5-Speed Options
Q I have a ’79 Chevy 3⁄4-ton 4x4 with a nonrunning 350 engine and four-speed manual transmission. I’m planning to install a big-block 454 out of a ’78 1⁄2- ton two-wheel-drive truck that was hooked to an automatic. How difficult would it be to swap the four-speed for a five-speed manual from a newer 3⁄4- or 1-ton Chevy? Would I be forced to make major modifications to the transmission mounts, crossmembers, driveshafts, and so on? Would my current transfer case work with a newer transmission, or would I also need a different transfer case? Do you have any idea what model or year I should look for that would be close to being a direct swap? Or am I overthinking this?
Bill Stansbery
Via nuts@4wheeloffroad.com
A There are a couple of different routes you could take with your project. The first would be to source an NV4500 from a later Chevrolet truck. These were offered starting in 1992 or 1993 and were reportedly available all the way up to 2003, but in my experience they get pretty rare after 1998. Of these, the ’92-’93 models are the most highly sought, as these have a 6.34:1 First gear as opposed to a 5.61:1 First in later transmissions. NV4500s were also used in Dodge trucks, so be sure you get one from a Chevy truck.
While the transmission will bolt to the back of your big-block, you will need an adapter to work with your truck’s NP205 transfer case. Using a transfer case that came behind an NV4500 is not really an option for two reasons. First, the later transfer cases all have a driver-side front output that does not match your truck’s passenger-side front axle. Second, an NP205 is a bulletproof transfer case that you should keep with your build. A transfer case adapter is available from Advance Adapters (advanceadapters.com), but it’s expensive because there’s quite a bit to it.
As far as other modifications go, you will need a hydraulic clutch assembly and modifications will be necessary to mount the transmission in the truck. More than likely you can make the original crossmember work with a modified transmission mount, but driveshaft modifications will probably be necessary. Keep in mind that NV4500s can be hard to find and they usually command a premium when you do find one, so the whole project is going to be fairly expensive.
There is another option that will take fewer modifications and could end up being cheaper in the long run. Your truck has an SM465 transmission, which is every bit as bulletproof as your truck’s NP205 transfer case and has the added bonus of a 6.55:1 First gear. Advance Adapters manufactures the Ranger Torque Splitter, which is an auxiliary gear box that mounts between the bellhousing and the transmission. This self-contained unit has a 27 percent Overdrive gear built into it, and since it is mounted in front of the transmission, it can also be used to split all the transmission gears, turning your four-speed truck into an eight-speed truck! The Ranger is designed to bolt into place, so there are no adapters involved, and you would continue to use just about everything you already have. The Ranger Torque Splitter is about 71⁄2 inches long, so it would space back the transmission and transfer case by that same amount. This means driveshaft modifications, but your truck has plenty of wheelbase to handle the extra length and driveshaft modifications really aren’t all that expensive. The Ranger has been around since the 1960s, so Advance has them pretty well figured out. The whole combination could easily handle a built big-block. Though the unit itself retails for a little over $1,500, I’d be willing to bet the total cost involved would be much less than an NV4500 swap.
Say No to Plastic
Q I recently picked up an ’85 Jeep CJ-7 equipped with a fire-breathing four-cylinder engine. The Jeep actually runs pretty well, and I was able to pick it up cheap because it has the little four-banger. I plan on doing a V-8 swap in about a year, but in the mean time I’d like to drive it through the summer and enjoy it while I gather up the parts for the swap. The problem is that the engine leaks around the valve cover like you wouldn’t believe. At first I thought I’d just throw a valve cover gasket at it, but when I pulled the valve cover off I discovered it’s made of plastic! Some moron overtightened the valve cover at some point, which caused the gasket flanges to warp, hence the leaking. I can find aluminum valve covers for the six-cylinder engines, but nothing for the 2.5L. I don’t want to spend much fixing it because I plan on swapping the engine out anyway, but it leaks bad enough that I won’t park it in my driveway. What are my options beyond buying another crappy plastic valve cover?
Michael K.
Via nuts@4wheeloffroad.com
A Ah yes, the infamous plastic valve covers of the mid ’80s, a gift from AMC that just keeps on giving! All kidding aside, your Jeep should be equipped with an AMC 2.5L four-cylinder, which is not to be confused with the GM 2.5L Iron Duke that was used prior to 1984 and in some early ’84 CJ-7s. You are correct that there are no aluminum valve covers available, at least to my knowledge, but all is not lost. The next time you visit a junkyard, keep your eyes peeled for a YJ or a Cherokee equipped with a four-cylinder and a stamped steel valve cover. These valve covers will bolt right on to your earlier engine. You’ll need to make some light modifications to the breather hose and the later cover may not have a PCV valve; instead, it will have a special nipple with a tiny metered hole that basically serves the same purpose as a PCV (this should be hooked to manifold vacuum or can simply be plugged, as in the photo). If you’re confused, take a look at how the valve cover ports are hooked up on the later engine and mimic them on your engine. Use the later valve cover gasket, and be sure to nab the valve cover bolts. At $5-$10 for the junkyard valve cover plus the cost of a gasket, you should be able to enjoy a topless summer and still park in your driveway.
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