Summer comes at different times in the various geographic regions of our great country, with some areas having long hot summers, while some are short and sweet. One common denominator that you can count on is heat!  Summer brings out the travel trailers, the slide in campers, and especially the long drives hauling us to our respective recreational activities.

We anticipate the summer heat by practicing good preventive maintenance, (usually performed in late winter or early spring), but are we doing enough.  Most of use love and care for our trucks with a passion not always understood by our friends & neighbors, but then we also torment these chariots by grossly overloading or hauling a trailer that should be handled by a 500 HP Freightliner.

People, animals, and even plants have instinctive behavior of self- protection in summers heat.  Our trucks have only us to rely on to keep them cool and happy.  There are several things you can do to ease the burden on your truck, but keeping the engine and driveline cool is the best way to extract those extended, worry free miles.

As you may remember, my article in last Issue of TDR spoke about the failure of a clutch pilot bearing failure.  This is a no maintenance unit, not usually serviced except at clutch replacement.  With that being said, I don’t see how I could have prevented the failure I experienced in “Midnite”.  No warning, no noise, just an unexpected inability to change gears or stop without lugging that old Cummins B to a noisy halt.  Like I said, the pilot bearing is not a maintenance item.  I had replaced the pilot bearing about 65,000 miles ago at clutch time.  I feel like I did everything right, but it failed nonetheless.  So, I was left with no alternative but to remove the gearbox and install anew bearing or bushing.  With all that labor, I decided to install a new clutch.  I’m always looking for ways to improve my truck, so I decided to try a set of  “Fast Coolers” for my NV0-4500 gearbox.  Here is the story with some pictures and some very important “Details” that hopefully will help you when it comes time to replace your clutch.

There are several brands of automatic transmission coolers available, but you don’t see manual gearbox coolers everyday.  I spoke with Mr. Fast himself, and I decided to try a set of his aluminum coolers.  Verlyn was right, the installation is simple, with the hardest part being (as usual), getting all of the gear lube in.  I handled that with the help of my “E-Z Funnel”. 

The Dodge / Cummins uses a needle roller bearing as a pilot bearing. It is pressed into the flywheel.  Sometimes this bushing is pressed into the end of the engine’s crankshaft.  Like I mentioned last quarter, there are reported failures of this small bearing.  Mine had turned to dust from failure of the lubricant I guess.  Kenny and the guys at Southern Precision Gear in Smyrna Georgia fabricate bushings made of Kevlar.  Standard Transmission products in Texas can supply you with and “Oilite Bronze” bushing.  Both of these are good solid alternatives to help overcome this failure.

I opted for the Oilite bushing.  It fits right in place of the supplied needle roller bearing.  This bushing is self-lubricating, and now I’m anticipating a long service life from it.  We’ll see!   By the way, an Oilite bushing has oil impregnated into the brass / bronze material, and again, clean is the word here!

It’s always nice when it’s cold outside, to be able to use a lift in a heated garage as opposed to lying on your back in a cold driveway.  So here is “Midnite” on the lift at my friend Russel’s garage.  He was kind enough to let me use his 15,000 pound lift, as well as his transmission jack. Russel’s Automotive is located in Hampton, Georgia adjacent to Atlanta Motor Speedway less than an hour from our home.  Midnite is a ’97 12 valve with a NV 4500 5 speed. It’s a 4X4 so naturally it’s fitted with a transfer case for the front differential.

Be sure to mark your drive shaft before you remove it.  Two-piece shafts need to be reinstalled with the u-joint crosses aligned or phased properly to avoid vibration.   Mark it with a punch or scribe so it go back exactly the way it came out. Be sure to keep everything in order as you remove parts.  An instant or digital camera helps if you don’t have a shop manual.

I installed a new flywheel, because mine was poorly machined at the previous clutch change.  At the very least, have the flywheel resurfaced, use “NEW” flywheel to crankshaft flange bolts, and as pictured, use a torque wrench!  Improper toque is a common cause of failures in late model machinery.

I suggest a good clutch line up shaft as you install the new clutch.  The plastic ones suffice, but a metal input shaft has much closer tolerances, and when you are hefting that big gearbox back in, you do not want to wrestle with it, and risk damage to the clutch disc hub.   Be sure the flywheel is squeaky clean, and do not touch the friction material or get grease / oil on it.  I selected a Ceramic friction material, with a high performance pressure plate.  This is a fairly aggressive clutch, but now that I’ve driven it some, it behaves well!

When I first drove Midnite with her new ceramic clutch, the clutch shudder was intense.  It took me about a month of driving before it settled down.  Now it works perfectly, and bites like a shark!

I’ve included some pictures of the old flywheel complete with trashed pilot bearing.  As I mentioned, the clutch was only about 65,000 miles old, and was an OEM LuK unit.  It worked well, until the pilot bearing failed.  I’ve also included a picture of the old clutch.  It was still in good shape (lots of miles left), but while I had this all apart, Midnite got everything new!  Be sure to inspect the pilot-bearing surface on the input shaft.  If it is galled or pitted, get a replacement shaft and input bearing.  This is easily changed in the NV4500, if you are lucky enough to end up with the proper main shaft clearances.  The shims are at the rear, so adjustments mean gearbox disassembly.  This should be left to a pro with experience and the tools required to measure and adjust the end clearances.  If the clearances are not correct, you will eat a gearbox pronto!

One other note, be sure to inspect the release bearing collar that retains the input shaft & bearing.  If it has ridges or grooves, replace it or the clutch action can be erratic.  The release (thro-out) bearing can hang up on the grooves during clutch release, and cause a grabby or chattering clutch.Once it’s all back together, be sure to check all fluids. Front and rear differentials, transfer case, etc.  Lubricate any grease fittings on the drive shafts.  Once I had it all back together and on the road again, I installed the “Fast Coolers”.  The kit is complete with gaskets, hardware, and an easy to understand instruction sheet.  The only additional thing I recommend is a tube of # 2 Permatex.  It makes a great sealer to use with paper gaskets, and is non-hardening.

I drained the oil, and then dropped the front drive shaft away from the front differential yoke.  That little trick gave me extra room to work.  You can install the left side cooler and bolts on a 4X4 without removing the drive shaft, but it’s a trick, and then the torque wrench has no room.

Believe me, I spent the time to learn the combination of bolts in the coolers and putting it all up together.  It can be done, but for the effort required to remove the four cap screws that retain the front u-joint to the differential yoke, swinging the front drive shaft out of the way makes an already simple job go faster and easier.  You will also get more accurate torque readings.

Once the trans is drained, remove the PTO cover plates, scrape the gasket surfaces clean (taking care not to get anything inside the gearbox), the fast coolers bolt right up.  Be sure to follow the instructions and torque the coolers to 30 – 35 foot-pounds.  Remember, it’s aluminum sandwiched between a steel plate and a cast iron gearbox housing.

Robert suggested that since I already have a differential temperature probe in my Mag-Hytech cover, that I should hook up a gauge to the transmission.  So Geno’s Garage can supply you with the “Dual Temperature” gauge and sending unit or thermocouple that uses a 1/8-inch pipe thread.  The hole in the fast cooler is ¼ inch pipe thread, so a brass reducer did the trick.  A little Teflon tape or thread dope is all it takes.  I can now monitor both trans temp & differential temp.  This can be a great way to spot a low fluid level if you should spring a leak while hauling a camper on that long summer vacation.

The last operation consists of refilling the NV 4500 with the correct gear fluid.  Be SURE to use only the specified oil.  The synchronizer rings have clutch material on them, so if you want the gearbox to last and shift properly, be sure to use the specified fluid.  I also added the correct amount of Lubegard Gear Fluid Supplement.  This adds and extra measure of lubrication, while making the oil a better heat transfer fluid.  Be sure to drive it for a while, get it hot, and then inspect for leaks.  That’s all there is to it.  Did I mention the Jay’s E-Z Funnel?  It attached directly to the top of the gear fluid bottles, and made it a snap to refill the gearbox.  By the way, be sure to check the transfer case lube.  It uses Mercon / Dexron ATF.  It’s all in your owner’s manual!

Now it’s off to check the valve clearances, change the engine oil & filter, fuel filter, set the tire pressures, and get ready for a summer of fun. Now I can keep an eye on the driveline temperatures to ward off any potential problems.  That’s what I call “Anticipation”.  Till next time, Happy motoring!

Sam