4L60E Hard shift 1-2, CEL light
Thread Starter
Intermediate
Joined: Jul 2023
Posts: 25
Likes: 0
4L60E Hard shift 1-2, CEL light
Hi guys, I recently swapped out my 2.73 rear gears for a 3.15. I took it to a tuner to have the speedo, and trans recalibrated for the new gears. The speedo works fine. The trans worked fine for a while, but now is shifting extremely hard between 1st and 2nd gear, and throws a CEL light, with the code of 10 PCM 1870. The gentleman told me that when he recalibrated the shift points, it may shift a little harder than I like, and to bring it back, if I didn't like it. Well, it was doing fine, but obviously, it's not now.
Is the tune on the trans wrong, or is this just a coincidence that my trans just started slipping now too? For reference, my car is a 99, with 111K miles. My regular mechanic cleared the code, and reset the PCM to "relearn" the way I drive. This worked great for 1 day. Now I am back to hard shifting, and CEL. My regular mechanic says I should start by flushing the trans, and putting new fluid, and filter in it, before any more drastic measures. I'm not sure which way to go from here. Is my trans toast? Should I go back to the tuner? Should I change the fluid and filter? Any helpful advice would be greatly appreciated.
Is the tune on the trans wrong, or is this just a coincidence that my trans just started slipping now too? For reference, my car is a 99, with 111K miles. My regular mechanic cleared the code, and reset the PCM to "relearn" the way I drive. This worked great for 1 day. Now I am back to hard shifting, and CEL. My regular mechanic says I should start by flushing the trans, and putting new fluid, and filter in it, before any more drastic measures. I'm not sure which way to go from here. Is my trans toast? Should I go back to the tuner? Should I change the fluid and filter? Any helpful advice would be greatly appreciated.
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It's tough to determine the cause, however with the recent tune and reprogramming, it could simply be a case of trying to teach an old dog new tricks. The trans has operated a certain way for it's entire life and now it's being told to shift differently based on the new tune and the new gear ratio. New fluid/filter would be the most cost effective action at this point, however it just may be timing due to the age of the trans.
Drifting
Joined: Jul 2004
Posts: 1,677
Likes: 691
From: Pingree Grove IL
I had a RPM 3.73 gear put in along with a 3200 stall. I did this 2 years ago and everything is still fine, my trans shifts fine. It shouldn’t shift hard, you need to find a different tuner, and have them change the fluid and filter. I wanted a shift kit in the 4L60, my tuner said not on a 20 year old trans, he wouldn’t do it, he said if the transmission shifts fine, leave it alone, all they did was adjust my shift points, they did not mess with the firmness of the shifts.
In all honesty, I’m the original owner of my 2004, and with autoX, drag strip, and HPDE, I’m surprised my trans is still intact. I’m prepared as far as funds for an RPM level 4 or 5 trans.
Go back to the tuner and tell him to put everything back to stock and just adjust the shift points.
In all honesty, I’m the original owner of my 2004, and with autoX, drag strip, and HPDE, I’m surprised my trans is still intact. I’m prepared as far as funds for an RPM level 4 or 5 trans.
Go back to the tuner and tell him to put everything back to stock and just adjust the shift points.
Thread Starter
Intermediate
Joined: Jul 2023
Posts: 25
Likes: 0
Thanks for the reply. I'm pretty sure that's all he did, was adjust the shift points. I have a call into the shop- It's a holiday week, so it may take a bit. I've read good and bad about this trans, but a lot of replies say the 4L60 E is actually pretty stout.
Burning Brakes
Joined: Jun 2022
Posts: 758
Likes: 366
So no change in line pressure ?
4l60e transmissions are not that strong and you may have had one going out that got finished off. Any converter slippage at lock up? You would need a way to check like HP tuners
4l60e transmissions are not that strong and you may have had one going out that got finished off. Any converter slippage at lock up? You would need a way to check like HP tuners
Safety Car
Joined: Aug 2011
Posts: 4,449
Likes: 409
From: Portland OR
P1870 thinks the trans is slipping. To compensate, the ecu cranks the trans pressure to max. Hence the now extra harsh 1-2 shift.
Clear the code and see how long it takes to come back.
Next question is the trans really slipping? Or maybe the trans tune is a bit off?
Clear the code and see how long it takes to come back.
Next question is the trans really slipping? Or maybe the trans tune is a bit off?
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