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Author Topic: Cat 3126 Shuddering at 1600-1700 rpm  (Read 1034 times)


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Cat 3126 Shuddering at 1600-1700 rpm
« on: June 12, 2012, 11:40:01 AM »
I have a 3126 in a Freightliner FL50 with approximately 350k on it, trans is a 7 speed Spicer.  It's used to drag aroung a 5th wheel and our gross weight is about 27,500.

Last year returning from down south I noticed that between 1600 & 1700 rpm under heavy pull and full boost pulling grades that I would get a mild shudder and a slight drop in boost.  I took it to T&E in Billings Mt and had them do a diagnostic on it.  They dyno'd it and told me that the injectors were fine but that I had a U-joint that was going to fail eventually and that probably was what I was feeling.  I had them replace the U-joint.

Now I'm finding that I am getting that shudder and slight boost drop again under heavy load.  It only happens in 7th gear which has me a little confused.  I've put about 10k on it since the U-joint replacement.

If this was an injector issue wouldn't I get the same symptoms no matter what gear I was in?  Also I'm a little curious as to whether a fuel filter might produce this symptom.  I don't have a fuel pressure gauge and the filter has about 10k on it or there abouts.  I'm going to change the filter out with one from hopefully Napa if they can cross reference the part number for me but I won't know if it makes any difference until I hook back up to the camper in a few days for our final push back to Wyoming from Colorado.

Any thoughts on this would be appreciated.

2008 Victory Lane
1998 Freightliner FL50
Cody, WY when it's not covered in ice.