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Human

'95 CS convertible fails to upshift in turns

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Human

So I took my '95 Cutlass Supreme convertible (3.1L automatic) out for a drive this evening and noticed an exceedingly odd behavior. After making a turn, left or right, the transmission would fail to upshift and just keep winding up the RPMs until I would take my foot off the gas. At that point, I would feel it shift and it would be back to normal until the next turn. The first couple of times, it caught me off guard and the engine would get up to almost 5,000 RPMs in about three seconds. After that, I recognized a pattern and would react more quickly. Otherwise, the transmission shifts smooth as silk. The car has a touch under 125,000 miles on it and my understanding is the transmission was rebuilt at around 90,000 miles. It was dark when I got home but I'll check the trans fluid tomorrow.

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Human

I checked the ATF a little while ago after cranking the engine and letting it run for a minute. The fluid level reads dead in the middle of the crosshatched safe zone on the dip stick. Of all the different fluids and additives I have on hand, ATF fluid isn't among them so I'll pick some up next time I'm out (too blasted hot this afternoon) and top it off, although it doesn't seem like it really needs it. 

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Schurkey
55 minutes ago, Human said:

I checked the ATF a little while ago after cranking the engine and letting it run for a minute. The fluid level reads dead in the middle of the crosshatched safe zone on the dip stick.

How hot is the transmission when it's been run for "a minute"?

Sounds to me like it's OVERfilled now.

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Human

The transmission was probably no hotter than the ambient air (~95 degrees F) and certainly cooler than if I had driven the car around for a few minutes. I've had the car for almost two years and have never added any ATF. Yesterday was the first time it had acted up.

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Schurkey

I'd change fluid and filter, and see what happens.

When I say I'd change fluid, I mean ALL the fluid, by draining the pan via the trans cooler return tube, with the engine running.  Use a drain pan that will hold the entire contents of the transmission, plus a few quarts.  As soon as the trans pan empties, shut off engine, remove trans pan, inspect for debris, clean trans pan and gasket surface on the case, replace filter, install pan and ~5 qts fluid, then have a helper start the engine while you add more fluid and watch the fluid spewing into the drain pan.  When the fluid coming out of the return tube is virgin-pure, reinstall tube, top off fluid as needed.   You'll need to buy enough fluid for the entire capacity of the transmission, plus some additional.

Fluid level needs to be checked with the trans at normal operating temperature, and after running the shifter through the gears and then back into Park or Neutral.

Edited by Schurkey

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Cutlass350

You have the predecessor to my 4T65E tranny. You have an 4T60E tranny.
But, unlike on my 4T65E tranny, it doesn't seem like the accumulators on a 4T60E are a known wear problem.

It seems like the vacuum modulator is a wear item, and can cause similar issues to what you're having.
The good thing is that it's not very hard, nor very expensive to change.
So, it may be worth a try.

Otherwise, imho, you should see what the error codes are, and then go from there. But, few scanners can read the tranny error codes. My guess is that you'd need a Tech-II?


https://www.amazon.com/Fram-FM2333-FRAM-Transmission-Modulator/dp/B000C2ZJ7U

61Zax3jPjHL._AC_SX569_.jpg

FRAM 2333 Transmission Modulator
Price: $24.66

 

 

 

Transmission modulator replacement (early GM 4T60-E models)
Feb 17, 2015
Mr10Alpine

 

Good Luck!

Edited by Cutlass350

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Human

This has been a hellishly busy week that's also been blisteringly hot outside so the 'vert has stayed under the carport until this afternoon, when the highs only topped out in the upper 80s and the humidity was bearable. But having posted my final summer school grades (I'm a community college professor), I decided to take the car out for a brief drive and at first, it was doing fine but as the transmission got hotter, it started delaying that first shift again until almost 4,000 RPMs. After about half an hour, I pulled back into the driveway and checked the transmission fluid. Whaddyaknow! It's down just into the "add a pint" range. I guess I'll put that fluid on my shopping list and maybe a new modulator as well.

Cutlass350: Thanks for the video. That procedure doesn't look bad at all. It's surprising that the new modulator was so much smaller than the one it replaced.

UPDATE: So a few minutes after I posted the above, I watched the video again and then grabbed a flashlight and took a peek under the hood. I was very surprised to find that I have the old style modulator and it looks pretty gnarly. I'm really surprised it wasn't replaced when the transmission was rebuilt. It would seem to make sense to put that on the shopping list as well.

Edited by Human

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Cutlass350

Fwiw, that symptom sounds similar to the upshift problem I had with the worn accumulator pistons on my 4T65E.
I found put that my 4T65E tranny is also sometimes called a 4T60E tranny.  It's the "third" generation of that platform.  Your car has the "second generation" of that platform.

Initially, I thought that I was going to need a new tranny.  :-(
About 100K miles ago, I got a 100% brand new tranny from GM.  I even had a GM dealer install it.  I was very happy that still GM had them, and was selling them at a low-cost (to get rid of them :)).

 

When I started having upshift problems, I  did the change tranny fluid.
That helped for ~9 months.  Not bad.
But then, as the weather got hotter, the tranny upshift problems came back, then got worse.

One of the semi-scams/jokes is that there's a "shift kit" that is sold (with stiffer springs only), to cure the upshift problem on the 4T65E trannys.
BUT, it costs more that 100% brand new - from GM - accumulator pistons.
The accumulator pistons are what mainly wear.  The wear on the accumulator pistons is visible and measurable.

However, I don't know how much wear the bores have, compared to new.  So, maybe new accumulator pistons in old bores may last only ?~50K miles?.  So, for the ?$45? shift kit springs, and not worrying about this after the next 100K+ miles, I also put in the shift kit.  :-)

Regardless, my tranny shifts fine now.
Because of the shift kit, the tranny does shift a little firmer than pillow-soft stock shifting .  But, I no longer notice it, nor care.  :)


Good Luck!

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Human

While I was out running errands today, I picked up a quart of the proper grade of ATF and added half of it to the convertible's transmission to make up the pint deficit. That seems to have solved the problem for now. Instead of making the first shift at around 4,200 RPMs, it now does so at around 2,800 and now I hear the shifts more than I feel them. I also found a modulator at Amazon, I guess it was a return, for a shade under $7 shipped, so that will arrive on Wednesday. I'll put it on the next reasonably cool day we have. 

UPDATE: Forgot to mention that in addition to shifting more smoothly, it also seems to have addressed another issue I was having with excessive play in the shift lever where I'd think I was in drive but would actually be in third and have to nudge the stick ever so slightly forward to get it to click into drive.

Edited by Human

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Human

The modulator arrived a little while ago but I was stymied by the 13mm nut holding the original modulator in place. It is stuck but good. I messed with it for about 45 minutes, spraying tons of penetrating lube on it and trying every 13mm wrench I could get my hands on but it simply wouldn't budge. I eventually decided it was time to cut my losses, call it an afternoon, come inside and cool down. I figured that since the existing modulator seemed to be working and adding ATF seemed to solve the immediate problem, I'd just scratch that off of my list of things to obsess over and put the new modulator in the trunk until it's truly needed--or at least until the weather is a good 20-30 degrees cooler.

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rich_e777

As your attorney I would advise you to replace the vacuum hose to the modulator as well, maybe even give that a shot before replacing the component. You might try adding some heat to the area around that bolt to get it to loosen up too, or a 6ft piece of metal pipe around your wrench.

Sometimes you can use an additional combo wrench of a similar size to use as a breaker bar as well, old mechanic trick thats hands down guaranteed to either bust the bolt/nut loose or bust your knuckle against something hard. Or punch yourself in the face, I`ll never forget when I did that to myself. I was so pissed off and had no one to hit back. Still looking for that 3/4 combo in the woods too.

 

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Human

I took the 'vert out for a sunset run this evening and it's never run better. Shifting is so smooth, I can hardly feel it, even though I can hear it and see the evidence of it on the tachometer. Even though I didn't replace the vacuum line to the modulator—it still has the original hard line—I must have gotten it seated better than it had been when I buttoned things back up after this afternoon's aborted attempt to replace it. At this point, I'm quite content to let things ride, no pun intended.

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