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Any automatic transmission experts?

VolvoGuy123

Iron Man.
Joined
Mar 17, 2016
Location
CT
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!
 
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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.

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?
 
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. ;)
 
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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?
 
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.
 
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
 
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.
 
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.
 
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.
 
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. ;(
 
*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?

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.

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?
 
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.
 
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. ;-)
 
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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