We no longer supply conversions for NV4500 retrofits, but we still have a lot of inquiries on this subject so we have left this page up. You have probably given the matter some thought already, but there are a few important things to consider when contemplating this type of conversion. Final cost, mechanical modifications, fabrication requirements, and electrical issues must be carefully weighed before embarking on an NV4500 retrofit installation.
NV4500 CONVERSIONS
The NV4500 transmission is a heavy duty 5 speed overdrive transmission. The 4500 is readily adapted to many vehicles that originally were equipped with light duty 5 speeds, 3 speed manual transmissions, 4 speed manual transmissions or automatic transmissions. The transmission has a cast iron main case, large gears and weighs approximately 200 pounds. NV4500 transmissions are original equipment on both Dodge and GM vehicles up to one ton. The transmission was introduced during the 1992 model year and still remains in production.
Manual transmission to manual transmission conversions usually require at least a new bellhousing and clutch lever. For most applications a new transmission mount, clutch assembly and transmission to transfer case adapter will also be required. Modifications to the crossmember, floor pan, driveshafts, and exhaust system are needed for some applications. Parts costs for the basic adapter kits start at about $350 with an average cost of about $650 plus the cost of the transmission.
Automatic to NV4500 conversions are generally much more expensive due to the numerous additional parts you will need. Figure on a new flywheel, flywheel bolts, clutch assembly, clutch bolts, bellhousing, clutch fork, clutch release system, clutch pedal, brake pedal, transmission mount, transfer case linkage, and hardware. You will need to cut the cab floor/carpet to accept the shift tower, rewire the backup lights and cruise control. Late model vehicles may require major electrical changes including changing the engine computer. In most cases you will also need to have driveline modifications done. Some models will also require crossmember and/or exhaust fabrication and/or relocation. Body lifts or cab floor alterations may be needed for clearance. Unless you have a donor truck to cannibalize most or all the parts from, this is usually one expensive conversion. NV4500 conversions for gas engine trucks will typically run from $3500-$5,000 for all new parts including the transmission.
BUYING A USED TRANSMISSION
Well over 1 million NV4500 transmissions have been produced so finding a used unit is not all that difficult. Some of these can be save you big bucks over the cost of a new transmission, however, you can really get burned unless you buy wisely.
First is the transmission you are looking at even compatible with the proposed conversion? NV4500s' were built for numerous applications. That great deal on e-Bay may take extensive modification to fit your application or require a total rebuild.
Two wheel drive transmissions are generally less expensive then 4x4 models. However to convert one of these to most 4x4 applications will require at least changing the mainshaft and tailshaft housing.
Dodge and GM were the primary users of the NV4500. Early GM units differ from all other by having a wider gear ratio and different bellhousing bolt pattern and index diameter. Dodge transmissions have longer input shafts, but shorter output shafts. Early GM and all Dodge applications used external clutch slave cylinders, while later GM transmissions had a internal concentric slave cylinder.
Any transmission with 150,000 miles or more is almost certainly due for a major overhaul which should include bearings, seals, synchronizer rings, and small parts. Kits are available with and without tools for those who wish to do a rebuild themselves. For a professional rebuild, beware of the rebuilder who uses imported aftermarket parts. While some of these parts are OK, many are not worth a hoot. We got badly burned by major import parts like mainshafts and small parts like shift fork pads. Many rebuilders also substitute lower rated wheel bearings in place of the premium original equipment bearing numbers. In any case, a complete, quality, professional rebuild will most likely run $1,000 or more.
Most used transmissions do not come with a shift lever which can run as high as $100. Some don't even have shift towers which will cost another $100 plus.
So beware of that great deal on a used (or rebuilt) NV4500 until you thoroughly check the facts.
TWO SPEED AUXILIARY OVERDRIVE TRANSMISSIONS
If you have a Ford, Chevy, GMC, Jeep, or Toyota with a 4 speed transmission and you want to add overdrive, a cheaper and more versatile option is to install a Ranger 7" long, two speed auxiliary transmission between the bellhousing and transmission. A reliable and heavy-duty unit with both direct drive and a 27% overdrive. Will convert your 4 speed to an 8 speed. Allows you to "split" gears and is ideal for trailer towing applications. Lowers engine rpm 27% in overdrive for improved fuel economy, less engine wear, and reduced engine noise. Contact advanceadapters.com
Driveshaft modification are required. Crossmember must be relocated 7" back. Floor modifications required. Transfer case shifter mount must be fabricated.
Two Speed Auxiliary transmission fits between the bellhousing and transmission. It weighs about 80 lbs, is rated for 420 ft-lbs. of torque and can be used on vehicles with Gross Combined Vehicle Weights of up to 25,000 lbs.
NV4500 CONVERSIONS USUALLY REQUIRE
• Special Bellhousing, Fork, and Hardware
• Conversion Specific Clutch
