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AW 55-50 Transmission Glad to help!

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Old Jun 25th, 2009, 05:31   #1
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Smile AW 55-50 Transmission Glad to help!

I am amazed to see that all over the world through the different volvo forums ive come across this transmission has been the bane of so many! well I have had my love affair with this transmission for quite some time now, in fact it has been an obsession. all I can say is....... there is always a solution. fire away il be glad to help out as best i can and save you a lot of trouble.
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Old Jun 25th, 2009, 09:46   #2
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In England we can buy any number of Volvos quite cheap due to having a faulty AW55-50SN and there are lots of them on the road with faulty boxes where the owners just keep running them , I have a 2001 V70 2.4T which I bought for spares but I want to get it running properly again . Do you think that an amateur mechanic could take one of these apart and rebuild it without having specialist equipment ? I am willing to risk trying because there is nothing to lose because if I cant get it working right then I will use the car for parts but I am told it cant be done . One problem I see is there are parts suppliers in USA and one or two in Sweden but they want to sell complete kits of parts when you may only need one clutch band or one small part which they wont supply on its own . This box used in the Volvo I am told is very similar to those used by Toyota / Vauxhall / Nissan plus others but how similar is it , can you directly interchange all the parts because if this were possible it should mean the parts could be sourced cheaply , do you have a good parts supplier ?
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Old Jun 26th, 2009, 06:57   #3
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first you have to describe whats going on w/ the gearbox? is it shifting hard? slippinig? what gear? does it happen often or once in a while?... with regards to your other question , if you have the spare time there is no harm in opening up the box, it can be done, but it does need some form of specialized equipment if you might call it that. im refering to the volvo diagnostic equip. so you can reset adaptation values for the TCM. in my experience these boxes even when they dont run anymore rarely burn their clutches & band which is what conventional diagnosis and thinking might suggest. as a further suggestion I would recommend doing a pressure reading first and il help you interpret the readings. it gives a significant description of whats wrong inside. yes this box is used for many other makes usually you can interchange the hard parts ie. planets & drums also linings. the only thing to watch out are the solenoids some makes use different configurations ie. normally open & normally closed. Automatic chice in europe is a good source for parts ive got some from them and im half a world away.
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Old Jun 26th, 2009, 15:45   #4
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The auto tranny on my 2004 base model V70 2.4 non-turbo 168 hp is an AW55-51 S as best I can read the metal tag. This is a 5-spd auto, but without the 'Geartronic' shifting. So do I have it right that this tranny has not had the troubles the Geartronic ones have had?
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Old Jun 26th, 2009, 16:16   #5
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you have the upgraded ones,. but on a side note the aw 55-50's geartronic or not suffer the same problems especially the 2001 -2003
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Old Jul 3rd, 2009, 18:11   #6
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Do you know what is happening to my gearbox please, its a 2001 AW55-50SN that, only sometimes shifting up from second to third will let the engine rev to about 4/5K rpm and then change with a mighty clunk and then for the rest of that journey the gear changes will be sluggishly erratic. Once the engine has been restarted everything is fine again.
To be honest I'm not that worried about it as it only does it maybe once every two weeks but I would like to know!
Thanks in advance.
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Old Jul 3rd, 2009, 22:15   #7
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I think that will be the valve body.

What happens in that case, from what I understand, is:

1. TCM requests second gear disengage and third gear engage.
2. Pressure valve moves, gearbox disengages.
3. Pressure valve moves, third gear engaged.

(Not sure which valves are involved, although I think from what I recall 3rd gear involves the well-known B4 solenoid.)

If you get a delay between (2) and (3) above, then the gearbox will be in neutral for a time and the engine free to rev up. This can be caused by old fluid causing the valves to stick, or some other valve body problem. The B4 servo cover is also a problem on 2001 boxes, serial numbers around 01C-01L (March '01-December '01 build date) if I've remembered correctly.

The danger is that the sharp "lurch" is two bits of gearbox moving at very different speeds coming together - a bit like revving up the engine then dumping the clutch in a manual. It's what, over time, helps cause the entire box, rather than just the valve body, to die.

btw, have you had the B4 servo cover checked out? It's a known issue on 2001 models, and 2-3 shift flares are one of the most common symptoms for it having failed. Dead cheap part, saves replacing an entire gearbox later.

Last edited by Timberwolf; Jul 3rd, 2009 at 22:19.
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Old Jul 5th, 2009, 14:25   #8

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I've just been reading 'bout the B4 Servo Cover problem experienced with some 55-50SN box's & wondered if mine hade the matching Serial Number.

Info on my box is, 55-50SN, 9480902, SN 00KV717736

I just wondered if anyone could tell me how this information reads?

I copied this from a B4 Servo Cover thread;

The first 3 digits of the serial number on the affected transmissions will be between 01C (March 2001) and 01L (December 2001).

So looking @ the SN on my box it looks like it was made prior to the ones with the doddy B4 Servo Cover?!

Can this info be relied upon?



Last edited by sae70; Jul 5th, 2009 at 14:28.
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Old Jul 5th, 2009, 22:50   #9
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I have also wondered about this. I have a July 2000 V70 and the 2 to 3 gear change can be a bit slow to changed up the first time I run the car from cold. The ATF has been replaced and the box seems fine a part from this.


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Old Jul 6th, 2009, 12:00   #10
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Does it behave itself once the car's warm?

On these boxes there's a "catalytic convertor protection/warmup mode" which delays upshifts until the engine reaches a certain running temperature, which helps the cat get to temperature earlier and prolongs its life/improves fuel economy.

It's actually nowhere near as bad on the Volvo as my old (four speed auto) Omega with a similar setting, which I swear had a thing for making me look a right idiot on winter mornings as I went roaring up the road with the engine at about 4000RPM in first. :-)
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aw 55-50 help on the way, vaiotag

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