Jeep Junk or Jewel?
Q I have a Jeep '95 YJ Wrangler with 33s and a tired four-cylinder engine with over 250,000 miles. I have an older carbureted GM 305 that I would like to put in the Jeep. I've been told that none of the drivetrain is strong enough to hold the additional power of the V-8. Is this true? Will I have to change everything from the motor to the tranny/transfer to the axles? Can I get away with the engine swap? I keep getting conflicting answers, and my questions seem to spark heated debates.
A Your transmission is likely an AX-5, and your transfer case is probably an NV231 with a Dana 30 front axle and a Dana 35 rear. Though all are fine with a stock four-cylinder engine, the added torque and horsepower of the 305 will definitely max them out. Now, I'm sure there are guys out there who have a 305 with all the stock parts and giant tires and have no issues at all, but that doesn't make it right. For example, I have a friend who has a V-8 in his old Willys Jeep with the stock drivetrain. His T90 three-speed should have blown up by now, but he's a careful driver so it hasn't. If it were me, I'd replace at least the transmission to start and save up to replace the axles. I would change the transfer case last, as I think it's the strongest part in your drivetrain.
Nuts, I'm Confused!
Ups & Downs
Q What should I set my 4x4 suspension ride height or sag at? Modern dirt bikes all have about 12 inches of suspension travel, and all of the major manufactures recommend that the sag be set at roughly 4 inches (90-100 mm) or 33 percent of the total suspension travel. So basically, with the rider on board, the bike should sit with about 66 percent uptravel and 33 percent downtravel.
I have never seen ride height or suspension sag for 4x4s discussed in this type of detail. Everyone talks about how much lift they have or how much travel they have, but so far I have not seen any good information or "standardization" for ride height and sag on a 4x4 as it relates to total suspension travel.
I recognize that the ideal setup is probably different for a hardcore rockcrawler and Trophy Truck racer, but it would be nice to have a starting point.
A A vehicle's suspension moves in two main directions: down as the wheels drop into a hole or the vehicle comes off the ground in a jump, and up as the wheels go over an obstacle or the truck comes to a landing. I have found that most competitive rock buggies have a lot more suspension downtravel than up, and this is done to keep the whole vehicle low. However, these 4x4s are not very good at going fast, as the suspension quickly bottoms out.
Trophy Trucks and desert race vehicles aim for more uptravel than downtravel (droop) so they can soak up a big hit. Stock vehicles are close to the middle of the road, though they seem to err on the desert suspension setup. I like to run about 60 percent down/droop-travel and 40 percent up/bump-travel for my trail rigs, as this allows for good all-around suspension without getting too tall.
Desert trucks are often just the opposite at 30/40 down and 60/70 up (similar to a dirt bike), and dedicated rockcrawlers are closer to 80 down and 20 up.
This type of question tells me you are more interested in how a suspension works than in just clearing big tires, and that is important for today's four-wheelers. For this I'm awarding your letter this month's Nuts, I'm Confused prize: a set of General tires. General tires are found on a lot of different off-road vehicles, from desert trucks to rockcrawlers. General's new Grabber tire has been a big hit in the off-road racing scene, and you can get a set for your 4x4 if you're looking to explore the backcountry. For more info on General Tire check out www.generaltire.com