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TH 400 Auto to Tremec TKX Manual - 67 GTO

11K views 147 replies 12 participants last post by  RMTZ67 
#1 ·
I almost didn't buy my 67 because of the auto, but since the car was mass produced, without any rare options, I don't see converting it to a 4 Speed as likely to hurt it's value.

I love Muncie M20's, most people don't. Everyone says that the Tremec conversions are the way to go, but the price deters them. I've been searching for months, and I'm not seeing the Muncie being any cheaper than the TKO stuff.

Where are these "cheap" Muncies that everyone is seeing?

Also... I own a welding shop and I've installed a few of the TKO conversions for Chevelle customers. They completely change the floor and then I wouldn't be able use the GTO console. That would be a deal breaker for me. I'd want the car to be like a 67 GTO, with console.

I've read the conversion threads and visited the sites... no one seems to mention the console and everyone says that the Muncies are much cheaper. I'm looking to get this ball rolling!

Of course, anyone looking for a new, numbers correct, TH400, console, and Hurst HH, or knows where to find a 4 speed parts car, let me know!
 
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#2 ·
I have been kicking around installing a T56. The car I checked out last spring had a T56 on the floor, no console. Not the best adaptation to me. I have seen pictures of some with consoles I dont know if they used the automatic console or fabricated one. My console has a wood grain top so if the stick comes up in centered. I can adjust the hole and put new wood grain on top. I have a vinyl covered console in my mercury. It is factory but not a good look to me.
 
#3 ·
Some years ago, one of my customers brought me a Keisler 5-speed od to install in his factory 4-speed, console car. What an abortion! We would have had to swiss cheese the floor so bad that the console wouldn't have worked. I got him a Richmond 5-speed od and only had to do minor surgery to make it work. He had a used, junk console modified to clear the shifter and it looked great.
 
#7 ·
Wow. I'm impressed how good that actually looks. Does that work out so well because the shifter is not offset toward driver's side like it was with original four speed consoles? If that's the case, the original four speed console probably would not work for you anyhow.
 
#13 ·
I dont know about ARMY but that is a number I can live with.. I have spent more having a trans rebuilt for my truck (Well they ended up rebuilding the transfer case and rearend too. And only to got two more years out of it. For my car I have TH400 and a two speed that both have issues. So I am sinking good money no matter what.
I will buy a beater truck and drive it for 10 years and sink the money of a new truck on my 67. Money well spent in my book.
Why a 6spd? Have you ever been to Kansas? The faster its in your rear view the better. Driving across the plains is mind numbing.
 
#15 ·
I dont know about ARMY but that is a number I can live with.. I have spent more having a trans rebuilt for my truck (Well they ended up rebuilding the transfer case and rearend too. And only to got two more years out of it. For my car I have TH400 and a two speed that both have issues. So I am sinking good money no matter what.
I will buy a beater truck and drive it for 10 years and sink the money of a new truck on my 67. Money well spent in my book.
Why a 6spd? Have you ever been to Kansas? The faster its in your rear view the better. Driving across the plains is mind numbing.
My cousins just bought 1000 acres in Kansas, for $500. I thought they got a deal, but maybe not!
 
#19 ·
I have been reading up on the TKX manual trans and they claim no modifications are need to the tunnel and have 3 different shift positions and will bolt up to a GM bell housing without an adapter. I am looking to turn my 69 Nova into a five speed. A little off topic but I am also looking at Gear Vendor bolt on overdrive unit that lets you split all your gears or just run it as an overdrive only, but that unit is 3k on its own.
 
#20 ·
I have no problem spending money for value. I just don't like automatic cars. I don't mind welding in a new tunnel... Not that I'm in a hurry to do it, but I'm a welder and I've already done two Chevelles, so it's just a day of work, and 90% of that is paint.

The consistent dilemma here is the console. I gotta have a walnut console in the 67. It's just too iconic to ditch. A muncie cannot use the Hurst auto console, because the shifter is offset. The TKO is centered, so "it has been said" that the Hurst auto console will work with it. If so, then TKO it is! Honestly, I do digital templating, so making a new console for the Muncie would also be easy, but I'm finding the TKO to be the same price as the Muncies, now.

Pro's of the TKO are that companies sell it as an all inclusive package, and you get over drive. So even if it's another $1000 it's just worth it. Plus, my rebuilt TH400 would likely bring a nice penny
 
#21 ·
the TKO is good but the new TKX is more of a" direct fit"/ replacement for the muncie, it is a trimmer unit. I a not sure if the driveshaft needs to shortened or not but I imagine that it would need some modification and the five speed would be a blessing on the highway. If I do pull the trigger on a new gear box I will probably sell the muncie, unless I get a new project to put it in.😂😂
 
#23 ·
I decided to update this thread, since I'm going ahead with the conversion.

Here were my considerations:
  1. Overdrive didn't matter to me. Nice to have, but I don't drive a 67 GTO for economics. So, in this regard, the Tremec TKX is no better than a Muncie to me.
  2. Console preservation. Although I lean in the Muncie direction, it requires a "one year", rare 4 speed console. The TKX does not, because the shifter exits through the automatic shifter opening.
  3. Price. It got very deceptive here:
    1. On average, most of the Muncies are all going for $2500-$3000, and very few have the speedometer on the right side. So... Even if you find a great Muncie for $1500, you still need the rare 4 speed console and doghouse... This easily brings the cost into Tremecville.
    2. Linkage: A hydraulic Mcloud setup, with a slave, stainless steel braided lines, heim joints, and a hydraulic, self adjusting throwout bearing is $600. The old z bar set up is at least $350 and it requires frame welding.
    3. Clutch and bellhousing costs are equal.
    4. The new TKX shifts better and it requires no mods to the floor.
My out the door, shipped cost will be $5000. I could not assemble a Muncie package for less than $4000 (unless I went with used or an unverifiable rebuilt). When you figure in; no frame, doghouse, or console mods, and the added overdrive, I just can't resist.
 
#25 ·
Unless I missed it, none of the other TKX threads address using a manual transmission with an auto console, and since that's the single most critical aspect of the conversion for me, I'm reviving my old thread.

A few popular issues:
  1. If you have an auto and you simply want a manual, and overdrive is NOT important, you may be considering a Muncie. After one year of searching I was not able to find any quality Muncie, for less than $2000. And most were significantly more! I don't consider buying a 50-year-old Muncie off ebay, from a stranger who rebuilt it, an option worth visiting, but if you're big on trust and are willing to potentially gamble with hundreds of $ shipping back and forth, go for it. Bottom line... 50-year-old Muncie 4 speed = $2500 from a reputable source VS. Brand new TKX with over drive for $2800.
  2. A factory 4 Speed GTO has an offset shifter, forward. A factory TH400 car has the shifter centered and back. If your car is original, you have a problem. 67 was a one year console and the manual version is not reproduced. Even if you do find a used one, you then have to buy a dog house, weld it to the floor, and then buy new carpet. So, since my car is all original and since I was able to use a factory auto console in the SS Chevelle that I converted, I'm going to make my auto console work.
Concerns:
  • Will I need to mod my driveshaft? There's less than a 1" difference in trans length between the TH400 and TKX.
  • Can I buy offset dowels, in advance, in case I need them?
Note's:
  1. Currently, wide ratio TKX's are tough to get.
  2. Currently, bell housings are only affordable at one place... So, get one while you can, or pay $800 for a Lakewood or Quick Time.
  3. I'm going into this, assuming that I'll need to use offset dowels and mod my driveshaft.
  4. I'm holding the TKX shifter to the back and hopefully it will come up through the hole where the factory Hurst His and Hers, currently resides. If not, I'll weld up my own offset. I'll starting out with an 8" rise Hurst lever, with a 3" back pull.
  5. Using a Ram Clutch and Flywheel and a Mc Cloud hydraulic clutch and throw-out bearing.
  6. I bought new auto carpet and I plan on stripping and painting the floor at the same time.
 
#26 ·
I didn't use Silver Sport, because they (repeatedly) werent easily grasping the concept of needing to use my original console. They kept trying to sell me a dog house, and they had no idea that it would require new carpet and a new console... AND, I was not able to convince them.

Also, they seemed insistent on my using a z bar setup... which may save some coin, but requires welding to the frame in an inaccessible area.

Finally, they got a little attitude with me, so....
 
#30 ·
So will a manual console not fit or too expensive, wouldn't you want one instead of modifying yours? ...I would think it would look nicer but I haven't seen one converted either. An inch difference is big on the drive shaft I think, so if you have to have one made I would get a nice chrome molly one made up with forged yokes so you have piece of mind that it isn't a weak link. I know everyone has their opinion but my trans guy only uses McLeod clutches, I have the super street pro. Lastly I don't have experience with hydraulic clutches but what are the advantages, only thing I know is Solar68 is having some issues with his but maybe it just needs adjusting and my friend with a 66 Fairlane had his blow out with hardly any miles on it. Just wondering out loud ;)
 
#32 ·
So will a manual console not fit or too expensive, wouldn't you want one instead of modifying yours?
A manual console will fit if I weld in a dog house, change my carpet, and find a magic lamp, get three wishes, and use one to find a one year, 67 GTO manual console. I wont need to modify mine.

I would think it would look nicer but I haven't seen one converted either
It'll look like a four speed. Personally, I like the way the Hurst His and Hers looks.

I know everyone has their opinion but my trans guy only uses McLeod clutches
Personally, I like OEM LUK and have always used them. Bob Hanlon is the one who recommends RAM. I think they're all fine.

Lastly I don't have experience with hydraulic clutches but what are the advantages, only thing I know is Solar68 is having some issues with his but maybe it just needs adjusting and my friend with a 66 Fairlane had his blow out with hardly any miles on it. Just wondering out loud ;)
Advantages are never having to adjust, smoother and more consistent engagement, less pedal effort, not having to dismantle your car and weld a tab on the frame, fewer parts, more efficient, less to wear.

Disadvantages are cost.
 
#31 ·
You won't know if the console will work until you get the trans/shifter installed. Maybe check with your buddy, or he might be able to use your car for a prototype shifter extension that he can then market - and you get a free one. (y)

 
#33 ·
I talked to Bob for about an hour yesterday. I have the distance from the block that the shifter will protrude on the TKX, now I just need a sunny day to get under the car and do some measuring. The His and Hers is definitely further back than the 4 speed, and flipping the TKX shifter will give me 3 more inches (TWSS). After that, Bob can make an offset if I need more, but I could also make my own.

Ironically, they vacation all summer long, one mile from my home, and I vacation all summer long, one mile from their shop.
 
#41 ·
@PontiacJim

What's your take on Ujoints?

The Tremec TKX comes with 1330's, and stock 67 GTO is 1310.

So, should I have the driveshaft shop put a 1330 end on my driveshaft, or just use a conversion joint? Any bene?

Like Baaad65, I am using the larger 1350 sized u-joints. My 9" rear uses the 1350 pinion yoke and then I got the 1350 trans yoke. I will have to have a driveshaft made up and it will be for the 1350 joints.

You should have the 1330 u-joints - the bigger size that Pontiac used. The smaller size, 1310, is the Chevy size.

You can go 1330, but my personal opinion, if you have to purchase a new driveshaft, is to go 1350. Get a 1350 trans yoke, driveshaft ends made for 1350 u-joints, then get a conversion u-joint that has the 1350/1330 caps so you can mate the driveshaft to the Pontiac rear.

Check this guide out from Currie. You will see the different types of u-joints and scroll down and see the conversion type u-joints.

 
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