Project Jeep Therapy: NV4500 Conversion
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By: Jeff Layton - 5/2000

"Couldn’t find what you needed?" the counterman at the small-town Texas wrecking yard asked.

"No - the a/c unit you had is serpentine - I need V-belt. The air conditioner on the AMC wagon would have made a fine on-board air system for the 258 Six in my Jeep (this was a couple years back). Guess it was from California - I heard they had serpentine out there.



On my way out the door, the counterman said "thanks for coming - if there’s anything else we can help you with, c’mon back"

"Naaw - that was the only thing I needed." I knew the next major project for my CJ would be a engine and trans swap, still several years away. But, I thought, being that this wrecking yard was way out in the Texas boonies, maybe they’d have some good heavy-duty parts due to the many ‘cowboy cadillac’ crewcabs. It wouldn’t hurt to ask…"you wouldn’t happen to have a granny low 5 speed from a late model GM pickup, would you?"

"Nope - sure don’t…unless…Billy, is that Chevy truck 5 speed still in the barn?" Billy nodded. "Can you take this gentleman out to look at it?"

My heart raced at the thought of actually finding one in a wrecking yard. "But what are the odds" I said to myself, trying to prepare for the disappointment. "What’s it out of?" I asked my guide.

"One-ton dually, I think" he replied. My heart beat faster. "Only has a couple thousand miles on it"

In the barn, under a workbench, covered with dust, sat what appeared to be a genuine NV4500. I’d seen a hundred of them in magazines and catalogs. Using a paint pen on the input and output shafts, we put it in 1st and counted revolutions. Turning the input shaft exactly one revolution, we counted the output shaft: "…3, 4, 5, 6…and about a third" The choicest of all NV4500s is a 6.34:1 first gear - six and a third is just right.

Back at the counter, I desperately tried to hide my excitement, thinking it would cost me dearly. "How long have you had it?" I asked the counterman. "Couple-a years now. Bought it from the dealer in town - it was a warranty pull." I didn’t detect any bad noises or binding when turning the input shaft, but was concerned about the origin of my newly-found prize. "Warranty pull?" I asked. "Yeah - seems the owner never owned a granny low before and complained that 1st gear made too much noise. "Musta’ been pretty bad for the dealer to replace it" I said with disappointment. "Not for this guy" he replied, "seems he called Chevrolet, wrote letters - was a real pain in the butt. The dealer finally just swapped it out." Knowing it turned freely and that I could replace any synchros when I swapped the mainshaft, I figured it wasn’t too risky. Still, I wouldn’t be willing to pay a premium with its origin in question.

"How much ya want for it?" I asked.

"Uhhh…$450" he replied.

"$450? For a manual transmission?" I asked with a tone of disbelief. "How’s $400 cash, including tax?"

"Well……….OK"

I couldn’t believe it - I just bought a NV4500 for $400!!!! With the use of a $10 Advance Adapters NV4500 booklet, I confirmed the identity of my prize: a 1992 2wd GM NV4500 with the coveted 6.34:1 first gear -perfect for my swap.


The tranny cleaned up pretty good with a liberal application of a wire wheel to the rust and solvent and a rag to the aluminum. Here you can see the "GBW" markings GM used in the factory - this positively identifies it as a 1992 with a 6.34:1 1st gear. With a fresh coat of paint on the steel case and the shift lever pulled, it’s ready for the metamorphosis.

The top cover comes off easily, revealing some beefy gears inside! Some surface rust is visible on the shift rails and shift forks under the top cover. The front bearing retainer pulls right off after removing the four bolts holding it in.

You can see the input shaft is held in place without the bearing retainer simply by the meshing of the input gear on the countershaft. One quick pull with a slight twist and it pops right out - just like a distributor. This is the first trick from John White at JB Conversions - put the transmission on its face for the mainshaft removal. Here you can see some additional rust on the surface of the gears.

The tailhousing comes off easily. My 1st big surprise: 5th gear isn’t in the case, it’s in the tailhousing! Here’s 5th gear parts, clearly visible outside the main case. Besides the one shown, there’s a couple more oil holes hidden by the gear.. Fifth gear parts come off easily after the removal of a couple retaining pins with a small punch.

After removing the rear bearing retainer, the mainshaft can be tilted out... .…and removed easily…as long as you can lift 100 pounds! This baby is heavy! This is the 1st big removal secret that JB Conversions helped me with. I’d have struggled a lot if not for John White’s advice. Here’s the countershaft remaining in the transmission. You can see the accumulation of surface rust. (The trans was missing the shift tower boot when sitting in the wrecking yard - some moisture must have gotten inside) I’ll have to get a small wire brush and scrub pad down there before reassembly.

Now for the hard part. Read carefully: don’t do this! I rented a large puller and tried this on a Sunday. I should have also rented a bearing separator to open up some space between this gear (5th) and the bearing to allow a better grip with this puller. The jaws are pretty big, so all I could grab on to was this strange flange on the gear - and took a small piece out of it. The puller worked well on the speed sensor ring though (already pulled in this picture) Once 5th gear is off, the remainder of the pieces come off fairly easily - as long as you can remove the snap rings; like most things about this trans, even the snap rings need a gorilla. The easy things almost fall off in your hands; the hard ones are really, really hard. The garden-variety snap ring pliers won’t even open up enough to take the ring off. A couple snap rings were tweaked in the process and had to be replaced…only Chevy had the correct size, meaning two snap rings cost me $5. The bare 2wd shaft is about the length of my forearm and hand.

All removed pieces were labeled carefully. The numbers shown correspond to the item numbers in the drawing in the NV4500 Manual. All small parts were bagged and tagged…I finally had to buy my wife a new box of ziplocs! If you look closely you can see two shift lockout tabs and springs missing. Be careful - it took me 20 minutes to find them after they bounced around the garage. Here’s the next big piece JB Conversions helped me with - they supplied the conversion kit necessary to convert the trans to fit the Jeep. That, plus the very knowledgeable technical support, and the quality of the conversion components (OEM Dodge), means they’re my one-stop conversion shop. Here the OEM dowel pins are shown already installed into the JB Conversions-supplied tailhousing.. A little Scotch-Brite pad removes the tiny amount of surface rust from the new mainshaft, using the old tailhousing as a convenient work stand. Compare the length of this new shaft to the 2wd one in previous photos.

Most of the gears dropped right on as easily as they came off. Don’t forget to reinstall the snap rings. Of the two tiny thrust-washer locating pins removed, only one is reused. The booger 5th gear wouldn’t go on at all…until I used JB Conversions’ thermal expansion trick: after heating the gear in the oven for 30 minutes, it dropped right on easier than a wooden ring on a Coke bottle at the county fair. Sounded like one too! Within seconds it had cooled, forming a tight fit.. Here’s the new mainshaft, complete, ready for installation, still sitting in the old tailhousing.

The cheap autofocus camera that blew this shot has been canned; nevertheless, here the endplay is set to .003" with a dial indicator. The input shaft and front bearing retainer went on as easily as they came off. Using a special retaining nut tool and a torque wrench, the retaining nut is torqued to 250 ft-lbs. Putting the input shaft in a vise (with aluminum jaws) and adding about 250 pounds of me helps to keep the trans still. The new tailcover is torqued to spec.

The top cover and shift levers install easily, leaving the completed transmission ready for installation. The OEM Dodge tailshaft and tailcover mate upperfectly to the Jeep Dana 300 (which shares spline count and bolt pattern with the NV241 used by Dodge) Here the Dana 300 is bolted up, along with the new Advance Adapters trans mount.. No human can lift the combination - a rented engine hoist is used to get the trans in position for installation of the bellhouising.

The JB Conversions-supplied bellhousing is an Advance Adapters unit, and comes well packed. .Here’s the complete kit for the front of the trans, shown with dust cover painted. The bellhousing bolts right up and the Dodge dustcover slips right into place.

   
  The OEM GM forged clutch fork pops on to the screw-in ball stud, and the transmission conversion is complete. Don’t forget to refill the trans with GM-spec synthetic gear lube - standard dino lube is not the right stuff and will result in failure..  

I had never done anything like this before and was pretty nervous throughout the whole event. John White at JB Conversions calmed my fears and gave sound technical advice. Doing it myself I was able to inspect each and every gear and synchronizer and am confident of the condition of my new transmission and the quality of the assembly. I’m also intimately familiar with the innards should something ever go wrong. With the exception of a couple special tools (under $50 total not including torque wrench), it was a simple ratchet-and-socket affair, and the $19 spent on the NV4500 manual helped keep the parts straight. In all, I’m glad to say I did it myself.

Sources:

JB Conversions
Dept. ORN
P.O. Box 2683
Sulphur, LA 70664-2683
phone +1 (318) 625-2379


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