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Old 11-09-2021, 09:41 PM   #1
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Join Date: Jan 2014
Location: Colorado Springs, CO
Default M45–>M47 Clutch/Flywheel Compatibility

Howdy y’all! Picked up a weirdly clean and cool 1977 244 with an M45. There is an M47 on local marketplace. Aside from driveshaft length (I’ve got an m47 shaft in the shed), is the front end of the transmission compatible? Like, can I just bolt the m47 in, or are there clutch/flywheel issues? Car has a brand new clutch before I picked it up, like 600 miles ago.


P.S.-I’m thinking now that the m47 wouldn’t have a speedo drive…that’s annoying…
1993 245
1968 122s
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Old 11-09-2021, 10:18 PM   #2
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Join Date: Nov 2011
Location: So Cal

Unless you got a really early M47 it won't have a provision for a speedo cable.

The clutch splines are course on early transmissions. You may need a different disc if it still has the original trans. Also, the clutch fork on the M47 uses the later style T/O bearing but you should be able to swap the early fork onto the M47.

Other than that the trans should bolt in.
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Old 11-19-2021, 05:44 PM   #3
the real Towery
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Join Date: Sep 2002
Location: VA, USA

You may need to fab a small sheet metal cover for the spot in the bell housing where it is clearanced to fit around the crank position sensor, if the M47 is from an '89 or newer car that used LH2.4 or LH3.1.

The shifter is different, I believe (pivot ball / bushing/cage differences) so have the M47 shifter on hand. I squeezed an M45 knob onto my M47 shift lever, and I would recommend it strongly over the soft M47 knob.

I can't think of anything else. The clutch disc spline count and lack of speedo hookup are the major differences.
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Old 11-19-2021, 11:30 PM   #4
Kjets On a Plane
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M46 is probably the easier swap unless you convert to an ABS strut housing or diff tone ring and some means to drive the speedo (seen it done with the early cluster/late everything else, but long way home).
Just a speedo cable & driveline and some OD electronics if -78 M46.

If 1979+ make sure you've got the lever/bracket and all that as well as a clutch disc.
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