Vibration, differing opinions puzzle car owner

Q. I read your column regularly, though I am not any good with autos. I have a question about my 2005 Nissan Pathfinder with 94,500 miles.

In late 2012, I received a notification from Nissan that some Pathfinders, as well as other trucks, experienced radiator leaks into the transmission. The notification said a judge decided the customer would have to pay a deductible of $2,000 for repairs on vehicles with 80,000 to 90,000 miles, and $3,000 from 90,000 to 100,000 miles.

In April, I took my truck to a Merlin’s auto shop because it was vibrating similar to when they replaced my u-joints. I went for a ride with the owner to get the truck to react the same. It vibrates around 40 mph and 1,500 rpms. He thought it had something to do with the transmission. He then informed me he needed to add 1 gallon of coolant during my oil change.

I then proceeded to Woodfield Nissan with my notification. They told me the trans and radiator are fine but that I needed new timing chains. A few friends of mine, who know more about cars than I do, don’t think the timing chains should be bad.

I don’t know what to do now since I am trying to save for the repairs and don’t want to keep paying for diagnostics. How can I truly determine if it is my transmission or timing chains?

A. After reading the information on your Pathfinder, I am left with more questions than answers.

It is true there is a problem with coolant mixing with the transmission fluid because of a problem with the radiator. It should be obvious though if a gallon of coolant went into the transmission fluid.

Would it cause a vibration? That is not typically one of the symptoms I would expect. However, coolant in the transmission oil would be catastrophic to the transmission.

I would expect you to get a “Check Engine Light” and you could possibly get a shudder when shifting.

If the coolant did not go into the transmission, where did it go? What was the reason given for needing timing chains?

Typically if there is a timing chain problem, it will start by making a rattling noise in the engine — but I would not characterize it as a vibration.

I would recommend taking the vehicle to an independent third party to get to the bottom of all these issues. Right now we have two concerns:

1. Where did one gallon of coolant go and is it low again?

2. What is the vibration you are feeling?

When these two concerns are diagnosed properly, you will have the cause and the recommended correction. If the answer is transmission failure because of coolant intrusion, you can go back to the dealer armed with the information.

Ÿ Douglas Automotive is at 312 S. Hager Ave., Barrington, (847) 381-0454, and 123 Virginia Road, Crystal Lake, (815) 356-0440. For information, visit douglasautomotive.com. Send questions to underthehood@dailyherald.com.