Differential swap causing p1870??
Thread Starter
Drifting
Joined: Jun 2004
Posts: 1,483
Likes: 0
From: St. louis, Missouri
Differential swap causing p1870??
I went from factory 3.15 to 3.42(some of you know this). Anyway Driving a few days ago on the interstate, cruising at 70mph, MIL light comes on, scan it, P1870 Transmission Component Slipping. Again some of you know I went though and beefed up the internals and swapped to a 3.42 rear.
So I read on Mike Mercury's site that since RPMs have increased so has slippage.
Now, GM states that factory spec Torque Converter slippage is -25 to +50 rpms, w/ factory converter and either 2.73 or 3.15. Since the 3.42 are not optioned w/ A4.
Running 3.42, is there anyway to bring down the TCC slip w/ a reprogram? I'm seeing 110-130rpm slippage at 70mph As of now, I have not had the car programmed since the upgrades.
So I read on Mike Mercury's site that since RPMs have increased so has slippage.
Now, GM states that factory spec Torque Converter slippage is -25 to +50 rpms, w/ factory converter and either 2.73 or 3.15. Since the 3.42 are not optioned w/ A4.
Running 3.42, is there anyway to bring down the TCC slip w/ a reprogram? I'm seeing 110-130rpm slippage at 70mph As of now, I have not had the car programmed since the upgrades.
Team Owner
Joined: Apr 2001
Posts: 54,204
Likes: 180
From: S.W. Ohio. . . . . . NRA Life Member
So I read on Mike Mercury's site that since RPMs have increased so has slippage
actually the amount of "slip" with the converter locked has not changed; but there is a perceived slippage increase.
The PCM looks at engine RPM and MPH with the converter locked; then compares this to "slip table" values.
Even if there were zero rpm of slip; the BCM sees an increased RPM (when compared to the cars MPH) due to your rear axle ratio upgrade. The P1870 is set; but it's from a false-report of slippage. The reprogram that you need will readjust this "slip table" to include the up-to-date (higher) RPM values for the MPH traveled with your new ratio (and there's other reprog tricks that can give the same result).
Either way; you'll need a reprog. For the time being, you can clear the code and drive with the shifter in "3" . This should stop the P1870 code from being set.
Team Owner
Joined: Apr 2001
Posts: 54,204
Likes: 180
From: S.W. Ohio. . . . . . NRA Life Member
there's a few forum vendors advertising $99 mail-in tunes; but you hafta be without your PCM module for whatever time it takes.
Last edited by Mike Mercury; Jan 12, 2008 at 12:58 PM.
Thread Starter
Drifting
Joined: Jun 2004
Posts: 1,483
Likes: 0
From: St. louis, Missouri
So on a reprogram, what tables do they have to change? I'm going to my tuner on Sat. to get it adjusted, but was curious on what needs changed.
He uses HPtuners. Any problem w/ that?
He uses HPtuners. Any problem w/ that?
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Safety Car
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From: You can't get there from here NJ
St. Jude Donor '08-'09
ECS just did a 3.42 swap for me and a tune. However, I get that code every once in a while, but I clear the codes, and it eliminates the hard shift I get from 1st to 2nd. They are going to go over it again to correct it for me. I only had the gears done last week, so I will bring it back, and according to them, the re-tune will correct this.
