Expert Advice, August 2002 edition

Synthetic Chevy Silverado Variations
Q: I own an '01 Chevy Silverado 1500 with the 5.3L V-8. I changed the oil and filter with conventional oil at 3500 miles. The truck now has 6500 miles. When can I start using synthetic oil? Do you recommend any particular synthetic? At what intervals would you recommend changing synthetic oil for regular-duty driving?

A: Synthetic oil is a wonderful thing. Its biggest advantage over conventional motor oil is its ability to maintain viscosity during extreme high and low temperatures. It won't thicken below zero or prevent proper flow to engine parts on cold startup as much as conventional oil, and, when you're hot idling in Death Valley, synthetic oil won't thin out and break down causing insufficient lubrication to the degree conventional motor oil would. Start using synthetic motor oil in your Chevy truck whenever you're ready. A lot of new performance cars come from the factory with synthetic oil. Cheaper brands are out there, but if you're willing to invest the added expense of synthetic oil into your engine, we suggest going all the way with a premium brand (around $25 for a six pack right now). Statements about not having to change your oil as often when using a synthetic lubricant are unfounded. Most labels strongly suggest sticking with the manufacturer's recommended oil-change intervals. Synthetic oil collects dirt and contaminants just like any other oil and needs to be changed in order to keep your engine clean.

Ford F-150 SuperCrew Transmission Woes
Q: My '01 Ford F-150 SuperCrew is making a loud knocking noise in the transmission. It occurs when I decelerate to 15 mph and then accelerate. I've taken the truck to the dealer three times and nothing has been done. The last time, the dealer told me this was a characteristic of the truck. I feel like I have to accelerate slowly, or I'll harm the transmission. Do you know what might be the problem?

A: Without using an electronic stethoscope under your truck, I can't be sure of the noise. It may come from a number of areas in the drivetrain or suspension. The dealer might be correct: the knock or clunk you're hearing is normal drivetrain slack and simply a characteristic of the F-series pickup. The best way to confirm or disprove that theory is by taking a ride in a similar truck. If every other one has that same characteristic noise, it may be something you'll have to live with, but if the road test proves your point, and the other trucks are quiet, then the dealer still has some work to do. I made a Technical Service Bulletin search on the SuperCrew and came up with one that could possibly have something to do with the noise you've described. The problem involves incorrect installation of the Planet Support Spring on '99-'01 F-150s with the 4R70W automatic transmission. This spring keeps the planetary gear support secure against the transmission case, and, when not installed in the correct position, will allow the support to shift and make contact with the case during a transmission downshift. To keep it simple, the transmission must be removed and disassembled in order to put this spring back in the right place. Contact your dealer's service department to find out if this has been previously eliminated as a possible cause of your problem.

'02 Avalanche Rearend Noises
Q:I own an '02 Avalanche. Since new, the rearend sounds like it has 100,000 miles on it when slowing down from 60 to 40 mph. I took it back to the dealer, and the shop foreman drove it, heard the noise, and had the ring-and-pinion set replaced at 3000 miles; however, it still made the noise after replacing the gears. We then drove three brand-new ones, and all of them made the same noise after the fluid warmed up. I like the service department, but this noise is driving me nutty. What do I do now?

A: You've already done what I would've suggested by taking the same vehicle for a ride and comparing noises. This confirms it's a characteristic of the vehicle's drivetrain and not an actual failure within the rear-axle assembly. It may be the new-style body structure of the Avalanche that allows the transfer of rear-axle noise to the passenger compartment in larger amounts than, say, the Silverado pickup or Suburban SUV bodies. Currently no reports are available that Chevrolet is pursuing repair for the problem. Check with your dealer next year to see if there's been a Technical Service Bulletin published addressing the noise. In the meantime, there's not much you can do. It's being considered a normal characteristic of the latest in pickup and/or SUV design.