Yukon Trans Problems

[Adios447]

Hi,

I have an '02 Yukon XL, 5.3, 2WD. The trans blew up (literally) at about 140K miles. I had a re-manufactured trans installed from what I thought was a reputable re-man shop. (not a dude working on his garage floor.) After the installation, the trans has always had a very hard 1-2 up-shift, but only when hot from driving at freeway speeds for 20 - 30 miles. After it cools down it shifts normally. Around town it runs and shifts smoothly. It coded P1870. The re-man company sent me a new valve body which I had installed and it still does the same hard 1-2 up-shift when hot.They then sent me another re-man transmission, complete with torque converter. I have not installed it yet since I'm not convinced that throwing another $500 at the problem to install it would fix it. The car now has about 160K. I just ordered a Transgo "4L60E 4L65E 1996-2006 1870 P1870 CODE BUSTER UPDATE KIT" shift kit that supposedly will fix the problem. Also, I now have a trans leak (drip) at the front of the case.
This is making me NUTSO please help!!!
--
Regards,
Randy Jacobs

 

[Tahoebigdog03]

Man I feel your pain my guy I just forked out 2100 for a fully rebuilt unit in my 03 Hoe. Search the forum I'm you will find so similar folk with the same problem.

 

[Adios447]

Another thought, since the trans only acts up when "warm" what if I lowered the temp by installing a 160 degree thermostat or an auxiliary transmission cooler??

Randy

 

[Rivieraracing]

When you say hot, are you referring to coolant temp or trans temp? Also, what temperature degree are we talking about for either?

 

[Adios447]

I'm not sure...but it only acts up after driving on the freeway for 20 - 30 minutes. I am assuming that by doing so, the trans is reaching full operating temp. My logic tells me it's a temp related issue. It I lowered the coolant temp, wouldn't that lower the trans temp, since the trans oil is cooled from the radiator?
It doesn't ever hard 1 - 2 up-shift during even extended around town driving.

I am assuming it has a standard 187 degree coolant thermostat, but the gauge reads 190 - 195 degrees. I don't have a trans oil temp gauge. Is there a convenient way to temporarily hook one up?

 

[afpj]

Our 02 yukon did the same thing last year with same code, got reman tranny and good now. I suspect your reman tranny has a bum component ( like TCC regulator or something). The following TSB, although for earlier models, I think is helpful (IIRC it was extended to include 2002 MY)

TSB # 01-07-30-023A
Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body)
1996 Buick Roadmaster
1996 Cadillac Fleetwood
1999-2000 Cadillac Escalade
1996-2000 Chevrolet Camaro, Corvette
1996-2000 Pontiac Firebird
1996-2000 Chevrolet and GMC Light Duty Truck Models
1996-2000 Oldsmobile Bravada
with 4L60-E Automatic Transmission (RPO M30)
Built Prior to January 15, 1999 (Julian Date 9015)
This bulletin is being revised to update the Parts Information.

Please discard Corporate Bulletin Number 01-07-30-023 (Section 07 -- Transmission/Transaxle).
Condition
Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated.
Diagnosis
Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs.
The scan tool may show a DTC P1870 set as a history code.
A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93°C (200°F).
Cause
The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply.

Important
DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code.
When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result.
This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle).

When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code.
When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL).
Correction
Install a control valve body with the revised TCC regulator and isolator valves. These valves are used in all transmissions produced after January 15, 1999 (Julian Date 9015), and all of the service parts currently available through GMSPO contain revised TCC regulator and isolator valves.

Important
If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body.
Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears).
The torque converter is not blue or overheated.
The transmission fluid is not burned or has no burned odor.
The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments

 

[Adios447]

Thanks for the info....interesting reading and also interesting how long GM has known about these problems and not taken adequate corrective / recall actions.