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Old 10-09-2017, 07:44 PM   #1
VolvoGuy123
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Default Any automatic transmission experts?

My car: 1995 Volvo 940 Turbo (w/ AW71)

My question is concerning the "accumulator mod" on an AW71. Basically whenever I do anything I like to push it "right to the limit" and use precise measurement. So when it comes to shimming the accumulators and I make them "barely" shorter than the spring using a micrometer, etc and measure everything up and end up shimming them just a hair too much, in theory what would happen?

...Because I did this, changed the filter, gaskets and added all brand new Mobil 1 atf and ended up frying 2nd gear. (Everything was done precise, cautiously and of proper procedure) The results were pretty much immediate upon first test drive. before this, my transmission was working well and holding between the 1-2 shift. Now it does not shift firm to 2nd gear and slips into and during 2nd gear under WOT. Besides that every other gear and shift is nice and firm! Actually, I put the boost back to stock for now and under normal driving and even some spirited driving it feels really great, its actually a shame really! If the 2nd gear clutch didn't 'let go' than it would be perfect.

Can it just be a coincidence that this happened or is it possible I shimmed one of the accumulators (1-2) just a little too much? Thank you for any input on this matter TB!

Last edited by VolvoGuy123; 10-09-2017 at 07:47 PM.. Reason: because OCD. :)
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Old 10-09-2017, 07:49 PM   #2
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How much movement did you allow the pistons?
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Old 10-09-2017, 07:51 PM   #3
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Sounds like not quite enough wiggle room for that piston. I would shorten it up an 1/8-1/16" and try again.
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Old 10-09-2017, 07:55 PM   #4
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How much movement did you allow the pistons?
Maybe about 0.5cm? Clearly noticeable movement when pressed/depressed. It seemed like 'just enough' to make the clearance to properly seat the valve body.
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Old 10-09-2017, 07:59 PM   #5
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Originally Posted by KeizerBrickGuy View Post
Sounds like not quite enough wiggle room for that piston. I would shorten it up an 1/8-1/16" and try again.
but after a few test runs and some frustration, I could smell the clutch frying like you would with a manual trans with a bad clutch. isn't it too late now to fix by just shortening the accumulator shims some more?
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Old 10-09-2017, 08:21 PM   #6
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If in theory 'it is possible' to shim the accumulator pistons too much and the error is mine than my new question is now "is it worth it for me to pull it all apart again and redo everything?" (Did I do too much damage with a few test drives and a couple WOT redline shifts?) and if so, Do I need to replace all the gaskets again? I know I cannot reuse the fluid even though it was $10 a quart! lol. ;)

Last edited by VolvoGuy123; 10-09-2017 at 08:23 PM.. Reason: ocd.
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Old 10-11-2017, 12:54 AM   #7
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*I also have an additional question regarding the proper adjustment of the kick down cable; I tightened it up before the mod but put it back to factory spec after. Can I do both and have my shift points elevated by the cable mod with the 'accumulator mod' performed or not a good idea?
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Old 10-11-2017, 10:07 AM   #8
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you didn't smoke 2nd gear by shimming an accumulator. you smoked 2nd gear by either introducing a leak that bled pressure from it (most likely), or it was just happenstance that it let go when it did.
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Old 10-11-2017, 12:09 PM   #9
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try type f fluid may help for a while, but I'm guessing if you could smell it burning which has never happened to me it's probably over with
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Old 10-11-2017, 03:18 PM   #10
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Originally Posted by VolvoGuy123 View Post
Maybe about 0.5cm? Clearly noticeable movement when pressed/depressed. It seemed like 'just enough' to make the clearance to properly seat the valve body.
Yes but did you measure this cold or hot? Quite possibly when hot the measured clearance disappears? Don't know if this is what caused the problem.
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Old 10-11-2017, 06:11 PM   #11
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Thanks again for all the replies, I appreciate it.
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Old 10-11-2017, 06:14 PM   #12
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you didn't smoke 2nd gear by shimming an accumulator. you smoked 2nd gear by either introducing a leak that bled pressure from it (most likely), or it was just happenstance that it let go when it did.
This was my first thought. Could it be because my first test drive I had not set the kick down cable back to factory spec? *I still had it set to increase line pressure from before the mod was done.
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Old 10-11-2017, 06:16 PM   #13
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Yes but did you measure this cold or hot? Quite possibly when hot the measured clearance disappears? Don't know if this is what caused the problem.
This is also a good thought, I was only able to measure when cold and did not think to account for heat expansion.
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Old 10-11-2017, 06:33 PM   #14
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I would reset the kick down cable to factory adjustment while you're there. It's amazing what a readjustment can do.
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Old 10-11-2017, 06:50 PM   #15
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Quote:
Originally Posted by KeizerBrickGuy View Post
I would reset the kick down cable to factory adjustment while you're there. It's amazing what a readjustment can do.
I did that right away, maybe too late though? I did it after the first few test runs when I noticed it was slipping in 2nd gear. ;(
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Old 10-13-2017, 04:20 AM   #16
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Originally Posted by VolvoGuy123 View Post
*I also have an additional question regarding the proper adjustment of the kick down cable; I tightened it up before the mod but put it back to factory spec after. Can I do both and have my shift points elevated by the cable mod with the 'accumulator mod' performed or not a good idea?
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Originally Posted by VolvoGuy123 View Post
This was my first thought. Could it be because my first test drive I had not set the kick down cable back to factory spec? *I still had it set to increase line pressure from before the mod was done.
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I did that right away, maybe too late though? I did it after the first few test runs when I noticed it was slipping in 2nd gear. ;(
Can you have the "kick down cable tightened up" to increase line pressure and shift points while having the "accumulator mod" installed? or is this too much for the transmission and possibly my initial cause to the problem?
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Old 10-13-2017, 11:04 AM   #17
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nah you can pull the kickdown cable full tight if you want, with or without the accumulator mod. it won't over-pressure the transmission or anything like that.
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Old 10-13-2017, 08:48 PM   #18
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Originally Posted by linuxman51 View Post
nah you can pull the kickdown cable full tight if you want, with or without the accumulator mod. it won't over-pressure the transmission or anything like that.
Thanks, knowing that def helps alot. I thought that might have been the breaking point, glad to rule that out.
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Old 10-22-2017, 03:40 AM   #19
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I must say that even having to drive around for now at stock boost levels and only having "WOT capable" 2-3+ shifts at the moment (until I find a replacement) that the accumulator mod really makes the shifts so enjoyable on the parkway! so hard and so fast, I love it! its really a shame this trans didn't hold up in second tho, lesson learned to always perform this mod FIRST on every future car! *cant wait for 25+ lbs of boost. lol. ;)
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