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Converting a 68-72 from auto to 4sp with pictures

71K views 44 replies 35 participants last post by  DZAUTO 
#1 · (Edited)
We have been converting my son's 68 4dr 300 from a PG to a Muncie. This has been a VERY slow ongoing process since he wrecked it a few yrs ago, but now the progress has speeded up.
I had the pictures in BENCH RACING and the moderator suggested I put the pictures (especially proper clutch linkage) here. So here is a PG car converted to Muncie with all the correct parts (except the Hurst).

This is what we have been working with (yes, we have all the parts, it's just been taking time to get my son motivated to work on it).

Except for cutting the hole in the floor for the shifter hump and a hole in the firewall for the clutch push rod, converting an auto tranny 68-72 car to a manual tranny is a 100% bolt-in swap.








The ORIGINAL cross member is retained (depending on which tranny is installed, all frames have multiple holes for proper positioning of the cross member). All the cross members are the same. FACTORY 4sp cars have a couple of brackets welded to the cross member for the factory Muncie shifter, but original FACTORY Muncie shifters will eventually become troublesome, thus it is wiser to go with a Hurst shifter and install one of the bolt-on replica MUNCIE shift handles (sold by Ground Up).


This is the bench seat hump installed. It is an ORIGINAL hump from another car (the repo humps are excellent).






 
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#2 · (Edited)
His car is a NON-pwr brake car, thus the pedals are even with each other (the clutch pedal is always higher on PB cars).
The shiny triangular metal piece (behind the clutch pedal) is the retainer for the clutch pushrod boot which is installed from INSIDE the car. The 3 holes for the bolts are already there.
One MINOR part that needs to be added (which is NOT obvious), is a rubber bumper for the clutch pedal. The bracket (up under the dash) for the clutch/brake pedals already has the slot for pushing in the bumper (shown below). The brake pedal already has this same bumper. Yes, you have to be a contortionist to get that little bumper in. :D




All correct clutch linkage from a donor car.
UNLIKE the 64-67 Chevelles, ALLLLLLLLLLLLLLLLLLLL 68-72 Chevelles already have FACTORY punched holes in the frame for the frame mounted Z-bar bracket. Also, the bolts are self threading and the 2 bolts required are ALREADY on an auto tranny car. On the side of the frame of an auto tranny car, there is a bracket for the shift linkage (which is not used on manual tranny cars). That bracket is attached with the SAME self threading bolts thar are needed for the Z-bar bracket. So you won't have to search around for correct Z-bar bracket bolts. Put some healthy down pressure on a socket and they will screw right into the frame holes. :thumbsup:






 
#6 ·
I can't thank you enough for these photos. I just dropped a 350 in my 69 Chevelle and have a Richmond 4 speed trans installed. I put my headers on yesterday and took the Z bar just to see the fit and it looks like my pedal rod is too long because of the angle to the block. What I didn't factor in was the brace on the frame held by those two bolts you mentioned. In addition, you gave me all of the proper hook-up with the rods and return spring for the clutch fork. I assume that the pedal rod for the automatic is the same length as for the 4 speed? If not are there aftermarket pedal rods for a 4 speed setup? Please advise.

I thank you for just making my weekend more encouraging.

Good luck with your Son's build.
 
#7 ·
Thanks for the pics Tom. Hey I saw you driving around OKC this morning while I was there picking up my newly balanced driveshaft. I would have honked and waved but I was in my old F*** truck so I didn't think you'd recognize me:yes:
 
#8 ·
His car is a NON-pwr brake car, thus the pedals are even with each other (the clutch pedal is always higher on PB cars).
The shiny triangular metal piece (behind the clutch pedal) is the retainer for the clutch pushrod boot which is installed from INSIDE the car. The 3 holes for the bolts are already there.
One MINOR part that needs to be added (which is NOT obvious), is a rubber bumper for the clutch pedal. The bracket (up under the dash) for the clutch/brake pedals already has the slot for pushing in the bumper (shown below). The brake pedal already has this same bumper. Yes, you have to be a contortionist to get that little bumper in.

Tom, any idea where to buy the "shiny triangular metal piece" stated above? Thanks in advance, Dean.
 
#10 ·
Nice pics Tom good detail. I like Leo,s idea of making a sticky out of it and where you got any aftermarket parts for it . Incidentally Tom what is that black coating on the floor looks like good stuff. I would be interested to know what it is and where you got it from. Alex
 
#11 ·
Some outstanding photos, thanks for taking the time to photo and post this!

I am heading in this direction with the 66. I see this car has the return spring on the clutch fork. Irrc, somewhere I saw the 66 era cars having a spring, or another spring on z bar end of the pushrod from the pedal? Is this correct and would there be two return springs?

There seemed to be a bracked welded to the footwell to hold the firewall end of the spring.

I am probably going to use a clutch pedal and linkage kit from Ground Up.

I believe they sell the clutch rod rubber boot and the metal retainer (shiny thing).

However, it appears this requires cutting a hole in the plate that fastens the steering column to the firewall, anyone reproduce that part? So far this is the only sticky item I see for this conversion.
 
#15 ·
IIRC there is a spacer on the shaft that the pedals pivot on that needs to be removed to put the new clutch pedal on. Pretty easy, just a little tough to get to while still installed in the car.
 
#29 ·
#21 ·
Would like to see the missing pics too.

Had a problem with my '59 and four speed.
Triple deuce 348 engine, LOTS of torque.
Could not seem to get a clutch to last more than a few days.
Finally gave in and bought an expensive high pressure clutch.
That failed too, but the mechanical clutch linkage failed first, welds on the Z bar slowly broke!

So anyone ever do a hydraulic clutch set-up on these cars for a Muncie?
I know they are probably needed for the six speeds.
 
#22 ·
I have read this sticky and used the search function and still can't find the info I need. I have a 70 that I am converting from bench seat auto to a bucket seat 4 speed with a Hurst shifter and console. The body is off the frame. I need PICS and MEASUREMENTS for welding in the shifter hump. I have read that it is best to have the body on the frame to be sure the hump fits the shifter. That makes sense but at that point my paint work and undercoating will be finished. If I weld in the hump now and it is in the right place all is good. If it is not right then I'll move it or modify it. If the pics and info are here somewhere please let me know
 
#25 ·
I am converting a 70 SS 396 from the original to an M-21, I need to locate the aftermarket shifter hump on the floor. anyone have any good instructions on locating that, and I am assuming the auto console base will either not work or have to be trimmed to fit?

Thanks,

Tomcatt
 
#26 ·
Silly ?, Bench and bucket seats use the same hump?

Need the lost pics back but my question of the moment is to confirm that bench seat and bucket seat cars use the same shifter hump?
I expect that GM did not spend an extra nickle unless they had to, but did they?

I've stripped my floor and fit my bucket seats.
I want to put in new carpet before final seat install, so getting the hump in now would be a big help.
The 4-speed install is probably waiting for a while.
Think I'm going to design my own hydraulic slave cylinder mount system after seeing the kits price.
 
#28 ·
Need the lost pics back but my question of the moment is to confirm that bench seat and bucket seat cars use the same shifter hump?
I expect that GM did not spend an extra nickle unless they had to, but did they?

I've stripped my floor and fit my bucket seats.
I want to put in new carpet before final seat install, so getting the hump in now would be a big help.
The 4-speed install is probably waiting for a while.
Think I'm going to design my own hydraulic slave cylinder mount system after seeing the kits price.
the hump on my bench seat car was the regular [non-console] floor hump...:yes:
A 4 speed hump for a console car is different than a 4 speed hump for a bench seat car.
this is correct; but all bucket seat with floor shift cars were not all console equipped,
so if you are going to use a console you want a console style hump:thumbsup:
 
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