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Discussion Starter · #1 ·
Hey guys, haven't posted here for a while. Recently I enjoyed the heck out of a manual 997 and am considering to do a manual swap for the R. The TF80sc is still running strong, hence I am slowly sourcing an M66 for a the swap, maybe later this year. While doing my research here, does anyone know if an M66 from an S40 T5 AWD is a direct bolt-on for the R?

I checked the part diagrams for both transmission (attached, R M66 upper, S40 M66 lower), and seemed the casing is identical (though there are a couple attaching parts that are different and they seem to be interchangeable). Not sure if the gear sets and gear ratios are the same with R M66s though.

Thanks.

<img src="https://www.volvopartswebstore.com/images/parts/volvo/fullsize/GR-276444.jpg" width="411" height="601" alt="M66 S60" />
<img src="https://www.volvopartswebstore.com/images/parts/volvo/fullsize/GR-372116.jpg" alt="M66 S40" />
 

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Not worth the time, money, and effort to swap. Better off buying another R. It would be cheaper. And then you’d have 2 Rs. There’s no reason not get an 04 MT R. Only the AWD changed in the later years for the MT cars really.
 

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I wouldn't discourage the swap, I've been wanting to do this myself you can learn a lot and feel awesome and satisfied (when done) when doing a swap like this. I am curious too if the m66a from an s40 would work as well.
 

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Discussion Starter · #4 ·
Hi Hound thanks for your input. The R's been with me for 6 years and I would be sad to buy another R to just replace her. I am not inclined to buy a 3rd used car after getting the 997 manual... But the more I enjoyed the 997M, the more I wanted to do a swap for the R. Isn't that strange? :p
 

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Discussion Starter · #5 ·
I wouldn't discourage the swap, I've been wanting to do this myself you can learn a lot and feel awesome and satisfied (when done) when doing a swap like this. I am curious too if the m66a from an s40 would work as well.
This^
 

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I thought it wasn't a direct swap. Even if it was, what about all of the ancillary stuff like the cables, spaceball, interior trim, pedals, etc?? Seems like a crap ton of work for not a lot of performance gain or money saved. Probably would just wait for an M66 R to be parted out nearby, then buy the entire trans assembly, axles, trans, interior, cables... ie the whole shebang. Or, just buy a manual R and sell your current one....
 

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I'm also interested in the compatibility. I think my M66 is blown and here (Spain) this car is very rare so It would be almost impossible to get a M66 from an R.
I'd thank a lot some more info about S40/V50 M66 compatibility.
 

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I wouldn’t replace your current R. Supplement it. They’re so cheap now it’s probably the best option. Then you have the best of both woRlds.

I believe there are some differences in the M66s. With regard to mounting and shift cabling. The ratios will also be different. The M66C is very very short. Which is very very fun. And very very detrimental to fuel economy. Great in traffic though. Ultimately the internals to the boxes are probably identical (it’s a getrag box afterall). If the mounts are different and the P1 box is all you can get I’d surmise you could swap the case.
 

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AWD M66 Trans will swap from one (P1 to P2) to the other. P2 shifter assy is different, you will need the counterweight/shift arm for a P2 asthe P1 shift design is not compatible. Gearing for AWD M66 is the same, as far as I recall. FWD M66 is different.
 

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Discussion Starter · #10 ·
AWD M66 Trans will swap from one (P1 to P2) to the other. P2 shifter assy is different, you will need the counterweight/shift arm for a P2 asthe P1 shift design is not compatible. Gearing for AWD M66 is the same, as far as I recall. FWD M66 is different.
Thanks, that's also what I gathered, just not 100% sure though...
 

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Discussion Starter · #11 · (Edited)
Ok guys, lately I did a bit of research on M66s and here's what I found: (Also thanks to theshadow27 for our meaningful discussion)

TL;DR: If you are looking for a M66C, S60R/V70R is the only platform to source from. The M66s from S40/V50 T5 AWDs might bolt on, but they are NOT M66C.


There are mainly two variants of M66 AWD transmissions out there (diesel gearboxes not considered here, nor M66D and M66Es as they seem never present in the US): M66C (M66CA21 to be exact) and M66W (M66WA33 to be exact)

In the US, M66CA21 only comes in 04-07 S60R/V70R as we've already known, while M66WA33 comes from S40/V50 T5 AWDs. I verified this by querying all the S40/V50 T5 AWDs for sale that provide a VIN through a paid VIDA subscription (which supports querying the factory specs of any VIN from Volvo's database) and they all point to M66WA33.

These two gearboxes look pretty much identical, however they have gears with different ratios. Part number for M66CA21 includes 8252140, 9482302, 9482343, 9482369, 9482417 (they all refer to the same part and are interchangeable, minus different shift levers). Part number for M66WA33 includes 8252157, 9482340, 9482368, 9482415, 9482424 (these are also interchangeable).

Tag pics:



Gear ratios:
M66CA21:
1st: 3.39
2nd: 2.05
3rd: 1.43
4th: 1.09
5th: 0.87
6th: 0.70
FDR: 3.77

M66WA33:
1st: 3.39
2nd: 1.91
3rd: 1.27
4th: 0.95
5th: 0.78
6th: 0.65
FDR: 4.00

There seemed to be a belief that S40/V50 T5 AWDs were also equipped with M66C, however I find this not true and during my research I did not find any concrete evidence of a M66 box from S40/V50 T5 AWD showing M66CA21. (Refer to my above experiments with querying S40/V50 T5 AWDs' VIN to check for the gearbox equipped out from factory). I intend to conclude that no M66C was ever paired with S40/V50 T5 AWDs. I think the misconception is caused by folks thinking there's only one M66 AWD box out there and the box on S40/V50 T5 AWDs is indeed a M66 AWD (just it's not M66C). Also the fact the FWD cars equipped with M66s (M66WF23 to be exact, has same gear ratios as M66WA33, except for a FDR of 3.77) makes it further confusing if we just combine "M66 AWD box" with "3.77 FDR" to incorrectly assume a M66C.

The Quaife LSD page seemingly also lists S40/V50 T5 AWD having M66C, which I believe is also due to the above misconception. But the LSD does fit on S40/V50 T5 AWD M66WA33, reason being the LSD is just to replace the original differential in the M66 box while retaining all its original gears (thus the gear ratios actually doesn't matter here, as long as the dimension for the differential is the same. In this LSD installation guide, note the step where the ring gear from the old differential is transferred to the new LSD).

Hope this could clear the cloud a bit and I'd be happy to learn from you guys if any part is wrong!

And lastly comes the real question: does anyone have a spare M66C for sale? :cool:
 

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Interesting, so if someone installed the wrong m66, I'm assuming the car would throw gear ratio errors? Or some sort of message would appear in VIDA?
 

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Discussion Starter · #13 ·
Interesting, so if someone installed the wrong m66, I'm assuming the car would throw gear ratio errors? Or some sort of message would appear in VIDA?
I doubt the car would throw any errors for a different m66. Being a manual, the car has no idea of the gear ratios in the box. But it definitely will rev differently due to different gear ratios. Plus folks have been swapping both P1 M66s and P2 M66s without a problem. I think in order to make AWD work on a different gearbox, using the original angle gear and rear diff should suffice (needs to make sure there's no fitment issue between new gearbox and angle gear in the first place of course)
 

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I don't know if it will bolt up or not, but the S40 M66 has an engine mount on it, and attaches to the frame near the wheel well, so there are significant external differences.
 

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Since the final drive ratios are different, wouldnt you have issue with the awd since the rear ratio won't match the front?

Sent from my SM-N960U using Tapatalk
 

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Discussion Starter · #16 · (Edited)
AFAIK, no. The angle gear ratio and the rear differential ratio will compensate each other thus making a 1:1 gear ratios for the combo (E.g., if the angle gear ratio is 1:K, the pairing rear differential will have gear ratio K:1, to make the entire AG + rear differential combo a 1:1 ratio). The front wheel and the rear wheels will always rotate at same speed (going straight of course). And the final drive ratio of the entire drive-train is solely determined by the transmission (M66CA21 3.77 vs M66WA33 4.00)

That's why it's crucial to use a matching AG + rear differential (either use the original pair, or replace them in pair)

Also check this thread for a detailed read: http://volvospeed.com/vs_forum/topic/104900-rear-drive-ratio-for-99-v70r/

Since the final drive ratios are different, wouldnt you have issue with the awd since the rear ratio won't match the front?

Sent from my SM-N960U using Tapatalk
 
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