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97 Disco Transfer Case Adventure


TIm Wilson

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Since the transfer case was turning freely before I torqued up the bolts, I assumed one or more of them was binding the gear train somehow. The four installed from the rear pass through the interface flange of the TC and into the transmission adapter housing, but the two installed from the front are threaded into the transfer case itself. The upper of the two front-installed bolts was the culprit, and with it removed the gears turned freely again. Turns out those two front-installed bolts are 5 mm shorter than the ones installed from the rear … a fact I hadn’t noticed when I removed them. I damaged the heads of two or three of those bolts when I took them out to remove the transfer case, so I replaced all six (including the stud removed from the rear upper-right location) with 12-point ARP bolts like these …

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They are available here: http://www.allensfasteners.com/search_results.asp?txtFromSearch=fromSearch&txtsearchParamVen=ALL&txtsearchParamMan=ALL&txtsearchParamType=ALL&txtsearchParamCat=ALL&iLevel=1&txtsearchParamTxt=arp+12-point

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So for the record, here’s a map with the correct bolt sizes. Three M10 x 1.5 x 40mm bolts install from the rear of the transfer case and thread into the transmission adapter housing at these locations …

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One M10 x 1.5 x 45 mm bolt installs from the rear here. Note it’s 5 mm longer than the other three to accommodate a wiring harness bracket …

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And two M10 x 1.5 x 35 mm bolts install from the front and thread into the transfer case at these locations …

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One additional detail: I tried installing a 40 mm bolt into the housing of the transfer case I removed at that upper front location (the uppermost arrow in the picture directly above), and it bottomed out instead of locking up the gear train. Obviously, the housings are different and my replacement transfer case housing does not have this feature, even though is has a higher serial number and presumably is of newer manufacture. Go figure.

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Here’s a view of the transfer case in position and ready to be bolted up. Input shaft cover is off and the alignment pins removed. Homemade handling fixture is visible beneath. Once the bolts were installed in the correct locations, the gear train moved freely again and the input shaft slid easily into place. If I were doing this again, I wouldn’t even try to install the transfer case without first pulling that cover and shaft.

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With the transfer case bolted back up, I reinstalled the input shaft cover plate. The LT230 rebuild manual calls out Hylosil 2000 as a sealant for the bearing retainer and Hylosil RTV 102 for the cover plate. Neither of those products is readily available in the states … at least I couldn’t find them. However, Permatex Anaerobic Gasket Maker is a good substitute for the Hylosil 2000 and Permatex Ultra Black RTV for the Hylosil 102. Both are readily available at auto parts stores in the US, but you may have to ask. At least one parts store guy told me he kept the Anaerobic Gasket Maker behind the counter because “the good stuff tends to walk away.” Pics below … you’ll need the anaerobic surface prep to properly apply the gasket maker:

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Note the bolt pattern of the cover is clocked, so it only goes on one way. I didn’t realize this at first and had to pull bolts reorient the cover and reinstall a couple times before I got it right.

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The difflock linkage attaches to the shift mechanism at the locations shown in the pic below, and to the transfer case by a washer and nyloc nut. Flats in the hole through the attachment plate and the short actuation shaft of the TC lock the two together. There are supposed to be two nylon bushings installed in the lower of the two holes shown in the picture, LR part FRC-4499, but I managed to lose both trying to put them in. So I installed the linkage without them. One turned up on the garage floor later, but the second never did.

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Here's a shot with the transfer case jacked back into position and the mounts installed. I replaced the plastic wiring clips with Adel cushioned clamps, available here: http://www.allensfasteners.com/search_results.asp?txtsearchParamCat=40

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I didn’t try to route wiring the way the factory had it installed, but put it where it made the most sense. So there’s a bracket and clamp at the upper left fastener (the longest one installed from the rear), and a clamp at the heatshield. I routed the RH O2 sensor wiring up over the transmission / transfer case. The connection lies above and to the right of the TC … you can see the connector hanging loose in the picture above.

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The emergency brake drum and driveshaft installation were straightforward. Note the front driveshaft joints are clocked, while the rear are in a straight line. I marked these as recommended by Rave before I took the driveshafts down … the front driveshaft orientation drawing from the manual is below.

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I used new 3/8-24 nyloc nuts at all eight locations, purchased from McMaster-Carr, here: http://www.mcmaster.com/#catalog/117/3183/=b4vh4f . I used the low profile nuts, which are not quite as thick as the factory nuts, but offered more joint clearance than the standard profile nuts listed in the McMaster catalog. I didnt torque them down until I had the battery reconnected and could shift the transfer case into neutral and rotate the driveshaft.

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