Tremec T5
Problems and Rebuild Cost

The T5 showed up in the early 1980s and ended up behind almost everything that needed a light 5-speed: Fox-body and SN95 Mustangs, third and fourth gen Camaros and Firebirds, S10 and Sonoma pickups, Ford Rangers, some Jeeps, and a long list of four and six cylinder cars. Tremec took over production from Borg-Warner later on, which is why you see both names on the same basic box.

It is a good transmission. Light, smooth when healthy, and cheap to rebuild. It was also designed for early-80s torque and then bolted behind a lot of V8s that people kept adding power to. Most T5s on a bench are not worn out. They are broken.

Identify What You Have First

A T5 has an aluminum case, a top cover, the shifter mounted on the tailhousing, and five forward speeds with reverse. On most units there is a small metal tag held on by one of the tailhousing bolts. That tag carries the assembly number, and the assembly number is how a parts counter or rebuilder knows which gear ratios, input shaft and countershaft design are inside.

The big split is World Class versus non-World Class. Ford V8 Mustangs moved to the World Class design in the mid-80s, and that is the one you want behind a V8. The commonly cited difference is tapered roller bearings on the countershaft that can be preloaded, versus the older design, along with revised gears and synchros.

You will also hear about the Ford Racing "Z-spec" and later heavy-duty T5 variants, which use stronger gears and better synchro materials. They raise the ceiling, but not to T56 levels.

What Actually Fails

3rd gear and the synchros

If you only remember one thing about V8 T5s, remember 3rd gear. Hard launches with sticky tires, power shifts and big clutches all hammer it. When it goes, the debris travels through the whole case, so a "just replace 3rd gear" job can turn into gears, bearings and synchros once it is apart. For the symptom side of synchro wear, see our synchro wear guide.

5th gear pop-out

5th lives out in the tailhousing area on its own and gets less love than the main gears. A worn 5th synchro, a worn fork, or a 5th gear that has moved on its shaft will let it walk out under load or on coast. More on the general causes in our popping out of gear guide.

Bearings and noise

Noise in 1st, 2nd, 3rd and 5th that drops out in 4th points at the cluster and its bearings. Noise only at rest in neutral with the clutch engaged points at the input bearing. Noise that changes when you touch the pedal is usually the throwout bearing, a clutch job. Our throwout bearing guide covers that split.

Front bearing retainer

The throwout bearing slides on the snout of the front bearing retainer. Many T5 retainers are aluminum, and after a few clutches the snout is grooved. A grooved snout makes the bearing hang up, chirp and wear unevenly. Replace it if it is scored. Replace the input seal while you are there.

Torque Limits, Honestly

Factory and aftermarket ratings vary by year and version, and you will find different numbers depending on who you ask. As a rough rule, the later World Class Mustang units sit somewhere around 300 lb-ft, the heavier-duty and Z-spec style versions a bit higher, and non-World Class units well below that.

The number on paper matters less than how the car is used. A stock-ish 5.0 driven on the street can run a T5 for a long time. Add boost, drag radials and a grabby clutch, and the same box can break on the first good launch.

What It Costs

Ballpark ranges; they swing with labor rate and what is found inside. Removal and installation alone is a large chunk of every shop number, which is why doing the clutch, retainer and input seal at the same time is almost always right. For bench parts, browse our hard parts category, our tools category, or our sister store CoreTransmissionParts.com.

Rebuild or Swap?

• Rebuild it if the car is near stock, the case is not cracked, the shafts and cluster are reusable, and you are fine with T5 limits. A clean World Class rebuild is good value.
• Swap it if you have already broken one, you are adding a supercharger, turbo or big cam, or you want a box for track use. See our TKX swap parts and cost breakdown and the T56 Magnum vs TKX comparison.
• Plan the driveshaft. A swap usually changes driveshaft length, and many builders go to a stronger shaft at the same time. For 1987-1993 5.0 Mustangs with the 5-speed, we carry a DSS 3.5 inch aluminum driveshaft. If you get a vibration after the work, check our driveshaft vibration guide.
• Use the right fluid. Most T5s take ATF, not thick gear oil. Our manual transmission fluid guide covers why it matters for synchros.

FAQ

How much horsepower can a T5 handle?

Think in torque, not horsepower. Late World Class Mustang units are generally rated somewhere around 300 lb-ft, and the heavier-duty aftermarket versions a bit more. Real life depends on tires, clutch and how you drive. A street car on radials that is driven with mechanical sympathy can live above the rating for a while; a car on drag radials with hard launches will usually break a stock T5 well under it.

Is a World Class T5 better than a non-World Class?

Yes, for anything with a V8. The World Class redesign is generally credited with tapered roller bearings on the countershaft, which can be preloaded, plus revised gearing and synchros. Early non-World Class units are fine behind four and six cylinder engines but are not the box to build on for power.

What fluid does a T5 take?

Most T5 applications were filled with automatic transmission fluid from the factory, and that is still what most rebuilders run. Do not pour in thick hypoid gear oil; it slows shifts, especially cold, and can be hard on the brass synchro rings. Confirm the spec for your exact application.

Can a T5 from a Camaro or S10 go in a Mustang?

Not as a bolt-in. The cases, bellhousing patterns, input shafts, shifter locations and output splines vary by maker and application. Internals can sometimes be swapped between units by someone who knows the interchange, but buy a transmission tagged for your car.

Should I rebuild my T5 or swap to a TKX?

If the car is near stock and the case and shafts are healthy, rebuild it. If you have already broken one T5, are adding a lot of power, or want a stronger gearbox for road course or drag use, put the rebuild money toward a TKX or T56 swap instead.