Rev after cold start to engage gears?

[C420sailor]

5R55E tranny, 204k since new, 64k since rebuild. Fluid flushed at 30k (since rebuild), filter changed and fluid flushed just the other day. Fluid has looked and smelled great since the rebuild. Trans drives and shifts great all day, no codes, no flashing OD OFF light. The only issue...

Every now and then, on a cold start, I'll select a gear (any gear) and the transmission won't engage. I can cycle through the gears all I want---nada. Bring the revs up to about 2k for a few seconds, let her idle down, shift into gear---like nothing ever happened. No banging, just a normal engagement. Drives great for a few weeks, then she'll do the same thing. If I'm not paying attention and I put it in gear and it doesn't engage and I step on the gas, she'll bang into gear and I'll cringe. I can't remember when it started, but she's been doing this for a while now.

My brain is saying that it's a pressure issue (revving brings the pressure up?). The lack of any other problems, even under high load, makes me think the pump is fine---maybe whatever it is that regulates pressure in there is sticking open? What say you, transmission experts?

 

[JK080]

You are describing converter drainback, it feels like its not engaging because the converter doesn't have enough fluid in it. Once the pump fills the converter it can drive the transmission input shaft and things work normal.

To test this check the transmission fluid level like this.

Check the level of fluid with the dipstick with the engine running to make its full.

Then shut the engine off and check the level again, the level should be higher on the stick because the pump is not pumping, make a mark or note were the level is at on the stick.

Let it sit for the amount of time it should take for the delay to happen then check the fluid level again before starting the vehicle.

If the level is higher than the mark you made when you checked the level just after shutting the engine off when hot then this would indicate the fluid in the converter has slowly drained back into the pan.

The fix for this is to replace the bushing in the back of the pump stator, you will have to remove the tranny and pump to do this...

 

[C420sailor]

I'll check it tomorrow. I JUST swapped in another motor last month---had I known this, I would've pulled the converter and done this. Oh well.

If this is the culprit, is it anything to be worried about? Will it eventually lead to other problems/failures? Thanks!

 

[Robert7x]

Got this same issue today... been getting the O/D light for a while... only issue was no overdrive. Today after about 90mile drive, this happened. I revved it to 3k, then all came back to normal.

I'll check the oil tomorrow... but i did a filter change and added about 7 quarts when i did it... checked it based on youtube videos and the drip drip technique... It was fine. No leaks that i can see...