Overdrive shift too soon or late

Tiny
KCAUTO
  • MEMBER
  • 1989 CHEVROLET CAPRICE
  • V8
  • 2WD
  • AUTOMATIC
  • 113,000 MILES
305 engine with a 200 transmission? Throttle is working fine and adjusted. Forty to forty five mph overdrive shifts in-out depending on conditions. Highway or short city, no problems. Seems overdrive wants to shift too soon and causes a jerking or lugging like it is trying to stall? I was told there is an electronic module on the transmission itself that can fix this? Is that true? If not help please.
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Friday, March 6th, 2009 AT 5:29 PM

9 Replies

Tiny
JAMES W.
  • MEMBER
I checked two different sources just to make sure, but the only electronic control on your transmission (TH200R4) is the lockup of the torque converter clutch. The only adjustment on shifting points is the control cable, and I remember from experience, they can be a bugger to get set right. Even half a click on the cable can make a difference. Sometimes the cables get st reached just enough that one click either way is either too much, or not enough. Hope this helps.
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Saturday, March 7th, 2009 AT 9:18 PM
Tiny
KCAUTO
  • MEMBER
Thank you James for the reply. I have had those shift points adjusted and the car really does extremely well all the way up to sixty to seventy "if I keep the accelerator going". It is when I am traveling forty to forty five steady either flat or up hill and the overdrive wants to jump back and forth into gear. A letup on the pedal or a tap either direction and it shifts into or out of but with a tug or sort.
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Sunday, March 8th, 2009 AT 4:32 PM
Tiny
KCAUTO
  • MEMBER
One last thing, I have read about the "Check Engine light issue" on code 12 and how that relates? Is this a factor also in this puzzle? The light comes on about once a day and then goes out till the car sits a long period of time and re-warms up.
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Sunday, March 8th, 2009 AT 4:35 PM
Tiny
JAMES W.
  • MEMBER
The code 12 will flash three times and then flash any stored trouble codes. All code 12 means is that the ECM is in diagnostic mode. If you are driving down the road, and the CE light comes on, what ever made it come should be stored as a code.
On your transmission, this up/down overdrive shift problem was very common in the 200 and 700R4 transmissions. If I remember correctly, there was a replacement valve and spring kit available to solve or lessen this problem. You may want to check on this at your local transmission service shop.
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Sunday, March 8th, 2009 AT 6:53 PM
Tiny
STOWER17
  • MEMBER
I have a 1989 Caprice that had the same transmission problems. It felt like the overdrive would engage too soon and start making a clanking sound and would be under powered. I took it to a transmission shop and they told me it was a switch that engages the lockup torque converter and that it was a very common problem with these transmissions. Runs great again and fairly inexpensive to replace.
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Wednesday, April 22nd, 2009 AT 10:50 AM
Tiny
JERRY CHASE
  • MEMBER
The real problem with my 1989 Chevrolet Caprice is no engine braking in overdrive, but there is in direct drive. I am told that such is controlled by the car's on board computer. Can my on board computer be safely modified to allow engine braking in overdrive, like there is in direct drive?
Does the lock-up torque converter only work in overdrive?
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Saturday, May 26th, 2018 AT 8:22 PM
Tiny
KEN
  • ADMIN
The transmission does slow the car naturally you must have a sprag inside the transmission that has gone out.
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Sunday, May 27th, 2018 AT 12:15 PM
Tiny
JERRY CHASE
  • MEMBER
Ken, my car does slow down when off the gas in direct drive but hardly, if at all, in overdrive. Thus, unless there are separate sprags in direct vs. Overdrive, this does not seem correct. Also, I had the transmission re-built by the premier older-car transmission man in New England, Steve Peluso, in July, 15, with only 77,400 miles on it because the shifting became erratic when fully warmed, like the clutch needed to be pushed down when in a manual transmission when slowing to a stop. That problem was solved and corrected. But I still do not like the extremely limited engine braking when in overdrive. I will be bringing the car back to said transmission man for a re-check, though I expect that he will say that it is functioning normally, and as designed &and engineered. Since the car does slow down properly in direct drive, then that suggests to me that the on-board computer tells the transmission something different when in overdrive vs. Direct. And if it is the car's ECU controlling it, can that be safely modified such that the proper slowing down in direct could also be established when in overdrive?

When the car is driven normally and in overdrive, it almost feels like there is a large dashpot, or hydraulic door-closing mechanism, on the natural return to normal idle speed of the engine, this process being delayed by this "mechanism", which I suspect is part of emissions equipment, because we know the allegation that emissions are greatest when intake manifold vacuum is high, such as when decelerating.

Also, is there an outside electrical switch on the transmission that controls the lock-up torque converter? Do I have a problem with this switch or do I have a problem with the car's on board computer?

And, for the record, I never get a "check engine" light coming on. I never have in the whole ten years that I have owned it.
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Sunday, May 27th, 2018 AT 5:46 PM
Tiny
KEN
  • ADMIN
Does the check engine light come on when the key is on engine not running? I do not think this is a computer problem it is going to be a transmission issue. Can I ask if you had this problem before the rebuild and if not how long after did the transmission start doing this?
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Monday, May 28th, 2018 AT 9:54 AM

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