1965 to 1970 Mustang T5 Conversion Kits Explained
T5 conversions are probably one of the most asked about modification for the older Mustangs. We are going to cover two areas of confusion. First, what year and model to look for. Second the ins and outs of actually doing the conversion.
What T5 do I need?
Through the years, Ford made many improvements and variants of this transmission. Actually Borg Warner made the improvements and then Tremec made some more. The T5 was introduced in the early 80's. In 1985, the world class version was introduced and was used up to 1995. Each year, they were improved on increasing the torque capacities and quality. The 1994-95 models are basically the same internals as the prior years however, they have a longer input shaft making them not the way you want to go for this conversion. The 1986 to 1993 versions are the best for the swap. Little side note, 4 & 6 cylinder T5 will not work! These models have a very low torque capacity and different input shaft diameters.
Ford Racing now offers the M-7003-Z Heavy Duty model. 330 lb-ft and a steel input shaft retainer are some of the high lights of this transmission. This one by far is the best one to use.
One other note, Tremec offers other 5 speed options like the 3550, TKO, 400/600, etc. These models are heavily upgraded 5 speeds but are also re-designed for some serious horsepower applications. They are larger in size and require modification to the tunnel as well as a custom cross member. The T5 cross member will not work with these transmissions.
Ok, let's look at the transmission up close. The input shaft is a standard 10 spline and compatible with the early 10" and 10.5" clutch disks. The front electrical plug is for a neutral safety unit that isn't used when doing the swap.
On the driver's side, half way down the housing is a 2 prong switch. You guessed it, back up light switch. This can be utilized to work but will require some electrical reworking.
Under the tail shaft housing on the driver side is the speedo cable opening. This is the same diameter as the older T-10, Top Loader, 3 speed, & c-4 autos. The speedo driven gear is still the old design and in some cases, compatible with the old ones. You will still probably need to change it to correct the speedometer reading.
The T5 is equipped with an internal shifter linkage. The shifter unit is conveniently located in the perfect spot. When installing the T5 into the older chassis, the shifter is centered in the shifter opening in the tunnel. You normally don't have to modify the opening if the stock shifter unit is used. For some short throw shifters, you may need to notch the opening for clearance.
Installing your new T5
Now that we are more familiar with the T5, let us see about actually installing one. First thing to evaluate is what you have to work with. If your car is already a manual transmission, you are ahead of the game. You can reuse all of your existing components like the clutch linkage, flywheel, clutch, & bell housing. Conversions from automatic or manual transmission vehicles will all need a new cross member, mount, and yoke
Manual Transmission Conversion. Manual transmission conversions use an adapter plate that attaches to the back of your original manual bell housing. When using the adapter, depending on what bell housing you have, you will need to transfer 2-3 holes into your bell housing. These are blank holes and do not require any tapping for threads. Using the spacer will also allow you to use the factory clutch, fly wheel, and linkage. This makes this option the cheapest way to go.
Automatic Transmission conversion The T5 bell housing is a better option. As long as you have a 289, 302, or a 351w with the 6 bolt pattern, the T5 bell housing will bolt directly to the block. This option opens up a lot of choices. You can set your car up with the factory styled linkage or go with one of the new cable conversions . If the original linkage is used, you will need to mount a fulcrum and spacer into the housing to support the old styled release fork. Now if the cable conversion is used, the housings already have the pivot mount for the late model release lever. The fly wheel that is needed would be a 10.5" diameter 157 tooth flywheel from Ford Racing designed for a 10.5" clutch. The Ford Racing Billet Steel fly wheel is a great choice for pre 1981 28oz balanced motors. You can utilize a 10.5" clutch kit from a late model application. The clutches are thinner in design and require less travel to disengage. The block plate, (located between the block and the fly wheel), will also need to be changed. The T5 housing relocates the starter so that the original plate will no longer line up.
Once you have bolted your T5 manual transmission into place, you need to install your cross member and mount. The T5 cross members are an easy bolt in. The 1965-66 model is equipped with the emergency brake bracket so there isn't any modification needed.
Once the transmission mount and bracket are in, time to look at that driveshaft. Most applications will need to be shortened. There really is not a standard length. It is determined by the engine and rear end. Some of the different 3rd members will have a longer input and require less to remove. The best way is to get the transmission mounted in and the car either on the ground or supported by the rear axel so that it is in the natural position. Just measure the length required and allow for about 1" of play at the end.
The T5 does require a different yoke. Some of the original yokes will fit into the tail shaft. As tempting as it is, don't use it. The older yokes do share the same spline however the T5 yoke is shorter and does not extend so deep into the tail housing. The longer yoke can damage the tail bushing by restricting the flow of oil down the shaft.
Shifter Options. What type shifter do you want? Unlike the late model mustangs, the shifter needs to be installed before it is installed. You can't change it through the floor opening. There are many options to choose from. The factory shifter that the T5 comes with works fine but is a little sloppy for some people. The Steeda Tri-Ax is a great choice and is a direct bolt on. It utilizes adjustable positive stops front and back so it may require you to notch the opening in the floor for clearance. A factory late model shift lever will work however they are a reach to hit 5th gear. We carry a new lever that bolts to the T5 and aftermarket shifters. This lever is longer and looks exactly like the 1965-67 4 speed handles with the reverse lock out. These are a great option for those who want to retain a stock or original look.
We also offer a nice selection on custom T5 shift knobs to complete your installation.
Another question that comes up is rear end gear selection. Our salesman Dennis currently owns a 1965 with a 5 speed as a daily driver. It was originally equipped with 2.79 gears. With a tire size of 225/50/15 on all four corners, it would be turning around 1700 RPM @ 70 MPH. This is great for freeway and long halls. Depending on your engine set up and power band, changing the gears may be a good idea. Currently Dennis's mustang has 3.55 gears with the same size tire. With these gears, this mustang can turn about 2400 RPM @ 70MPH. This is great for all around driving and is a good compromise between acceleration and mileage.
We always get the question of what oil to use. The T5 does not use standard gear oil! It will damage the transmission. We recomend using Dextron 4. Dennis switched to the D4 and actually noticed easier shifting and less friction.
Over all, I would recommend this swap to anyone who enjoys driving and crusing in there classic mustang. It is a great way to increase the mileage and drivability of your car.
Please click here to view our T5 conversion kits and components.