3 speed manual transmission possible interchanges for 1939 Buick Special series 41

C

Charlie B

Newbie
I am hoping that one of you will know, if the three speed manual trans used for the 39 Buick (6 bolt top) was used in any other GM cars of any other years than 39. I am also asking is are there any other GM 3 speed manual trans (Buick, Chevy, Olds, Pont, Cadillac) that will bolt to that period L head straight eight engine?

* I read the thread that said the 5 bolt top trans that came with the 39 Special are known for problems and they are weak, which makes me very dubious about rebuilding the 5 bolt top trans that she probably has in her now. so, I am thinking, find a better, stronger core trans that will bolt on and rebuild it. I am open to suggestions, so tell me what you think?

Sarah (my bride of 2 years) and I just purchased and 1939 Buick Special 41, 4 dr sedan with L head straight eight (supposedly from a late forties Buick. It is a Buick L head eight) I have always thought it was one of the most beautiful cars ever made. This cars drivability was misrepresented and I didn't fly 1200 miles to personally check it out. I can only blame the guy I shave every morning...

We call her Molly and she pours oil like a sieve, she likes to hop out of third gear, the clutch chatters a little, her shocks are dead, the steering wheel has almost a 1/4 turn of play and the rear window needs to be removed and have a new rubber seal installed. We have found a mechanic who restores and repairs classic cars for over 40 yrs here in Tulsa and has a good rep. So he will evaluate her problems next week and we will decide where we go first.
 

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Congratulations on the BUICK and welcome!

Ignore the wailing and gnashing of teeth over the transmission! They are a problem ONLY when and if one beats on them.

The 1939 was a one year [ and FIRST column shift ] transmission.

Before doing anything drastic, I would check, and probably replace, the motor mounts and transmission mounts. Transmission problems are often caused by bad mounts.

Dennis Marordas will probably have all the gears, bearings, etc, needed. 606 237 6648.

The difference in the 5 bolt top and 6 bolt top is simple. The 5 is used on the 248 ci engines. The 6 is used on the 320 ci. engines. The two will not mix.


The Buick engine is an "overhead valve" engine, not an L head engine. Some folks do refer to them as an I 8, or inline eight. I use straight eight.

Again, welcome

Ben
 
Even if the transmission has a reputation of being on the weak side, if you are not hotroding the car a good rebuild will probably last longer than you:) especially when you consider how many miles you are likely to put on it.
Car looks GREAT!
 
To all,

If anyone cares the 5 bolt can be swapped for a 6 bolt.
I went through MANY on my '55/264 Special.
Came from the factory with 3.90 rear gears stock.
The ONLY problem is when I swapped in a 401 bored to a 425.
This is WAY before I knew anything about the ole 'Nails".
It definitely didn't like fast shifting 1st-2nd.

Tom T.
 
tom telesco said:
To all,

If anyone cares the 5 bolt can be swapped for a 6 bolt.
I went through MANY on my '55/264 Special.
Came from the factory with 3.90 rear gears stock.
The ONLY problem is when I swapped in a 401 bored to a 425.
This is WAY before I knew anything about the ole 'Nails".
It definitely didn't like fast shifting 1st-2nd.

Tom T.
Click to expand...

Is it a direct swap, Tom?

Ben
 
The late Earl Beauchamp was a collector and driver of numerous '39 Buick Specials. He would often take off from a dead stop in second gear. Don't think he would do that in a car with a weak transmission.

BTW, all Buick straight eight engines are overhead valve (OHV). L head engines are flatheads.
 
I think (reasonably sure) that the v8 engines used the stronger 6 bolt transmission in the first place. I'd not bet a nickel on a direct interchange between a 5 bolt transmission from the five bolt to the six. But I've been wrong before...
 
I just looked up (hometownbuick.com) the factory service manual for a 55 special... it does show it using the six bolt cover for the transmission.
 
Another issue is that the six bolt transmission is two inches longer starting with, I think, perhaps as early as 42. I know for sure that the later transmissions force the torque tube and thus the rear springs out of alignment as I have a friend who made that mistake with his 1941 Roadmaster convertible sedan.

It kind of/sort of worked, but the results were not good.

I think I would choose to rebuild the correct transmission the car came with in the first place. If parts are available.
 
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