I just turned 40k, and recently when I first start the truck in the morning and shift it into drive, the motor will rev and the truck won't move. Sometimes it takes off slow like I have a load behind it. Sometimes it takes off normal.

After it's first initial glitch it runs fine, and shifts fine. I put 70k on my 05 and never had this problem.
Any thoughts?

 

Drain back valve is sticking and allowing the TC to partially drain while sitting.

Put it in neutral for a minute or so to allow the TC to charge and fluid start circulating before you take off.

 

FYI. Tranny pump doesn't run in park but does in neutral.

 

Why would it all of a sudden start acting like this? Time for a flush??? Replace something??

 

Your K&N filter caused it, gotta be the problem.

The drain back valves are problematic and will just stick open. More often than not there is a piece of clutch material of metal under the ball seat.

If anything removing it is the best solution. Its a garbage trap and a cooler restriction.

 

Nice one!!!

 

This is all true, a good built tranny will never take off cold, they have to sit in neutral for a few seconds.

 

Not true. Mine has from day 1, even after sitting in parking for 5 days, taken off with little or no warmup.

As long as the drain back valve holds, or the pump circulates in park, and, your trans is good shape and the pump builds pressure correctly they will roll out almost immediately.

A lot depends on how tight all the internals are and how well the seals are functioning cold. The 48RE's have been the best of them all due to the higher flowing pump, better selas, and better fluid.

 

Your VB is still set up stock then(no drain back). This has nothing to do w/ seals and how tight internals are. Let me re-phrase what I'm trying to say. Stock trannies should take off as soon as the truck is started, every built tranny I've owned and ridden in will take a couple seconds for the fluids to circulate due to valving.

 

My 05 never did this, and my 07 just started doing it. In fact this last week it hasn't done it. All operations normal.

 

VB is not stock, drain back valve is removed, trans circulates fluid in park.

Every built trans I have ever had would hook up and light the tires almost immediately on firing the engine. As long as the TC charges it should hook within 15-20 seconds of fluid flow starting.

If you get the mushy rev the engine to get things rolling and it still feels like it is slipping something is interfering with the TC charging immediately. On a stock setup the TC does not charge in park and if the drain back valve leaks you have to give 30 seconds or so in neutral to circulate the fluid and charge the TC.

On a modified unit that should not be a problem as the line pressures are bumped and it charges the TC immediately. I have a built trans in one of my trucks that has enough wear and slack in the drive train that it will take a 3 count to engage cold. The TC is charged but the clutches are not engaging immeditely when put in gear, if you hit the throttle too soon the truck will literally jump when the clutches engage.

The problem the OP describes is common when the drain back valve leaks and allows the TC to drain. The easiest fix is neutral for 30 seconds. If it still doesn't help then there a shuttle valve that controls flow to the TC, cooler, and dump to the sump. That may also be sticking when cold and not routing fluid correctly.

 

My truck revs when I move from park to drive or reserve. What could be the problem?

 

Mine has done this since I had mine built by Dave.. Put it in nuetral and wait about 5 seconds and she is ready to go. Dave told me this was normal