Tranny question

Whenever I shift into reverse after a cold start the tranny slams into gear with somewhat of a bucking motion. When the engine is warm, it goes in no problem. I don't have any problem shifting into drive, or any other gear, and infact, when I shift into drive and then back up to reverse it doesn't slam into gear either. Any ideas as to what this might be?

One of my cars had a similar problem. I can't remember which tho, it was either the Contour or the Bonneville. But I remember shifting into drive would be almost violent. Sorry I can't be more help now but I'll try to remember more.

could be a vac leak, a faulty modulator, low fluid, maybe even a bad tranny mount.

anyone know if the 95's are vac controlled with the same modulator as the 96's?

my car would actually do the same thing. my tranny fluid was about 2.5 qts low. check your fluid level. you have to do this with engine running in park. the fluid should be red if not get it flushed.

^^^^^^^
Check the fluid level

THANKS!

I'm going to check the fluid as soon as I'm off work. It's been doing this for awhile now.

I'm also going to take a look over the tape-work done to one of my vac lines.

Tranny mounts and modulators are beyond what I'd be looking to work with, lol.

I don't think you have the option of not looking at the engine and tranny mounts. At the age/mileage of your car they often need replaced. There is not muuch to the mounts (at least, not much to the rubber part) and so by ~120,000 KM they are usually shot.

Albertj

jamie wrote:

THANKS!

I'm going to check the fluid as soon as I'm off work. It's been doing this for awhile now.

I'm also going to take a look over the tape-work done to one of my vac lines.

Tranny mounts and modulators are beyond what I'd be looking to work with, lol.

The modulator is actually probably the easiest thing you can replace on a 95-96 Riv. Click this Link!

...and you probably want to replace that taped-up vac line. Use vac or fuel line from a parts store like NAPA or Autozone.

Albertj

I've found now that since I had to use the car over the weekend with it's tranny problem, if I rev' the car up in 1-2-3 gears, it will eventually start to move.

No reverse or OD (well, OD keeps the same RPM as 3).

If after verifying you have enough fluid and all vacume lines are ok, it might be time to drop the pan and check for metal, the 4t60e was probaly only good for 150,000 miles if lucky and been maintained, sounds like you're no longer building enough pressure to shift, most likey because the rings and seals are worn. The warm performance would seem to verify this as everything in the tranny expands slightly and makes up for the blowby...I was originally thinking a torque converter problem but if you need to drop it and re-build, you're going to need to replace that as well. If you find no metal in the pan just replace the filter gasket and what fluid you lost and see what happens, I've seen this problem taken care of for a few thousand miles with just the added viscosity of that little bit of fluid but don't kid yourself...they don't last much beyond 150k.

Currently waiting for a friend to get the time to take a look at it, luckily, he's probably the top tranny guy in town, so I'll soon have no worries

On a side note, I had to drive it last night. While I was driving, my engine light shut off, previously when this happened, I lost acceleration, and the engine just rev'd until the light came back on, and then it would go back to 1-2-3 gears only.

This time, when the light went out, I was still able to drive, and I brought the selector up to OD. To my astonishment, it shifted, and I was in OD. My cruise control worked, and I had reverse.

Just before I got home, I lost accel again, and when the engine light lit back up with a few rev's but I only had 1-2-3 gears once more.

Edit: I checked the fluid, and it's full.

Could this be a computer or something along those lines malfunctioning?

You will have to use a Tech I or Tech II and pull the codes (your SES light is on) to get enough info to eliminate causes. The codes won't tell you if you have a bad motor or tranny mount - and at this mileage odds are you do. The point is that the codes will tell you if something else is failing that you can\'t readily see but since the code is not always lit, you'll need to try to trap it in a way that lets you see what else is going on at the same time. Reading the codes with an OBD-I/II reader is not as effective in helping you find a problem that turns the light on intermittently. That is - the code is stored but information about what else is going on at the same time is desirable, and might be necessary in order to fix the car.

The main point behind my point is that cars have a \"design lifetime\" and to a certain degree unrelated stuff starts to fail simultaneously when that lifetime is reached. And I suspect you are looking at simultaneous failures. In order to work for the design lifetime, some things have to be engineered very well - the 3800 Series II engine for instance. And some things can be relied on to quit pretty much around their design lifetime - the front MacPherson struts, for instance. So poking around to (learn how to) do good diagnostics would not be a waste of your time. And although there is a lot we can tell you from experience with these cars, you will likely have to rely on more than just our comments to get good value out of your Riv.

So if you can, connect a Tech I or II and take a log of the sensor readings while driving. If your car fails while driving it can be easier to figure out what\'s up by looking back at the logs. It would not be unreasonable for you to get a dealer or independent shop to charge you an hour\'s shop time for the needed idagnostics (just don\'t be surprised if it sets you back about $100.00). Many but not most independent shops have portable scan tools that will take logs.

Another choice for diagnostics is Alex Peper\'s \"Car-Code,\" which takes comprehensive driving logs as well, that would work - you need to get the software (free) and dongle (small bucks, see the web site http://www.car-code.com). Once you have driving logs you can see which sensor sets the light on, what is happening as that occurs, and make better decisions as to what to do about what you learn.

Since you just got the car, I gather, don't despair or panic - it may take a while to catch up on the maintenance needed to make it a reliable driver.

Albertj

Sounds like you have a dying PCM or a bad wiring problem! Make sure the big electrical connector on top of the trans is plugged in tight and not drowning in some kind of oil!

albertj wrote:

You will have to use a Tech II and pull the codes.

If you can, connect the Tech II and take a log of the sensor readings whiel driving. IF it fails while driving it can be easier to figure out what's up by looking back at the logs.

Alex Peper's "Car-Code" takes comprehensive logs as well, that would work and the software (free) and dongle (some bucks, see the web site).

Albertj


Albertj

Don't forget he's '95, OBD-I

...and one other thing.

When your engine is cold it is idling faster. The 'buck' is probably not a function of the mechanical state of the transmission as it is that the engine idles at 700-something RPM warm (no buck) and significantly faster when cold depending on how cold the temperature sensors tell the ECU that the engine is.

Albertj

We put the Riv' on a ODB reader last night, it came up saying the speed sensor failed, but my speedo still works, so I don't understand that. Even if it was just a speed sensor, would that keep me from getting into reverse?

do you have a factory service manual?

Albertj

Vehicle speed sensor (VSS) is a little magnetic pick-up that does several things other than just send a signal to the gage it also sends information to the TCC based on load and input for shift timing. If you're moving it will indicate it but may no longer be generating the required pulses for the other things like Torque converter (TCC) apply and release, cruise control, fuel delivery or idle speed control.
It's a fairly inexpensive fix and easy to replace just 1 cable and one bolt on the extension housing...with bolt removed theres just an o rng holding it in...make sure the bore is clean before putting the new one in and lubricate the o rng a little for a good seal...may be worth a try, see if it clears your code at least, you may get another code but just keep moving throught the damn codes until it's working again.

Thanks man! I'll look into this further now, with that newly found information

albertj wrote:

do you have a factory service manual?

Albertj

Unfortunately, no.

Are there any other vehicles that share the same speed sensor as our cars?

It should be the same for all 4T65-E transmissions for that same model year but I'm not sure...most GM parts have the p/n on them and most dealership parts guy's will gladly answer this question for you when calling for price and availablity.

The VSS is a $50 (more or less) part you should be able to install yourself with a wrench and a small schmeer of 'tune-up grease.' Look under electrical parts on http://www.rockauto.com.

That said - I suspect the VSS is not the only problem here, although it's a good place to start.

Albertj

albertj wrote:

That said - I suspect the VSS is not the only problem here, although it's a good place to start.

Albertj

Please elaborate