strength make it a popular choice as a conversion or replacement for competing transmissions. It is rugged and dependable, but the diesel engines in which it was mated to eventually outgrew it. Several versions of the transmission exist; 1994 and earlier model year GMs had different ratios than the 1995+ GM and Dodge variants. The NV4500 designed for the Cummins diesel and Chrysler V10 engines is a heavy duty version and has a larger input and output shaft than transmissions designed for other gas engine applications. All NV4500s feature a cast iron case with an aluminum shift cover.

NV4500 Transmission Ratios








1994 - 2005 Ram Cummins diesel
1995+ GMC/Chevrolet 6.5L diesel

5.61 : 1

3.04 : 1

1.67 : 1

1.00 : 1

0.75 : 1

5.61 : 1*

1994 & Earlier GMC/Chevrolet

6.34 : 1

3.44 : 1

1.71 : 1

1.00 : 1

0.73 : 1

6.34 : 1

*Reverse ratio changed from 5.61 to 5.04 : 1 beginning the 1998 model year

New Venture NV4500 Transmission Specs


New Venture NV4500


5 speed manual transmission


New Venture Gear (formerly New Process Gear)




1994 - 2005 Dodge Ram (5.9L Cummins)
1992 - 1998 6.5L GM


All forward gears

Case Material:

Cast iron case w/ aluminum top cover

Case Length:


Max Input Torque:

460 lb-ft


~ 195 lbs dry

Oil Capacity:

~ 4 quarts (1 gallon), fill to bottom of fill plug hole

Fluid Type/Spec:

Castrol Syntorq synthetic 75W-90 GL-4 or equivalent specification (details in next section below)
Lubricants that meet the Syntorq spec include:

MOPAR 4874459 synthetic 75W-85 GL-4 manual transmission fluid (supersedes MOPAR 4637579)

GM 12346190 synthetic 75W-85 GL-4 manual transmission fluid (supersedes GM 12346191)

Amsoil synthetic 75W-90 GL-4 manual transmission fluid


• Carbon fiber composite dual cone synchronizers
• Dual PTO provisions (passenger & driver side)
• 10 spline, 1.25" input shaft for diesel and V-10 gas engine applications, 1.125" input shaft diameter for gas V-8 engine applications
• 29 spline 1.50" output shaft

Shift Pattern:

NV4500 shift pattern

NV4500 Manual Transmission Fluid Spec

The NV4500 features carbon fiber composite synchronizers and is therefore highly sensitive to transmission fluid type and viscosity. Failure to use an acceptable fluid may ultimately result in excessive synchronizer wear and/or failure. The original fluid spec is Castrol Syntorq synthetic 75W-90 GL-4. The fluid has become difficult, if not impossible to source (no longer produced by Castrol?). However, Chrysler and GM continue to offer their formulations, part numbers 12346190 (replaces 12346191) and 4874459 (replaces 4637579) respectively. The ACDelco oil is spec'd as a 75W-90, while the MOPAR fluid is spec'd as a 75W-85; both oils are the correct GL-4 lubricant developed for the NV4500. Amsoil 75W-90 manual transmission fluid is a popular alternative that also meets the NV4500's fluid specifications at a much lower cost. DO NOT confuse MOPAR's NV4500 compatible fluid with transmission fluid for the NV5600; the oil specs are entirely different. Avoid MOPAR 4874464; this is compatible with the NV5600 and NOT the NV4500. The OEM fluid is relatively expensive, however frequent transmission service is unnecessary and total long-term service costs are therefore relatively small.

An important component of the fluid spec is that it meets API GL-4 specifications, but this does NOT mean that any GL-4 gear oil of the same viscosity will suffice. This also does not infer that a GL-5 oil that meets GL-4 spec is compatible. Lubricants developed for synchronized manual transmissions such as the NV4500 must exhibit characteristics that include a balance between gear/bearing lubrication and synchronizer friction. Certain formulations may provide greater lubrication characteristics and reduce gearset wear, but at the expense at more rapid synchronizer erosion. A synchronizer requires a degree of friction in order to increase or decrease the angular velocity of a gearset and allow for smooth gear progressions. In addition, the NV4500's carbon fiber synchronizers may deteriorate if an incorrect fluid is used. NV4500 owners are therefore ill advised to stray from the factory intended fluid spec and should err on the side of caution by selecting an OEM transmission fluid or confirmed suitable alternative.

NV4500 Loss of 5th Gear

Though the strength and reliability of the NV4500 is relatively high, it does have a fatal flaw - the 5th gear lock nut has a tendency to back off, making the transmission inoperable in 5th gear. The problem is limited to Dodge Cummins applications, and GMC/Chevrolet trucks equipped with the NV4500 do not typically experience the problem. When this occurs, it becomes physically impossible for a driver to place the transmission in overdrive. The problem is fairly common and often caused by frequently lugging the engine in 5th gear. As a result, owners are advised to avoid high load (towing), low speed operation in 5th gear. Although the Cummins engine makes excellent low end torque and exhibits the performance characteristics necessary to lug the engine down low, it adversely affects transmission reliability.