Gear Ratios:
The Dodge NV4500 and GM NV4500 currently share the same gear ratios. Early GM units (pre 96') were built with a lower first gear ratio of 6.34 to 1.0. These low-geared GM boxes have since been discontinued and are more difficult to obtain. Beginning in 95', all GM units were built with the same gear ratios as the Dodge unit. The current GM and Dodge NV4500's are sold new with zero mileage and carries a set of gear ratios which are much more streetable than the early GM model.

Design:
The NV4500 cannot be compared to older 4 speed boxes when it comes to engineered performance. We constantly receive questions regarding the NV4500 in comparison to an older NP435 or SM465. Due to large gears and bearings and a thick cast iron case, the old 4 speed boxes have a long, well deserved history of being super durable. In many cases, the NV4500 features larger gears, better bearings, and heavier duty output shafts. The shifting characteristics of the fully synchronized Dodge NV4500 (even reverse) are excellent. Short, crisp shifts make the NV4500 a luxury to operate compared to the long throw, clunky shifting of earlier 4 speed boxes. The following are a few specifications taken from NVG data.

The bellhousing bolt patterns of all NV4500's are different than any older GM 4 speed bellhousing. This means you cannot bolt a NV4500 directly to an older GM bellhousing. In the early years of the NV4500, the GM and Dodge units did not share a common bolt pattern on the front of the case. In 95' and newer models, the front case bolt patterns of all NV4500's were retooled to the Dodge configuration. Input bearing retainers and input gear sizes/lengths remain different among the Dodge and GM variety as do tailhousings and output shaft spline specifications.

The NV4500 is a top loader style transmission. The lever located in the top shift cover operates the shift forks and rails directly. The shift forks and rails are all located within the aluminum top cover which is bolted and dowel pinned to the top of the gear case. The control handle that protrudes out of the top of the transmission cover has been changed three different times. The handle that fits onto the top of the transmission can be purchased from us directly or from your local GM or Dodge dealership. Tapered roller bearings support the input shaft, main shaft, and counter shaft in the gear case. Drive gear thrust reaction is controlled by a needle-type thrust bearing which is located between the input shaft and main shaft. The main shaft gears are all supported on cage-type roller bearings. This particular design provides excellent lubrication and a minimal amount of gear noise.

Lubrication:
The synchronizer design of the NV4500 demands a specific 90W synthetic oil. The leading cause of GM and Dodge warranty claims on NV4500's are failures due to improper oil choice. The factory service manual for the NV4500 indicates the first oil fill is a lifetime factory fill. If you receive a new NV4500 and it is empty it should be filled with the factory specified oil and not changed unless contamination occurs. The easily identifiable look and smell of the OEM synthetic oil is like no other oil. The GM part no. for the correct oil is 12346191. Use of ANY other oil in the NV4500 will lead to failure and also voids any chance of a warranty claim