Following is the image of my Volvo’s birth certificate and subsequent posts show the ID plate on my transmission which confirms it is the original transmission, Karl's website that states that both M40 and M41 were installed in P180's and the transmission is p/n 254409 as the image of its ID PLATE shows, yet the Parts Book doesn't seem to show it specifically by part number, so what models have compatible parts to replace #28?

My question comes out of needing to replace the train of four gears because two teeth on the second gear are missing, well not so much missing as not where they belong since they are laying on the garage floor after draining the oil!

The part I need

Not to be snarky but your question seems to be self answerable. If it has OD fitted it is an M41. No OD, it's an M40. Later models (the E & ES) are sometimes fitted with the M410 transmission. - Dave

It has OD but this is its ID, in addition nowhere is the p/n254409 to be found in the parts books so it makes it difficult to search for the correct gear cluster to replace that with the broken teeth

Clearly from the filler position my M40 is an M41 it just doesn't seem to be identified as such.

I can't find that part number 254409 either.

I have seen at least 1 other obviously M41 that had a tag that said it was an M40 before.

Regardless, if you want to replace the cluster, there should be a part number stamped into it.

We just rebuilt a customers early M41 and it had a damaged bearing surface inside 1 end of the cluster and the part number is clearly stamped in the area between a pair of the gears.

And in case you didn't know, M40 clusters are used in M41s, but you do have to make sure to use the same part number as there are several different clusters because Volvo updated the transmissions several times and you have use matching gears.
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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

Eric, this is helpful, thanks
I’ll dig down and get the number off the cluster.
Do you you have any idea what would cause two teeth to completely break break off on second gear without any memorable cause?

There are a number of things inside the transmission and from the shift cover that can come apart or break and get caught in the gears.

If it were back when we used to do some drag racing, I'd blame it on a 1st to 2nd gear slam shift. In fact at 1 point, we had half a dozen clusters sitting on shelf, most of which were missing most of if not all of the 2nd gear teeth. And 1 day, my brother's former business partners mother came over to the shop and saw all of the broken clusters and asked us to clean a pair, paint them silver and she used them as gear head candle sticks for her house.

I suggest you do a thorough tear down on your transmission as you may need enough parts to warrant sourcing a whole different transmission. FYI, we almost always have the parts in stock to do a normal rebuild on all 3 basic styles of M40/M41 like new synchros, mainshaft and cluster bearings, cluster shafts, thrust washers, shift dogs springs and gasket sets. We also have some whole transmissions, some of which might be rebuildable.

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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

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I was already to do a full rebuild with bearings, seals, gaskets and synchros, a new countershaft is just an added bit that would have come out and gone back in regardless of its condition. Just sourcing one to install amidst the confusion my ID tag was causing me.

Gearboxes that are ID’d as M40 with OD it seems are likely to be M40s converted with the extended output shaft to take the OD, not as in my case a gearbox born at Gothenburg(with birth certificate to prove it) having an OD and an M41 casting but ID’d as an M40.

There is some story here as to why this anomaly and it sure would be great if someone with knowledge of the production line at the time could fill it in, be it a mistake in punching the tag, a change after the tag was punched but before the casting drilled and taped for the fill plug or what have you.