Sometimes between gears 1 and 2, there's a split second hesitate, and then it shifts into gear with a slight jerk. Has anyone had this problem before?

99 4x4 5.4L

 

Is it an E4OD? Does it change with how hard you accel? I believe it will be an internal problem.

 

not sure of the e4od. However, it does change with how hard i accel. For instance, if I keep my foot steady on the gas, it's fine. Howver, if I am gradually decreasing gas, it'll do it.

 

With alot of miles on it. It could be some leaking from around an internal seal. As your foot pressure goes up, so does the trans pressure,(harder accel makes more trans pressure) which will hide the seal problem. All I would do is drive it till it craps out, which might be a long time. Also saw your fuel mileage question. 18 mpg is very good for a 4x4, 20, I believe will never come.

 

The E4OD was discontinued in '98, so you likely have the 4r70w(unless it's a Lightning, then it has the 4r100w).

Anyway, I wouldn't get too worried about a slight jerk. I'd agree that there may be a slightly leaky seal somewhere causing a momentary loss of pressure. Unless it starts hesitating on other gears, or takes a long time to "grab" a gear, I wouldn't worry.

You could try a bottle of a transmission seal conditioner, it's typically a pint or so you mix into the trans fluid. If that doesn't seem to help, try dropping the pan and changing out the fluid and filter. If the trans has more than 60k on the original juice, then it's due anyway. DO NOT flush the tranny(some shops only do this), that usually leads to more problems than it fixes.

 

Mine does something similar accept its not on the 1-2 upshift. Its right after the 1-2 up shift and always between 20-30mph. It feels just like a slight hiccup in the acceleration. Common sense would say its the converter locking up, but i just don't think that is what im feeling.

Does this sound familiar? The reason I say this is because unless your paying close attention its hard to distinguish the hiccup from the 1-2 shift. It helps that I have a shift kit.

EDIT- Im planning to put a switch on my converter in the fairly near future so I guess that will answer the question if it is that or not.