2001 V70 How to tell if B4 band is not working?

Locky2001V70 · Post by **Locky2001V70** » 08 Jun 2014, 22:07

Is there a quick way of telling if the B4 band has been disengaged on an AW55-50 5 speed transmission?

Normally a mechanic or previous owner may have done this via the removal of the retaining nut on top of the transmission in an attempt to speed up refilling of the

Symptoms are no engagement of 3rd gear- just continuous slip until 4th clunks in.

I have my suspensions as there is light marking on the nut, however it is extremely tight and doesn't look to have been removed.

If it has been removed then I have read it is possible to re capture the band.

Post by **precopster** » 09 Jun 2014, 07:41

There is a measurement I devised to see if the band is:

1) Moving freely due to being dislodged by somebody removing the bolt.

2) Worn beyond limits

It consists of a pushrod marked at 85mm with a scribe which is inserted through the B4 servo bore after removal of the B4 piston and cover. Once the 85mm scribe is matched with the cover circlip line there should be around 6mm of spring loaded movement before the band closes around the drum. If the movement feels totally limp the band is dislodged.

If the movement feels spring loaded yet moves more than 8mm the friction band material has disintegrated. 85mm happens to be the total length of the B4 piston plus cover. 8mm is the amount of bore left at the end of the piston which operates the band clamp.

There is an eBay seller providing the friction set with servo band for around $115 USD plus postage.

Post by **JRL** » 09 Jun 2014, 09:36

He has no 3rd gear, he has a lot more problems than to measure the band
They screwed up his tranny big time

Post by **precopster** » 09 Jun 2014, 14:53

JRL the OP is on a hunch that the nut was removed. If you read his thread THOROUGHLY as well as his other posts, you'll see that he bought the car this way. I believe that the band is destroyed in this case, not dislodged, which will probably mean that a friction rebuild of the entire set of clutch facings is necessary.

The measurement I devised will determine if the band is dislodged by someone removing that 27mm nut. If the nut has been removed, removal of the B4 servo piston will allow an extra 3mm of movement clockwise in the band making it easier to capture.

For the OPs sake details of band capture are over on Swedespeed however none of them realised that removal of the B4 piston would make the job far easier.

Post by **precopster** » 10 Jun 2014, 07:54

Photo added

Locky2001V70 · Post by **Locky2001V70** » 16 Jun 2014, 07:48

Thanks Mike,
I will be taking the B4 servo cover off and measuring the play in the spring as you have suggested.

It does seem like the B4 band is completely worn.

I thought the other night when I was driving it, that I might have had 3rd gear, but may just have been forth.
I read somewhere that in DICE you can change the P,R,N,D to read gear numbers, so I may do that to help problem solve this issue.

On another front, got a screw lodged in one of my back tyres, so I'm up for a new tyre (pair).

Post by **precopster** » 16 Jun 2014, 07:58

Locky where are you located somewhere in NSW or QLD most likely-!!! I have a 55-50SN on a bench and can show you what you're measuring.

I shot a video of the measurement with the side cover removed so you can actually see the band clasping the drum but haven't uploaded it yet.....perhaps soon.

Post by **precopster** » 14 Sep 2014, 06:17

Just to update this thread with some photos of the removal of the side cover on the 5 speed transmission to replace the 3rd gear band.

WORN BAND WELL PAST WEAR LIMITS-THIS MUCH WEAR GIVES 20MM OF PISTON TRAVEL WHICH THE B4 BORE CAN'T SUPPORT

BURN MARKS ON 3RD GEAR DRUM SHOWING BAND ANCHOR'S LAST ATTEMPTS AT BRAKING THE DRUM.

A GOOD BAND ANCHOR'S FRICTION MATERIAL.

TO BE ABLE TO DROP THE TRANSMISSION THIS FAR YOU NEED TO DISCONNECT A LOT OF WIRING.

THE SIDE COVER REMOVES EASILY ONCE YOU GIVE IT A TAP WITH A HAMMER

THE SIDE COVER BACK ON AND RESEALED WITH GASKET CEMENT

Road test to folllow shortly; let's see if I can regain 3rd gear!!

Post by **precopster** » 18 Sep 2014, 03:25

Road test and adaptation performed on my 2002 XC70 with 395,000 ks (244k miles) this evening. Car drives as it should and 3rd gear is restored

At first there was a 2-3 flare however the adaptation reset and fluid counter reset sorted it out after about 6-7 starts.

A B4 SERVO BAND SHOWING THE HOLE THAT THE 27MM BOLT PROTRUDES THROUGH.

For reference purposes I rebuilt the valve body afew months ago then it lost 3rd gear on the way home from a long afternoon drive. I was getting tired of hearing it needs a full rebuild when 3rd gear is lost on this and other boards.

So I devised the 85mm marked rod to measure the travel of the band around the drum and compared it to a transmission I had on the bench which had a good band. The difference was 6-8mm of travel vs almost 20mm on the car with no 3rd gear. I hope this thread gives hope to any other lost 3rd gear victims who have gone nowhere near the 27mm nut.