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Old 05-11-2021, 11:24 AM   #1
spock345
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Default M40 rebuild questions, bearing part numbers

While I sort out my overdrive transmission conundrum I've decided to rebuild the M40 as the oil was filled with glitter and an exploratory surgery found bad input and output main shaft bearings and deep pitting on the lay shaft. This is partly for entertainment and partly to have a backup gearbox. I am kind of amazed this thing ran relatively quietly.

I've read that there are generic bearing part numbers that can be had for cheaper for the M40 and M41. Does anyone know what those are?

The transmission seems OK inside but I've noticed a couple problems. One is that the layshaft gear cluster bearing surfaces are a bit messed up. I've got a local source for that part. The gears inside are OK except for one tooth chipped off a synchro and chips out of the reverse gears. I could find a parts box locally for that but I am stumped on how to get the idler gear out without the special puller from the green book. Is it ok to just have a couple chips out of the reverse gears?

I've read that different bearing and layshaft sizes were used throughout the years, does anyone know the measurements for those so I can tell what I have?
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1967 122s, B20F, M40
1989 240 B230F (V15 cam, chipped EZK), M47 (Lost a fight with a Chevy express van)
2012 VW Tiguan 6 speed auto (oh the joys of carbon buildup).
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Old 05-11-2021, 11:59 AM   #2
c1800
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Your bearing should have parts numbers on them from the manufacturer, timken, Skf etc. There are bearing cross references on the net or see a bearing supplier.

Not sure I’d go through all that work and reuse a gear with chips in it.

There’s rebuild procedures for M40 and M41 on YouTube IIRC.
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Old 05-11-2021, 12:13 PM   #3
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Quote:
Originally Posted by c1800 View Post
Your bearing should have parts numbers on them from the manufacturer, timken, Skf etc. There are bearing cross references on the net or see a bearing supplier.

Not sure I’d go through all that work and reuse a gear with chips in it.

There’s rebuild procedures for M40 and M41 on YouTube IIRC.
I've been using this guide along with the Haynes manual (surprisingly good for the 122).

https://advrider.com/f/threads/volvo...ebuild.641530/

Still can't find anything about removing that idler gear though.
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Old 05-11-2021, 12:38 PM   #4
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Here’s one of those videos , might be some help.

https://m.youtube.com/watch?v=d6JbNWbFP6c

He also has many other videos on other Amazon repairs.

Good luck.
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Old 05-11-2021, 01:49 PM   #5
hiperfauto
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If it were me I'd be looking for another trans to rebuild. There's just too many things wrong with that one to make it worthwhile.

Drive the reverse gear shaft out from the inside with a long drift. It may leave some marks on the end of the shaft but it won't damage anything critical. A bent drift will make it a bit easier.

There are several variations of M40/41. Small cluster shaft with small reverse gear shaft, small cluster shaft with large reverse shaft and large cluster shaft with large reverse shaft.

There are 5 different reverse gears, 2 for the small shaft and 3 for the large. Changes in the cluster gear made it necessary to modify the reverse gear so there are a lot of variations.
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Old 05-11-2021, 02:07 PM   #6
spock345
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Quote:
Originally Posted by hiperfauto View Post
If it were me I'd be looking for another trans to rebuild. There's just too many things wrong with that one to make it worthwhile.

Drive the reverse gear shaft out from the inside with a long drift. It may leave some marks on the end of the shaft but it won't damage anything critical. A bent drift will make it a bit easier.

There are several variations of M40/41. Small cluster shaft with small reverse gear shaft, small cluster shaft with large reverse shaft and large cluster shaft with large reverse shaft.

There are 5 different reverse gears, 2 for the small shaft and 3 for the large. Changes in the cluster gear made it necessary to modify the reverse gear so there are a lot of variations.
Turborg apparently has some gearboxes in need of R&R. Still waiting on a reply. If all else fails I've got some spare parts.
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Old 05-13-2021, 09:26 PM   #7
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I had a bent large flathead screwdriver sitting in my toolbox that I turned into a drift punch. That worked pretty well after warming the case a bit around the shaft with a propane torch (it didn't take much heat).
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