Making Our Old NV4500 Transmission New Again
The NV4500 five-speed transmission in our high-mileage diesel-powered '95 Chevy 2500 pickup was exhibiting some bad behavior. Part of the problem was that the clutch wasn't releasing completely when the clutch pedal was depressed. This made selecting First Gear a grinding challenge. Eventually, the main driver of this rig quit using the clutch during standard gearshifts because it wasn't disengaging anyway. Another problem was that as the transmission began to age, it began to leak. In a pinch, someone ignored the requirement of Castrol Syntorq LT synthetic oil (or equivalent) and fed it petroleum-based oil. Things quickly went from bad to worse as the synchronizer rings objected to the wrong oil. It wasn't long before the trans was becoming very hard to live with.
Since we're not manual-transmission rebuild experts, we took the truck to someone who is. Larry's Automotive is located on the outskirts of Rock City, Illinois. The owner, Rick Jacobson, has been wrenching on trucks and cars since he was 12 years old, so he knows his stuff. His knowledge is vast and varied, and his resume includes a couple of years fabricating and wrenching for noted off-road racer Scott Taylor. Jacobson and his team of technicians not only have a working knowledge of vehicles (including heavy trucks) from end to end, they also know the intricate workings of both automatic and manual transmissions. Best of all, Jacobson is a 'wheeler, so he's intimately familiar with how we use our rigs.
Jacobson and his crew removed our crusty trans and then they totally disassembled it and gave us the tally of what bad things were lurking inside. The list of parts we needed was lengthy. Normally, they'd just order the parts and complete the rebuild in a few days, but we wanted to utilize specific companies, so we hit the phone.
The first place we called was Rockland Standard Gear. RSG, as they're called, has been in business for more than 25 years, and they're one of the largest suppliers of manual transmission and transfer-case parts in the country. Here's some mind-boggling facts: They are the only aftermarket company ever selected to rebuild transmissions for ZF; they are one of five Master distributors for Borg-Warner transfer-case parts; they are one of 10 Elite distributors for Tremec; and they are a major distributor for New Venture Gear. Needless to say, we knew they could handle our NV4500 needs.
Since the clutch in our Chevy was original, our second call was to Centerforce. The company has been around since the early '80s and was started by Bill Hays, the founder of Hays' Clutches in the 1950s. Bill Hays designed and patented the Centerforce Weighted Clutch System, which increases pressure-plate clamping force while maintaining easy pedal effort. Further, his new design solved the sticking-over-center problem of diaphragm clutches. Centerforce offers a full range of clutches and flywheels for a number of applications.
What follows is a synopsis of the major items addressed by the team at Larry's Automotive. It'll give you a good idea of what you can expect if you plan on having your NV4500 rebuilt.