Hesitation under kickdown m104 722.3

[aka$h]

I have a problem on one of the E36's. Bare in mind the engine is very similar to the e320 so any help would be much appriciated.
When driving at around 80mph, if you give it full throttle and kickdown, the car will go down the 3rd. The revs rise from 3000 to 3700rpm, when the gear is engaged. But for a second the revs sit on 3700rpm and the speed and revs do not move, after a second the revs and speed begin to rise.

What am I looking at?

Ive had a long think and here's a list of thing I could come up with:

Air Mass sensor-been replaced 6 months ago with OEM part
Throttle actuator-changed 2 years ago new OEM part fitted
Gearbox-was rebuilt 10000 miles ago, but Ive been driving it hard since
Lamda probe, not been changed, but could it cause this sort of fault?
Charcoal filter behind the front wing-again not sure of symptoms
exhaust, a possible restriction?

To clarify, after the 1 second pause, the car accelerates quickly and goes to 6500 rpm, and the change up is smooth.

 

[grober]

Control pressure cable needs adjusting ?? If your car has one of course.

 

[kth286]

Are you saying this is suddenly happening, whereas it would change down OK previously?

Or is this the first time you are subjecting the car to this type of performance since making some upgrades?

 

[BlackC55]

Simal, I think its gearbox related.

I went out in it this AM to give it a run.