We're all familiar with the cutesy saying, "all Jeeps mark their spot." In case you're not, it's what all vintage Jeep owners tell themselves to deal with the fact that virtually every Jeep's Dana/Spicer T-case leaks like a sieve. For us, we can't say we've ever had a Spicer 18 that didn't puke. And likewise for the Dana 20. And most recently, the Dana 300. It's annoying, so to see what we could do about it we called up Novak Conversions for one of the company's Dana 300 gasket and seal kits. They're high-quality and relatively inexpensive. While we're not covering a step-by-step procedure like the factory service manual, here are a couple tips to ensure your leaker at least slows to a moderate weeper.
Naturally, you're going to...
Naturally, you're going to have to remove the T-case from the vehicle, drain the fluid, remove the shifters, and the front output yoke. Remove the intermediate shaft lock plate and drive out the shaft from front to rear. Be careful not to damage the thrust washers if they drop down off the intermediate gear.
The gasket and seal kit comes...
The gasket and seal kit comes with a new intermediate shaft O-ring. Remove the old one, clean out the groove, and lube the new O-ring with some clean engine oil to prevent galling upon reassembly. Carefully work the new O-ring on so you don't tear it.
The interlocks need to be...
The interlocks need to be pulled before the front cover can be removed. Notice the old RTV in the interlock bores. Clean up any old sealer and reassemble with a very light coat over the plug threads.
Remove the set screws from...
Remove the set screws from the clutch forks. If your T-case has been rebuilt, they're probably gunned down with red Loctite. If they're really stubborn, break out a small propane torch and carefully apply heat to release the Loctite, but don't get carried away because you could potentially ignite any residual gear oil in the case.
A notorious area for leaks...
A notorious area for leaks is the shim pack. We cleaned and reused our shims, but the gasket and seal kit comes with new ones if needed. If you replace them, carefully measure the thickness of the old pack so you can duplicate the shaft's end play with the new pack. Coat each side of each shim, the T-case, and the retaining plate with Permatex Aviation Form-A-Gasket.
With the front cover off the...
With the front cover off the case, now is the time to drive out the old front yoke seal and install the new one from the kit. We used a thin bead of RTV strategically applied with a finger instead of the paper gasket included in the kit. Try to leave enough free space so any RTV that oozes when you tighten the cover to the case doesn't seep into the bores for the shift rods.
If needed, reseal the input...
If needed, reseal the input and output shaft housings with a little RTV, and then reassemble the needle bearings inside the intermediate gear. Heavy grease is okay for this step, but it doesn't always dissolve well into 80-90W gear lube. We use Dr. Tranny's Assembly Goo, which is a thick, waxy goop that really holds small parts together well, yet completely dissolves once the T-case comes up to operating temperature.
Getting the shift fork poppet...
Getting the shift fork poppet and springs to stay down during the shift rod installation can be an exercise in frustration. Ultimately, carefully depressing the poppet with a flathead and smacking the end of the rod with a dead blow hammer to drive it over the poppet worked the best for us.
With the rods back in the...
With the rods back in the case, we used some red Loctite on the shift fork set screws and then greased the lip of the seals. A 7/8-inch impact socket works well for driving these seals into the bores.
We dutifully coated both sides...
We dutifully coated both sides of the inspection plate gasket with Aviation Form-A-Gasket as well as the T-case and cover mounting surfaces. Naturally, it leaked once the t-case was back in the vehicle and filled, so we pulled the cover plate, scraped off the gasket, and reinstalled it with black RTV. For some reason, we have poor results with paper gaskets on T-cases.