Hard shift from 1st to 2nd and more

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pauly1119

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Servo is for 2nd AND 4th gear. Its sole purpose is to hold the 2-4 band against the sunshell to make it stationary shifting into 2nd and 4th. 1-2 hard shift only can be attributed almost all the time to a busted 1-2 shift accumulator spring and/or worn piston/guide pin. The hard quick shift hurts nothing other than your neck. In fact its better for the clutches and will make them last longer but who wants to be snapped backwards in their seat everytime there is 1-2 shift. The spring is almost always busted in half on every 4L60E that gets on a bench for rebuild.
Thanks for the info, I’ve done them on cars but never a truck. Weird it felt like 1st to 2nd was firmer as well. They even advertised it as 1st to 2nd as well. I agree on the shift accumulator, I figured try the servo before opening it up.
 

rockola1971

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Thanks for the info, I’ve done them on cars but never a truck. Weird it felt like 1st to 2nd was firmer as well. They even advertised it as 1st to 2nd as well. I agree on the shift accumulator, I figured try the servo before opening it up.
"1st to 2nd" is a 2nd gear shift. There is no automatic shift into 1st gear UNLESS we are talking about downshifting. So 2nd gear accumulator applies to 2nd gear and the 2-4 servo only applies to a shift into 2nd or 4th(OD) which of course would be shifting from 1st into 2nd and 3rd into 4th.
 

pauly1119

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If you plan on keeping the vehicle for some time then I would replace the wiring harness and ALL solenoids. The separator plate will be peened from check balls so it will need replaced. Both accumulator pistons should be replaced. All bores in the valve body need closely inspected along with their valves for wear and burrs, out of round, etc. Replaced as needed.
If you need to go the cheap route then just the accumulator pistons and separator plate. Getting to solenoids is easy enough if/when they die.
You might look up on rockauto a replacement valve body and price check.
What’s your opinion on changing it to a Sonnax version and removing the pin with the kit? Or just put the plastic OEM one back?
 

rockola1971

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What’s your opinion on changing it to a Sonnax version and removing the pin with the kit? Or just put the plastic OEM one back?
Its a common mod to block off accumulator by double stacking. In my experiece I just make sure a new aluminum one goes in during the rebuild. I would not reuse or use a plastic one. The plastic ones wear in the center on the guide pin and then the piston gets seized in the bore which is bad news and burnt up clutches.
 

NickTransmissions

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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.
 

pauly1119

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Thanks, Tom. Feel free to ask any additional questions here ill respond as soon as im able to.
I have a question, new thing just happen today. I feel it’s when I’m shifting from 2nd to 3rd and driving easy I get a RPM drop right at the shift. Drops to around mid 500 rpm’s and then corrects itself. Throttle body has new gaskets and a new position sensor installed a few weeks back and has been fine. Only happens at the shift.
 

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