Wants Jeep J-Truck Info
I have an '80 Jeep J-20. I love almost everything about this truck, except finding the lift kit I want and certain parts. I'm sure I'm not the only one having a hard time finding full-size Jeep parts. I am running 33x12.50-16.5s now with the stock suspension. I have a set of 37-inch tires but want to leave room for 39s in the future. I don't want a spring-over conversion, so I've been looking for a 6-inch lift with no luck at all. I am also rebuilding both the engine and tranny (360 V-8 and 727 TorqueFlite), and I have no clue what transfer case and axles are under it. I'm planning on using it as a mud runner/daily driver. Any advice, tips, tricks, and axle ratios that would be optimal would be very helpful. I also have spent a lot of time at BJs Offroad and International Full Size Jeep Association.
Your transfer case is (we're best-guessing here; fullsize Jeeps ran a lot of gearbox combos over the years) the full-time chain-drive New Process 219, which is relatively rare because it was only used for a couple of years in fullsize Jeeps; these vehicles also came equipped with the NP 208 part-time 'case, but only with the six-cylinder/automatic and/or manual combo, not the V-8/auto. Your axles are six-lug 30-spline versions of the Dana 44 with 3.73:1 gearing-and frankly, the axles will be iffy in terms of strength with 39-inch tires. But if you don't hop up the 360 and drive reasonably sanely, they will probably hold up.
If you've gotta have a 6-inch suspension lift, Rusty's Off-Road offers a 6-inch kit for your Jeep. Superlift, Skyjacker, Rancho, Rough Country and BDS also have suspension kits available, but they are all in the 4-inches-and-under category. For ring and pinion gearing, it all depends on what tire size you go with. For a ballpark estimate, divide your new tire size by the original tire size, then multiply that number by your current ring and pinion ratio. If you go with 39s, then the formula would be: 39 ÷ 31 (your original tire size, 9.50x16.5, not what you have now) = 1.25 x 3.73 = 4.66, which means you can go with either 4.56:1 or 4.88:1 gears and keep the V-8's cruising revs within their optimal range. For greater flexibility when wheeling in low-range or under a load, though, we'd go with the lower gear set. We'd also ditch the transfer case for a 205 instead, but that's for another letter.
TH 350/Dana 18 Clearance Issues
I was wondering if you know of any company that makes a transmission pan for a GM Turbo 350 that has the right edge cut off at an angle so the front driveline will not hit the pan off a Dana 18 transfer case. I made mine, but it leaks some, and I would like to have one professionally made. I have looked online but could not find anything.
We don't know of any companies that manufacture a custom one-off part such as this, though it's possible that a company that specializes in mating and adapting gearboxes, such as Novak Conversions or Advance Adapters, might be able to point you in the right direction. As an aside, Novak recommends installing the engine (assuming it's a GM) 11/4 inch offset to the driver's side to ensure proper transmission pan-to-front drive yoke clearance with the TH 350/Spicer 18 combo. Which is another way of saying, you may need to relocate the engine (and trans) to make this driveline setup work optimally.