Jump to content
CaddyInfo Cadillac Forum

1989 SdV - Transmission Oddity


Recommended Posts

Hello All,

Since getting my '89 SdV at the start of this year I have been loving it, and still do. As time has gone by, however, I've noticed a very specific quirk in how the transmission is behaving and I don't know whether what's going on is indicative of "a small problem" or impending transmission failure.

When the car is under acceleration at low speed or cruising along at highway speeds everything is silky smooth. The issue only occurs when I'm going up a grade and am traveling under 25 MPH.

If I'm traveling up a grade at relatively low speed when the car tries to downshift (or at least I believe it's downshifting) the shift itself seems to go into "slow motion." You can hear the engine rev higher and then the transmission engages, giving me a pronounced "clunk". This is not a massive slamming sensation or loud noise, but you know that the transmission has disengaged, allowed the engine to speed up, and reengaged. I have been able to induce this behavior, at least sometimes, by taking my foot off the gas when coming up my street and am very nearly at the top then hitting the gas again (and not flooring it, just gently pushing on the accelerator to where it had been). I'm typically doing no more than 15-20 MPH at this point. It also happened the other night when I encountered a steep grade in fairly heavy traffic and had to take my foot off the gas.

I don't think any damage is being done, but I also know this is not how "things are supposed to be." So far, in all other respects, the car is behaving flawlessly. I have yet to find an accessory or option that is not working as it did when it left the factory. The prior owners appear to have been quite fastidious in its care.

Any theories as to what would cause this very specific behavior?

Brian

Brian

Forums_Pic.jpg

Bri the Tech Guy   http://britechguy.com
britechguy@gmail.com   (540) 324-5032
"If it's got you screaming, I'll help you stop!!"
Link to comment
Share on other sites


First things first; have you checked the transmission fluid level? Low level can introduce air into the system and possibly produce the symptoms you describe.

Chuck

'17 XT5, '04 Bravada........but still lusting for that '69 Z-28

Link to comment
Share on other sites

And too much fluid will cause foaming. If you have not done so, I would drain the fluid, and add Dexron VI. A little fresh fluid can bring some life back to the seals, and valves, and some of the inherent improvements in the improved formulation might be an added benefit as well.

DO NOT HAVE A TRANSMISSION SHOP PERFORM A FLUSH.

Link to comment
Share on other sites

Gentlemen,

Thanks for your input. The transmission fluid level is correct, or was when I last checked. One of the first things I did after acquiring the car was to have the transmission serviced and the fluid changed. That was on January 9th.

The shop I used does not believe in doing power flushing. The transmission pan is simply dropped, emptied and cleaned up and a new filter installed. Fluid is then added to bring things back to the correct level after the pan is put back on with a new gasket. My invoice indicates that 6 quarts of Dexron were used. I am fairly certain that the fluid used would conform to the Dexron-III specification (regular petroleum base) rather than the Dexron-VI specification, which has a synthetic base.

Brian

Brian

Forums_Pic.jpg

Bri the Tech Guy   http://britechguy.com
britechguy@gmail.com   (540) 324-5032
"If it's got you screaming, I'll help you stop!!"
Link to comment
Share on other sites

  • 2 weeks later...

There is no such thing as Dexron III anymore; GM recommends Dexron VI for nearly all automatic transmissions. It's possible that your shop has a supply of something offered as Dexron III compatible, but GM no longer licenses Dexron III or certifies that any product meets its standards and does not allow the label Dexron III to be used on new products.

There is a gear oil for some transfer cases and other such that used Dexron III and are not best served with Dexron VI; I don't recall what the name for that fluid is. If you *really* want to use Dexron III, you can use that.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Link to comment
Share on other sites

Jim,

I've been away for a few days. I realize that GM no longer licenses to the Dexron III specification, but there are *lots* of fluid makers that make fluids that are compatible with the Dexron III spec, and that's what I meant. Whether or not GM officially licenses to that spec many products that meet that specification still make reference to it (usually with a little proviso somewhere noting that GM no longer officially licenses/endorses it).

As of yet, I don't have any definitive diagnosis on my issue. It occurs within a very specific speed range, 18-20 MPH, only going up a grade, and only when the accelerator is backed off on and the car needs to shift. In all other circumstances things are very smooth.

Brian

Brian

Forums_Pic.jpg

Bri the Tech Guy   http://britechguy.com
britechguy@gmail.com   (540) 324-5032
"If it's got you screaming, I'll help you stop!!"
Link to comment
Share on other sites

Still just guessing here, but did the symptoms start after the tranny service; if so, maybe the filter wasn't inserted properly (completely), and again, maybe some air getting into the system (at angles).

Chuck

'17 XT5, '04 Bravada........but still lusting for that '69 Z-28

Link to comment
Share on other sites

barczy01,

This never happens around corners or turns, or at least I can't feel it if it does.

I can't say I'm noticing a slip (although I'm guessing what one would feel like, as I've never had one in my cars). It does have the quality of feeling like you've shifted into neutral, very briefly. I think this is always going from second back into first, as it always happens at low speed, when going up an incline, and when you're easing off the gas. I've now noticed that it tends to be at 18 or 19 MPH when this occurs. There's no nasty loud thud or lurch when the transmission reengages, but you definitely have a second to a second and a half where it seems like you're in neutral before the shift decides to complete.

Brian

Brian

Forums_Pic.jpg

Bri the Tech Guy   http://britechguy.com
britechguy@gmail.com   (540) 324-5032
"If it's got you screaming, I'll help you stop!!"
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...