Transmission shudder and spark plug fix | Ford Explorer Forums - Serious Explorations

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Transmission shudder and spark plug fix


New Member
June 19, 2016
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Year, Model & Trim Level
2008 Mercury Mountaineer
First, let me say that I've found the posts of others to be extremely helpful and I want to say thanks.

So, I just bought a 2008 Mountaineer with the 4.6L 3v V8. (My '05 Ex was going to die.) Not long after buying it, I noticed the dreaded 45-55 mph transmission shudder. Of course, no check engine light or any codes showing up on the scanner. If I drive around with the o/d off, no issue. But who wants to drive around like that.

First, I went to the fluid change route. Took it to a local shop to have the transmission fluid changed. It has 125,000 miles on it and I have no idea if the fluid has ever been changed so I decided that I'd just get that done. No issues with the fluid change, but unfortunately the shudder was still there.

That took me to step two, the changing of the spark plugs and coils. Again, I had no idea if they've ever been changed so I decided to do it. The spark plugs and coils are very accessible, so I decided that I'd take on this job myself.

However, after reading all the posts and knowing that my V8 is of the old design I went the safe route. I ordered some Autolite HT15 spark plugs, coils, spark plug socket with extension and the Lisle spark plug removal tool from Amazon.

I downloaded the TSB for the spark plug removal and went at it.

The first four came out no problem. However, the previous owner didn't replace them all as I was pulling out different brands of spark plugs and then I came to the Motorcraft plugs. I broke three of them.

Two of the broken spark plugs had the thread and nut separate from the porcelain. I'd turn and turn and nothing would happen and there was no way those were coming out. I couldn't figure out what was going on as I'd never heard or seen such a thing where the nut breaks free. When I finally figured out what was going on I had to use a screwdriver down in the spark plug well to snap the porcelain. Then, I had to use needle nose pliers to grab the tip of the spark plug and pull the broken parts out. That left me with just the broken tip stuck in the head.

Time to get out the Lisle tool. Trust me, if you are going to take on the task of changing the plugs, buy the Lisle tool. If you don't end up using it, then return it, but if you don't have it you're screwed! Needless to say, the Lisle tool is exactly what the doctor ordered! Works like a charm. I got the three broken plugs out - no problem.

I put in the new Autolite HT15 plugs and coils and it started right up.

I took it out on the road and the transmission shudder was gone! If you search the internet, you'll see this common transmission problem and I don't know why changing the plugs and coils fixes it, but for me it did the trick!

Happy motoring!

Great write-up! Thanks!
For some it's the plugs/coils. For others it's the transmission pan-drop that solves the problem. Not a flush, just a drop and filter change.