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Discussion Starter #1
At some point it seems that Muncie switched from 5 hole shifter bolt hole tail shaft case to a 6. Does anyone know when this happened and which one is the right one for the 1966 Chevy II Nova SS with console?
 

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The tail shaft housing that you need is part/casting number 3857584
It is a 6-hole casting with the speedometer drive on the passenger's side.
The housings pictured below both came out of Nova SS coupes with consoles.
The one in the second (lower) photo is the original transmission from my '66 L79. The other is a spare that I bought from a friend who had it in his drag car.



 

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Discussion Starter #4
Dave B

Can I replace my tail shaft casing with the correct one without more transmission changes. Or In other words is my Muncie Trans incompatibile with the proper tail shaft casing?
 

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According to the Muncie info I found, the 3846429 tail with drivers side speedo was used from 64-70 and the 3857584 tail with pass side speedo was used from 66-70. It's a fairly simple swap and I have two of the 3857584 tails if you are interested.
 

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Discussion Starter #6
Jim

I am interested in the 6 bolt / Passengers side speedometer Tail Shaft case. Before I dive into it, Can you give me an idea of what needs to be done. I just put a new balanced drive shaft in the car and one thing I am wondering if the driveshaft length changes and the splines etc.? what about the Speedo gear? What kind of expense am I looking at? just my luck to buy a 1965 Transmission for a 1966 Car. Thanks for all your help. Without you and Dave B and Bob I would still be in the dark. Dave J
 

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The only thing that could be different would be the position of the speedo gear on the output shaft and I'm not sure that is different. I can measure the position of the speedo driven gear on the two different tails tomorrow or maybe someone on here knows. The most you would have to do is move the drive gear on the shaft either forward or backward if the location of the driven gear is different fore and aft. The length of the tails is the same and the spline is on the output shaft, that you won't be changing, so no mods there. The tail housings are interchangeable since they used both from 66-70 depending on what vehicle the trans was going into. I'll sell the tail for $50 plus shipping, I think it will fit into a USPS flat rate box.
 

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Discussion Starter #8
Jim could you get an estimate on shipping to 37663. Meanwhile I will check with Trans guy to see what he will charge since I don’t have a lift I might as well let him do the swap and put the spacers and relocate the shifter. Thanks Dave
 

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Dave and Jim, I would appreciate it if you could handle the possible purchase by Private Message (PM). Buy/sell/negotiate is to be kept out of the regular forums. Thanks.

Bob
 

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Dave
The speedo hole on the pass side is about 9/16" further to the rear than the hole on the on the drivers side tail. Your trans guy will need to use a puller and pull your drive gear 9/16" to the rear, no biggie, he'll know what to do. Other than that, there will be no modifications needed. Everything from your trans will fit into the 3857584 tail housing and it will bolt right up. I guess further communications between us will need to be by PM, but I thought this speedo gear position information might be useful to someone else. I'll PM you a shipping estimate when I get to the post office.
 

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Discussion Starter #12
Dave B


For myself and others who might try this conversion- which 3 holes does the ITM shifter mount to and which ones need the special spacers?
 

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PM sent to you on shipping.

A guess on the mounting holes is probably the front three holes. Since spacers are involved and the front hole/boss is 1" further out than the other 5 ( see picture above), 1" spacers would be needed to make the shifter plate sit flat.

Jim
 

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Discussion Starter #14
Jim I got the housing in and everything hooked up just like you said it would so I am grateful for that. I’m only two steps away from completion of my 327 SS 66 Nova. As you had earlier predicted the speedometer gear is not lining up after I did the switch over to the passengers side. Do you know the fix? As soon as I get this resolved I am installing the Console and then I will post pictures so if anyone else tries this conversion they won’t have to work so hard to get to the finish line. Thanks all you guys for helping me with this project. Dave Jordan
 

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Muncie tail shaft case

Sounds like you have already changed it out, I was just going to add to be careful when you remove the the tapered pin holding the reverse shift shaft in place, it removes from the bottom up and allows you to disengage the shifter fork from the reverse gear. Most people that have never removed one drive it down and break the aluminum shift shaft boss on the tail shaft housing Good Luck.
 

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Muncie tail shaft case

As far as the speedo gear any transmission shop should have a speedometer gear puller that they can adjust your speedo gear to the right location. A 2 minute operation!
 

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Hey Dave, glad everything's fitting up for you. Unfortunately, to pull that drive gear back to where you need it, the tail housing needs to be off the trans. That's why I mentioned having your trans guy do it when he swapped the tail. Oh well, back under the car again. Probably best to take the trans to him, you need a long puller to pull the gear back on the shaft. As 409gasser said, easy job (once the trans is out and the tail housing is off). Good luck, it'll all be worth it once you're driving it.
Jim
 

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I had to swap t/housings on both of my son's transmissions, and was so tempted to do it myself - it's better that I took them both to my gear guy (Jody's Transmissions in Reading, PA) who not only swapped them out but also rebuilt them entirely for me. I would have been that guy who drove the pin the wrong way and then hammered the speedo gear back 3/4"!! :eek:
 

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Discussion Starter #19
Jim, my Trans guy is pulling the trans to get the speedo gears to line up and he recommends replacing the gears as the gears are worn and with the changes to the rear end and rear tires he says we are going to 10 mph off anyway. I read somewhere on here there is a trans shop or store where they can tell you and sell you the exact speedo set you need. Do you know who that could be? Dave
 

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Way back, GM used to have a chart in the parts catalog. Everything is computer now so I don't know if they still have access, might be worth a call if you know a friendly GM parts guy. Also there are Muncie parts places online, google should bring them up.
 
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