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'95 CS convertible fails to upshift in turns


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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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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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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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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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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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Posted (edited)

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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Posted (edited)

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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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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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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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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  • 1 month later...

This morning was nice and cool so I decided it would be pleasant to take my '95 Olds Cutlass Supreme convertible (3100 V6 automatic) out for a little ride. It was indeed very pleasant until I got about three miles from my house and suddenly it acted like it was in neutral, regardless of where I put the gear selector. I am totally puzzled by this since it happened suddenly, without warning and with no bad noises. One minute it was driving fine, then I stopped for a red light and when it turned green, the car coasted forward because it was facing downhill but was otherwise acting like it wasn't in gear. All I can say is thank goodness for AAA. The tow truck got there in about 10 minutes and amazingly, he was able to get the car up onto the rollback under its own power but he said he had to put it all the way down into low gear because "it just wasn't pullin'". I had him take it to a nearby transmission shop that's been in business since the late '50s, according to their sign. I guess it'll be Tuesday before I can find out what went wrong.

I don't know why the universe hates me so much this week. I had to replace the HVAC system in my house, then I had to replace most of the A/C system in my Buick LaCrosse, and now this. When will it end?!?

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Bummer!
I'm sorry to hear that.  :(

Wish I had good news.  But, it sounds like one of the bands went.
A used tranny may make sense, depending on the overall condition of the car, and how long you plan/hope to have it.

Fwiw, a similar thing happened to my 2000 Intrigue.
It was driving fine.  I pulled into a car wash, came to a complete stopped to turn left, and ..... barely anything at all.  The car was barely able to get to the side.  The car/tranny had ~~90K miles on it.

This was many years ago.  I had the car taken to a dealer, and thankfully there were still 100% brand new trannys available from GM at the time.
That tranny now has ~150K miles on it.  It had that bad hard-shift for a while.  Otherwise, cross-my-fingers, it has otherwise been okay.
I've changed the fluid at least once every 50K miles, with GM fluid - bought from a GM dealer.
There are a ton of counterfeit products out there.  Tranny fluid is super simple to counterfeit.  Just make a similar bottle, then put the cheapest cr*p tranny fluid possible in it - sell for a massive profit.
 

Good luck.
 

Edited by Cutlass350
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digitaloutsider

This is an extremely common failure mode for 4T60s and 4T65Es. Both the 4T60 and 65 can chew up forward apply bands, it's VERY common on 65s, and I've had probably three fail this way over the years. The 65 can also have no forward movement due to a worn input clutch piston. It likely has nothing to do with the quality of fluid and most everything to do with the fact that GM sucked at building transmissions in the 90s. Seal failures, apply pistons literally boring out the valve body, shitty solenoids, etc. The list goes on and on. There's a reason why Sonnax makes so many 4T60/4T65E aftermarket parts which are specifically made to fix design deficiencies in the original GM product. 

I frankly never realized just how poorly the stock transmissions function until I had Dave at TEP do my rebuild. 

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Yeah, the 'vert has 125,000 miles on it and the tranny was rebuilt at around 90,000 miles, according to the person I bought it from two years ago. I've put just over 5,000 on it since I've had it. I'd like to continue to enjoy the car for awhile but we'll just have to see what it's going to cost. I don't know how much more my wallet can endure right now.

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I talked with the transmission shop late yesterday afternoon and it needs another rebuild. How many times can a transmission be rebuilt before it needs to be junked and replaced? The cost will be somewhere between $1,600 and $1,900, depending on what they find when they get inside it and it will have a three year / 30,000 mile warranty. This has been one helluva triple-whammy between my home HVAC system, the Buick's A/C system and now this. My bank account is taking about a $10,000 hit in the space of two weeks. I guess my next decision when I get the car back is going going to be whether to go ahead and get it inspected and renew the registration to keep it or cut my losses and sell it on to someone else.

Edited by Human
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On 9/9/2020 at 10:33 AM, Human said:

I talked with the transmission shop late yesterday afternoon and it needs another rebuild. How many times can a transmission be rebuilt before it needs to be junked and replaced? The cost will be somewhere between $1,600 and $1,900, depending on what they find when they get inside it and it will have a three year / 30,000 mile warranty.

Repeat failures point to improper rebuilds, or operator abuse/error.

The TH700R-4 in my '88 K1500 pickup cost $2600 to rebuild a month or so ago.  I'd have expected a FWD vehicle to be more expensive, not less.

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I can't speak to the former owner's driving habits but I'm a pretty non-aggressive driver and have been fairly gentle with the car for the 5,000 or so miles I've added to the odometer over the past two years that I've owned it. That said, there's always been a little slop in the shift lever such that when putting it into 'Drive' it would often slip instead into Third, even though the gear indicator was clearly on the "D'. A very gentle nudge on the shift lever would click it into 'Drive' without the indicator registering any change. I may have inadvertently put some strain on the transmission on those occasions when I failed to notice that right away but neither will I completely rule out a subpar rebuild several years before I bought it. Hopefully, the shop that has it now will do a better job.

Edited by Human
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I just got off the phone with the guy at the transmission shop and he said they had to order a core unit for it, which I guess means the transmission was so far gone it was better to get another transmission and rebuild that to put in it. Not looking good for the bottom line. He said the core should be in on Monday and the car would be ready midweek.

Edited by Human
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That doesn't make sense to me, they're rebuilding YOUR transmission. Shouldn't need a core. If your current trans was so far gone then they would be ordering a replacement. Maybe they had a rebuilt unit at another location and are using it instead to get you fixed up quicker.

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I agree. To my understanding, a "core" is a bad part that's been removed from the car and then usually sent off to be rebuilt or recycled. Once a part has been rebuilt, it's no longer considered a core but is then a re-manufactured part. It would seem like kind of a crap shoot to acquire another transmission to rebuild in place of mine unless, as you say, mine was too far gone to be rebuilt. This scenario has some plausibility since my transmission had already been rebuilt once.  From a time and labor standpoint, I can see where replacing it with an already rebuilt one would seem to make a certain amount of sense. Less time and thus lower labor cost would at least somewhat offset the cost of rebuilding the unit in house and allow them to move more cars through the shop each week. I'll be interested to see what they have to say when I pick the car up in a day or two.

Whatever broke on my transmission broke pretty much instantly and silently because the car was driving fine, shifting smoothly--and then it suddenly wasn't. There were no grinding noises or anything to make me suspect something was wrong when I came I came to a stop. But when I went to pull away from the stoplight, there was simply no power to the wheels, as though the car were in neutral.

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When my TH700 died, it had run perfectly normal until I shut it off at a gas station.  When I restarted, I had nothing but neutrals--no forward, no reverse, and no clue as to "why".

Best I can tell, the filter plugged from all the debris of a failing 2--4 band, and planetary gears ground to dust.

Needing a different core points to a catastrophic failure that damaged the case, or so much of the internals that the core cost less than all the needed "hard parts".

Or they're just scared of your repeat failure, and they don't want to take a chance on some oddball problem that would take time, money, effort, and enthusiasm to find and correct.

 

Tell them you want your broken transmission returned to you.  You can take it apart at your leisure, see what the guts look like, and maybe even have some fun in the process--since there's no reason to get it returned to functional condition when you're done.

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That's an interesting idea but I have neither the time, facilities nor expertise to tear the dead transmission apart. That said, I do plan to ask to see it, if they haven't already scrapped it. I'm hoping to hear from them today that they have it ready to go.

Even though my technical knowledge of transmissions is next to nothing, I have to agree with the wisdom of starting over with a different donor transmission, given the history of mine, even though it is a bit of a crap shoot whether the new one will last any better than this one has. Hopefully, it will.

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