# 4 spd conversion



## Inda_bebe (Sep 11, 2011)

My th350 trans is out of commission at the moment and I was thinking of replacing it with a4 or 5 speed. What affordable transmissions are available for my 400 motor. I will be taking to a trans shop to do the conversion. What price out the for should I be expecting before committing to it?


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## BearGFR (Aug 25, 2008)

One of the big questions is, how much torque/power does your 400 make? "Not just any old" transmission is capable of surviving behind even a stock Pontiac 400.

"Affordable" is a relative term too... 

There is a long-running thread over on the Performance Years forum about a guy who has put a TKO600 6-speed into his 68 GTO. He seems to like the end result a lot, but sure had some 'trials and tribulations' getting it done. It's good reference material for anyone considering a similar conversion, I think. The thread is entitled: "TKO600, the Odyssey Continues..... "

Bear


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## geeteeohguy (Feb 2, 2008)

For a straight, factory type conversion (Muncie 4 speed), you are looking at about $2000 and up. You'll need the trans the bellhousing, the linkage, the Z bar, the pedals, the shifter, the flywheel, driveshaft/yoke, and the frame tab. For a 5 speed aftermarket, prices really soar: $2500 to $6000. IMO, you'd be better served spending 1-2k on a beefed up rebuilt automatic overdrive trans, like a 200r4 or a 700r4. Most of the aftermarket 5 speeds require heavy floorpan fabrication to make them fit.


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## Bensjammin66 (May 12, 2009)

geeteeohguy said:


> For a straight, factory type conversion (Muncie 4 speed), you are looking at about $2000 and up. You'll need the trans the bellhousing, the linkage, the Z bar, the pedals, the shifter, the flywheel, driveshaft/yoke, and the frame tab. For a 5 speed aftermarket, prices really soar: $2500 to $6000. IMO, you'd be better served spending 1-2k on a beefed up rebuilt automatic overdrive trans, like a 200r4 or a 700r4. Most of the aftermarket 5 speeds require heavy floorpan fabrication to make them fit.


:agree

This is spot on. I converted my '66 from a TH350 to a TKO600 5 speed. NOT a cost friendly conversion. Hays flywheel, Ram clutch, driveshaft shortening, new tunnel, pedals, zbar, etc etc etc and i was well over $3,000 in. I'll tell you what though, with 3.73 gears and a 2000rpm 70mph on 27" tires i am THRILLED with it! Oh and you can use your crossmember with tremec you just need to slide it back 4" and drill the frame. No biggie. 

A muncie 4 speed is an ok option. Same driveshaft, crossmember, simple floor mod to allow the shifter to pass through. Pedals and Zbars can be had on EBAY cheap too. Your crank is "probably" drilled for a pilot bearing but make sure you check. Ive seen rebuilt m21 muncies at swap meets that'll handle moderate torque for $1,000.00. Fresh rebuilds mind you. My TKO was $2300 new.

What they need are rebuilds with new customizable gears for Muncies. That 1:1 4th really sucks. If they made a .70 4th conversion I may have never bought a 5 speed. The TKO is .64:1 5th. 

The 200R is a 2.74 1st and a .67 4th. 
The 700R is a 3.06 1st and a .70 4th.
The TH350 is 2.52 1st and a 1.0 3rd. <-- Easy to see why you hate it... 

In conclusion the 4 speed is cheap gear bangin fun with high rpms in 4th if you have any sort of "fun" gear out back. The TKO is gear bangin fun with no down side other than cost. The autos, well, 3 speeds are 3 speeds and between the 4 speed autos id say the 700s are more abundant and have a better first gear, but get one thats been built. My brothers old sbc monte carlo destroyed one and it makes no where near the torque your 400 does.


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## Inda_bebe (Sep 11, 2011)

i guess ill ride this tranny till it is shot then ill feel better about doing a permenent upgrade. for now, ill just have fun w/ what i have. thanks for the advice


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## RunninLeMans (Apr 3, 2014)

First post on this forum, did some reading, glad I joined. I'm in the middle of this on a '64 LeMans, and yea, I have about $2,000 into parts, and I got a good deal on the M20. Traded a 1935 Mosin Nagant worth $250 for one with an Autogear case and spent $400 on a rebuild. Getting ready to rig in the tranny and shifter this weekend to see where the hole in the floor lines up and see how the not-yet-modified console goes together. Good news is when I peeled back my carpets, my floors were solid and spotless! Bought this car a year ago for the good steel body, but the motor was bad, so that used up some of the winter. Will post anything interesting I learn along the way....


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## geeteeohguy (Feb 2, 2008)

Runnin', if you already have the shifter porch (doghouse) for the 4 speed, it will fit the floorpan perfectly in only ONE spot. Slide it on the tunnel until it fits perfectly, then outline the perimiter with a magic marker. Mark another perimiter about 1 inch inside the tracing (there needs to be a flange for the porch screws) and cut it out with a cut-off wheel. You will have a perfectly located hole. No guesswork or measuring required. But you MUST have the factory shifter porch.


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## RunninLeMans (Apr 3, 2014)

Thanks for that reply, I did actually test-fit the porch yesterday, and it did not quite fit perfectly, but pretty close. I bought a used original unit, unless someone beat up a new one and left it out in the rain for some surface rust! Maybe my floor pans are replacements and not quite original....


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## geeteeohguy (Feb 2, 2008)

That could be. Measure to make sure, before you cut!!


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## PontiacJim (Dec 29, 2012)

The assorted conversions already listed are about right. I looked into replacing my factory 3-speed manual with a Muncie 4 sp. I am not too keen on rebuilt transmissions, but know they do make new parts to provide a solid unit. Building a stout 455CI, I wanted the M-22 Rockcrusher, I like the whining sound of the straight cut gears and they can handle most engines. Used and rebuilt M-22's are expensive because they did not produce a big number of factory units.

Next option was a new manufactured M-22 Rockcrusher with some internal upgrade to make it even better. The price was $1800 (plus shipping) when I was looking. Then you need the shifter, which was another $375 for the Competition Plus. So, you got almost $2200 in the transmission and no overdrive.

The Tremec TKO-600 (they also offer the TKO-500) I got at the time was $2100 (free shipping) which has the built in shifter/slider rail and all you have to do is add the handle -which I have in my parts "stuff". So now I have a trans that will handle 600 ft lbs of torque AND overdrive. I can run some 3.90 gearing and have acceleration and cruise economy (if that is possible with a built engine). There is another website that uses the Muncie case and parts, and changes the gears inside to create an overdrive, BUT, it then is basically a 3 speed with 4th being your overdrive.

Now the TKO requires some floor mods to fit, drive shaft shortening, a different input shaft, speedo cable adaptation, and moving the trans cross member back. There is a complete kit to do a bolt-in, but the price goes up. As said earlier, now you need all the pedal hardware, bell housing, flywheel, clutch,pressure plate, through out bearing, clutch fork, and small parts. This adds up as well. So the whole deal is not so inexpensive.

I like the idea of installing a modern 4-speed automatic with overdrive. Not too difficult and the conversion has been covered in the Pontiac magazines. Still not inexpensive when you buy a prepped transmission and matching torque converter from one of the name brand trans builders. For example, Butler Performance offers a TCI TH2004R OD unit complete, and rated to 750 HP, needing no bellhousing adapter and will bolt in for $2900.......or maybe the 6 speed for $6,950 (ouch). Probably going to have to buy a trans shifter, a trans oil cooler/lines, and most likely alter your drive shaft length.

Was going to mention the Keisler 5-speed, but appears they have gone bankrupt.

So, you have options either way. If you can do it yourself, you certainly save. If you have a shop do it, labor prices push the costs higher.


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## 1972LeMans (May 4, 2014)

So, I recently blew my engine and am going to rebuild it. I want to lower the gears in the back because I currently have 4.10s in the bank and want more of a cruiser and also want to put in a manual and am thinking of a Muncie 4 speed. Will the manual help take some stress off the engine better than the turbo 400 in there now? 

Sent from AutoGuide.com App


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## ALKYGTO (Mar 29, 2010)

Not really since both have a 1 to 1 fourth gear. Either invest in an overdrive and/or change to a 3:23 or numerically higher rear gear.


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## 666bbl (Apr 13, 2014)

Nothin like a havin a Muncie trans, huh? When asked what you have in there and just sayin it has some onlookers in love with your ride. Now for the buzzkill, did you ever notice how many of those things have the ears welded back on? Why is that? Most likely because it was beat on like 4spds simply have a way of MAKING YOU DO IT  I might suggest a simple upgrade to a BW Super T-10. Literally millions made and many lived behind Pontiac or Olds 400/403 motors in T/As. Pretty much a "nut and bolt" install and you have something a little tougher back there. Did I say they used to be much less than a Muncie? I haven't priced one in a while but they were always HUNDREDS less and a little tougher too. If you want real tough you could find and older iron case version but most of those are dedicated to early stuff like Vettes and maybe some Ford products. If you have a mild motor and just want to cruise there's a way to build Saginaw 4spd with a mechanical OD unit from a Sag 3spd. There's some parking concerns and they don't like to be beat hard. If you just shift, no power shifting, they'll last a good long time but start playin "Ronnie Sox" and you'll make sad memories. Just some alternatives...


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## the65gto (Oct 9, 2008)

I ground up my Muncie once back in 68. :nonod: Got a BW Super T-10 as a replacement. Tough unit, ain't as easy getting it back in place because of the added weight.


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## geeteeohguy (Feb 2, 2008)

Funny, my experience and research shows that the Muncie is a_ stronger _unit than the T-10, in pretty much every case. The T-10 is a good box, though. As for a 4 speed being easier on the equipment, just the opposite. An automatic with torque converter cushions a lot of the driveline shock. A manual trans does not. Much easier to break parts with a manual trans. I have owned many old GTO's, and all the automatic cars had their original engines in place. Not _one_ of the stickshift cars did.


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## the65gto (Oct 9, 2008)

It might have been my full throttle shifts in my younger years:eek2: It came apart from the inside, front shaft had a lot of play. I remember some thing about a "rock crusher" version around that time????


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## Rich1 (Jul 26, 2014)

Hello all.
Just joined this forum. The comments have made me ponder...I have been looking at 64 GTO with an auto for purchase--with the intention of converting it to a 4 speed. After reading comments--I may let that one go and keep looking for a manual.


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## RunninLeMans (Apr 3, 2014)

Rich - that's what I'd do, mine's done and I have $2,500 in it down to the last backup light switch. It was also probably 30, 40 manhours of work, uh, I mean awesome garage time....


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## PontiacJim (Dec 29, 2012)

RunninLeMans said:


> Rich - that's what I'd do, mine's done and I have $2,500 in it down to the last backup light switch. It was also probably 30, 40 manhours of work, uh, I mean awesome garage time....


Yes, $2,500 also included some horse trading for your 4-speed, if I read your earlier post correctly. Your total price would most likely be increased if you had to purchase the used Muncie 4-speed outright. So I think I may be safe in saying that $2,500 would be fairly close to "as low as you can go" with around $3,000 a closer average for a used/rebuilt Muncie conversion/installation? Now I also assume you did all your own work and did not farm it out other than the 4-speed rebuild, correct? If so, then those who do not have the mechanical skill would have to include labor for the conversion/installation as well.

Your conversion is based on a used/rebuilt 4-speed. The new Muncie 4-speeds were (last time I looked) about $1,800. More added expense if you decided to go new as some prefer.

Then there is the TKO 5-speed that many use and it seems to be $2,100 to $2,300 and up depending on where you buy it and how you spec it out. This will also require some floor mods to fit, driveshaft work, etc.. So again, this becomes even higher in overall pricing -and whether you install it or have it done for you.

So a good follow up. I think this is some honest pricing/options for anyone who is thinking of doing a 4/5 speed install or conversion.

Let me know if I may have missed something or miscalculated as I think this would make a good "sticky" for others wanting to know what the costs are.:thumbsup:


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## geeteeohguy (Feb 2, 2008)

When I helped a good friend restore his '67 GTO about 4 years ago, he converted it to a 4 speed. It cost him nothing, really. Because: he's owned the car since 1977, and had ALL the parts that he got in the late '70's, including the console. That, and he rebuilds Muncies for fun. So, if you have all the parts, and are a skilled technician, it's easy. If you're a regular Joe, even a good tech, but need to buy anything, it gets very, very expensive. Not a personal fan of the 5 speed conversion, although it 'updates' the car. I like mine with an uncut floorpan and a Hurst shifter, the way it was intended.


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