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.

BDK did give some good advice. You need to know what you currently have and the PHS is a good start. It will at least tell you what the car came with from the factory. If for example, the 3:08 'economy' axle was ordered that would be a big reason why the car doesn't accelerate well. However, Pontiac engineers wouldn't have offered it as an option, if they felt drivability would be affected.

If you drive primarily in town then a rear axle upgrade may be your best bet.
If you plan to drive to Reno, Salt Lake or SoCal often then stay with what you have.

4 bbl carb and a cam are always nice but thats horsepower that is used primarily at higher RPMs.
A six cylinder gearbox will help but it's designed for a six, not a V8.

So between now and the time your PHS documents arrive, educate yourself on how to check your rear axle ratio and the differences between a Saginaw, Muncie and Dearborn transmissions. They're all good transmissions but were designed for specific applications.

Finding your rear gear ratio is easy as long as you’re able to jack up the rear of the car safely and get under it.

Mark one rear tire so you can count the rotations. Jack up that tire and leave the other on the ground.

Now mark the driveshaft yoke and rear end.

Turn the shaft and count the number of turns of the shaft needed to make the tire make two full revolutions. If the shaft turns 3-1/4 turns you surely have 3.23 gears, a little more than 3-1/2 turns then you have 3.55 gears. This assumes you have an open rear end, no limited slip or positraction.

If you have posi get both wheels off the ground and count the turns of the shaft do one full revolution of the tires, assuming the posi is in good working order.

You don’t need to look for codes or buy a PHS report to know your rear end gear ratio.

For a peppier takeoff get a Saginaw 4-speed with a lower first gear ratio than a Muncie or T-10. The Saginaw with a 3-something first gear will be less able to withstand abuse but they’re fine for normal driving. Higher numerical first gears are inherently weaker than lower numerical first gears as a general rule no mattter what make of transmission.

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.

I think this is the part that he was referring to as "AI slop", not what you had to say.

Thank you Ed.

Now I have a basis for where to start, much appreciated.

Thanks b-man. Figuring out the rear end gear ratio will be this weekend.

Went ahead and bought the PHS report so I can know the info on the car.

Appreciate the info on the different transmission types and will now research which best fits my vehicle and my desired driving.

I think there is some good information in this thread. It is hard to make an accurate recommendation based on your description without details. So as requested previously, please find out your axle ratio. I agree the best/easiest option will be a 4spd Saginaw with a 3.11, or 3.50 first gear ratio. I run a 3.50 ratio with my Sprint 6 and 3.08 rear gear. Works well and drivability is good.

Rear end 3:08
3 speed saginaw

Will upgrading the rear end and swapping to a 4 speed improve the acceleration that I want?

With a 4 speed (wide ratio may be good), it will seem better just because the shift from 1 to 2 is a lot easier and quicker. Then with the momentum going into 3rd is nice then 4th for cruising.


Then a rear gear change will make it quicker at the low end not sure the 326 would help anything at upper speeds/RPM.


:)

Thanks John!

Keep the 3.08 gears.

Put in the Saginaw 4-speed with the 3.50 first gear.

It’ll be good all around.

My air conditioned 326 2-barrel ‘64 Le Mans convertible was originally equipped with a 2.93 rear gear and a 2-speed automatic. Plenty of the 326 2-barrel cars without factory air conditioning and automatic transmission had a 2.56 rear.

The 3.08 is still a decent highway gear, don’t switch it out for a 3.23 or 3.55 would be my advice.

Thanks B-Man.

Will probably wait until the rear main seal leak or clutch need to be addressed . Then swap to 4-speed. Have found a few M20's locally and within driving that are pretty reasonable. Some with shifter.

B-mans advice is solid. Find a 4-speed Saginaw with a 3.50 1st gear. It's the least expensive option to accomplish your stated use for the car. The Saginaw with 3.50 1st gear is easy to identify, there are 3 rings on the input shaft. While it may be "lighter duty" it will be adequate for your engine combo, especially if you don't beat on it. If you put a Muncie in it you will gain nothing in acceleration (essentially the same 1st gear ratio) unless you also change the rear gear ratio and then you'll wish you had a 5 speed with overdrive. Good luck with your project and keep us updated.

Thank you everyone.

Where are the best places to try to locate a saginaw with 3.50 for first gear? I have been looking on here, facebook marketplace, offer up. I see many muncie’s but not many Saginaws.

Been deciding on what my budget for the car is and exactly what I want. For the money I may just buy a second car that has a larger engine and already has a 4 or 5 speed and then have a cruiser(my lemans) and something a little quicker(maybe a firebird).

I have a decent size tax return coming and was thinking of throwing about 5k into this car including labor on things I would not feel comfortable doing myself.

The clutch and flywheel are definitely getting replaced when I have the transmission pulled to take care of the rear main seal leak.
Any further recommendations with that size budget and wanting to keep it a cruiser with a little pep.

Appreciate the advice, some local guys and from reading on here my thoughts to get to where I want:

Performer intake 2156
4 barrell carb- edelbrock 1406
New Clutch
New Flywheel
Potentially transmission swap
I am also redoing some of the interior including carpet and sound deadening but those are already purchased and I will install myself so don’t affect the budget.


What the car is now
1966 Lemans
326
2 barrell
Dual exhaust
Disc upfront
3 speed saginaw
3.08 rear

You can also look for another 3 speed Saginaw with the 3.50 1st gear. It has the same 3 ring input shaft markings. Then it's a very simple swap...no new shifter needed.