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Quick Questions and Answers - Technically Speaking

James Berry Dec 18, 2014
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The great news is that we’re getting lots of letters from our readers. The not-so-great news is that the questions are piling up on my desk. So for this installment of Technically Speaking, I’m not going to be as detailed as I normally am so I can get several questions answered. As you know, trying to give a quick answer to anything is difficult for me, but I’m going to give it a shot. Thanks and keep the questions coming.

Q: I am having a problem with my ’08 Corvette coupe with factory navigation. When I am driving the car, at times the navigation screen will go blank. The radio will continue to play but the controls for the radio and navigation will not work at all. If I shut the car off, then restart the car, everything works fine for about 10 minutes then the navigation screen goes blank again.


A: This condition may be caused by a radio software timing anomaly. There is a Technical Service Bulletin (TSB) “#09-08-44-019: Intermittent Navigation or Radio Screen Blank after Vehicle Starts, Radio Controls May Not Function (Update Radio Audio Software Using Disc)” regarding your problem.

This requires you to take your vehicle to the dealer to have the radio audio software updated. The update programming disc covers all ’07-’09 Corvettes with navigation radios. The blank screen syndrome is one of the issues that this programming update covers.

Check with your dealership since you live in a small town to see if they have the update disc. It is only shipped to dealers that request the disc for vehicle repair. The disc is PN 20906717. Thanks, and good luck Paul.

Q: Hello Vette. My problem is that my steering column sounds like a little girl screaming when I turn the steering wheel slowly, like in a parking lot, for instance. It sounds like it is coming from a rubber boot near the firewall.


A: I am not sure what year Corvette you have but the repair is simple. Locate the opening at the lower bearing where you can inject lithium grease. This will eliminate the rubbing or squealing noise when the steering wheel is turned. Mike, that is the shortest answer I have ever given. Thanks and good luck.

Q: I just finished reading your column in the October issue and found it very informative. I still have some questions, including clarification of the clutch reservoir refill. I own a ’08 Z06, which I bought brand new. The car currently has 1,625 pampered miles, and I drive it on a limited basis each month to local car shows.

Over the past two years, I’ve noticed intermittent, difficult/notchy-shifting during the 1-2 and 2-3 shifts at mid-range to spirited rpms. I notice this issue less when the car is hot and driven more than 25 miles at a time.

I continually monitor the condition of the clutch fluid, and replace the fluid using GM DOT 4 clutch fluid before it becomes darker than honey. The clutch reservoir has two markings: “min” and “max.” Following the owner’s manual, I never fill beyond the “min” marking. I am wondering if I’m doing this correctly, or could this be contributing to the shifting problem.

I am also curious if the factory replacement fluid is the best choice? I am considering purchasing a return spring kit from Lingenfelter as a precaution. I do not want to have the car disassembled or wrenched-on at this time if it’s not imperative. Can you further advise?

Richard Kachadurian
Lakeland, Florida

2008 Chevrolet Corvette 2/3

A: Richard, there is a Technical Service Bulletin (TSB) regarding the issue of difficult/notchy-shifting during the 1-2 and 2-3 shifts on vehicles equipped with a Tremec manual transmission when the vehicle is cold.

The repair is a new transmission synchronizer design for the 2008 and 2009 models. The new synchronizer will make a noise on the 1-2 shift in temperatures at or below 32 degrees F.

This noise/feel is a normal characteristic and will go away after the transmission warms up. Warm-up should occur after approximately 15 miles of normal driving. This condition is normal and requires no repair by the dealer.

Richard, I always recommend using the factory fluid and you are correct in replacing the fluid when it becomes dark. When bleeding the clutch system, one of the more difficult things is accessing the bleeder screw, which is difficult to see without using a mirror.

Look where the master cylinder line connects to the slave cylinder and just above the lines at the very top of the transmission you will feel a hex-shaped rod about two inches in length. That is the bleeder screw.

To bleed the system on some models you will need a 7/16-inch thin wall socket. Take care not to drop the socket or it will end up at the bottom of the bellhousing, making it difficult to retrieve. It may be a good idea to tape the components of your tools together. On other models the bleeder screw is much easier to access and you will only need a 9mm wrench.

1. If you plan to bleed the clutch traditionally, you will need two people. One person under the car operating the bleeder screw and another person in the car to pump up the pedal and keep the reservoir full of fluid.
2. Open the bleeder screw and let the fluid run out until it becomes clear. Be sure to keep the clutch reservoir full so no air can be introduced.
3. Once the fluid is clear, close the bleeder screw, then pump the clutch pedal 50 to 100 times. Open the bleeder again and look for air or dirt in the fluid. Repeat this step until a steady stream of clear (clean) fluid comes out.
4. After you think all of the air, dirt, and residue has been removed from the system, pump the clutch pedal again 50 to 100 times with the bleeder closed and take the top off the reservoir. Let the vehicle sit for about 30 minutes while you have lunch or a few beers.
5. Fill the clutch reservoir roughly 1/16-inch below the “min” mark so when the clean, dry moister barrier and lid are installed the fluid will read between the “min” and “max” marks.

Hopes this helps you out and good luck, Richard.

Q: I own a fairly stock ’62 Corvette that I drive every day. My question is that I am running my vacuum advance on ported vacuum, is this correct for performance? My ’69 GTO is using manifold vacuum for the vacuum advance. I know these are different vehicles; I just want to make sure this is correct.

Thanks for your help,
Greg Smith

Manifold Vacuum 3/3

A: Greg, for optimum engine performance and driveability on stock pre-emissions points-style distributors used on Corvettes or any GM vehicle you need the vacuum advance to be connected to full manifold vacuum. The vacuum advance is intended to advance the ignition timing at idle, since the engine needs more spark advance at idle in order to fire the leaner fuel mixture. The vacuum advance is also designed to respond to sudden changes in operating conditions by helping provide the correct spark advance based on engine demand.

To test a port to determine if the vacuum is manifold or ported, connect a vacuum gauge to the port. At idle, if the vacuum gauge reads 15-20 inches of vacuum this is considered to be manifold vacuum, and if this port is not used it would be ideal to use for your vacuum advance.

If no vacuum is shown at idle, but as you open the throttle you start to read vacuum, this is considered to be ported vacuum.

Thanks, Greg. You should find you will get better performance and fuel mileage once you switch to manifold vacuum.


Got a question for our Tech Corner expert? Just jot it down on a paper towel or a lightly soiled shop rag and send it to us at VETTE Magazine, Attn: Technically Speaking, 1733 Alton Parkway, Suite 100, Irvine, CA 92606. Alternatively, you can submit your question via the Web, by emailing it to us at vette@sorc.com. Be sure to put “Technically Speaking” in the subject line.



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