ST300 won't really accelerate forward / switch to gear(s) after fully stopped

Hi,

I just got (produced?) my first problem:
After the car stalled on turning, I (guess) I hit the accelelator somewhat more than usual just after the car fired again and then - still at higher rpm - switched from N to D.

Now the car won't "engage" any gear, from a full stop (and being in D or L). Creeping is absolutely minimal, the gearbox sound in D/L is now like N and not like R as before, and the engine rpm won't drop as much as before either.
On the other hand R is working as usual.

The only way to get the car into gear is like this: Switch to L and then let the car sloooowly gain speed - at approx 15 mph try to switch to D. Most of the time, the gearbox will then "find the gear" and accelerate like normal.

But as soon as you stop again, the gear is "gone" and you have to start in L once more.

Could some kind soul give my any advice on what might have happend and how to solve this?

Cheers,
Harry (sad atm...)
 
Last edited:
Update:
After letting "her" sit for a couple of days (while I was browsing the web for any possible causes/fixes), the leSabre is somehow back to normal.
So, although this might sound great, I'd really love to understand what might have happend - to maybe avoid any possible errors on my side in the future. As far as I know the ST300 is just another simple hydraulic/mechanical tranny, without any electronics/computers that might develop some occasional hiccups.

So, what might have caused the (temp.) unwillingness to move forward? Air bubbles/pocket somewhere? Jammed valve/regulator?

Oh, btw: I checked ATF level of course, but found it somewhat impossible to get an exact reading using the dipstick.
I'm used to see the ATF level on at least one side of the dipstick as a definitive "clear mark", but whenever I pulled the dipstick ("hot tranny", car running in Park, level ground) the end of the dipstick is somewhat "smeared" without any clear mark. Are there any best practice to avoid this or maybe get an idea if the ATF level is "ok"?

When I repeat this with engine not running, the ATF level is absolutely clear (approx. 1/2" above "full"). Over that the ATF itself seems to be ok: reddish-translucent, clear, not smelling burnt.

Cheers,
Harry
 
Last edited:

LARRY70GS

Active Member
With the car running, it may be necessary to remove and wipe the dipstick numerous times in order to see a clear level. Try starting the car cold and immediately taking a reading. The level should be 1/4" below the add mark. With the engine off and cold, the level should be well over the full mark. Where is your level cold after sitting over night.
 
Larry,

thanks for your reply. Up to now I thought to be safely able to take a dipstick reading...until I came across this car ;)
When I pull the dipstick, its end is somewhat "smeared" most of the time, so as if there is something sticking in its tube that will wipe across and make the reading a mess.

I just took 10-20 readings in both "engine off + cold" and "engine just started" states. If I'm correct, the "engine off + cold" level is approx. 0.8" over full and the "engine just started" (running on choke) is about in the middle between add and full.

Cheers,
Harry
 

LARRY70GS

Active Member
Yes, that's satisfactory. With the engine off, and cold (sitting overnight), the converter drains back into the pan raising the oil level. When started, the pump fills the converter bringing the level down below full. As the oil reaches operating temperature, it expands raising the level to full.
 
Larry,

thanks again - really appreciated!

Do you maybe have any idea what might have happend with my tranny, when it temp. lost its ability to move forward?

Cheers,
Harry
 

LARRY70GS

Active Member
I have no idea. If I was you, I would drop the pan and replace the filter and fluid. You might have a loose filter or something blocking the filter. You can also inspect where the dipstick comes through the tube.
 
As to your other problem, do you think your transmission got converter got stuck in high stall or failed to shift to low stall?
 

LARRY70GS

Active Member
@Bob

If the converter was stuck either way, the car would still move forward - or am I mistaken?

Its really hard to describe...when you normally shift from N to R or D, the car jerks a little and tries to creep. Additionally the rpms drop and - at least on my ST300 - the "gear whine" stops.

When that problem occured, neither was the case (in D). Alternating between N and D did have no obvious difference. As soon as I released the brake, the car started to creep, but very very minimal. Hitting the accelerator did not do anything - seemed like still being in N.
R however was still working as before. It really felt as if the "forward clutch" was not working - or the tranny was not able to find its way from N to D.

@LARRY70GS

Thanks heaps!

Cheers,
Harry
 

LARRY70GS

Active Member
Gear whine might be from the front pump. The front pump provides the working pressures inside the transmission. If you have a problem with the pump, that would explain it. Might be time for a rebuild.
 
Larry,

yes, but there is just one pump for all gears, including reverse - right?
The thing is, reverse was working all the time. Only D + L were affected. So the culprit has to be a part thats only controlling the forward gears.

I'm already checking the ST300 section of the "Chassis Service Manual", but thats pretty complex...
Strange is that it is not mentioning my problem in the "Trouble Diagnosis" section - just the opposite "no reverse".

Cheers,
Harry
 
If you were not familiar with the switch pitch converter, and it was working properly, and you were a relaxed driver, you may never really notice you have one. Then, if suddenly your converter stuck in the high stall, you may notice that the engine had to increase to a higher rpm to move the car and it may be possible that it could be described like you said. It doesn't switch to high stall in reverse, as per your description. I suspect such a problem might be created with the switch wiring. I am not an expert!
 

tom telesco

Active Member
You screwed up by putting it in gear with the RPM,s too high. Something has to be broken internally. You can beat all around the bush all you like but the more the vehicle is driven the more damage you're causing.
Time for a rebuild.
Just my thoughts.

Tom T.
 
Tom,

yes, I probably made a mistake there, but this was not like "full trottle" or similar. Just a bit more to keep her running after stalling.
But so far the car is absolutely working like normal again - so I doubt there is something broken. We'll see if it occurs again. Luckily I got a spare "redone" ST300 here as a replacement. ;)

Cheers,
Harry
 
Top