1996 Riv SC transmission

I am looking at a 96 SC w/50K miles on it. I have a question about the transmission. When it was in the upward inclined driveway, I put it in OD to proceed back into the owner's garage. At idle the car slow crept backwards. I put it in 3rd and it stayed still (as I would expect it to), then I gently accelerated up the drive. I did not try to accelerate up the drive in OD.

It acted like a high stall converter in OD at idle. But it acted normal in 3 at idle. What in the heck is going on?

Note, I have had 4 98-99 Auroras (which I am pretty sure have the same transmission) and I never noticed this on any of those.

I am going back in a few days to look at it again. Thank you.

Sounds like it was in neutral despite what the gear indicator indicated. Look at the linkage or switch at the transmission.

Have to compare the drift in Neutral to the drift in Drive (OD as you say Rod) to suspect a problem on the linkage. Do you know if the transmission has ever been serviced?

As far as the car creeping backwards is concerned, I'd get an "old fashioned" pressure gauge and check line pressures at idle against spec. Also look at the diagnostic tree in the factory service manual, you will need to use a Tech I or Tech II or equivalent to get at some of the data but the point is to find out if the transmission has adjusted itself out of "tune" so to speak or if the base line pressure needs adjustment (easy to reach when you drop the pan). Or if some sensor, like the trans temp sensor, is wack; if the trans temp sensor reads wrong you can get weirdness. And just to be "complete" check fluid condition and level. If you don't like the backwards drift you can turn up the base line pressure, problem then is you'll likely get annoying vibrations in the cabin at idle and other issues.

As far as the different behavior in OD vs 3rd, I am not sure except I'd plug in a Tech II and check operation/sensor readings just to eliminate them from the mix.

Rod: IIRC the 98-99 Aurora transmission, it depends. The 4.0 N* 8 cyl Aurora has the 4T80E IIRC. Similar but not the same. The 6 cyl had the 4T60 or 4T65 I'm not sure which -- however be advised GM made *versions* of each transmission for different models of cars.

I could be flaming wrong here Larry... but I suspect it's just adjusted itself out. OTOH as a longshot, it may actually be low on fluid. Must check the fluid at op temp because if you check cold then when they read full they will actually be short +/- a pint.

I always like to eliminate the simple things first, so yeah, fluid level check is a definite. I think we need a lot more information before we go more technical. This same OP posted over on Buickforums.com with the same question. We will see if he gets back to us and go from there, but the track record over at the other website is not good. I've posted there before and waited weeks and even months to get a response.

Will try to do all that is recommended. 1st thing is I am going to try to replicate the situation. I will double check the shifter position and I will do another test drive. I will report back Sunday or Monday. Thank you one and all.

LARRY70GS wrote:

I always like to eliminate the simple things first, so yeah, fluid level check is a definite.  I think we need a lot more information before we go more technical.  This same OP posted over on Buickforums.com with the same question.  We will see if he gets back to us and go from there, but the track record over at the other website is not good.  I've posted there before and waited weeks and even months to get a response.

After Scott Wright (Steuben Auto Service, Savona NY) rebuilt my Riv's transmission, all my driveline problems have been minor/laughable.  One time during a maintenance fluid change Scott's technician decided to readjust the line pressures.  The car was shaking at idle because he turned the pressures up so high that it would move.  SMH. The shaking was a real PITA and the pressure bump gave me  -zero- actual performance improvement.   When I next had major maintenance I had the dealer use a flush machine to replace fluid (they have a tech who actually knows how to do it correctly) and while it was in the shop anyway, to check/adjust the base line pressure, "un-learn" the PCM to near factory spec and other work (PM me for details). It was in one more time to replace the transmission and oil sump pans, (my guess is somebody was trapping small animals and other foreign objects under the pans, and not telling me; was losing oils with the concomitant problems but other than slimy pans no evidence of leaks...  Happens.)  Point is when the fluid got low the transmission did all manner of stupid stuff like chuggle at driveaway after a stoplight.  

Also, every couple years I check all the grounds I can get to easily and I suggest you do the same.

Albertj

LARRY70GS wrote:

I always like to eliminate the simple things first, so yeah, fluid level check is a definite.  I think we need a lot more information before we go more technical.  This same OP posted over on Buickforums.com with the same question.  We will see if he gets back to us and go from there, but the track record over at the other website is not good.  I've posted there before and waited weeks and even months to get a response.

It seems performance oriented forums have people more apt to help out. Some car forums are primarily "vanity" forums. Thanks again.

skatterbrane wrote:

LARRY70GS wrote:

I always like to eliminate the simple things first, so yeah, fluid level check is a definite.  I think we need a lot more information before we go more technical.  This same OP posted over on Buickforums.com with the same question.  We will see if he gets back to us and go from there, but the track record over at the other website is not good.  I've posted there before and waited weeks and even months to get a response.

It seems performance oriented forums have people more apt to help out. Some car forums are primarily "vanity" forums. Thanks again.

This bulletin board is almost exclusively dedicated to the 95-99 Riviera, so it is probably your best resource. The Buickforums board is mostly for later model Buick cars, and I will answer questions there and not have a response for very long periods of time. I mean, I want to help, but I can't because I get no feed back, which is frustrating. As a result, I don't monitor that board and visit every so often.

It was not until 2006 that I ever owned a car newer than 1972. Heck, I took 4,000 mile trips in cars such as 1956 T-Birds and 1965 Skylarks. My first "new" car purchase was a 1998 Aurora Autobahn. There is a LOT more to know on modern cars due to computer systems, sensors etc. And changing shocks is a heck of a lot easier than changing struts.

Back in the day one could pay a shop to rebuild a turbo 350 for well under $800. Transmission rebuilds these days can cost more than the book value of a car! I looked in my 1998 Aurora/Rivera shop manual and I see to adjust the shifter linkage is almost exactly like adjusting the throttle cable and the kick down cable in a 1971 Malibu I had.

Yes, older cars are easier, and cheaper to fix. Click on the you tube videos in my signature.

Can't you retrieve codes and diagnostics through the HVAC controls? I can on my 94 Roadmasters.

skatterbrane wrote:

Can't you retrieve codes and diagnostics through the HVAC controls? I can on my 94 Roadmasters.

No, 96 and up is OBD2. You need a scan tool. For transmission codes, you need a tech2 scan tool.

Got it home. Transmission works perfectly. I must have had it between N and D. It seems that the almost new tires are either out of round or not balanced perfectly. I get a vibration I can feel in the steering wheel and throughout the car between 70 and 80 or there abouts. Definitely nothing under 70. I did not go much over 80.

skatterbrane wrote:

Got it home. Transmission works perfectly. I must have had it between N and D.    It seems that the almost new tires are either out of round or not balanced perfectly. I get a vibration I can feel in the steering wheel and throughout the car between 70 and 80 or there abouts.  Definitely nothing under 70.  I did not go much over 80.

You may be right - but in the threads on here you will come across a couple other causes of the vibration. One is weak struts. Another is bad control arm bushings. It can be maddening but if you keep at it you will fix it.

I do not think it is tires. I came across paperwork from Discount tires that they rebalanced these nearly new tires because of customer complaints of vibrations at highway speeds. I intend to replace shock and struts anyway so at least I will eliminate that possibility. Here's hoping it is not control arm bushings.

One of the high pressure gas hoses under the hood is leaking. I have NO IDEA how to replace those. I will do some research. I have a list of things I want to do. I need my cars to be 100%, then after the car is taken care of, the kids get fed (that's a joke as I do not have any dependents, my kid is in her 30s).

skatterbrane wrote:

I do not think it is tires.  I came across paperwork from Discount tires that they rebalanced these nearly new tires because of customer complaints of vibrations at highway speeds.  I intend to replace shock and struts anyway so at least I will eliminate that possibility.    Here's hoping it is not control arm bushings.

One of the high pressure gas hoses under the hood is leaking.  I have NO IDEA how to replace those. I will do some research.        I have a list of things I want to do. I need my cars to be 100%, then after the car is taken care of, the kids get fed (that's a joke as I do not have any dependents, my kid is in her 30s).

Most full-line auto parts stores sell kits to repair the nylon gasoline lines. Most come with instructions; basically you use heat to shape them.  I understand that you  can simply replace them with other same-ID neoprene fuel line, at least temporarily, although I've never had to. There is an old thread on this site, IIRC it shows part numbers and how-to.

FWIW my 96 will roll backwards on a hill or steep incline in D. Always has even with the race trans i put in awhile ago.
I think its because ours is vac controlled (vs 97+ electronically) and the line pressure isnt enough at idle when on a hill.

My 98 will do that as well. Think it has more to do with torque converter stall speed and converter efficiency at low engine RPM.

Thanks. My transmission is working just fine. Now I have a long list of things to work on. The only one that concerns me is the signature 70-80 mph vibration. But I will be replacing the struts and shock first to see where I sit with that problem afterwards.