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February 2007 4x4 Tech Questions - Techline

Posted February 1, 2007

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Four Wheeler
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Question: In regards to the letter titled, "Olds 455-to-K-Truck Swap" (Oct. '06), the '73-'87 generation of GMC K-trucks came equipped with the ill-fated Olds 350 diesel for a few years, which uses the same motor mount pattern as all '65-and-up "true" Olds V-8s. Just junkyard-shop for the proper motor and frame mounts.
Dana Reynolds
Chesapeake, VA

Answer: Wow, I don't know why I didn't think of this myself. You're totally right-they did use the diesel version of the 350 Olds gas motor in the '78-'81 time frame. Total brain fade on my part. Thanks for bringing it to my attention. I really appreciate it when readers help me out. The only problem with this is, it's my guess that it's going to be very difficult to locate one of these trucks as there were not a lot of them that came equipped with this diesel engine.

Question: My OEM tires (P265/70R17) on my '05 Chevy Silverado 1500 4x4 are bald already and I'd like to upgrade in size. With the bigger tires and different rim size (probably LT305/70R16) will I lose my ABS, or is that computer reprogrammable?
Michael Chachakis

Answer: Yes, the computer can be reprogrammed to handle the larger tire size and should be something that the dealer can do-but maybe you don't have to do so. Check with the tire dealer and see if there is any real difference in tire revolutions per mile between the two. It shouldn't be much, as the 265 is about 32 inches in diameter and the 305 is about 33 inches.

Dennis Franklin, my source on subject matters like this, tells me that you will need a 17-inch wheel to clear the brake rotor, as well as doing some fender trimming.

Question: I need to rebuild my burned-up 350 short-block and I've been looking into stroker rebuild kits. The 383 seems practical and affordable, but I've seen some claiming a 407 from a 350 short-block. Is it practical to do this to a 350? I think it would cost too much to build up a block that shouldn't be (or isn't) capable of such displacement, although cost isn't too much of a problem. I just don't want to waste money on an engine if it's bound to blow under that much stress.
Ryan Martin

Answer: Yep, you sure can, but it gets pretty darn expensive in order to ensure reliability. You can build a really nice 383 that will put out in the neighborhood of trail-friendly 330 to 350 hp and 400 lb-ft of torque using all factory parts, such as a modified 400 crank and rods, for a fairly reasonable amount of money. These motors really work great off-highway, and in fact, I have owned two of them, both installed in Jeeps. The only downside of using the short rods with the 400 crank is there is more side-loading of the pistons to the cylinder walls. This means the engine life won't be quite as long as if you had gone with the longer rods and custom pistons. However, it's not something to worry about.

Question: I have a '93 F-150 with a five-speed (the Mazda one, I think). I know now this tranny does not have a good reputation, but unfortunately I bought the truck before I knew this. Anyway, the problem I have is that it is very sloppy when shifting, the stick moves all around (even while in gear), and sometimes the shifter gates are hard to get right. It is extremely sloppy in this regard. Also, when I let off the gas to coast to a stop, especially at low speeds, it sometimes jerks really bad. It's like there is too much play in the gears. I don't know what the deal is-it just seems like it is out of spec or something. If I should get it looked at, I will do so, but if these problems aren't affecting the life of the tranny, then I can learn to live with it and let it go. It doesn't bother me too much any more, as I've learned to live with it already really. I don't want it to die on me if there is something I can do now, especially if it's as simple as changing a rubber bushing like other transmissions with similar problems.

Answer: If it is the transmission jerking, then you definitely should have the trans replaced. However, I doubt that this is the cause, but it's more likely something to do with the engine. The slop can be caused by several things, from a worn selector to shift forks to gears and bearings, and not just a worn-out rubber bushing. It's a pretty good sign that the trans is on its last legs. Consider a rebuild in the near future.

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