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Discussion Starter · #1 ·
I have a 66 with a 327 and a TH 400 tranny (3.08 rear). Really would like to have a 4 speed. There is a Muncie M21 for sale locally for $1000 from a 1969 Close ratio,hurst vertical gate shifter,621 reproduction bell housing. Will this be a good choice for a 4 speed conversion? Anyone have any experience converting to a 4 speed in a 2nd Gen?

Your opinions are welcome,
 

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I converted a 64 283/3 speed to a ZZ4/Muncie M-20 4-speeder. The M21 has a 2.20 first, so when hooked up to a 3.08 will be a perfect street combo considering the cost of fuel ,but slow on the launch if you plan on beating on it. The conversion should be cake with all that good hardware.
My second 64 now has a TH350 in place of original PG.That was really a cake walk!

I prefer the 4 speed. I never lost the enjoyment of shifting.
 

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I haven't done a conversion on a 2nd gen yet, but we've 2 5th gens and that 2nd gen should be much simpler. Honestly that sounds like a good deal for an M21, just make sure its good before you buy it. Manuals get pricey to rebuild. I have an M21 in my current 5th gen elco, does this one have 1 or 2 rings on the input shaft? 2 different ratios
 

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Discussion Starter · #4 ·
I am not sure what this M21 has as far as rings or ratios as all it had listed was what I posted. I don't know much about transmissions so any recommendations to look for would be helpful.
 

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Obviously you would want to make sure the tranmission turns, you can place it in gear by hand and spin in the be sure. Then there is the side cover where the shifter linkage bolts up. I would take the side cover off and look for worn gears or syncros, also keep and eye out for metal chips. Bring a flashlight with you.
The single ring M21 is the most common version of the tranmission is a really good tranny, the 2 ring design is less commonly known, and has a lower ratio. Mix that with some gears in the 3.00 range (i run 3.70's myself) and the launch is alot of fun.
 

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I have not done a stick swap in an elky but i did one in my 88 v8 s10 blazer. Really if you get the trans, peddles,clutch,flywheel,crossmember,ect, its straight forward. I made a crossmember out of box tubing, used a 80 camaro flywheel and clutch, and just a suggestion but i would go to a hydralic clutch. You can by a hydralic throwout bearing from summit racing http://www.summitracing.com/parts/HRE-82870/ easy install plus no clutch leg. I used a peddle assembly out of a wrecked s10. You could do the same or buy an after market peddle master cylinder combo. just my 10 cents.
 

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make sure you can get all of the clutch linkage and pedals,the pieces get pricey buying seperately but a very easy swap and well worth it in turms of driveing fun
 

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I sure miss my M21, but I was running it with a 4.56 in a truck and a Husrt Comp plus shifter. Loved it. The Th400 is certianly overkill with your 327 IMO. As much as I like manual transmissions and working a clutch, I've stayed automatic just for the simplicity and cheap cheap cheap compared to manuals, and alot less broken parts if you have any kind of horsepower. Notice you said the trans alone is $1000. Add clutch, linkage, bell housing, etc, it's going to get pricey. I can get at least 2 Th350's with converters for that $1000 and with a good shift kit and a nice B&M ratchet shifter, have just about as much fun.
So what actually are wanting to accomplish with the swap? I"m thinking your money might be better spent with a gear change and a locker or limited slip diff. :dontknow:
 

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Discussion Starter · #10 ·
Well I guess my first objective is to get it road worthy but I really want a manual 4 speed and just trying to weigh out the options as it appears that I might be having a torque converter issue. Figure that I should put the money to what I really want instead of repairing what I currently have. However if it exponentially more expensive to put a manual in then I will probably have to put that project off to another time.
 

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A decent remnn Th400 converter is less than $100. I think I'd get it road worthy first. Then a rear gear change with a locker second and then see how I like the Th400. After all that, if still itching for the manual swap, then go for it. I do feel your pain. I'd love to go manual too, but it's just pricey to do. Automatics are just to dang cheap in comparison. I'd love to find one already set up or originally manual trans.
 

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I guess i was just lucky i need a body of resto, i put mine on the floor. very easy to do, and since i put new floors in, i just order the 4 speed hump.

on a side note, i was glade i did, found a few bolts that were not grade 8 in the fly wheel.:nanawrench:
 

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Discussion Starter · #13 ·
Thanks all for the inputs. I really would like to do the manual conversion but in the meantime it looks like I should just get the auto working. By the way I may have found an expensive TH 350. How difficult is it to swap out the Th450 for the TH 350? Is it a clean swap or are modifications necessary?
 

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I think you mean, change from Th400 (th450) to Th350. You will move your crossmember to OEM position, the driveshaft length and yoke will need modified. Past the driveshaft mods, it is clean easy swap. Same flywheel, and you can even use the same torque converter, with exception, you've mentioned your torque converter is ailing, so you'd replace that anyway. Shift linkage is also the same. Vacuum line moves from right front of the trans, to right rear, but this should be easy also. You'll also need to hook up a detent (kickdown) cable for the Th350 to the carb linkage. In my opinion, now you're thinking more on the right track. The ONLY advantage a Th400 has over a Th350 is strength but that comes at a cost. For a mild 327, the Th350 would be the right choice and Th400 is overkill that does not have as good of a first gear, although minor, more weight, and more parastitic horsepower loss, meaning the Th400 robs more horsepower from the motor to operate it and turn the heavier assembly and gets less horsepower to the rear wheels and to the ground. I think you'd be satisfied with a nice firm shifting Th350 and still have dependaility and durability enough to hold up to your mild 327.
 

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One of the biggest issues of a 4 speed is the Z bar and mounting. If it is not a factory 4 speed car then there is no Z bar mount. Of course a welder fixes that with no problem. I did a 67 impala back many years ago, from a powerglide to a m21. Not to bad at all.
 

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If you have the cash you might want to get that deal. That bellhousing costs at least $ 200 and the shifter goes for $ 250 and up. So you would be getting the tranny for $ 600. That's assuming everything is in good condition. Besides the fun a 4 speed will add to your truck a clean factory looking conversion should easily add $3000 to $5000 value if you ever sell.
I would fix your auto now do some research and find the right parts then bolt in the conversion.
As for your original question the parts will work. Like mentioned if the muncie is a close ratio you may want to change gears if you drive in any stop and go traffic.
Russ
 

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Also for what it's worth, The Hurst Vertical Gate was my all time favorite for a 4sp.

I have also used a Long shifter for a doug nash 5 speed and that was a very nice shifter
 

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I don't have an answer for your bell housing question, but my 2 cents on the conversion to 4sp: do what you really want, and if you can't afford it right now, maybe sit a bit until you can? I wanted a 4-speed, just for the simple pleasure it brings me. I have had automatics with shift kits - I've even had them with manual valve bodies. That is all good too, I'm not bashing it. But if you want is to have a 4-speed, then line up the prices on everything you need, then decide if you want to do it or not. Getting the pedals up in there; mounting the Z-bar (and getting pushrods through the firewall); carving out the floor (console? rubber boot?); clearing exhaust from the clutch linkage; crossmember modifications; and the driveshaft will be the difficult parts. Make sure you get a flywheel that is balanced appropriately to your engine type too, btw. Get a good clutch, not a cheap one. But hey, if a 4-speed is ultimately what you want (and I dig that, it's what I wanted), you only live once, don't compromise, - make it happen. If you can be happy with a hard-shifting TH350, then they are awesome too. In fact, I actually have much love for powerglides, they are so simple, I used to build them myself. But there are several different versions of casings, and on and on. . . so a nice TH350 is a great choice for an auto on your small block (as mentioned). And when it comes to fun, shifting 3 times is better than shifting two (for me, anyway).
 
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