So with the temperature back above freezing the shudder following acceleration to 5th has returned after my third shudder free winter. Are there any theories as to why ambient temerature makes a difference?

Warm fuel foams easier. Have you bled it lately?

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2006 Sport CRD

Could the Aztecs have known, that in 2012 after a 4 year experiment, our country would cease to exist?

The theory is that, because colder transmission fluid is more viscous, it requires more pressure from the pump to move through the lines. This also exerts more pressure on the clutch actuators and such. That is one of the reasons that the shifts feel so harsh when you first start out down the road on a winter morning. as the temps warm, the oil thins, and if you have a leaky seal on the pump, it is harder for it to maintain pressure on the clutch. Or not.

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Manure green 2005 CRD sport4x4, GDE Hot tune, Cat Gut, OE skids, Draw tight hitch, Duramax lift pump, 160K on multiple varieties of fuel, XM radio, Escort live with Redline, fog light mod, GPS, Icom IC7000 all band radio call sign KC9QPF, Grabber AT2s on Soft 8s, FIA grill blanket.

Warmer air is less dense.

Are you using SEGR or ORM? I found that ORM significantly helped my 'accelerate-then-maintain-speed' shudder while off road.

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2005 CRD Limited Flame Red w/ Renegade rock rails & light bar, AirLift 1000. 225/75R16 MT/R's on cheap black steel wheels, dual MOPAR subwoofers, Ipod kit & seat covers, Samco hoses - totaled and gone. 2008 WK Laredo 3.0L diesel - AirLift 1000, wife won't let me mess with it much. 2013 JK Sahara on order.

dirtmover; you need to update your signature line. We don't know if you have a lift pump or any other mods which may be causes of shuddering. There have been at least two causes of shuddering identified here on the forum. One is transmission related and the other is fuel filter head related. If you have a lift pump the fuel starvation shudder is eliminated as a cause, leaving the tranny as a cause.

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Manure green 2005 CRD sport4x4, GDE Hot tune, Cat Gut, OE skids, Draw tight hitch, Duramax lift pump, 160K on multiple varieties of fuel, XM radio, Escort live with Redline, fog light mod, GPS, Icom IC7000 all band radio call sign KC9QPF, Grabber AT2s on Soft 8s, FIA grill blanket.

The truck is stock but I did run with the ORM for about two months and saw no difference. The shudder has been present since new but, of course, "cannot be reproduced" by the dealer. I'm coming towards the end of the warranty and am considering a lift pump.