Hello all,
I have about 210k miles on this 2003 Tahoe LT with the 5.3L engine. I have a hard shift from 1st to 2nd. There is a lot of info out there regarding this known issue that arises over time. But I am by no means understanding how these trannys work. I am going to drop the pan and when I do, I want to change solenoids as well as the accumulator and anything else you guys deem necessary. But I haven't been able to figure what is what under there. Can someone who understands this tranny give me a parts list comprehensive so I can order it all and get it done. Been staring at this for about 2 weeks and a bit confused. For instance some say to change out the accumulator, but it appears you can only by the shell and you have to but the innards separately. Is this what I should do?
In essence, I want to replace anything I can while down there so this will last another 200k miles. I have replaced the oil on this tranny 7 times since purchased so it has been taken care of well. Any help would be a treasure for me. Thank you!
Your hard 1-2 shift can be anything from broken 1-2 accumulator springs, 1-2 check ball stuck in the plate to the TCC regulator bore in the valve body or an excessively worn rear stator bushing on the pump.
1-2 Accumulator: To check the accumulator, remove the three 10mm bolts to drop the 1-2 accumulator housing then put a little compressed air in the feed port to remove the piston - if it's plastic, replace w/an aluminum piston and new o-ring.
Valve Body: Scan your PCM for DTC P1870. If that code is stored then you have either an excessively worn TCC regulator bore in the valve body (not as common on 01+ as it was on 96-2000 VBs), torque converter or worn pump stator bushings. You can also test the TCC bore if you have a Sonnax vacuum test kit and air pump but if not, no need to sweat it. Just install the replacement
Fitzall TCC Valve to fix the issue. This converts your PWM TCC apply strategy to an on-off which is healthier for your converter clutch.
Spacer Plate: Check the plate for check ball peening and repair the plate w/the Fizall repair kit (one kit will repair one entire plate or multiple plates if only the 1-2 check ball location is excessively worn). Pull the VB off, then the low-reverse hold down plate to remove the spacer plate and gaskets...when you drop the VB, 7 check balls will be in their locations on the plate-facing side of the valve body if you carefully lower it down without tilting it too much...that said, don't worry if you drop one or more of them as the locations are obvious when you look at the other side of the valve body. Repair the plate using the
Fitzall spacer plate repair kit.
- I suggest installing
Transgo's SK4L60E shift kit while you're at it will address some of these issues and give you a bit crisper shifts at acceleration (and maybe Sonnax's O-ring boost valve kit as well and use the Sonnax Outer PR spring and stock inner spring instead of the orange Transgo PR springs)
Pump Stator Bushings: In some extreme cases, harsh 1-2 upshift can be caused by worn pump stator bushings, ive seen it a few times...If the other remedies don't work (and you have P1870) then this may be the cause...R/R pump, replace bushings or replace w/remain pump then reinstall and reinstall trans/converter.
Solenoids: Replace all of them and the harness while you're at it as well as both VB gaskets. Also, put a Sonnax pinless accumulator piston in the 3-4 accumulator piston location (or at the very least, replace the existing piston w/a new one as they like to wear and cause leaks in the 4th apply circuit, stressing / burning the band.)
Reinstallation: Torque all valve body and the three 8mm reverse hold down plate bolts to 104 inch lbs...Make sure you put the three longer 8mm valve body to case bolts back in their respective locations and not anywhere else (putting them else where may lock up the sun shell which means no reverse, 2nd or 4th and case/internal hard part damage). Pan bolts get 98-100 inch lbs and go around 3-4 times to fully compress the gasket or leaks may occur at the pan.
Let me know if you need any more details/clarification on any of the above.
