From what I've seen after taking both transmissions apart there's a two-piece sun gear shaft with two sun gears with the 50sn and the 51SN has a one-piece shaft with a single sun gear. There's ring gear and sun gear tooth differences but from what I've calculated the 1-5 gear ratios are near identical, except for reverse which I can't confirm. There's also some difference in the clutch friction plate thickness for the C2 clutch I believe. There's likely some other differences that I'm missing but overall if the internal gear ratios are the same then the two transmissions are compatible and won't generate gear ratios errors if swapped out. Other considerations that doesn't have to do with 50sn to 51sn difference is the final drive ratio and wiring harness connectors compatibility. I can't guarantee anything in terms of compatibility between the two but if the final drive ratio, FWD/AWD differential and harness connections are the same I think there's a high probability the two types can be swapped with each other without issues.

 

Well I'm going from 51sn to a 50sn and the wiring connectors are different which sucks

 

Thanks for your info.


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Did you find out if it worked?

 

I have not yet pulled the trigger, quite a bit of work to change. I most likely will tho, my tranny is in a very sorry state. I will update this thread when I do.

 

I have not yet pulled the trigger, quite a bit of work to change. I most likely will tho, my tranny is in a very sorry state. I will update this thread when I do.

Did you ever end up trying?

 

I was on strike for the last 10 months so funds didn't allow. Just bought a s40 with AW55-50SN with a blown motor so I am going to use that instead.

 

I have a 2004 C70 and I think I need to replace it. Was thinking about trying one from the xc70.

Nice find! I'm sure you can get your money back in parts.

 

XC70 is AWD, going to be filament issues with the exhaust. FWD and AWD exhaust are different for clearance
Car was on $100 but it has sat for 6 plus years, sunroof drains ruined the interior

 

Very true. I'm having issues finding the like for like. Researching models now to see what might be a best option.

$100 is highway robbery haha. Good find

 

I got really lucky, friend knew I was into Volvos, start looking at other models that use same tranny. Big pain here small town Iowa. 10,000 people lol

 

Wow, 58k here. Still a pretty small place.

I don't what other volvos have these. I'm new to these cars. I'm currently reading about this now.

Any advice is appreciated

 

s40 all I know for sure, check the tag on the tranny

 

Well I have plenty of scrap yards I could check out for that. We have some UPULL listing but it's far drive on a gamble.

 

Sorry can't be more of a help

 

You have plenty helpful.

What is your current Transmission doing? I can't use mine out of winter mode. Second gear issues.

 

Ring gear backlash, starting to get very bad, but I do have 288,000 miles plus on it, and I run 17" steel wheels as my snow tire package.

 

Could be bad if that binds up.

 

Yup major clunking going on and off throttle, been getting worse but I put 300+ miles a week on it

 

That's a solid trans haha. Good luck with the replacement.

That last comment made me less worried about mine.

 

The GM Delco valve body swap is worthwhile, also comes with all new solenoids except for the one you would need to swap into a 2004. Minor harness soldering needed on 2004 and earlier. Good chance to clean the screen out by reverse flowing transmission cleaner when the valve body is out (see my late post on this subject to the transmission megathread on MatthewsVolvoSite)

 

I bought a partially rebuilt transmission from a fellow Volvo owner, he replaced all the bushings and then decided he will rebuild another transmission for himself. As an extra, he had torque converter rebuilt and case re-sleeved for me. What I was left with is installing the OPT rebuild kit and a new GM valve body (in a second attempt, after miserable failure with rebuilding my oldish Sonnax). Works like new.

 

I does it all gears going forward and reverse, thanks for the info from the both of you.

 

That's strange. Either it's not doing it in all gears and driving conditions, and then 99% it's a valve body problem, or you have a lot of wear in splines everywhere in drivetrain: differential satellites, CV axles, wheel bearings, angle gear collar sleeve and input shaft, driveshaft CV joints. Also dying Haldex electric motor can engage with jolts.

I've had all of the mentioned wear, btw. Cost a fortune to fix/replace everything. Once fixed, no more drivetrain jolts.

 

Mine is fwd, so no angle gear or haldex. I believe it is wear, car was not properly maintained until my ownership, has always has it just getting progressively worst. Have a donor now.

 

A worn case in the area that supports the transfer gear assembly can be repaired. The repair is not bad, but the shipping of the 1/2 of case is as much as the repair. Omega tool & machine in CA is the best place to have this done. They have done a couple for me.

Also, ALWAYS use a new torque converter, and flush the transmission cooler thoroughly!

Mark

 

Omega did my casing repair as well. They also sell these sleeves, you can find someone local to do the job.

 

I will be replacing the trans cooler and lines, and indeed troq converter needs to be replaced too. Am now 3 weeks an V50 owner, and I really like it. I do feel that my gearbox sometimes gives a small smack when it's at idle and I still roll down the road, when you give a little gas it so now and than gives a little punch. Anyway this trans should be at that point of worn down. 396K kms.

 

I should have also mentioned there are differences in a couple of linear solenoid connector locations, the early valve body revision had the connector located on the top side and later revisions had the connectors located on the bottom side, see photo, red lines with arrows shows the different connector locations. This may mean the wiring harness from the early revision valve body may require some wires lengthened to reach the connectors on the bottom side. You should be okay but you should be prepared in case the wires need to be lengthened some for one or both of the linear solenoids with different connector locations.

 

Thank you very much I'll find out about that tomorrow morning when I tear apart the other one to get the old wiring out of there so I can get the one that fits my car into it otherwise thank you very much that is definitely very helpful I I was thinking that I would see us like the filter screen there but I guess not anyway thank you for the information and I am most appreciate it