Chevy Autotrac. Uugh...... In 1998 Chevy introduced the Autotrac 4WD system to it's lineup. The NV246 transfercase is an electronic shift transfercase and combined with the computer system is what Chevrelet calls the Autotrac 4WD system. this system will automatically transfer power from the rear wheels to the front when any slippage is detected. The system operates transparently and can be left engaged indefinitely. It also has standard dash mounted switches that allow you to put the transfer case in 4WD High, 4WD LO, or 2WD High.

While having a AWD system can be very handy to the soccer mom who may only occasionly have their vehicle in inclement weather it creates some problems. The system leaves your front driveshaft spinning at all times. This creates a couple problems. If you lift your truck you will find that most kits require you buy a new front driveshaft along with it. The new driveshaft is CV equipped and is necessary because most trucks that are lifted with an autotrac will experience vibartions due to the short front driveshaft that is always spinning. This transfer case also features slip yokes on both sides which creat a longer t-case and more wear on the bearings inside the t-case. They also create a situation where you can't drive your vehicle without both driveshafts installed.

So why are we telling you how much we dislike the Autotrac 4WD system. Well take a look at the picture. Our NV243 transfer case recently decided to self destruct. Interestingly enough my nephews Autotrac transfer case broke almost identically about 3 months before this. A little checking around and I found many users who had also suffered autotrac transfer case failures. In fact there is somewhat of a shortage of them at the wrecking yards and even a used one will cost you $1200 and up. A new one will set you back closer to $1600.

Granted that our first autotrac transfer case had lasted us over 100,000 miles we still were not excited about replacing it with another one. So what were our options? Well I found many users who wanted to get rid of the autotrac but I could find very little information on users who had done any kind of swap. Basically the boltup options were either the NV241 or the NV243. Both were very common and found in many Chevy 1/2 tons in the 90's. The difference between the two is that the NV241 uses a manual lever on the floor board while the NV243 is an electronic shift t-case. Both have a u-joint yoke on the front and a slip yoke on the rear. The easiest coversion would be the NV241 but it requires you cutting a whole in your floorboard. We decided to go with the NV243 electronic shift and stick with push button shifting. This does give you an extra point of failure which is the shift motor on the side of the transfer case.

Short Shafting our NV243 Transfer Case

With the decision made to go with the NV243 transfer case we went to the wrecking yard and picked up a low mileage unit. The price of NV243 transfer cases was running around $600 which is nearly half what a NV246 autotrac case was.

Next was getting rid of the slip yoke on the rear. We knew that this was a common conversion on the Jeep transfer case so it seemed we should be able to do this conversion on our Chevy transfer case. JB conversions to the rescue. A couple phone calls to JB conversions and we had a new short shaft conversion on it's way. We did have to supply John with a picture of our transfer case. Evidently the type of speed sensor varies and therefore John needed to see ours so he could make sure to ship us the right kit. John makes Slip Yoke Eliminator kits for the Chevy 241 and 243 and also for the Dodge 241 transfer case. This kit is a must for those installing big lift kits on their Chevy's and especially the shorter wheel base vehicles like the blazer or two door Tahoe.. John sells two versions of this kit. A super Short kit and a standard kit. The Super Short kit will add 9" to you driveshaft length. We opted for the standard length kit which still increases the driveshaft length by a substantial amount and will give us good driveline angles in our Chevy 4 DR Tahoe.

Installation

This is the complete NV243 Slip Yoke eliminator kit from JB Conversions

We are not an expert mechanic by any means and have never had a transfer case apart before. But after looking over the excellent instructions provided with the kit from JB Conversions we decided to tackle the conversion ourseleves. The only additional thing we needed was a tube of blue RTV sealant so we could seal up the case when we put it back together.

After draining the fluid and finding yourself a clean work bench remove the 10 mm bolts holding the tail cone on.	NV243 with tail cone removed.

Break out your snap ring pliers and remove the retaining ring.	Now remove the 4 bolts holding the rear bearing housing and remove it from the main case.

Now remove the retaining ring above the tone wheel.	And remove the tone wheel. Behind it you will find one more retaining ring that needs removed.

Be very careful when seperating the case. Use only the two locations designed for prying.	Our NV 243 with the case split in half.

Now remove the spring on the shift fork and the retaining ring holding the front output sprocket on.	Now remove the mainshaft assembly and front output sprocket as one assembly.

Remove the mode fork and synchro hub ring. There is a top and bottom to the hub ring so pay attention.	Remove the retaining ring holding the main drive sprocket on then remove it from the shaft. See how much shorter the new main shaft is.

Install the main sprocket assembly on the new shaft and hold it in place with the new retaining ring supplied in the kit.	Install the mainshaft and the front sprocket and assembly into place. You will have to tilt the main shaft to get enough slack to slide the front sprocket into place.

Install the retaining ring on the front output sprocket and the spring on the shift mode fork.	Verify that the magnet is still in place.

Make sure the pump and pickup tube are in place correctly in the rear case half.	Install a thin bead of RTV sealant then install the rear case half and pump. Make sure the pump pickup tube stays in place.

Install the lower retaining ring then the tone wheelonto the mainshaft.	Install the upper retaining ring on the tone wheel then install the shim plate supplied in the kit onto the main shaft.

The new new Fafnir bearing supplied in the kit has a raised inner race that is eccentric in shape. This is normal.	Remove the old bearing and install the new bearing with the raised race pointing toward the front of the case.

Apply grease to the oil seal..	Apply RTV the housing and to the socket head bolts then secure the bearing retainer to the housing.

Apply a bead of RTV sealant then bolt the rear bearing housing to the case.	Now install the the rubber star washer supplied with the kit then the 1310 CV Yoke which is supplied with the kit. Use some RTV on the back of the lock nut and tourque in place.

Summary

The installation is now complete and it wasn't that hard. And I must say again that JB Conversions supplied one of the best installation manuals I have ever seen with a product like this.

Install your new transfer case and then measure for drive shafts. We contacted Six States to build us some new drive shafts for our new Short Shafted chevy. Six States has many locations around the Northwest and can also ship to and from.We will talk about the new driveshafts next month.