Hard Shifts

i have a little problem with my 98 riv.once in a while she changes gears very abruptly.( i hear and feel a very noticeable clonk sound )
it doesn't do it everyday but when it does i $h!† it.it feels like my tranny might fly off.
i've brought it to my mechanic. he says it's ok.he even took it to a tranny expert ,same result.
have you guys encountered this,if yes what did you do to stop it?

I had a similar problem a while back. After I found a vacuum leak, it seemed to go away. Might want to check that. I never knew if that was the exact cause because I also had a shift kit installed at the same time, so shifts were firmer after that.

http://tis2web.service.gm.com/tis2web

Enter your vin and then check if your pcm has had the shift software update.

Hey joe, I did the above and it comes up with service bullitens for me. Do I need to have those done?

sorry to steal the thread.

x2 mine has a few things too :/ how much would the dealer charge to reflash the pcm with the update? "Control module calibration" seems too vague for me to spend money on after 11yrs

Yeah, no spending money, but one I found interesting:

"Calibration improves fuel economy and reduces belt chirp"

Sounds like more torque management, nothing I would ever want.

But this sounds good:
"Calibration change to correct inoperative oxygen sensor heater and enhance EVAP diagnostics"

Mine was doing that at one time. I swore it was the tranny, but it was the PCM. Thanks to an honest transmission guy, he could have sold me a tranny and sent me on my way. The PCM should fix it.

I've had that link saved for a while. I think the list that is given shows the available updates for the PCM. I'm not sure if the ones listed have or have not been installed on your car. It would be best to call a dealership with your VIN and have them tell you what has and has not been done to your PCM.

thanks for the help guys.i'll post a reply when i get the update done.

I'm not sure if anyone remebers, but around last August, I was talking about how after a good hour or so of driving, my shifts into 2nd and 3rd were just slamming in, rocking the whole car.. I had a check engine code for my o2 sensor, so I tested it and it was dead, and I replaced it. It seemed to have fixed the problem, but last Friday I was driving home, and about 50 min. into my trip it started doing it.. And this morning on the way in, it started doing it again!! It seems to only do it during heavy stop and go traffic or after the car has been running a long time. I stopped for gas about 10 min. into this, the car sat for a good 7 or 8 minutes, and I didn't have a problem the rest of the trip, or on my way home. If it was my transmission going out, wouldn't it be a constant thing? what could cause this? When I say it slams into gear.. I don't just mean a vibration.. I mean it feels like I got rear ended by a car going 5 mph. it's bad..

could be a stuck PCS (Pressure Control Solenoid). The things are really really sensitive. If it's giving full pressure at all times you might get a reaction like this.

When's the last time you changed the fluid/filter? A flush _might_ help get it unstuck.

Check for vacuum leaks. I had a cracked hose that was causing a similar hard shift.

If the trans gets hot that can also dump it into limp mode that could give you a similar feeling.

I'm not sure when the last tranny flush was, the guy that flushed my radiator said i'd want to have it done within 5 months.

I'll check for vacuum leaks Aaron.

If all else fails, should I try a tranny cooler

At least change the fluid if you are not going to flush it. I am not a fan of tranny flushes what so ever. I have heard the horror stories about after the fact that makes me just change my fluid every 50K.

will do.

A flush will not hurt a transmission in good shape. Most don't flush until they have problems and then removing all the friction material laden fluid finishes things off.

If we look at the capacity charts for my car..

Pan drop and service 7.5 quarts
Trans rebuild 10 quarts
Completely dry + converter 13.5 quarts.

I left my pan off for about 4 days and needed 10 quarts. The only thing you really miss on a pan drop is the converter and coated surfaces.

Quote :

A flush will not hurt a transmission in good shape. Most don't flush until they have problems and then removing all the friction material laden fluid finishes things off.

I agree. Had mine flushed at 80k miles. No problems at all until about 150k miles. Clearly, the flush didn't cause mine to fail. Probably should have had it flushed again at 120k instead of only changing it out.

how many quarts will the riv hold if I change it? Has anyone used royal purple?

this comes with the pan seal right?

http://www.autozone.com/selectedZip,34668/initialAction,partProductDetail/initialpartType,00543/initialR,APP729769/initialvehicleId,2338202/shopping/selectZip.htm

yea that comes with a gasket.
before you go changing out the fluid, how does it look? smell burnt?

Try to use the old OEM rubber gasket if it's still in good shape. Better quality than some of the cork or thin rubber ones you get with the filter.

You do not want the aftermarket cork gasket. The OEM gasket should be reusable if you are careful removing the pan. The OEM gasket has spacers around each bolt hole that prevent you from warping the pan. It is also rubber-coated metal and reusable.

not sure about smell, but it's a darkish red.. i'm sure it's long due

I think I might have found the source of the problem. The past two or three times i've popped my hood, my tranny dipstick has been sticking out about 5 inches, I have no idea why or how it comes out but it does.. so I zip tied it to a nearby wire to hold it down, and I haven't noticed the problem so far. It seems logical to me.. the dipstick is open, hot air flows down into it.. it's a longshot but maybe..