How to swap a T-5 and Hydraulic Clutch into a 1968 Mustang

By Christoper Campbell

There are a several transmission options on the market when it comes to overdrive manual trans swaps in classic Mustangs, but our favorite for street and mild autocross and track use is the good ‘ol Tremec T5 for engines with less that 450hp. That’s not only because they enjoy a long history of being reliable and lasting a nearly forever when properly cared for, but just as importantly, they actually fit. T5s are fairly compact and round-cased transmissions, so they will tuck right up into any Mustang from 1964 ½ to 1973 with no cutting or permanent modification required.

The T5 swap has been around since at least the 1990s, so there are several companies that offer kits, with some wide variation in quality and components. Another problem, as anyone who has looked into exactly what it takes to swap a modern overdrive transmission into a classic Mustang will quickly discover, is that there is no such thing as a truly all-inclusive, everything-you-need package. Sure, there are a couple that get somewhat close and provide maybe eighty-ish percent of the necessary parts, but that last 20 percent or so can be a real pain to source because those small parts will come from various companies.

Starting with an American Powertrain T5 swap kit as the basis, and working with expert Mustang technicians at Mustangs Etc in Van Nuys, CA, the Summit Racing package are being trial fit to ensure as easy and straightforward of an install as possible. The first available kits will be for small block powered (289, 302, 351W) 1967-1968 Mustang and Cougar, with 1964 ½-1966 and 1969-1970 following soon after. If there is significant demand, big-block kits may come later.

We should be clear — these kits aren’t intended for those that like to piecemeal things together, junkyard hop, or eBay and Craigslist browse. These kits are intended for those who want a single part number kit with all brand new, brand name parts.

Could you piece the same kit together for less?

On top of all of that, everything in these kits is 100-percent bolt-in, meaning you could swap back to stock if you ever wanted to. That’s a bonus for our ’68 test car, because if a few years from now my mom is still enjoying her Mustang, but shifting that clutch is starting to become a problem, it can all be pulled out to put the C-4 back in it. We kept all the parts, just in case.

Scroll through the slideshow below to see how our T5 installation went.

American Powertrain includes all the parts necessary to swap from auto to manual pedal assembly, like a Scott Drake clutch pedal. As for the brake, you can retain your original automatic pedal and just trim the pedal pad to manual size using the new manual pedal rubber pad as a template (the pedals are otherwise identical, and the trimming does not affect structural integrity), or pick up on OEM original like the reconditioned one.
Since it’s very tight under the dash, it’s a good idea to bench prep the pedals before installing them. For our hydraulic clutch we need to mount a rod end included in the American Powertrain hydraulic bearing kit. The lower mounting hole on our Scott Drake pedal required a little opening up for this.
This smooth shoulder on the bolt will provide the surface for the rod end that will be starting point of the linkage that the clutch master cylinder will thread into.
Here’s the assembled clutch pedal ready to go under the dash on the new roller bearing shafts.
Regardless of the original transmission, all ’67-’68 Mustangs have circular spot on the firewall below the brake master cylinder for clutch linkage. On automatic cars like ours, the center needs to be tapped out. Be careful not to deform the firewall.
However, rather than linkage in that spot, we’re mounting a Wilwood clutch master cylinder on this very cool billet aluminum adapter from American Powertrain. The adapter is designed to position the master in such a way to mimic the angle of the rod for the factory linkage. Doing this maintains correct geometry with the pedal and eliminates the possibility of side loading the piston in the master cylinder. The adapter uses a backing plate that sandwiches the firewall for increased strength, and it makes a perfect template for marking the holes to be drilled.
Here’s the view from under the dash with the master cylinder installed. The backing plate/template will prevent the firewall from flexing.
With the pedals installed, the rod end on the clutch pedal can be attached to master cylinder rod. The pedal height can also be adjusted here via the linkage. This is also where we’ll set the pedal stop with the jam nuts to ensure that the bearing is not overstroked once we have everything installed.
If you have stock brake master cylinder and brake lines, there should not be any clearance issues with the clutch master cylinder. However, if you have a custom brake kit, there could be some changes necessary. For us, our Wilwood proportioning valve needed to be relocated to the other side of the brake master cylinder.
The Wilwood clutch master cylinder uses a remote reservoir, so it needs to mounted to a convenient place on the firewall. Just to the left of the master cylinder should be ideal for most cars and provide easy filling. While it needs to be elevated above the master cylinder and bearing for bleeding purposes, after it’s fully bled it can be mounted lower.
When it came to picking out the clutch for this kit, we wanted to hit down the middle with a clutch that maintained excellent drivability with a stock pedal feel and easy engagement, but with the ability hold big horsepower and some aggressive driving and clutch drops. Centerforce’s renowned Dual Friction kits are perfect for this. The Summit package even includes ARP clutch cover bolts (not shown in this pic), and the correct pilot bushing is included with the American Powertrain parts.
So here is where we need a bit of math to make sure we set up the hydraulic bearing correctly. We need the exact distance from the bellhousing face to the top of the clutch fingers. Use a straight edge, or a good piece of flat plate, to measure to and write the number down; you’ll need it.
No used junkyard transmissions with questionable history here; Tremec T-5. Those who know their trans specs will note that this T5’s torque rating is lower than our 408W produces, but we know from experience that they will live a very long time at our power level, provided hard launches on slicks aren’t in the cards.
With the throwout bearing on the input shaft, we need to measure from the face of the bearing to face of the trans where the bellhousing seats against it. Ignore our shims in this pic; we were already mocking up.
What we need is a .150-.200 clearance to the fingers, so using the stack of shims provided in the American Powertrain kit, we stack until we find the right number. The formula we need is; (Bell to fingers) – (Bearing face to trans face) – (.150) / (.054 thickness of Ford shims).
After establishing that, the bearing is indexed with a stud that replaces one of the front bolts on the T5. The pressure and bleeder lines are routed out through the original clutch fork window in the bellhousing. Speaking of bleeding, the system should actually be bled without even using the bleeder line; it’s for -worst case. American Powertrain is nice enough to ship the bearings fully bled, so basically all you have to do is slowly depress and lift the clutch pedal for a few minutes to push air out through the reservoir. It really is that easy!
The stock T5 shifter isn’t too bad, but there is a lot of room for improvement. Also, in the case of our vintage Mustang swap, that thick rubber boot actually causes some interference, so we’ll be swapping it out.
American Powertrain took the opportunity to develop their own short throw shifter dubbed “White Lightening Revolution.” Not only will it drastically reduce shifter throw, its low profile creates more room in the tunnel.
The White Lightening uses this adapter to move the shifter handle about 1.5 inches toward the driver for better ergonomics.
A standard T5 style shifter handle mount attaches to the adapter, which means you can use whatever T5 handle you choose on the kit. Note the offset vs. the stock shifter in the background.
It’s tight fit when sliding the T5 into place, but once in, the White Lightening shifter fits the factory automatic cutout like a glove.
American Powertrain uses a unique offset style crossmember that mounts to the rearward side of the factory tunnel brace to create an abundance of clearance for long tube headers. The included mount is an Energy Suspension poly.
Here’s a great visual representation of what we meant by the T5 fitting into vintage Mustang transmission tunnels so well. When properly positioned, there’s not a single cut or clearancing needed, and it looks like it could have been factory equipment.
Roughly a week after you send back the driveshaft spec sheet to American Powertrain a custom built steel driveshaft specifically for your project will arrive. Ours fit flawlessly.
Also included in the American powertrain kit is a new speedo cable with a black 20-tooth gear, which suits our 3.50 gears perfectly.
With the stick installed on the adapter plate, it’s easy to see that the small bit of offset works to center the stick perfectly in the stock automatic shifter opening.

One thought on “How to swap a T-5 and Hydraulic Clutch into a 1968 Mustang

  1. This article and pictures are great. Do you have one like this for the magnum 6 speed install. Please help about to buy a trans from your site. Looking to make it easier less figuring it out.

Leave a Reply

Your email address will not be published. Required fields are marked *