In the meantime, Ethan, there is a way to drive your truck without grinding the gears, assuming the only weak area is Second gear. The trick is called double clutching. In the ancient days of the automobile, manual transmissions didn't have synchronizers to match the speed of the two gears, which allows you to complete shifts smoothly. Back then, the only way to make the shift from one gear to the next was to match the speeds of the two gears. Here's how it works. After accelerating to the top of First gear, depress the clutch pedal and shift from First to Neutral. Then quickly release the clutch pedal with the trans still in Neutral. This will match the speed of Second gear to the engine. Now depress the clutch pedal again and shift into Second. The shift will be smooth because Second gear is now spinning at engine speed.
A similar technique can be used in downshifting. Depress the clutch pedal and shift, for example, from Third into Neutral. As you release the clutch pedal to spin the input shaft at engine rpm, slightly rev the engine. Then depress the clutch pedal again, shift into Second, and release the clutch. If you accurately match the rpm to the speed for Second gear, the shifter will drop effortlessly right into Second gear. It takes some practice, but you'll get the hang of it.
This leads us to the next trick of upshifting without using the clutch. Let's start in First gear and accelerate. Lift off the throttle and simultaneously lightly pull back on the shifter. As you lift the throttle, this will unload the meshing gears and allow you to pull the shifter into Neutral. Maintain a light rearward load on the shifter. As the engine speed falls, there will come a point where the Second gear speed will match engine speed and your light load on the shifter will bring it into, in this case, Second gear. Even with a dead synchronizer in Second gear, you can continue to drive your truck until you can rebuild the transmission.
Now, with all these tricks, you almost don't need to use the clutch at all except for coming to a complete stop. Try it, you might have fun with it.
Harry's point is that to reduce the twisting motion, it's best to test the Plastigage with
Plastic Fantastic
Harry Schlegelmilch, via CarCraft.com: I just finished reading the "Plastigage versus Micrometer" article in the Jan. '07 issue and have a question on some of your methods. I am a backyard builder and have built multiple engines over some 40 years using both the micrometer and Plastigage methods, seeing little difference between the two. When you checked the rod clearance in the story, it looked like you had only one rod in place. I have found that to be accurate, you need both rods installed on the journal, and I also use a feeler gauge to fill the side gap so when I torque the rods there is no twisting motion applied to the Plastigage. Also, when I do the main bearing, I use two pieces of Plastigage, placed 180 degrees apart, and add them together for the total clearance. I don't prefer either method, but I think Plastigage is a good product for the average builder. I would like to see an article where you take a crate motor from any manufacturer, disassemble it, and perform a clearance check. I think you would be surprised at what you find. Thanks for producing a great magazine, I wish it were larger each month.
Jeff Smith: You make several valid points, Harry, especially the one about only having one rod on the journal. That may have affected our test. Thanks for taking the time to share your experience with the rest of the readers. Several other readers wrote in suggesting that the indicated clearance should be multiplied by two because the Plastigage is a point reference. While that may be true, the procedure could be much more easily handled by the manufacturer's merely changing the size reference chart on the package rather than asking the user to do even simple math. By your own account, however, it's clear that the Plastigage is only accurate when you maintain very tight control over all the variables. To me, this merely reinforces that the risk of using a tool that is this inconsistent is probably not worth the saving of a few hours of work required to measure everything. In all the engines I have built over the years, I have never had a situation where using a calibrated micrometer and a dial-bore gauge was off by more than 0.0002 inch (emphasis on making sure your micrometers are accurate). That 0.0002-inch variation, to me, is more acceptable than 0.0015 inch. One more thing I do know is that the Car Craft reader is an independent rascal, so if using Plastigage makes you happy-by all means, use it in good health.