G/box: 70 Auto: - C70 auto 3rd gear flare/slip

twntechservices · Feb 1st, 2020, 18:44

Hi, recently bought a 2003 C70 2.4T with the Aisin AW55-50 transmission.

When it tries to change into 3rd gear it slips and the engine red lines. If you feather the throttle and let the car slow it then engages slightly harshly then all is well until it needs to upshift into 3rd again.

So far I have changed the fluid (JWS 3309), reset the fluid counters and transmission adaptions and replaced the B4 servo cover with the latest type (though there wasn't anything wrong with the old one). All still the same.

I was wondering if I should either:
remove and strip the valve body, hoping to clean it up etc;
fit a used valve body;
fit a new Chinese copy valve body;
fit a complete used transmission if the problem is more deeply rooted than just the valve body.

It's not economic to fit a new Aisin valve body or get the transmission rebuilt.

Problem is, the gearbox in this car is a AW55-50SN 8636767, whereas all I can find are 8636762 or 8636766. (I also have a 2004 C70 2.0T which has the 8636766.) Are these interchangeable bearing in mind they're all AW55-50SN from petrol Volvos?

Many thanks in advance for any input.

twntechservices · Feb 7th, 2020, 17:20

Well I fixed this, cost £0 and about 30 minutes.
Issue was that the rearmost 27mm head bolt had been removed at some stage from the top of the transmission, it looks like a filler but it secures the 3rd gear band.
I found this link below and it worked a treat, box is now perfect!

https://www.google.com/url?sa=t&sour...h6Z0Z1ZyWW7oJ_

Feb 1st, 2020, 18:44	#1
twntechservices Member Last Online: Apr 10th, 2020 14:16 Join Date: Feb 2010 Location: Aylesbury	C70 auto 3rd gear flare/slip Hi, recently bought a 2003 C70 2.4T with the Aisin AW55-50 transmission. When it tries to change into 3rd gear it slips and the engine red lines. If you feather the throttle and let the car slow it then engages slightly harshly then all is well until it needs to upshift into 3rd again. So far I have changed the fluid (JWS 3309), reset the fluid counters and transmission adaptions and replaced the B4 servo cover with the latest type (though there wasn't anything wrong with the old one). All still the same. I was wondering if I should either: remove and strip the valve body, hoping to clean it up etc; fit a used valve body; fit a new Chinese copy valve body; fit a complete used transmission if the problem is more deeply rooted than just the valve body. It's not economic to fit a new Aisin valve body or get the transmission rebuilt. Problem is, the gearbox in this car is a AW55-50SN 8636767, whereas all I can find are 8636762 or 8636766. (I also have a 2004 C70 2.0T which has the 8636766.) Are these interchangeable bearing in mind they're all AW55-50SN from petrol Volvos? Many thanks in advance for any input.

Feb 7th, 2020, 17:20	#2
twntechservices Member Last Online: Apr 10th, 2020 14:16 Join Date: Feb 2010 Location: Aylesbury	Well I fixed this, cost £0 and about 30 minutes. Issue was that the rearmost 27mm head bolt had been removed at some stage from the top of the transmission, it looks like a filler but it secures the 3rd gear band. I found this link below and it worked a treat, box is now perfect! https://www.google.com/url?sa=t&sour...h6Z0Z1ZyWW7oJ_

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