There are three bell housing choices to make when swapping in a T-5 or Tremec: Early, Late (5.0) and Aftermarket Bell Housing (Scattershield). Linkage for the clutch should also be taken into account when choosing a bell housing. The late model bell housing is ideal for those interested in a cable or hydraulic clutch setup. The early style is obviously better suited to the factory mechanical linkage. We run the mechanical linkage on our car with an early style Scattershield and have been very happy with it over the last 10 years. It did require some reinforcement to the Z-bar with a stout clutch however.

Regardless of the route taken, there should be little to no necessary modifications required to the car its self. The shifters from both transmissions come up through the original shifter hole, although the T-5 tends to be on the far right side of the hole and sometimes needs a little sheet medal trimmed. Cable linkage will require a small hole to be drilled just above the master cylinder to run the cable line through the firewall plus a bracket to be adapted to the clutch pedal to connect the cable. If you have headers routing the cable can be difficult as well. Its not uncommon to melt the cable line from the heat of the headers. This is where a hydraulic setup really shines. It should be noted that both the T-5 and the Tremec (3550 & TKO) will change your driveline angle as the motor will set back approximately 1" lower in the back than factory. With well over 15,000+ miles of hard driving including auto-x and drag racing we have experienced no problems with this. No U-joints have yet to fail or needed replacement. Some recommend cutting up the transmission tunnel to allow the original driveline angle to be restored by raising up the back of the transmission. It is our believe that the rear end pinion angle can be adjusted much easier than cutting out and fabricating a new roof for the transmission tunnel. For those converting to a Tremec (especially the TKO) this especially makes sense if you haven't yet converted your 8" housing to the stronger 9" rear end. For those running a T-5, a 9" rear end is pretty much overkill in most situations. Its heavier and robs more RWHP than the lighter 8" rear end. Either way, if you're concerned about your driveline angle we suggest correcting the issue via the rear end pinion angle.

The Tremec 3550 & Tremec TKO use the same bolt pattern as the original 3 and 4 speeds so there are no necessary modifications to the bellhousing. However, it too requires a spacer to off set the longer ¾" input shaft. There is a shorter input shaft available that can be installed to eliminate the spacer plate, but its little bit more expensive, and will make the shifter a longer reach.

You'll need a yoke and crossmember for the conversion. Talk to www.Dark Horse Performance for your Tremec parts needs, as the Tremec requires a different cross member than the T-5.

For those using mechanical linkage, the throwout lever must be adapted to the bell housing mounted on a ¾" spacer. There will be two holes that need to be drilled through the bell housing to mount the throw out arm and spacer as well. As with the Early bell housings, a cross member and yoke are necessary to complete the swap. When going this route, remember that late-model flywheels (82+) are not balanced for early 289/302 motors and will create severe vibration problems if bolted up. Ford changed the balance of the flywheel from 28 oz. to 50 oz. so be careful to use the right flywheel for your engine.

Tremec TKO * Tremec TKO 5 speed * Tremec shifter * 26 spline clutch disc * 31 spline drive shaft yoke * Tremec cross member * Original bell housing   Or Aftermarket Scattershield * Custom driveshaft   (53" from output shaft to yoke) * T-5 speedo gear * 65-66 Speedo cable * Original transmission mount * Original throwout lever * Original throwout bearing * Original Pilot bushing

We use an early style Lakewood Scattershield that replaces the original 3 and 4 speed bellhousing and requires the use of the ¾" spacer because of the longer input shaft of the Tremec. One advantage of the Lakewood besides safety is the ability to use either tranny without modification. The Lakewood comes with both bolt patterns so its easy to upgrade in the future (especially if you blow up the T-5 and go to a Tremec, like us!).

The Tremec 3550 was introduced to the performance market a few years ago. It was designed to be a stronger replacement for the T-5, which was noted for literaly coming apart after serious use (ie power shifting). Its a very durable tranny and will take a whole lot of abuse for the average strip/street user. For someone who wants to really drive aggresively, this is the tranny for you. Now, lets step things up yet another notch.

The bell housing is being replaced by a scattershield... extreme horsepower is a possibility in the future, and you're thinking even the Tremec 3550 just isn't going to cut it (you'll be running 11s at the track or better). Then step right up to the Tremec TKO. This bad boy transmission is the same size as the Tremec 3550 but features larger input and output shafts for additional strength. You'll need a 26 spline cluch disc because of this, but that's just a straight forward clutch disc swap. Talk to Dark Horse Performance for parts. You'll also need a custom driveshaft as the large 31 spline yoke (C-6 yoke) requires much larger U-joints than the stock drive shaft can handle. Other than that, it bolts up the same as the Tremec 3550. This is the probably the ultimate transmission for your classic mustang, providing both incredible strength for the track and overdrive for streetability.

Don't forget to use ATF tranny fluid in your T-5, It doesn't use gear oil!!!