3 speed to 4 speed swap
 

Hello. I recently purchased a 1966 Le Mans convertible. Pretty much stock. Has 3 speed and 326. Previous owner put a 2 barrel holley, new air cleaner, sway bar, and dual exhaust.

I am new to the hobby, not very experienced with working on cars but am fairly handy and willing to learn or pay for what I don’t want to learn/do(I am 51 so more strenuous stuff I will pay for)

I love the car. Engine runs great. I don’t really enjoy how sluggish the car is getting going. I have had a few manual cars in the past and this car feels like a dog getting going. First to second and second to third are fine. A few people at cars n coffee as well as reading some posts on here recommended going to a M20 4 speed to get more response from 1st gear.

So is it a direct swap or are there modifications that need to be done(like driveline length, etc)

Is this worth the time/cost? Any other suggestions?

I want the car to be a cruiser. I drive it 5-6 times a week and have no interest in lighting up the tires.

Sorry for the long post and if you made it this far thanks for reading my rambling!

Depending on the current first gear in your 3 speed, switching to an m20 may not buy you much (if anything) off the line. What 3 speed are you currently running? What is the ratio of your rear axle?

Something like a super t-10 with a deeper first gear may be more appropriate for your situation, but need more info to make any real suggestions.

First gear ratio
Saginaw three speed is 2.54:1
Muncie M20 is 2.52:1

You're not going to see any improvement there.

How do I find what transmission it is and what the rear end ratio?

I looked online as the car appears to be stock:

The 1966 Pontiac LeMans featured a standard 3-speed manual transmission, often a column-shifted Dearborn unit, with a heavy-duty floor-mounted 3-speed (frequently paired with the Hurst shifter option) available. These were "all-syncro" units with 1st gear ratios of 2.85:1 for I-6 engines or 2.42:1 for V-8 engines.

Gear Ratios (V-8): 1st: 2.42:1, 2nd: 1.61:1, 3rd: 1:1.

So car has 3 speed on floor with hurst shifter so I assume that is the correct ratio?

Is there an alternate upgrade that would help?

Intake/carb?

The Ford Dearborn was optional in the A body with a V8 and floor shift only.
The standard three speed was a Saginaw column shift.
The Dearborn is from the Ford Toploader family and is practically indestructible. Easily identified by the inspection cover on the top of the transmission and the FoMoCo cast on the left side
First gear ratio was 2.42:1

A 3:23 rear axle in your car was standard with the three speed.
3:36 and 3:08 axles were optional with the 2bbl 326.
You can install a set of 3:55 gears to help, but you won't like the 3000 RPM at 60-65 mph
A 4bbl and camshaft change will wake up that little 326.

As a side note, the clutch isn't slipping is it?

Clutch is not slipping but coming from a stop into first there is some chattering if you don’t give it enough gas. Clutch was replaced about a year ago and flywheel was resurfaced. Maybe not a great job on the resurfacing?(or my driving sucks?!?)

I swapped from a 3 speed floor shift Saginaw to a 4 speed Saginaw in a 1967 Lemans with an OHC 6.
Bolting in was easy. And Saginaws, even 4 speeds, are usually cheap.
Saginaws have several first gear ratios. I found a 3.11, the ratio that originally came with 67 sixes. It is noticably lower.
Getting a shifter and rods to match up with the console was a finicky business, however. In the end I used period pieces found on ebay.
Price it all out. If you're buying new and want asimple kit with shifter, rods and all, a 5 speed probably starts to come into sight.

Was it worth it to swap?

Car has a rear main seal leak that will be addressed in the not too distant future. Figured while the transmission is out can do a few upgrades.

Thoughts in my head:

New intake/4 barrell carb
Camshaft
4 or 5 speed transmission
New clutch, flywheel, pressure plate

Want to cruise the car not race.
Would like more response from a standstill but don’t need to light the tires up.

I appreciate the advice/thoughts of people with far more experience.

Depending on your wallet your biggest bang for the buck would be a transmission change to get a lower first gear.

As posted above a Saginaw 4-speed was available with a 3.11: 1 low gear,

I have used many of them in my Pontiacs over the years. Usually you can find one used for $ 3-500 and a new Hurst shifter will run about $700. This is the cheapest way, Same clutch, driveshaft, crossmember.

The best and most expensive ( aprox.4K ) would be a New TKX (which I hope someday to get one), their are several vendors that will sell a kit to make it a bolt in deal.

A four barrel carb is a nice upgrade, but your not going to get much improvement off the line.

And I would not go for a cam change if your just cruising it.

Just my opinion,Good Luck!

It was worth swapping to a 4 speed in my case. But 3 speed manuals are cool too. I would expect a well running stock 326 to easily pull first with a reasonable differential ratio.
You may have to visually id your transmission to verify what you have. Could have been swapped over the years. Same with the differential. Does it still have a 3.23 or did someone put highway gears in it at some point? That would bog you down.
A 326 2bbl should be pretty torquey. I had one years ago. A camshaft "upgrade" likely won't help with more off idle grunt.
Is the engine solid otherwise? Good compression on all cylinders? Strong vacuum at idle, etc.
Also, you mentioned chattering. I'm not an expert, but that is likely an issue unrelated to engine power. Everything put together tight and right?

Thank you for the ideas.

Would the current Hurst shifter in the car have to be replaced?

Thank you.

Have a mechanic buddy that checked vacuum, compression, timing, etc. All were ok.

Engine is solid. I drove it from San Diego to Vegas when I bought it in July.(drove at night to avoid any overheating).

Only issues I have had have been electrical. Those have been remedied.

Car drives great, holds generally around 170 degrees. Just seems like a dog getting going from a standstill. Maybe my expectations are different from the reality of the car.

Most likely yes. If switching to a four speed the shifter will have to be replaced.

Driveshafts are the same size for all manual transmissions, but you may have to replace the stub shaft If the output splines are different.

Have you ordered the PHS docs yet? They will tell you exactly how your car was built.
But it wouldn't be unusual for a previous owner to switch transmissions or rear axle gearing in the last 60 years.

I have a Dearborn (shown below) in my 68 with 3:55 rear axle. Still very smooth and quiet.

I have not ordered the PHS docs yet, probably should have been my 1st step. Will do today.

Car is getting front discs installed right now, when I get it back home I will take a look at the transmission to see the markings and will post.

So I am a little confused. One person says cam and 4 barrel, another says those will do nothing. Another person says transmission and another says that will not change acceleration from standstill. Another says rear end gear change.

Is this kinda standard that there is no standard? Just trial and error?

Trying to learn as much as I can so every little bit helps, it is one thing to do a google search. But I prefer to ask people with knowledge and experience.

Thank you for your time and advice.

I see you are considering a M-20 for your swap. You might want to look at Frank's Pontiac parts under transmissions as he shows a few M-20s in stock and he is located in Southern Cal which would be close enough for you to drive and pick up if you purchased a trans from him. His prices are a little high but saving on shipping may make it a viable option.

Youn need to gather all the relevant information about what you are working with right now (transmission, rear axle gearing, engine history, engine components if not stock, etc) before considering any changes. If you are working with a 2 series rear and add a hotter cam you will likely make things worse.

In the meantime spend as much time as possible reading old posts on this site as most of this stuff has been discussed many times over - there is a great search feature - use it. The 'info' in post #4 reads like AI slop and is not accurate as was already noted.

You need to move on if you feel the need to tell everyone else how their stuff is slop and crap. Your post sucks, is not helpful and is condescending. You are the reason people don't ask questions. If you just want to be a prick and appear like a jerk, well congrats. You are the type of person I avoid at car events. Woo hoo you know more about cars and aren't willing to share with people with much less knowledge.

Thanks G I will take a look. There are a couple locally on Facebook market also.

I didn't say anything about your stuff being 'slop' or 'crap'. I gave you some good advice - you should probably take it.