[OG68]

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.

[b-man]

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.

[TXSTARFIRE]

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.

[66 Le Mans Cruiser]

Originally Posted by OG68

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.

Thank you Ed.

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

[66 Le Mans Cruiser]

Originally Posted by b-man

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.

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.

[sprintbird]

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.

[66 Le Mans Cruiser]

Rear end 3:08
3 speed saginaw

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

[johnta1]

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.

[66 Le Mans Cruiser]

Originally Posted by johnta1

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!

[b-man]

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.

[66 Le Mans Cruiser]

Originally Posted by b-man

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.

[gtospieg]

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.

[66 Le Mans Cruiser]

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

[gtospieg]

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.