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Kill the Q-Trac
I have a ’78 Jeep CJ-7 with a 360 engine, TH400 and a Quadratrac transfer case. Do you know of a used transfer case I can bolt in place of my weak Quadratrac? I need one that will bolt in without an expensive adapter. I know I will have to change my rear end to one with a centered differential.
Anonymous — Via email
First off, the Q-Trac isn’t weak. Cranky and hard to get parts for, maybe, but not weak. You are in luck with the TH-400, because the older GM style t-cases can all be bolted on, though it won’t be quite as easy as you might wish. There will be a certain amount of fabbing for linkages, crossmember and driveshafts. Because the front axle of your CJ is offset to the passenger side, like most GM applications, you could use the t-case from any GM rig that had a TH-400. You’d need to make sure you also got the trans to t-case adapter with it and make sure the tranny output shaft spines and stick-out matched your unit. The available GM t-cases would include the NP-205, NP-203 (a full-time case) and the NP-208. I think the NP-241 (a newer cousin of the NP-208) was also used in the last years of the TH-400 (early 1990s). The strongest (practically unbreakable) choice would be the NP-205. It also has the advantage of a fixed yoke rear output (except for some late ones with slip yokes). On the downside, it has a marginal low range of only about 2:1 and is very heavy. The NP-208 is cheap, light and has a nice 2.6:1 low range like your Q-Trac. It’s pretty strong as chain cases go, but it has the downside of a slip yoke rear output that might cause problems with driveshaft length and angles. Ditto for the NP-241. The NP-203 is an oddball, it’s full-time and it’s huge. Not a contender in this case. I’ve only seen a GM swap done on full-sized Jeeps, so what I told you here is just directions to the right freeway turn-off. You’ll have to navigate the rest of the way from there.
D35 to D35
I have a ’95 Jeep Wrangler YJ and when I upgraded to 33 inch tires, I swapped out the 4.10 gears for 4.88s. I have a friend with an ‘02 Wrangler TJ 6-cylinder and a five-speed. We are both running Dana 30 fronts and Dana 35 rears. Will my old 4.10 gears work in his ’02 Wrangler.
Bill Reed
Signal Mountain, Tennessee
Not on the front. Your YJ has a reverse cut Dana 30 and your buddies’ TJ D30 is a standard cut ring gear. On the D35, maybe. The carrier break is 3.55:1, so if his current ratio is 3.55 or 3.73:1, then OK. Well, maybe. Another possible complication is whether his is the “Super” 35 with 7/16-inch ring gear bolts rather than the more common earlier unit with 3/8-inch bolts. I believe there are sleeves for the smaller bolts in the larger holes, or if a locker with a new carrier is in the offing, buy one for the earlier 3/8-inch bolts.
Getting Stuck in the Sandbox
I have a 1996 F-350 Crew Cab 4x4 7.5L V-8 automatic with 4.10 axles and all stock. When I tow my 26-foot toy hauler to the dunes, I sometimes get stuck. Other trucks, lifted with larger tires and towing bigger trailers, are not getting stuck. Does the lift make a difference? I have 285/75R-16 now. What would you suggest?
FCM30 — Via e-mail
You have observed several elements of four-wheeling physics in action. Number one is floatation. It’s all about spreading the weight of the vehicle onto the footprint of the tire. A bigger footprint comes with a bigger tire or with airing down. You’re limited to how much can be aired down with a load, but even a few pounds will help. If you can find out how much weight is on the front and rear axles with your trailer hooked and your normal recreation gear in the truck, then divide that by two for each axle, and you’ll have the weight on each tire (front and rear weights will probably be different). You can then find a load-versus-inflation chart for your tires (try a tire dealer for your brand) to get the minimum tire pressure for that weight. Complicated? A bit, but being able to run at the minimum pressure in the sand will get you stuck less often. Air back up for the highway. As for tire upgrades, 285s are about 32 inches tall (slightly different according to brand), but they’re narrower than a 305/70R-16, which is roughly the same height. A swap to a 305, such as a ProComp All Terrain, would likely fit your truck with no other mods. A 315/75R-16 (about 35 inches tall) would take a two-to-four-inch lift to fit. You could go bigger with a tire like the Super Swamper Trxus (36 to 38 inches) and need a six-to-eight-inch lift and a change of gear ratios. I’d caution you to stay with a nonaggressive, tread radial tire-aggressive treads can get you stuck fast in sand.