Replacing the 1-2 Accumulator Spring/Piston - Chevy Impala SS Forum
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Old 08-19-2011, 08:46 AM
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Default Replacing the 1-2 Accumulator Spring/Piston

Early last month my transmission sprung a leak at the cooler line and I ended up running it low on fluid. I fixed the leak, flushed the fluid and all seemed well.
I've put about a thousand miles on the trans since then and over the last couple weeks I started noticing a delayed and soft 1-2 shift. This symptom was especially noticeable after i flushed the trans a second time earlier this week. All other shifts are relatively firm and quick, the 1-2 upshift seems to be the only problem.

All my research points to the 1-2 accumulator spring/piston assembly as the culprit. I found the following replacements from the Sonnax catalog.
Sonnax Pinless Accumulator Piston and Sonnax 1-2 Accumulator Spring
Are there any other parts needed?
From the diagrams it looks like an easy fix but I am a noob when it comes to transmissions so i gotta ask a few questions. I'm more worried about putting it back together than taking it apart. It looks like just two bolts holding the cover to the valve body. I don't have a tq wrench, can i just snug them and be safe?
Are there one or two springs in the piston assembly, the pic in the link looks like it has two springs on top of the piston?
The Sonnax instructions mention something about driving a checkball into the piston pinhole because the new one doesnt use a pin. Can someone elaborate on this?

All tips, comments, questions are welcome. Remember I've only been in the pan twice so I'm somewhat familiar, just need a little guidance.
Thanks in advance
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Old 08-19-2011, 06:35 PM
CapSS9C1 CapSS9C1 is offline
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The pinless pistons are good units but I recomment getting a replacement stock piston because they are known for wearing out where the pin goes thru them, transgo sells a good replacement piston, instead of using the stock piston seals get a set of viton seals, it includes all the piston seals and servo seals. Its a good idea also to replace the servo seals with these viton seals. ive seen a few trannies already having the same symptoms as yours and it turned out to be bad servo seals. The checkball theyre talking about replaces the pin in the accumulator housing so fluid dont piss out of the top of it. its simple just use a punch to pop out the pin thru the top, and press the ball in and stake the housing around the ball to hold it in. Transgo sells a sk4l60e or 4l60e hd2 shift kits that i highly recommend doing if your gonna go that far. providing your mechanical know how. its not bad to do. the hd2 kit comes with vb gaskets and all the springs and valves necessary to do the job. you will be very happy with it. how many miles on the tranny? feel free to ask more questions.

Ive come to learn a lot about the 4l60e lately because i went thru 3 trannies from an old vendor on this forum in 1 year, and decided to rebuild my own with a lot of upgraded parts and electronics, and so far so good with it.
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Old 08-21-2011, 08:08 PM
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Those two will likely be all you need. That said, what I've often seen is the yellow spring in the 1-2 accumulator cracks, unevenly loads the piston, then the piston cracks where the pin goes through and gets lodged in the bore. If the bore is scraped up, you'll need to buy another housing, but you can usually find those for $15 on ebay or at a local trans shop. A good used part is fine.

There are three 10mm bolts that hold the 1-2 accumulator housing against the spacer plate. Be very careful not to tear the paper gasket between the spacer plate and the accumulator - if you do, you will need to remove the valvebody to replace that gasket. Again, be very careful on that.

You might also consider doing the Sonnax 4L60E-HP-01 shift kit while you're in there. It's pricey, but it's well engineered and only a year old so the engineering is much more recent than the TransGo kits. I have personally talked with the designer of that kit and I'll just say he knows his stuff. It also includes pinless accumulator pistons and good seals for the servo.

Don't forget to read the sticky on "how to flush your fluid" and it'll show you a much cleaner way to drain your pan than the old "undo the bolts and let it all flow out one side" method.
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Old 08-23-2011, 09:27 PM
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Thanks for the info guys. I found a good price on the Sonnax kit and at this point I am seriously considering having a local shop do the shift kit. I'm not scared of the job but at the end of the day if i ****ed something up I don't know that I'd recognize it and I can't afford to be throwing parts at the car.
I'll keep y'all posted.
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Old 08-24-2011, 06:38 PM
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Had a local shop drop the pan and pull the 1-2 accumulator for me. For $50 out the door I figured it was well worth it.
Turns out it was NOT the accumulator piston/spring. The technician let me verify this myself. Both springs are intact and the piston is not cracked as Sherlock mentioned. As explained to me, it is likely that when i ran the unit low on fluid I burnt up the bands(apparently it doesn't take much to do this), and while the car is driveable I will eventually lose 2nd and 4th gear.
Looks like the SS will be hard parked until I come up with the money to rebuild it. Gotta pay to play I guess, and I didn't even break 13s lol
Thanks again to Sherlock and CapSS for your help.
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Old 08-25-2011, 06:30 PM
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Don't throw in the towel just yet... How's the 3-4 shift? Does it shift softly (nearly too unnoticeable)? Previous suggestions are good ones.

I see you're not overly confident in working on the trans, but you could take time to check the servo assemblies. Make sure the servo seals are in tact. If not, a leaking seal around the 2nd gear servo may result in lack of fluid holding pressure buildup between the 2nd servo & piston housing. Then... I would look at the reverse input drum, along with the 2-4 band. An aged reverse input drum will likely have grooves in it. With that, the 2-4 band will become worn. If memory serves, those drums can be had for ~$70. Just a thought...
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Old 08-26-2011, 05:45 PM
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3-4 shift is still firm. What is involved in checking the servo assemblies?
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Old 08-26-2011, 08:32 PM
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Quote:
Originally Posted by QwkWx3 View Post
3-4 shift is still firm. What is involved in checking the servo assemblies?
Snap/Retainer ring holding the assembly in needs to come off. From there, the entire setup can be pulled out.
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Old 09-01-2011, 07:10 AM
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Just going to take it in for a rebuild, I'll post pics of the damage once its apart.
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