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Just bought a 2500HD DMAX/ALI (second hand) with 93,000 mi. This past weekend was first major haul up some fair size mole hills. We were hauling a 4-horse trailer goose-neck (5000lbs) with 2 horses (total 2200lbs). We were only travelling between 65-70mph so when we started uphill I would steadily put the accelerator down as we decelerated. When she downshifted around 60mph and increased power we experienced some quick hesitations (almost jerky) until it shifted up or I let off the gas. I noticed that this event doesn't happen below 60mph if she downshifts. I checked into the previous owner's service records and found that although he maintained regular LOF changes, his last fuel filter change was at 52K. Would a dirty fuel filter give me this hesitation or jerkiness at increased power needs?


I tried this without the trailer and could still feel the jerkiness over 60mph when I floor it.


Appreciate your input.


Since this post I have changed the fuel filter but to no avail. Is it possible that the transmission is acting up? I believe the trans warranty ran out at 60,000 mi. My mechanic is looking at it as we speak and he seems to think it is the transmission.


Thanks again.


Rick.http://dieselplace.com/forum/smileys/Cool.gif</TD></TR></T></TABLE>

Rick


What year is your Duramax? Do you have a O/D cancel button? Have you tried to recreate this problem empty? Ally might be downshifting into 3rd under that load in which case it will get jerky.


mike

I'm voting on the fuel filter. The Dmax gets mighty tempermental when she gets starved.http://www.dieselplace.com/forum/smileys/Ermm.gif

Rick


What year is your Duramax? Do you have a O/D cancel button? Have you tried to recreate this problem empty? Ally might be downshifting into 3rd under that load in which case it will get jerky.


mike





I too had the dubious pleasure of 5-3-4 shifting towing 4000lbs while in cruise on long steep grades. 5-3 results in much noise to include the missus hi pitched snarl, hi rpm for and instant then an upshift to 4th where it should have went in the first place. Someone else experienced the same thing also, when in cruise ~ whether we are assisting cruise or not. The OD lockout will take it directly into 4th ok but its supposed to be automatic and we're now talking manual intervention? The dealer just to start reflashed tcm etc but have yet to try it under load. Will know on the next trip in a couple of weeks. But thinking it may be nermal.

I mentioned this and many a few told me it don't happen. I think it's designed to go from 5 to 3 than back up to 4... than 5. Stupid if you asked me. Mine did it when I laid on the accelerator on the highway.

I often pull 12-13K @ 65-70 MPH with the cruise on in the tow/haul mode. Never had a downshift to 3rd. Not saying it doesn't happen but is it possible that it's only happening with the earlier models http://www.dieselplace.com/forum/smileys/Question.gif If so maybe a TCM reflash would help? Has anyone had this happen with the 02 and later models?

Mine was built late apr 02 ~ they did build thru May that yr. I don't recall if mine does it when not in cruise ~ T/H doesn't seem to make diff