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Discussion Starter · #1 · (Edited)
As the subject states, my tranny seems to have a really harsh shift when cold (seems the colder it is outside, the harsher it is, even when barely pressing the gas).

Once warmed up, tranny acts normal and the only time it shifts harder 1-2 is at WOT (which is what I want, LOL). In fact, the 1-2 shifts are fairly smooth at part throttle even with the Hypertech firming up the shifts (moderate throttle it's firm, but not hard).

I've read about the 1-2 accumulator spring going bad but also setting a code p1870 which I never got (no SES light so I assume I don't have that code).

Can I assume that what I describe is normal? Or is trouble on its way (if so can I do something about it beforehand?)

EDIT -- Or could it be that the outside temp was so cold (just below freezing) the viscosity of the fluid was very thick and just needed to be warmed up?
 

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Discussion Starter · #3 · (Edited)
I haven't yet, probably won't get a chance until the next time I drive it (this isn't my daily).

Also what I mean by hard shifts -- it isn't delayed. It just feels really firm quick and more abrupt when cold (but it isn't jerking the car).

Does the SES light come on for P1870? Asking because I don't have one.
 

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Action Taken When the DTC Sets


  • The PCM inhibits TCC engagement.
  • The PCM commands maximum line pressure.
  • The PCM inhibits 4th gear if in hot mode.
  • The PCM freezes shift adapts from being updated.
  • The PCM illuminates the Malfunction Indicator Lamp (MIL) .
Yes. Low fluid can cause harsh shifts and when the fluid warms and expands, can dissipate that condition. That's why I suggested checking it first before going further.
 

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Is there anything done to the transmission (shift kit, rebuild, etc.), or is it just stock?

An 1870 would turn on the Check Engine Light, and would command max line pressure for the entire drive cycle; ie. it would not have harsh shifts only when cold.

A faulty 1-2 accumulator spring (springs, actually) would be unlikely unless it has a Transgo kit in it. But in either case, it would not be faulty when cold and then fix itself when it warms up.

It is possible that your accumulator pressure regulator valve is sticking in the open position when cold, and then regulating properly when things warm up. I would not consider this real likely as they usually just stick and stay stuck, but it is possible.

You could have a temp sensor issue that is causing the PCM to command excessively high line pressure until it warms up. Again, not super likely, but possible.

You could have an EPC solenoid sticking open when cold.

At this point, I would put a pressure gauge on it and see what it tells you...
 

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Discussion Starter · #6 · (Edited)
The transmission is bone stock (with hypertech firming up the shifts). Has not been rebuilt (only 36000 miles). Has been serviced with a new filter at 30000 miles back in 2011 (harsh cold 1-2 shifts existed before the service as well). I think they even used dexron 6 last time.

Haven't checked the fluid level yet..
 

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Discussion Starter · #7 ·
Quick question about my "transmission service" line item from my 2011 Bill (shame on me for not asking the dealer at the time)...

If I see "trans flush kit" and "qty 12" of fluid, does that mean it was "flushed"? Asking because at the time I actually did not request a flush but did ask them to change the filter. Cost was also $250 for everything including filter (before tax).
 

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Discussion Starter · #9 · (Edited)
Thanks, I thought so since I believe 5-6 quarts would be lost/replaced from dropping the pan. Which actually makes me feel better since then the transmission service before that was just a flush w/o filter change at a quick lube (I know.....what was I thinking). At least now I have all dex6 fluid (no idea what was used at the quick lube).
 

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Discussion Starter · #10 ·
Tried checking it while warm and idling, seemed to be a bit overfilled on the dipstick (hard to tell if it was soaked by the residual fluid on the tube or something). Last time my fluid was low it shifted too soft (this was going back 10 years or so). Fluid is nice and red.
 
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