Advice/help with auto to manual swap 67 GTO
 

Hello all,

I recently acquired this 67 GTO. It has a 400 in it. The car came from the factory with a manual transmission (I'm not sure which one) but at some point it had a TH-400 swapped in. I would like to remove the auto and put a manual back in. I know a lot of people are doing Tremec swaps right now but I have no interest in that.

All I want to do is put an original style manual back as close to the stock configuration as possible. This will keep costs down, and cost is a concern - this is not a restored car - it's even more on the beater side of being what most would call a "driver".

From what I have gathered so far, a swap back to a Muncie M20-21-22 or Dearborn 3-speed would be fairly straightforward as the linkage mounting tab (I think) is still on the frame and the crossmember and driveshaft can remain the same. What I am hoping someone can help me with is a list of parts and maybe part numbers of the stuff I will need to start gathering to get the swap done such as bellhousing, clutch linkage, shifter and shift linkage, clutch and flywheel, etc.

I'm what most would call a backyard mechanic but I've gotten my hands into some semi-advanced stuff. I swapped a 5-speed into a Ford Crown Victoria and I can handle any kind of maintenance short of rebuilding motors, rear ends and transmissions. I feel more than capable of pulling this off in my garage, I just need some guidance as I am BRAND NEW to Pontiacs and haven't really worked on stuff much older than 70's and 80's vintage.

Thanks for any help. Car is in storage for the long NY winter right now so I plan to use the next 4 months to budget and gather parts and expertise and tear into it around May.

Get the correct 67 pedal set up.
You will need a console too.
Make sure the stud for the z bar is on the frame first.
I did this swap. Went Muncie first, now a tkx.
Not to hard to do.
Just use 1967 parts. Especially the pedals.

Sent from my SM-A136U using Tapatalk

Good choice to put it back as built.
I will add, to save a few bucks, you don't have to have a console.

https://live.staticflickr.com/65535/...52e2b617_h.jpg

Make sure you get an m20 unless you have a 3.90 or steeper gear

This company has nice stuff.

https://4speedconversions-com.3dcartstores.com/

Also, FranksPontiacParts.com is a good source for original parts.

Call SK speed at 631-957-9427. *I forgot about Brian at SK right there in New York. He's a Muncie guru with tons of parts.

Excellent info, thank you guys. And I do have the manual console!

Can anybody tell me what Muncie transmissions are compatible with the 67 GTO? Are there certain casting numbers/part numbers/donor cars I should be looking for?

X2 on both of these! 4speed conversions has been very helpful (and knowledgeable!) when I have contacted them.

Dennis Maroudas in Kentucky has also helped me out.

Good luck!

James Q

You will need a 60” driveshaft. The TH-400 driveshaft is a different length. The yoke is different also

You can use almost any Muncie 4 speed except long tail shaft big car transmissions. If you're not looking for originality you can use Chevy, Buick or Olds. There are minor differences that can be worked around. Make sure your clutch disc matches the input shaft spline of the trans you use. Get trans first then buy a clutch to match. Some trans have speedometer cable on the left and some on the right. You can get a cable length to match. You will need a pivot ball that screws into the side of the engine. If this is NOT the original engine make sure that the pilot bearing fits into the rear of the crankshaft. Some Pontiac engines that came with automatic transmissions never had the crank drilled for one. Good luck.

Over the life of my '67 I swapped back and forth between the original Muncie and a T400 several times and only had to change the driveshaft yoke out. The two driveshafts only differ by something like a 1/4" or less and I don't really know why Pontiac bothered with two driveshafts so close together..

Oh man that worries me. I know the engine in the car now is NOT the original and I have no idea what it's out of or if the crank is drilled for a pilot bearing. This was my brother's car and he passed away - I have no way of knowing what's there without pulling the TH400 and looking. What a colossal waste of time if it's not drilled.

Is there a particular flywheel I need to spec out, or just look one up for a 67? Did they have different diameter clutches in 67?

Thanks for all the info, guys. I'm assuming if I keep my current driveshaft there will be enough room on the slip to make up for 1/4" difference?

As far as the yoke, what will I need to source? Just a yoke from a manual trans car? What is different about the automatic yoke?

Also, has anyone used this kit or stuff from this company before? I know "OEM is best" and all but this kit would eliminate a lot of headaches for a decent price.

https://www.thepartsplaceinc.com/pro...bushings/16891

Also thanks for the info on the Muncie. I am currently scouring my local Facebook marketplace for one. They seem pretty common, all of them seem to go for around 850-1200.

That kit seems reasonably priced and complete. You won't have to waste lots of time searching for and then shipping parts. You still need a bellhousing. I swapped a 4speed into my 67 Tempest back in 1981 and used the original 2speed auto driveshaft, no problem. The yoke on a th400 IS different . We'd like to see better pics of the car please. PS I'm in Poughkeepsie.

I ran into the same problem with an automatic coded 66 389. After having the motor rebuilt ! We were able to custom fit a brass bushing into the rear of the crankshaft. Been there for 25+ years. The yoke you need is very common. A 350 automatic and 2 speed tranny use the same yoke.

I bought all my swap parts thru Ames, except I fabricated the clutch linkage with heim joints from McMaster. Everything fit well and I would recommend. As far as the flywheel, make sure you note if the flywheel you’re looking at is neutral balance or factory balance.

Ames p/n’s:
R135B pedals $99
R101 pedal pads $12
R167RK full linkage kit (z-bar, linkage, springs, fork etc) $259

A T400 driveshaft is a different length than one for a 2 speed auto, T350 or manual trans.

Based on what I've found, the TH400 driveshaft is like 5/8" difference. I assume that won't necessitate a new or modified shaft. The yoke - does anyone have a part number or just look for one off a TH350 or 2-speed auto?

Encouraging to hear that something like that is possible.

Yes, an original '67 GTO w T400 had a 59 3/8" long driveshaft with the med length 3R T400 yoke. For a '64-67 Pontiac A-body with a small output shaft Muncie, you'll need a driveshaft 60.00" long center to center on the 3R ujoints. Thats assuming your cars rearend is:
-the original or a replacement Pontiac 8.2 10 bolt rear,
-or a late '67-70 Type "O" Olds 10 bolt (smooth 12 bolt cover),
-or '68-70 BUICK 10 bolt.


There are no visible part numbers on original GM driveshafts. Just different styles, & lengths. Originally there were color bands that quickly helped the assembly line worker ID the version of driveshaft shaft. Have quite a few excellent condition used driveshafts & have sold several dozen others. One of the expenses is today's crazy shipping prices. When I ship a driveshaft, it's an oversize shipment & I typ ship in a section of PVC pipe from Lowes to prevent damage.

Keeping in mind the car was originally a manual, I'm curious if the manual driveshaft was mated to the TH400 yoke. Again, we're talking less than an inch difference. Like I said I've never had a car like this but worked on many others - that's a very small difference that can usually be made up with the slip yoke's travel without much if any vibration or issues. Am I completely off base?