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Eddie
Eddie, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2768
Experience:  I have 20 years professional experience in advanced engine controls and transmission rebuilding.
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I have a 2007 Trailblazer with 120k KM. I have it always in

Customer Question

I have a 2007 Trailblazer with 120k KM. I have it always in "auto" and today when I slowed down to make a hard left I felt a strong noise below the truck at the back and another at the front, like if the truck rolls over 2 stones and looses power and stability.
It looks like when the truck changes gears in "auto" when you reach a hard curve and need to slow down, it is not able to properly synchronize and loud noises come from below the truck. Like if gears or cogs are not assembled or not synchronized.
I changed to 2h and the truck goes fine. It only happens in "auto". I did not try 4H because I think something similar may happen and I don't want to make more damage to the car.
Any idea what is happening?
Submitted: 9 months ago.
Category: Chevy
Expert:  Eddie replied 9 months ago.

Hello Eddie here and I will do all i can to help. First, are you positive all the tires on the vehicle are the exact same size? You haven't changed a tire recently or put on a spare tire correct?

Customer: replied 9 months ago.
Thanks Eddie. I haven't changed anything. I noticed the light of "Monitor Air Pressure" is on. I put 32 lbs of air each tire and the light stop blinking. 1 day later it came back. I haven't put more air.
If I go in 2h nothing happens. If a switch to "auto" I have problems when taking hard curves and the truck is changing gears because of slowing down.Regulo.
Expert:  Eddie replied 9 months ago.

Alright, I understand. First thing I would do with this mileage on the vehicle is get the front differential and rear differential serviced, and put some friction modifier in each differential, this noise can happen if the front axle clutches or spider gears are not allowed to slip slightly, the far wheel turns more than the inside wheel does around a corner, this amount of "slip" is accomplished by the spider gears, and if you have a 4wd traction lock front and rear differential, I believe that is what you could have going on, I would also service the fluid in the transfer case, I would also put the recommended amount of air in the tires that is on the side of the tire, it is probably more than 32 psi, that will give you the best mileage and may help this problem as well. Barring any issue with the transfer case, if you do these things I believe it will take care of it. I would continue to drive the vehicle in 2H until you can get this done. I don't see any bulletins associated with this problem, so it does not look to be a widespread problem. Let me know if you have any further questions. Thank you!

Customer: replied 9 months ago.
Eddie: Thanks so much for your help. I am taking it to the car dealer on Tuesday. I will tell them to service it as per your advise. However I would like to have the opportunity to discuss with you their diagnosis. I don't trust their expertise but it is the only official GM dealer in my city (Caracas - Venezuela). Would you wait for me to discuss this input next week and then I transfer you the rest of the money?
Expert:  Eddie replied 9 months ago.

Absolutely Regulo, Take it to them tuesday, see what they say, if possible as well, take the service advisor or a technician on a test drive to show them exactly what it is doing, give them as much detail as possible. Then let me know what they say.

Customer: replied 9 months ago.
Thanks Eddie. I will keep you posted! :)
Expert:  Eddie replied 9 months ago.

Alright, Thank you!