brake hard, bog, normal.

[soryu]

lately that has been happening when coming to stop. also sometimes instead of bogging i get acceleration from 600 to 1k rpm then back to 600(when coming to a stop medium brake) and 1st gear seems to slip with medium accel. it's ok if i floor it.

anyone have any ideas what's causing it?
s13, auto.
trans fluid ok.

[soryu]

some more info.
engine revs up to 1k then comes back down to 600, 700 when stopping. car is trying to creep forward a little but then stops.
if i accelerate before it comes back down engine just revs and 1st gear slips a little then catches. If i wait for rpm's to come down after revving 1st gear is good.
this only happens when i brake fast if i take my time coming to a stop sign or red light.
doesn't happen the rpm's do still go up.