RedRocketZ28

iTrader: (19)

First off, this is in my 2004 Buick Rainier 5.3. When I purchased the vehicle a year ago it had the normal 1-2 shift-bang and was very soft. I have HPTuners and bumped up shift pressure a bit, and decreased shift time slightly, as well as took out some torque management. This seemed to help a bit but the 1-2 shift is extremely hard (cringe worthy) at part throttle at times and will sometimes shudder on the shift. I have tried messing with pressure and shift times to no avail really. I have not dropped the pan and taken a look at the fluid...yet, but if I am going to do that I want to replace some of the common easily accessible parts that I have read relieve these symptoms.

Forgive me for this next part, but I am not transmission savvy. I have installed a couple of HD-2's in some 80e's, and I can easily follow directions with success. With that being said, will simply installing a new 1-2 accumulator piston alleviate some of these issues? I have come across two different Sonnax part numbers put not sure which one is actually needed. I understand that one can be installed without removing the valve body, but want to make sure I am replacing the correct parts.



The transmission shifts great at anything above part throttle in all gears, and the 1-2 at WOT is quick and seamless after tuning it. I am just looking to hopefully get two years or so out of the trans as I plan on getting rid of it sometime in the near future. The trans currently has 105k on it and is not throwing any codes whatsoever.

If there is something else I should be doing, or anything else I can try in the tune, please let me know. I appreciate any help.

coryforsenate

iTrader: (1)

From the list of 30 common 4l60e problems:
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"3. 1-2 Shift shudder at WOT (Wide Open Throttle); delayed or abnormal 1-2 shift; There's a problem ONLY on the 1-2 shift: 1-2 accumulator piston cracked or stuck cocked in the bore. Check the yellow spring inside the accum housing for breakage. Also, if the accumulator housing walls are scored, the housing must be replaced."
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Your first link can go in either the 1-2 or 3-4 accumulator. The 1-2 accumulator can be replaced without dropping the valve body. 3-4 requires dropping the valve body.

I think I recall there being enough clearance to replace the forward accumulator without dropping the valve body, but you'd have to let somebody else confirm.


If you plan to drop the valve body, there's kits that will have lots of goodies (for more money, of course). It really depends on if you want to buy just the 1-2 accumulator and see if that solves your problem without dropping the valve body, or if you want to buy a kit, drop the valve body, and recondition it.

I installed the Sonnax Performance pack on my 4l60e (which includes the 1-2, 3-4, and forward pinless accumulator pistons) and the shifts are all very crisp. Of course, I completely rebuilt the transmission so I can't say how much a role any one part played in the crisp shifts.

bbond105, mrvedit, and other experts could give you some good suggestions on where to start.

There will probably also be a suggestion to check the line pressure with a pressure gauge.

RedRocketZ28

iTrader: (19)

Thanks. I would prefer to do as little as possible as this is just a DD and I don't intend on keeping it forever. If I can make it another 1-2 years without issue then I plan on selling it for a 09+ GM Truck or Avalanche.

coryforsenate

iTrader: (1)

Assuming that replacing the stock 1-2 piston and spring fixes the problem, that would be the easiest and cheapest fix.The piston/spring you listed, tranny fluid, and a new pan gasket should be less than $50. Replacing about 1/4 of the total fluid in the transmission is a nice bonus to a pan drop. Depending on the last time it was done, you could also change the transmission filter. A kit with the gasket and filter (about $20) isn't much more than the gasket by itself (about $10).

Careful pulling the 1-2 accumulator housing off so that you don't damage the valve body gasket. It'll probably be a bit stuck.

bbond105

You can remove the 1-2 accumulator housing and inspect the piston. Most are made of plastic and tend to broke a lot. The Sonnax pinless 1-2 accumulator piston is a good piece to use in place of the plastic piston. If it not broken now it will break at some point.

RedRocketZ28

iTrader: (19)

Thanks all. I plan on dropping the pan and changing the fluid and filter. I will go ahead and install a new 1-2 accumulator piston as well since I will be there.