Driving the other day, I down shifted from 2 to 1 at a light, and the rpm's raised as expected but a second later they dropped to idle(should have been at like 3500). no motor breaking when decelerating... When on throttle everything in trans works fine.

Here is the problem.
1:
Place trans in 1st.
Run up to 4000 rpm's
Let off throttle.
Rpm's drop down to about 2000
Back on throttle and goes back to 4000,

2:
Same thing but leave in drive, car shifts fine.
Get up to say 60 (car in od)
Let off throttle.
Rpm's again drop down
Back on throttle, motor catches up to trans and is ok...

3.
Driving 60,
Down shift to 2nd
(hear the trans shift)
Rpm's stay down.
will not decelerate or raise rpm's

I hope it made sense the way I explained it.
What would cause this in the trans? possibly the converter?
I checked the detent line. everything shifts fine when on peddle...

hope some has the diagnosis.

Thanks
-T

 

first 700r4 to ever do this??????????????????????

 

??

 

?

 

All tran's does this more or less, I don't know how, but it protects from over-rev'ing. The question is just how much more "protective" your tranny has become, and why. Usually, this is only noticeable when downshifting to 1'st. If you leave it there while allowing the speed to drop, you should get to a point where the tranny engages again. Has that point gone completely down to 0 in your tranny now? Stupid question maybe..
Anyway, it seems that the converter "looses" 2000 rpm when engine braking instead of locking up the reverse rotation?
Hmm, could there be a problem with the overrun clutch in the tranny or maybe the stator roller clutch in the converter (in which case you should get poor accelleration in either low or high speeds)? I'm just guessing here, I'm not experienced in these matters at all but I hope to initiate something.
Here's what the 700-R4 diagnosis says about No Overrun Braking - Manual 3-2-1:

External linkage - Not adjusted properly.

Valve Body Assy - Valves stuck.Input clutch Assy - Turbine shaft oil passages plugged or not drilled.

 

Thanks fulsizewagon,

I can feel faint rpm differences when if I’m off the throttle and down shift. I can hear the tranny speeding up when the rpms are in range to allow the next lower gear... I would say the overrun point is correct or near correct.

I’d say that my acceleration is fine, I ran at the track last weekend (pitiful ET’s but having some tuning issues).

Now the converter could be suspect. It’s possible that it’s acting like a 1 way bearing and “freewheeling” when not increasing speed (make any since?). I wouldn’t have even suspected it.

I have a new tci 1700 sizzler ready to go in, but I’d hate to yank the Trans and replace the TQ when I will have to remove it again if that’s not the problem...

Thanks, you may have gotten the ball rolling.

-Twolfe

 

I don't know if it's possible for the converter to be faulty in a way as to produce this phenomenon - it was just a thought, but somewhere along the line something must be frewheeling. I'm hoping for someone else to chime in.
To check the stator roller clutch when you pull the converter - insert a finger into the splined inner race (the bigger one) of the roller clutch and try to turn it in both directions. It should turn freely clockwise, but be hard to turn counterclockwise. This test should save you a double operation.
If it seems to be in order then the fault must be in the tranny, which I guess is most likely.
All I can say now is good luck..

 

My grand am did this before i got rid of it. ended up being the torque converter was bad. I was be doing 55mph down the road, let off the throttle and it was drop right to idle. Check your converter is what i would say.

 

thanks,

Ill check that bering when I yank the tranny in the next week or 2. Ill toss in the TCi if everything feels ok.. worst case, I can get a deal on a rebuild if that ends up being the problem..

thanks again fellas

-T