Ok guys a truck came in with low power and surges. When it is in park or neutral it runs great. Revs up fine idles at about 8-900rpm. When you put in gear however it almost dies and pulls down to 4-500rpm and surges. Seems to me the converter is locking up. The only code it has is a trans code P0753. The customer says he has taken it to several transmission shops and they all say the trans is fine. When you try to power brake or brake boost it, it will not build boost or do much of anything. It will come up to about 7-800rpm.

My guesses are the converter is locking up or several gears are and going in at once.

I checked everything fuel related and everything seemed ok.

And ideas?

 

I just had the same issue, it was the converter locking. Make sure the oil cooler lines are free flowing. Remove the check ball in the coller line too. It can stick closed and cause a failure.

 

Im going to second this especially the check ball id remove that any way if it is the problem or not