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Answering Your Questions
We receive a lot of good questions in the comments both here on FYI and over on FastLane. Recently we received a lot of questions that seemed like a good fit for our friends over at GM Service Parts & Operations to answer. Here are their answers. If you've got a question you'd like to see GM SPO answer, send them our way. -Alicia Dorset, blog editor
Q: My car is rear wheel drive with a limited slip differential. Can changing out the rear diff fluid after a few thousand miles help quiet and smooth out the performance of the rear diff?
A: Additives in the fluid can break down over time. Adding or replacing the fluid will also replace these additives, which can improve the differential's performance. Be sure to use only the fluid recommended by your vehicle's manufacturer.
Q: Please let us know the difference between Ceramic brake pads and metallic brake pads - which ones would last longer and which are quieter and stop better?
A: The trend is moving toward using brakes with more ceramic materials, which perform the same as metallic brakes but may be quieter. Some work well; however, some applications will take the vehicle out of compliance with FMVSS (Federal Motor Vehicle Safety Standards). Be sure to follow your vehicle manufacturer's recommendations for brake pads.
Q: How much effect does changing the screen and flushing all the fluid out make?
A: The benefits of transmission fluid/filter changes and fluid flushes will vary, based on operating conditions and mileage. High temperatures and contaminants can break down the fluid over time, which is why GM recommends a fluid change every 50,000 to 100,000 miles, depending on how the vehicle is driven. Although it's not required, flushing does a more thorough job of replacing all the fluid from the transmission and the converter. It's important to use the vehicle manufacturer's recommended fluid to keep the transmission working as designed.
Q: Are there any real good ways to keep the seals on the pistons from hardening (vulcanizing) or is this inevitable?
A: Today’s automatic transmission have seals and other components engineered for increased service life and it is important to use the recommended fluid to keep the transmission working as designed. High temperatures and contaminants can break down these additives over time. Following the manufacturer schedule for fluid and filter change may help prevent this from occurring.
Q: Are flushes really effective at keeping the internals of an engine clean?
A: The normal oil and filter change, at the proper intervals and using the recommended engine oil, is the most effective way to keep your engine clean. An engine oil flush is not a commonly recommended service, however you check your owner's manual for your manufacturer's recommendations for your vehicle.
Q: Which oil is the best for the cost (we prefer Mobil 1) what do you mechanics suggest?
A: Refer to your owner's manual for your vehicle's recommended engine oil. While synthetic oils tend to last longer and may perform better in extreme conditions, as in a high performance engine, they can be more expensive. Unless the manufacturer specifically recommends synthetic oil, it may not provide significant benefit. Most multi-viscosity oils identified with the American Petroleum Institute (API) Certified starburst and marked as "energy conserving" will perform well, but it's best to always follow the manufacturer’s recommendation.
Q: And when comparing Tremec's manual transmissions to GM's new 6-speed automatic, under similar circumstances, and barring the clutch-disk in the Tremecs, which will last longer?
A: The question depends on the application and driver preference. Both products are validated to perform with durability and reliability by GM Powertrain. The 6-speed automatic (6L80) is rated for maximum engine torque of 439 lb-ft (595 Nm). The Tremec TR6060 6-speed manual transmission is rated for maximum engine torque of 470 lb-ft (637 Nm).
Posted by Editor on January 4, 2008 5:31 PM
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Comments
Why does it take so long to get Saab parts? (it shouldnt since your parts distribution system is one of your strengths)
Posted by: gtjeff on January 4, 2008 10:53 PM
Thanks for responding GM!!!
In the future though please be a bit more clear on your answers. Otherwise I'd gather that it really doesn't matter what oil you use, when its flushed or which are really better. I know engineers tend to be conservative on their answers, but there has to be a better way to answer these questions other then "it depends" and "consult the manufacturers recommendations". Surely GM can say "after a simulated 200,000 mile and 1.N million shifts transmission X proved to be reliable comapred to transmission Y" Or at least "Gm has designed both these products to handle X miles and Y shifts with a typical driving style of....."
As a potential customer I would like to hear some real information from the mouth of GM with some test data to back it up. I can ask any educated mechanic the questions mentioned and get similar answers. But keep up the good work answering our questions to the best of your ability. It is afterall better then no feedback.
Posted by: Nate on January 7, 2008 2:21 AM
My daughter has a 2001 Yukon. Over the past year, the odometer and PRNDL display has been disappearing and reappearing from the display. It now appears to be gone for good. Recently, my husband received a recall notice for this 2003 Tahoe that is for the exact same problem, but it says not to bring the vehicle in unless the problem is occurring. If this is a known problem, why didn't my daughter get a recall notice for her Yukon?
Posted by: Marge Frazho on January 7, 2008 12:31 PM
The problem with giving "better" answers is, someone will hold GM to that answer even though it may not be specific to their vehicle. Then they blame GM for giving incorrect information and get sue-happy. There is nothing wrong with saying "consult your owners manual" with some of these generic questions. Because sometimes, it "does depend."
Posted by: Tim on January 8, 2008 9:30 AM
on the new duramax diesle is there an easier way to change the fuel filter? If not can you make it a hex shape so you can hold it better.
Posted by: nick hendricks on January 8, 2008 7:29 PM
I'm sorry to bother you but I have been looking for Elect. help for my 1993 Chevy. truck can you guide me to the proper area? I have many dealers & professionals look at my truck but can't find the problem. If I let the truck sit for a few weeks it won't start runs batteries down. We have been trying to find problem for years.
Thank You
Barb
Posted by: barb on January 9, 2008 12:28 PM
Barb said: "I'm sorry to bother you but I have been looking for Elect. help for my 1993 Chevy. truck can you guide me to the proper area? I have many dealers & professionals look at my truck but can't find the problem."
Barb,
There is no reason for you to apologize. In fact, it should be the other way around -- GM should be apologizing to you because their dealers can't fix the electrical problem in your Chevrolet truck.
Even though your truck is 15 years old, GM should stand behind it and give you the quality maintenance support you deserve as a loyal GM customer.
Master Maintenance Control
This is just another example of why GM should have a hotline to a master maintenance control desk in Detroit where there would be technical experts standing by 24/7 to answer their customer's questions about vehicle operations and maintenance.
If I were Mr Wagoner, Mr Lutz, (or even Mr Barger) and read your post, I would immediately pick up the telephone, call the zone manager's office for your location, and direct they attend to your problem.
Showing true concern about customer satisfaction would do wonders for GM's image. Designing quality vehicles that people want to buy is only half the job -- the other half is providing quality maintenance support.
Best,
Gary Dikkers
Posted by: Gary Dikkers on January 11, 2008 5:40 PM
"the other half is providing quality maintenance support"
Gary,
GM is already doing an excellent job here. Take a look at JD Power's 2007 Service Satisfaction Ratings
http://www.jdpower.com/corporate/news/releases/pdf/2007112.pdf
Buick, Cadillac, Saturn, Pontiac, GMC and Chevrolet ALL have higher service satisfaction ratings than Honda and Toyota's main brands.
GM is not promoting its strengths. Too much of its advertising budget is being spent promoting the dumb model renames that were forced on marketing by someone higher up.
Posted by: gtjeff on January 13, 2008 2:18 AM
gtjeff said: "Buick, Cadillac, Saturn, Pontiac, GMC and Chevrolet ALL have higher service satisfaction ratings than Honda and Toyota's main brands."
GT,
That may be true, but it's still unsatisfactory that Barb can't find a GM dealer whose service department can fix her Chevrolet truck.
It's unsatisfactory whenever a GM customer can't find a dealer who can fix a maintenance problem with a GM vehicle, no matter what JD Power says.
If I was the VP in charge of GM's dealer maintenance, I'd be kicking butt and taking names.
Regards,
Gary Dikkers
Posted by: Gary Dikkers on January 13, 2008 10:11 PM
Hello,
I have a 2002 GMC Envoy and have enjoyed few issues over the years. The one problem I am having is with my temperature display on my rear-view mirror. The compass works fine but the temperature only shows "OC" and shows no numbers. Please help.
Posted by: Jeffrey Holton on January 16, 2008 11:19 AM
