Interesting evening tearing the M46 down, the first time I've torn down a gearbox.
It seems to be in really nice shape! That's not entirely surprising though, as it is the crispest manual box I've ever had by a mile. I got lucky as this was from a car I dragged from a field outside of Dubbo back around 2013/2014. Teardown was uneventful, I followed greenbook TP30056-2. I checked the input shaft, layshaft, and main shaft bearings, and only the input shaft bearing was making any noise. Given removing the other bearings is something of a mission without some special tools, and the fact that they're like $50 a pop, I opted to leave well enough alone.
I've ordered a bunch of stuff from GCP - new gearbox mount (1221967), input shaft bearing (183827), gasket set (271574) and overdrive output shaft seal (1232013). I also ordered a new shift boot because the old one had split.
Interestingly my gearbox is stamped 1023534 and K2, and has serial number 801022. Volvo's diagnostic manuals never mention a gearbox starting with 1023, they all have different numbers starting with 120xxxx, so not sure what the deal is. This one originally came from a 1980 244 GL.
Other things to note
The fill and drain plugs were pretty galled up, as this is a steel-case gearbox it doesn't take metric plugs with a washer like the newer aluminium ones. I measured mine and they are both 1/2" NPT, and the drain plug has a magnet in it. Easy to buy online.There are a variety of small parts and shims and such, if you're tearing down an M46 for the first time, pay close attention to where they come from and bag and tag them so you can put them back in the right placeNot much required in the way of specialty tools other than a set of drifts and a pair of circlip pliers. To take the shafts out entirely you need some way to pull the rear bearing from the mainshaft.Be fastidiously clean, keep using clean lint-free rags, these gearboxes will not filter any junk you put in themBe careful the following items don't drop into the casing:gear selector ball bearing and spring (exposed as soon as you remove the lid)The bronze pads on the ends of the shift forks. Lift the forks out being careful not to keep the ends level. Not sure how much it matters but try to avoid mixing up the pads. I put tape around mine to hold them in placeIf you start peeling a gasket and it says "ASBESTOS", don't panic! If you peel it further, you'll find it says "NO ASBESTOS". That one had me concerned for a moment!Volvo painted the inside of the gearbox, presumably to improve oil drainage. Pure class.There's a seal at the rear of the gear selector shaft (part #947705) it should be included in the gasket set (part #271574).There's a rubber o-ring that sits between the ball on the back of the gear selector shaft, and the extension arm that goes to the bottom of the shifter. In yet another victory for people who buy head gasket sets and don't throw away all the extra bits, it's the same part number as a K-Jet injector o-ring (upper).The Laycock J-Type overdrive unit has a total weight of 11.9kg. The more you know!
