1966 Buick skylark 455 convertible swap to manual transmission

and yes I was just wanting to know the cheapiest way to swap the transmission from a Buick 455 with a TH400 to a 4 speed on the floor like which tranny 4 speed fits in easyiest with least mods and cheapiest that would still hold the power also and have overdrive I can’t remember if manuals have overdrive I’m pretty sure they do but didn’t want to sound stupid but that question sounds kinda stupid ig haha or if any 4 speed trannys fit onto that TH400 bellhousing already on there or anything?

 

and I’ll post a pic or 2 of the rear end best possible ones and if there’s any numbers also on the rear end also and but wat do u think the gearing might be now and wat was the gearing stock like I heard or researched and a lot was 3.07 was that the stock gear ratio for that car?

 

Car looks good!
A 8.5 rear means the inner ring gear is 8.5 inches compared to the previous 8.2 inch ring gear.
You can check what ratio it is your self and if it's a posi.

Jack the rear of the car up on both sides and safely support the car. Put the tranny in neutral.
If you spin one wheel by hand and the other side wheel spins in the same direction it generally means its a posi.

To check the gear ratio mark the drive shaft with a spot from a piece of chalk or what ever else might work.
Turn any rear wheel one complete turn and count how many times the drive shaft turns in that one revolution.

If it turns 3 times plus a tiny bit its most likely a 3.07, if it turns 3 and 1/2 times its probably a 3.42 or 3.55.
Less than 3 times means its a 2.93 or so.
It's pretty simple, so if it turns a little over 4 times its a 4.11 etc..

 

Also what would y’all think y’all would value my car at since I can’t find really any other 1966 Buick Skylark Custom Convertible with 455 engine automatic transmission and has a new Holley sniper EFI master kit installed can’t find 1966 skylark convertibles with a 455 engine like mine but Jw? Lol

 

I was going to chime in about the THM-350, but Tom (who is far more knowledgeable then I when it comes to such things) beat me to it. The THM-350 can be built as strong as you want. There are lots of performance parts available for it, and the transmission is simple enough that if the idea of tearing down an automatic gearbox doesn't scare the hell out of you - you can rebuild one yourself. The THM-350 is the ideal "first" transmission to overhaul. Get a good manual, I found one - GM Turbo 350, How To Build and Modify by Cliff Ruggles. and have a go at it. I did just that although I used an older manual put out by Hot Rod Magazine. My THM-350 was attached to a beefed up SBC 400 in a Malibu wagon. It was a torquer - it felt pretty much the same as a Nailhead, and the tranny lasted as long as I owned the car. If you don't want to tackle the transmission yourself, any transmission shop that has any idea of what they are doing can do one for you, and as automatic transmissions go, they are cheap to rebuild.

 

Yes sir thanks for the info but I have I believe the TH400 if not then TH350 in my car already and i hate not having overdrive and or manual transmission if I could pick any I’d have the TKM5 I think it’s called or tremec one 5 speed manual overdrive installed but was wondering there a lot more expensive but do they fit perfectly in cuz my buddy owns a shop and can get them a lot cheaper but if not I’d want atleast overdrive or manual or if I could both of them but like if I got a M20 or something like that also can y’all list all the extra stuff I’d need to buy to swap it out? Jw

 

Ok perfect thank u and also I ended up buying a T56 tremec 6 speed tranny manual to put in it 2.66 and last is .50 and going to convert rearend to a posi trac 3.73 I think or 3.55 or 3.90 but 3.73 equals 9.9 also so almost 10 lol and has the overdrive and double gears and manual stick at same time but he said it should have a th350 tranny in it now not a th400 but one of them but I know I’m in for a good project but I already ordered the bell housing adapter that’s suppose to let me use all GM parts on the tranny now so easier to find parts but do u know maybe input and output shaft spline count for Buick 455? And also if I did slider engine mounts would I still have too cut the tunnel? And any other advise on it I was going to go with 5speed or 4 speed with hopefully a overdrive somehow manual stick and the 2.87 rear ratio would be way to tall I’d probably never use 6th unless like 120+ so even if didn’t do posi trac I’m changing red ratio to 3.73 I believe if not then atleast 3.55 or 3.90 don’t wanna go to 4.10 wanna drive highway comfortable too lol but just wondering? And also if u know I got hood scoop since GS vents are insanely expensive I am in middle of putting on all GS stuff to make it a GS clone also add value except the vents I ordered scoop a double barrel one that u cut the middle of hood out and I hate the chrome pic that goes down middle of hood can you just take that off the hood and would it look good without it still? Just wondering if u knew also thank though very much