My new 66 Mustang
 

So I bought a 66 Mustang and I have plans to modernize it a bit,It's a stock 6cyl 200 with a 3-speed. I'm trying to upgrade most of it's components over time as I have access to a workshop for free. One of the main things that I'm trying to switch out is the transmission, that 3-speed is not ideal for where I live(Fort Polk, Louisiana...there's a ton of hills on post). Looking for recommendation on where and what to buy for a transmission, I see a lot of T5 transmission for the 66 but this is my first time working on a classic mustang. I'm not trying to restore it, I'm trying to enhance it as this will be my daily driver on base so AC, suspension, power steering, fuel mileage is what I'm looking at. I have no A/C so...that's big on my list as Louisiana is nothing like California and tends to be moist... oh and I've anyone have tips or a direction on how to muffle or dampen the amount of noise coming from the engine. There's a ton of heat and sound pushing through the firewall and it can be distracting when you're driving.

I had a t5 behind mine and my grandfather had a t5 behind his as well, great transmissions to put behind the 6cyl.

The best cure I found for the firewall / floor heat is to pull up the carpeting and lay down a nice thick layer of Dynamat or its equivalent. The thicker the better. Pulling the door panels and putting a couple pieces of that rubberized insulation on the door skin, and on the wheel wells in the trunk will also quiet things down considerably.

I went with Classic Auto Air out of Tampa when I installed AC in my car and I have no complaints. That said, I installed the AC before I took care of the heat issue and it was like pissing against the wind because you really need to stop the heat before you realize any real benefit from the AC system.

How's was yours on take off? Mine is slow like a turtle and can be worrisome when on a hill. I've tested taking off on second gear but it feels like I'm putting too much pressure on transmission. I'm not sure if I just got spoiled by todays manuals standards or there's something up.

Most likely you're just use to the gear ratios in the new transmissions and these 6cyls were rated for like 120hp back in the 60s too. Its been so long since I drove mine with the stock 3 speed that I can't remember much about it, I don't remember having any issues starting off. I feel like the T5 really changes the driving experience, my grandfathers 66 with a t5 is so smooth to drive, but he also upgraded the clutch to a hydraulic setup.

T5 is the way to go. And, if adding the t5 you can lower the rear gear ratio a little too and that will help big time. But, if you do that and are also planning in a bigger engine in the future, i would recommend changing the entire rear end out to a 5 lug 8.8 or ford nine inch. That way you can specify what gear you want and it will also be much stronger.

I just put in a Tremec TKO 5 speed in my 65' but I have plans on doing some auto-cross next year with it. The Tremec T5 is solid for a pro-touring, cruiser type of ride. With the TKO we had a little rework on the exhaust off the headers, EM brake cable and mount, there is also a little tunnel work but no new carpeting was needed. Not sure what budget is but tranny swaps here in SoCal where I'm at run about $5K to $8K, mine was on the higher end of this due to the extra work. You might check out what rear-end and gearing you have to because with the hills you're talking about what's in there now might not be enough, you might have 3:0 when you need 3:73 or something close. Finally with the new tranny you might run a little warmer but there are solutions for this like non-glycol coolant or a push/pull fan.

Good luck and keep us up to date!

Daily driver wish list
 

Engine: new head and carb...at least new Webber
upgrade ignition/ distributor, exhaust,
t5, remember you will never have enough hp to need more. Same with rear end, should handle most hp upgrades and normal driving.
i would go with vintage air...better compressors, have one from classic, ok but had to change compressor after less than 2 yrs, had a junk one from china. Mine worked pretty good, on interstate I could tell it needed a fan clutch.. worked better at lower speeds, I know Freon was good.
i also did a five lug conversion on all four corners, more wheel and tire options than 4 lug. 67 was easy, i6 spindles are the same as v8, found complete front v8 drums set up on eBay $150 and done, five lug conversion and brake upgrade all at the same time. Rear axels were re-drilled for five lug pattern by Modern Trany, they can make you a new drive shaft for the tranny swap too. I also did a fan shroud, had to make it from universal shroud , came out great! Electric fan might eliminate that, but I still think a full radiator size is better than fan electric fan size..all things considered. Add some tinted windows, a little insulation, oh yea, rebuild your factory heater before you put the under dash air in!!
cruise time..
https://cimg8.ibsrv.net/gimg/mustang...6f2369db55.jpg