A different issue with the B4 servo piston

Post by **oragex** » 27 Nov 2016, 18:35

Hello everybody, I spent a few hours inspecting the B4 servo piston on my 2003. Reason was harsh up-shifting 2nd to 3rd with some delay and harsh engagement. I wondered if the servo cover had the know issue, but the cover was in perfect condition. Rather, there was an issue with the piston itself, explained later in the video. At same time, I resume the already known difficulties of this not so pleasant job, hopefully it will help someone. The video is not the best given the location of the servo cover on the transmission

Tonyx · Post by **Tonyx** » 28 Nov 2016, 09:25

This is interesting observation. We know the shifting gets worse as trans oil warms up which means the piston you refer to also heats up and expands making gap between piston and cylinder smaller. And if any scratch is there, it will likely exacerbate mobility of the piston. Hmmm, interesting..,

Post by **oragex** » 28 Nov 2016, 10:01

That's right. This might be the fix for 2003-2009 that have transmission upshift issues from 2nd to 3rd gear.

Ragman · Post by **Ragman** » 29 Nov 2016, 07:51

Nice post. I believe I have the same issue with my 2007 V70 2.5T transmission, which seems to delay/slip into 3rd gear. I've purchased the B4 servo cover kit from IPD, but have yet to do the install. I was also going to change my fluid After the cover replacement , but now I will also look for the roughness on the piston and in the piston sleeve. Just wondering where I can buy the mesh/wire sponge you mention in your video? Thanks for a great tutorial.

Post by **oragex** » 29 Nov 2016, 09:44

It's a typical wire sponge for kitchen. A quality one is important so it doesn't break into tiny pieces. Also important part is to use a light one as there are also heavy duty ones and these may be too rough for the metal surface. Let us know if it helped with the gear shifting

Post by **precopster** » 29 Nov 2016, 13:41

Great observation on this piston problem.

Slamming or hard engagement from 3rd to 2nd gear may be attributed to this rough bore issue. As revs increase and the shift timing is compromised the transmission slams when the piston finally moves.

It pays to say here that when a new B4 cover is purchased you get 2 new o ring seals. One is for the piston and the other for the new cover. A new seal is recommended if it is at all damaged such as yours.

Post by **JRL** » 29 Nov 2016, 16:57

B4 servo has NOTHING to do with a bad 2-3 upshift or downshift, only 3-4
This is a VALVEBODY issue

Post by **oragex** » 30 Nov 2016, 01:33

precopster wrote:Great observation on this piston problem.

Slamming or hard engagement from 3rd to 2nd gear may be attributed to this rough bore issue. As revs increase and the shift timing is compromised the transmission slams when the piston finally moves.

It pays to say here that when a new B4 cover is purchased you get 2 new o ring seals. One is for the piston and the other for the new cover. A new seal is recommended if it is at all damaged such as yours.

Indeed, not having new seals at hand, I switched the damaged seal from the piston with one of the two from the cover.

Post by **precopster** » 30 Nov 2016, 02:28

For JRL's sake:
From IPD's website: The early AW55-50/51SN five speed automatic transmissions have an issue with shift “flares” and other odd symptoms related to shifting in and out of 3rd gear. This usually reveals itself by a “missed” shift (sometimes called "shift flare") from 2nd to 3rd gear on a random basis.

On XC70.com : http://www.volvoxc.com/forums/showthrea ... ervo-Cover

The B4 cover TOTALLY FIXED 2ND TO 3RD gear on my 2000 v70 NON TURBO 5 years ago (4TH to 3RD harshness is now its forte)

In fact if band is worn outside of limits there is NO 3rd gear as was the case with our own 2002 XC70. I renewed 3rd gear by replacing the friction band (a job not for the faint of heart by the way)

Post by **JRL** » 30 Nov 2016, 09:41

We can agree to disagree a bit here.
I tend to believe my factory rep (who is an engineer) who told me this.
ipd is not always the end to end alls regarding Volvo issues and they too can be incorrect at times.
While is may help on certain transmission, the B4 servo IS primarily for 3-4 shifts not 2-3 shifts.... up and/or down