We just pulled into Tampa last night from Portland. What a trip.......
We had to drive slow, around 50-55, so around those speeds the truck would start to shudder, at first it felt like a tire starting to blow out. after some reading here it almost seems like a VP. I mainly happens under 1500rpm. Any ideas, truck has no VP codes but they can go without codes. We where towing, kinda heavy too.

 

It can be the trans slipping at that RPM.
Gear it down, keep the RPM above 2000.

 

Under 1500 RPM locked or in OD?
Mine acts stupid in OD sometimes. Unless I can keep it above 1500, I just give it up and drive in O/d off mode (better for heat I hear too)

 

While its in OD. It also seemed to hunt shift in and out of OD, kinda like blipping the throttle, I turned OD off and that quit, this however is a new problem. So this happens the worse when its below 1500 and in OD. It also happens but no where near as bad in third.

 

Call DTT or visit their site.
DTT

 

?
Hope it all works out.

 

Have you tried resetting your APPS?

 

Yes I reset the APPS about a month ago. I'm getting ready to head up to the dealer to hopefully get the computer scanned, and to check out the new toys on the lot. I'm starting to set money aside for an aftermarket tranny. If it is the tranny hopefully it will hold out until the bank account says its ok to get the tranny.

 

I am far from being a transmission expert, but I have always read that you should not tow in OD at less than 1800 RPM. From what I understand the transmission does not generate enough line pressure at the lower rpm's to hold OD effectively. I know that when I am towing, I always manually turn the OD off when I am travelling slower (ie: less than 1800 rpm). Hopefully, someone with more info than me might be able to chime in.

 

Yip I was bad and let the engine get down to 1200rpm So hopefully it is the tranny. It is afterall a big block that prevents me from turning up the fuel anymore!