Transfer Case Rebuilding

by Bruce Stanley
America's love affair with the Jeep has a deeply seated root in the Spicer 18 transfer case. This particular case of gears is responsible for getting more Jeepers in trouble than probably any other transfer. Not because of its poor design -- in fact, just the opposite. This case was built for the CJ between 1945 and 1971. Think about all of the Jeeps out there that still run this antique, getting their owners into all kinds of 4x4 situations. The "18" is a great little transfer and will even live when pushed by a modest V8 conversion. I will not argue that there aren't better gear boxes out there -- that's not my point. But rather, for simplicity, strength and ease of rebuild, I would have to say that there are few that could compare.

If you run the "18" and are in the need of a rebuild, don't hesitate. This box is a great first timer! I will try to outline some of the steps when doing a rebuild here, but in no way can this be considered a definitive source. Get a good repair manual! There are a number of good sources out there. One company that I can honestly recommend is Brian's 4wd Parts. Not only does he have available the tech books you will need, but he has a supply of new and used Willys parts (remember your trasfer case problems?!)

The Weak Link

Shaft, bearings, bushings, gearWithout question, the main problem with the Spicer 18 was its intermediate shaft/bearings. The Model 18 transfer was produced with three different intermediate shaft diameters: 3/4", 1-1/8", and 1-1/4". The MB and CJ-2A with serial # up to 24196 use a 3/4" shaft, while afterwards, they were produced with a 1-1/8" shaft. All 3A's and the 3B built before serial #12505 use the same 1-1/8" shaft, while the CJ-5s and 3B's built after #12505 use a 1-1/4" shaft. If your 18 has a loud "whine" or if it seems to go clunk every once-in-a-while (I once thought that the clunk in mine was from my grossly overworked rear driveline which I will deal with later in this article!), you are a prime candidate for a rebuild experience.

Good news for 18 owners is that the intermediate shaft, intermediate gear, thrust washers, and bearings are all serviceable through the inspection cover on the bottom of the case. You don't even have to take the transfer down. Now how's that for simplicity! This thing could be easily (?) repaced on the trail in an hour or less. OK, OK, maybe a little bit longer. But, it certainly is not a major tear-down item. According to 4 Wheeler Magazine's excellent "Beginner's How-to" (February 1987, pgs. 72-76) "the intermediate shaft/bearings are good for 30,000 or so miles." I can attest to that, as mine had about 29,000 on it and it played nasty games inside of my case. If you don't know for sure how many happy trails yours has on it, now's the time to pull the inspection cover off of the bottom and give the intermediate gear a look-see. I waited too long and it cost me a new intermediate gear, output gear, and mainshaft gear.Remember my reference to the clunk? It turned out to be broken pieces of my intermediate gear meshing with its friends! If you wait as long as I did, you will be rebuilding the entire box. Don't despair. The biggest job is just getting the thing down and that's not too bad of a project. The 18 weighs about 80 lbs. (approx. 35 kilos for our metric friends). I never did actually weigh it, but it is a load. Unless you can't leave your macho Jeep mentality behind, get ready for a workout! I suggest using a floor jack for support if you decide to remove the case.

Getting to the Weak Link

Broken piecesAs I mentioned earlier, the intermediate shaft is accessible from the bottom through the inspection cover. Drain the gear oil from the case. Loosen the cap screws and remove the cover. This is your first good look at the gear and shaft that causes all of the grief for the owners of a Spicer 18. Inspect the teeth for wear and check for up and down movement of the shaft. Also, the gear should have very little backlash (forward and backward movement on the shaft). If there is any visible wear or movement and you've been having a hard time hearing your wife yell at you as you Jeep down the trails because of the whine out of the transfer, plan on replacing the shaft, bearings, and gear (On second thought, maybe you don't want to hear your wife. Replace the shaft and buy a set of earplugs!).

While you're on your back looking at the intermediate gear, inspect each of the other gears for wear. If you see any suspect parts, replace them -- if you don't, you'll have a mess like I did. Count the number of teeth on each row of the intermediate gear. There are two gears that have been used in the 18, a 34/21-tooth and a 39/18-tooth. Also, when you order the parts, you will need to know if you have a 3/4", 1-1/8" or an 1-1/4" shaft. The shaft is visible from the front of the case. Measure the shaft as accurately as possible -- should not be too much of a problem. You are now ready to order your parts.

Removing the Transfer Case

Tranny and TCIf you have choosen to remove the transfer for a complete rebuild, your job will not be that difficult. If you will only replace the intermediate shaft and its bearings, all that will have to be done is to remove the rear driveshaft, the emergency brake components, and then the "clip" that holds the shaft in place. Drive the old shaft out from front to rear with a drift (the case provides an interference fit in the front, preventing removal in the opposite direction,) keeping track of the intermediate gear as you drive it out. The gear is now lowered out the bottom.

Keith Lowe recently did a shaft/bearing replacement without lowering the transfer case. The following is a snip from an e-mail sent to me. "I replaced my intermediate shaft in my truck this week and eliminated almost all of my noise problems. If you have a truck or wagon you won't have to drop your driveshaft or remove an overdrive (I left mine in place). The only difficult area was with step 1 -- it was extremely difficult to drive out the old shaft. The problem is finding the room to swing a hammer. After about spending a hour or so with a hammer and brass drift I recruited the help of a neighbor. Using a steel rod 1/2" in diameter about 3 feet long, I placed this against the forward side of the shaft and had the neighbor hit it with a heavy hammer. Once we broke it free the remainder of the job was trouble-free.

"After loosing the shaft, the installation of the new shaft, bearings and washers took less than an hour. I elected to make a dummy shaft the width of the intermediate gear around 1-6/64" in diameter. I then inserted a 1" long piece of dowel (also 1-6/64"in diameter) into the forward hole, protruding just enough to hold the forward thrust washer. To hold the rear thrust washer in place I cut a 1/2" ribbon of aluminum flashing and bent this into a ring by wrapping it around the wooden dummy shaft. I then inserted this into the rear hole just deep enough to hold the rear thrust washer. While looking through the aluminum ring I then moved the gear into position . When the gear was in place I stuck my finger through the ring and pushed the dummy shaft forward just enough to displace the dowel that was holding the front thrust washer. I then removed the metal ring and drove in the new intermediate shaft. Simple! The truck is now extremely quiet except for a rattle that is coming from my shift tower (slight pressure on the shift cane eliminates all the noise). I was able to purchase an intermediate shaft repair kit from Carl Walck for $36.00 that contained a new shaft, caged bearings and two thrust washers."

Photo by Bob ChristyIf you are going all the way with your rebuild, remove the front shaft, transfer case shift levers and speedo cable, and then begin removing the attaching bolts. Remember I mentioned something about needing help when lowering the case? This is where either a friend or floor jack come in real handy!

The most difficult part is about to come. Before removing the last few bolts, take the mainshaft cover off the back of the case (the mild steel plate that is attached by 5 cap screws). The mainshaft gear cotter pin and nut will now have to be removed. Gently slide the gear off without pulling on the mainshaft. If the gear is tight (mine was not), and you are running the T-90 stock 3-speed, it must not be your lucky day! Because of the mainshaft's needle bearings in the transmission, if you pull on the mainshaft too much, you will be playing "pick-up sticks" with those rollers as they will fall to the bottom of the tranny. If you cannot get that pesky gear off, you must remove the top cover of the transmission and wire the shaft in place so that it will not slide to the rear as you pull on the gear. If the gear will not come off easily this is a must unless you care to learn how to rebuild the T-90 also! Once the transfer is down, thoroughly clean all parts. Prepare your bench for the freshly cleaned 18 and wait for your parts to arrive.

Driveline Angle

Now is a good time to take a look at the crossmember mounts and inspect for tired parts. On my CJ-3B, I had installed a Rancho 2-1/2" suspension and also aftermarket shackles that increased lift by another 1". The result was really excessive rear driveline angles -- more than what I prefer. Getting the shaft back to a reasonable angle so that the u-joints will live a long and healthy life is not difficult. I made "lowering" blocks for my rear transmission crossmember out of 1-1/4" square tubing. Very easy to do and now my rear shaft is nearly perfectly aligned. A couple of small problems: If you are running the stock clutch linkage, you will need to re-drill a hole for the lever arm that attaches between the transfer and frame rail about 1-1/2" below the orginal hole so that there will not be any binding. Also, if you have the popular Chevy "mouse" engine conversion, the distributor will get very close to the firewall if you do much lowering as the engine will now tilt a little and may actually make this modification impossible unless you have notched the sheet metal some.

Other Jeepers report to me that they do not have any trouble with driveline vibration or getting their u-joints to last without lowering the case. I think they've been out in the sun too long! Seriously, I don't think anyone will argue the benefits of getting the driveshaft angles close and this conversion is a snap if you have the clearance. Before starting your rig, check all components for clearance. I had to slightly bend the fan blades to clear the radiator shroud. Check for proper clutch action too.

Installing the New Parts

Without going into detail about the entire rebuild (remember the shop manual?), I will discuss the how-to on the intermediate shaft and gear, as this is the most likely and hopefully the only parts you'll need. If not, the complete rebuild is not difficult.

If you have not driven the intermediate shaft out yet, do so now. Note how the thrust washers space the gear in the case. Discard the washers. Inspect the intermediate gear for wear (spalling, especially). The shaft is not expensive (approx. $15 or less) and in my opinion should be replaced. 30 miles out on a trail somewhere is no time to realize you tried to save a few bucks. If you have the 1-1/8" shaft, you will find it very easy to replace the caged roller bearings and thrust washers with the new set. If you have the 1-1/4" shaft, prepare for a little more work -- not much though. In any case, it is a good idea to fabricate a "dummy" shaft out of wood or metal that is a few thousandths of an inch smaller than the original. This will support all of your new parts in the case while you drive the new shaft in place. My old shaft was still too tight to work well. I constructed a wooden shaft on my lathe that worked great. Use a high temp grease and lube all parts well. If you have the individual needle bearings, grease each liberally as you place them inside the intermediate gear. (Did you inspect the inside of the gear? These bearings have to live inside of that bore!)

Completed rebuildPlace all components in their proper order as you carefully slide the dummy shaft in place. Double check their alignment -- the thrust washer must fall into a slot to prevent movement and facilitate lubrication. Now drive the new shaft into its bore with a brass drift, checking for proper alignment. Rotate the gear and make sure everything is OK. Replace the "stake" that holds the shaft in place, and the other parts in the reverse order of removal. Your rebuild is essentially complete. Now wasn't that easy?

One last hint for those of you who went the complete route. When replacing the detent springs, balls, and the interlock for the shift levers, I prefer to leave the interlock out. This allows 2WD LOW which is great for crawling along when 4WD isn't needed. Only problem with this conversion is that it now doubles the amount of torque to the rear driveline and axle. If you have a heavy right foot, I suggest leaving the interlock alone unless you like the appearance of twisted shafts!

Note: This article is not meant to be a substitute for a good repair manual, but rather an encouragement for those who might want to give the rebuild a try!

Thanks to Bruce Stanley for this article, which was one of the first pages of detailed Jeep technical information posted on the web. It was part of Bruce's website from 1997-2003. Thanks to Bob Christy for the photo of his TC, and Frank Porfidio for the shot of his tranny and TC. -- Derek Redmond

Also on CJ3B.info, see Transfer Case Tech Tips, including gear options and springs.

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Last updated 16 August 2003 by Derek Redmond redmond@cj3b.info
All content not credited and previously copyright, is copyright Derek Redmond