The T5 is a great street transmission for small-block Fords as long as you don't treat it too harshly.
This is the era of the manual transmission. Sure, automatics are easy and comfortable, but there's nothing like rowing through a sweet five-speed and listening to a motor sing through the gears. For the Ford clan, the T5 has become the attractive, lightweight overdrive trans of choice. Ford has been building World Class transmissions by the thousands since 1985, so we thought we'd take a close look at the choices for rebuilding or buying Ford-based five-speed transmissions.
If you're not already aware, there's a whole industry built around this stout little transmission. The T5 is not for everyone, and it's certainly not suited for either big-block or nitrous use, but there are all kinds of uses not only for the T5, but also for its aftermarket performance derivatives like the Tremec 3550/TKO five-speeds that have now become the latest-generation Tremec TKO 500 and 600 boxes.
For this story, we took apart a basic 3.35 First gear T5 and went through it to show you some of the highlights of assembling a T5 with an all-new gearset from our pals at D&D Performance. If you're in the market for a five-speed, we've done much of the research for you.
If you want a good swap trans, look for a '90-or-later Mustang with a T5 in the boneyard, as these boxes are equipped with the better internal components. You can't have the trans out of this car-it belongs to McGean.
History of the T5
While the '83 5.0 Mustang is where performance enthusiasts were first introduced to the T5, its lineage can be traced all the way back to the '81 AMC Spirit. The trans has been used in well over 200 applications and continues to appear in multiple production applications. The T5 can be split into two main categories: the early Non-World Class (NWC), rated at 265 lb-ft of torque capacity, followed by the World Class (WC) version beginning in 1985, rated at the same torque. The WC boxes are the only ones worthy of performance applications, but they still exhibit a couple of weak areas. We've outlined the gear ratios for all these boxes below. There are myriad T5 boxes used just within the Mustang world. D&D offers a chart on its Web site that identifies specific boxes along with their gear ratios and torque capacities.
While the World Class tag sounds impressive, the reality is that it wasn't until 1990, when Ford updated the T5 to 310 lb-ft of torque, that the transmissions could really be used in any kind of aggressive performance capacity. The latest version, the so-called "Z" box that was used in the '93 Cobra, is equipped with the best of all the updated parts including hardened gears, shortened shifter throws, a bearing collar made of steel, and tapered output-shaft bearings. The trans is available through many sources, such as D&D and Ford Racing.
The Ratio GameThere are two categories of T5 transmissions used in the 5.0 Mustang, commonly differentiated by the First-gear ratio. There are also varying Third- and Fourth-gear ratios, depending on the year of the trans. This information comes courtesy of The Official Ford Mustang 5.0 Technical Reference & Performance Handbook by CC alum Al Kirschenbaum. It covers in excruciating detail all the tech information you'll need on 5.0 Mustangs. You can buy the book from Ford Racing or through Summit Racing.
RATIOS 1ST 2ND 3RD 4TH 5TH REVERSE '83-'84 2.95:1 1.94:1 1.34:1 1.00:1 0.72:1 2.76:1* '85-'89 3.35:1 1.93:1 1.29:1 1.00:1 0.68:1 3.15:1 '89-on 3.35:1 1.99:1 1.33:1 1.00:1 0.68:1 3.15:1 Tremec 500 3.27:1 1.98:1 1.34:1 1.00:1 0.68:1 3.01:1 Tremec 600 2.87:1 1.89:1 1.28:1 1.00:1 0.64:1 2.56:1 Tremec 600 2.87:1 1.89:1 1.28:1 1.00:1 0.82:1** 2.56:1*Ford also offered a 0.63:1 Overdrive ratio in 1983.
**This trans is the road-race option where the rpm drop between Fourth and Fifth is much narrower.
This is a '90 five-speed with a 3.35 First gear rebuilt with a stronger 2.95 gearset.
To determine any car's overall First-gear ratio, multiply the transmission's First-gear ratio by its rear-gear ratio. If your Mustang has a 3.35 First gear and a 3.55 rear gear, the overall First-gear ratio is 3.35 x 3.55 = 11.89. Anything greater than 9.5 could be considered overkill for the street. Ever driven a Mustang with a 3.35 First-gear trans and a 3.73 rear? First gear is virtually useless, since the overall ratio is 12.49. This is why a 2.95 First-gear T5 or the Tremec 600 2.87 trans is far more desirable if your plans include deep rear gears.
To determine the Overdrive ratio, simply multiply the rear-gear ratio by the Overdrive. For a 3.73 rear gear and a 0.72 Overdrive, that's the equivalent of a 2.68 rear gear in Overdrive. If you're considering the Tremec 600 trans, a 3.73 with a 0.64 Fifth gear equals 2.39. This is a great way to lower the highway cruise rpm. Just remember, this combination will create high driveshaft speeds if you attempt to do a top-speed run; the driveshaft and the rear gears are spinning 36 percent faster than the engine!
Trans Strength
The strength of a manual transmission is related to four main design functions consisting of cluster-to-mainshaft center-to-center distance, First-gear ratio, gear-tooth pitch, and the alloy of the steel used to make the gears. The center-to-center distance is the dimension between the centerlines of the input shaft and cluster gear. A greater distance between these two gears increases gear diameter and strength. Note on the chart that the T5 has the shortest center distance while the much stronger T56 six-speed is more than 10 percent larger.
First-gear ratio is determined by dividing the tooth count of the driven (cluster) gear by the tooth count of the drive (input) gear. As First gear becomes deeper (higher numerically, as in 3.35 versus 2.95), the input-shaft gear-tooth count becomes lower, making the gear smaller, while the cluster gear-tooth count and size become larger. In the case of our 3.35-geared T5, several input-shaft teeth broke, which destroyed both the input and the cluster.
Tooth pitch is also a consideration. A straight cut or spur gear is the strongest but is also extremely noisy. As the pitch or angle of the gear tooth changes, it becomes quieter, but at the price of reduced strength. Another way to increase strength is to improve the quality of the steel used to make the gears. Since changing the center distance would require designing a new transmission, the T5's strength updates are limited to ratios and metallurgy improvements. Factory gears have evolved from 8620 to 4620 and 4615 alloys to improve strength. If you want serious strength, G-Force makes a helical-cut 2.94 low gearset for the T5 out of 9310 nickel alloy with a 26-spline input shaft, but it's pricey.
The bottom line on production-based T5s is that as long as you don't ham-fist the box with repeated power shifts, it will probably live a long and useful life. Abuse it, and count on becoming proficient at R&R-ing transmissions.
Aftermarket five-speeds
If you discover that rebuilding your existing T5 might not be cost-effective, an alternative could be the aftermarket derivatives of the T5. From the Ford camp, the strongest factory trans (rated at 330 lb-ft of torque capacity) is the "Z" trans (due to the letter Z found in the Ford part number) available from Ford Racing Performance Parts (FRPP) or D&D.
In the aftermarket, Tremec first built the 3550 five-speed, which was later superseded by the TKO. Both the 3550 and now the TKO have been replaced by the TKO-500 and TKO-600. The numbers refer to their advertised torque capacities. The 600 uses a 2.87 First-gear ratio while the 500 employs a deeper 3.27 low gear.
CENTER DISTANCESTRANSMISSION
CAPACITY
CENTER
DISTANCE
The input shaft on '94-'95 T5s is 0.625 inch longer than earlier T5s.
Rebuilding the T5
We started out with a broken T5 purchased from a friend for $25. Then we contacted Don Walsh at D&D Performance to find out what we had. This is a case of doing it backward-we should have done our research first, but the price was right. "You have one of the crappy 3.35 boxes," Walsh told us. "The best way to go is to rebuild it with one of our 2.95 low gearsets. Then you'd have a nice trans." That's what we did.
The Tremec TK-500/600 can trace its roots all the way back to the Ford Top Loader four-speed and retains the same trans-to-bellhousing bolt pattern.
What showed up a few days later was a 2.95 gearset along with a complete rebuild kit that included all those tough-to-find small parts. We talked our pal and consummate car crafter Tim Moore at Moore Automotive into taking us through the rebuild. Manual transmissions are no picnic, and since we'd never done one before, it was an education. Other than a hydraulic press and some metric sockets, there aren't any specialty tools required, but this is much more of a job than we can show here in a step-by-step sequence. After watching Moore work, we can't recommend that a rookie attempt to rebuild this trans. If you'd rather purchase a professionally built version of this 2.95 box, D&D will sell you a rebuilt T5 with all the same parts for $999 plus the core.
We'll show you some details and include a couple of things we learned along the way if you want to take a stab at rehashing your own T5. Our first recommendation is to go to Tremec's Web site and print out the free T5 rebuild manual. Tim used it to help him through the T5, although he did find a couple of areas that were a bit ambiguous. Here are a few of the major points.
Boneyard Warning
The T5 used in the 5.0L Mustangs is very similar externally to T5s used in numerous other rear-wheel-drive applications-mostly in turbocharged SVO and nonturbo'd, four-cylinder Mustangs; the '89-'93 T-bird SC; 305ci Camaros and Firebirds; S-series pickups; and the '84 Nissan 300 ZX to name a few. These boxes all used different, and mostly weaker, First-gear ratios, with one as deep as 4.05. The one exception is the 305 Camaro/Firebird 2.95 WC First-gear boxes from '88-'92. According to D&D, these boxes are basically as strong as the comparable WC Ford 5.0 transmissions. Do not be fooled into thinking you can adapt the other T5s into a high-output, V-8 application. We don't need to tell you the Nissan boxes do not interchange with the Ford units, do we?
