C2 - M20 tail housing

[Rick N.]

I am rebuilding the tranny from my L75, late '64 (Jul '64 build). I have a 3857584 extension/tail housing w/passenger-speedo. Do I need to find a 3846429, thick web, driver-speedo housing to be correct for this car? All the other trans castings numbers check out. Is it possible the 584 was put in originally? It has been in there since at lest '74.
Thanks, Rick

[Joe L.]

Re: C2 - M20 tail housing

Rick------

The 3846429 would be the only one considered "correct" for the car. Also, GM says this was the only one installed for 1964. Could the '584' have been originally used? I wouldn't absolutely rule it out.

[Rick N.]

Re: C2 - M20 tail housing

Thanks Joe. Am I correct in that I need a 'thick web" vs a "thin fin" 429 housing? I think I'll look for a good 429 while I have the tranny out and apart. Rick

[Wayne M.]

Re: C2 - M20 tail housing

A few other checks you can make. The passenger side trans tail shaft "584" speedo requires a longer speedo cable than for the "429" drivers' side. Also, there should be no clip and rivet on the RH firewall and passenger side trans tunnel to support this cable, if not originally installed. Thirdly, the firewall grommet through which your tach cable enters the engine compartment will have a 2nd hole for a passenger side speedo cable, but only 1 hole for the "429"-equipped car.

[Rick N.]

Re: C2 - M20 tail housing

Thanks. I'll check the housing. Is it possible that the 584 was put in to support the Hurst Competition Plus shifter that's been in my car since I bought it? It looks like there are 6 left side mounting holes on the 584 vs 5 that appear in pictures of a 429. I've ordered a repro stock shifter, so, does that mean the new '64 shifter wouldn't fit on the 584?
Rick

[William C.]

Re: C2 - M20 tail housing

Should be the same number of holes, a couple of things to keep in mind if you change from the 3857584 tail to the 3846429, the most significant one being that the position of the speedo drive gear is different and has to be adjusted to the specs in the '64 service supplement rather than trying to leave it in the '65 position. I suspect that you will find that the whole trans is not original to your car, as the trans mainshaft in the '64 Muncie did not have a long enough registration surface on the shaft the adapt the speedo drive gear to the '65 up location. One sign would be to look at the date on the stamped date on the main case, or check the configuration of the top rear boss on your maincase. The '64 case used a boss with a rounded end facing toward the front of the car, while the '65 used a boss that was squared off.