Mark Houlahan
Mark Houlahan Tech Editor, Mustang Monthly
May 22, 2019
Contributers: Mark Houlahan

In our July 2019 issue of Mustang Monthly, we introduced you to the process of rebuilding your own T-5 manual five-speed transmission for your Mustang project with Part 1 of this series, in which we disassembled this T-5 for a full rebuild. (If you missed it, you can find Part 1 online at: mustang-360.com/how-to/chassis-suspension/1904-rebuilding-a-t-5-five-speed-part-1-disassembly. ) Be it the original T-5 found in the tunnel of your Fox-body Mustang, or perhaps you're working on a low-buck five-speed conversion for your classic Mustang, handling the rebuild of your T-5 yourself is not only a great learning experience—it also provides the satisfaction of handling another aspect of your project yourself, saving you money in the process.

This month we embark on Part 2, where we provide you with the details you'll need to assemble a T-5 five-speed with new bearings, seals, blocker ring components, and more to make your T-5 ready for many more years of service. We'll be utilizing a Ford Performance Parts M-7000-A T-5 World Class Rebuild Kit for this. This 94-piece kit includes everything you need to rebuild a T-5 that has seen common wear and mileage. It will work with the following T-5 applications:

1985-1995 5.0L Mustang

1985-1986 2.3L SVO Mustang

1985-1993 2.3L Mustang (1987-1993 will require additional input bearing and race)

1985-1988 2.3L Thunderbird Turbo Coupe (1987-1988 will require additional input bearing and race)

1994-2004 3.8L V-6 Mustang with T-5 transmission

Ford Performance Parts M-7003-Z transmission

Ford Performance Parts M-7003-A transmission

Ford Performance Parts M-7003-X transmission

If you've disassembled your T-5 and found shaft/spline/gear damage, the Ford Performance Kit, while still required for your rebuild, won't help you there. You'll need to source replacement hard parts, either from another used transmission, or from an aftermarket parts source. There are a few new parts available as well as higher-end racing gearsets/shafts that will put a bit of a dent in your budget. One great source for internal hard parts—as well as conversion parts for classic five-speed conversions—is Modern Driveline [(208) 453-9800; moderndriveline.com]. You'll also find great info on the company's website, such as a T-5 history section and a T-5 specifications page where you can research your trans by tag number.

Let's grab our cleaned case parts and our M-7000-A parts kit and follow along as David Piercey of David Piercey's Mustang Performance assembles our fresh T-5 for many more years of service! Be sure to download Tremec's T-5 rebuild manual to aid in your benchwork at home if this is your first go at a T-5 rebuild (tremec.com/anexos/TRSM-T5-0510-R1_173.pdf).

 

The Ford Performance M-7000-A T-5 rebuild kit features two shrink-wrapped cardboard panels with a full inventory sheet that breaks down what parts are found on each one. Included are all the major wear parts like bearings, blocker rings, seals, and more—almost 100 pieces in total! If your T-5 needs additional hard parts, you'll have to source them separately.
There are a few sub-assemblies to tackle first before getting to the nitty-gritty of the T-5 assembly. David begins with the T-5's top cover and installs new shift fork pads.
At the rear of the cover this new O-ring is installed and seated in the groove. This O-ring seals the tailshaft extension to the top cover once it is installed.
David pulled this shift selector arm from his inventory to show the difference. The later T-5 uses the cast-in pin while the early version used the pressed-in pin. The pressed-in pin can loosen up and David will often peen them to secure them.
The main case prep begins next. The reverse idler gear is placed into the case and the reverse idler gear shaft is passed through the rear of the case and then through the gear. Lastly the O-ring is added and the shaft passes through the case boss and is secured by the roll pin as shown.
David starts assembling the synchronizer assemblies next. Here is the Fifth-gear synchronizer assembled with the new inserts and retaining springs, which are included in the M-7000-A rebuild kit. The retaining spring's tang should be inserted into the same insert (shown at the top here) on each side but rotate opposite of each other.
For the Third/Fourth-gear synchronizer David lines up the synchro's hub and sleeve, carefully placing the new inserts and retaining springs. The same goes for the First/Second-gear synchronizer assembly.
Generally, the countershaft front bearing race is only pressed out if you're replacing the tapered roller bearing that seats in it. David is indeed replacing all shaft bearings in this rebuild, so the race is pressed out and a new one driven into place flush with the front of the case.
After pressing the new roller bearing onto the front of the countershaft and applying a light coating of grease, the countershaft is positioned into the main case.
The main case is placed on end and David carefully seats the rear countershaft bearing with a hammer and punch, working his way around to prevent the bearing from binding as it is seated.
Assembly grease is applied to the bearing just like on the front countershaft bearing, and then the bearing race is seated over the new rear bearing.
If you recall from our Part 1 disassembly, there is a selective shim found under the bearing retainer. That measurement was recorded during disassembly and David measures the shims found in the M-7000-A rebuild kit to find the same dimension as a starting point for the rebuild.
David then places the shim(s) and bearing retainer in place over the rear countershaft bearing assembly and torques the four fasteners to 15 lb-ft using red threadlocker. While the case is still upright, David checks countershaft endplay with a dial indicator and a prybar (similar to checking crank thrust in an engine build). Factory endplay range is 0.001-0.005 inch. If the endplay is too much, increase the shim thickness; if it is too tight, use a thinner shim.
Once proper endplay has been achieved on the countershaft, use a punch and hammer to bend the anti-rotation lock tabs inward on the four bearing retainer fasteners.
Slide the Fifth/Reverse-gear shift shaft into the case from the rear, through the shift shaft block and into the front of the case. You'll need to roll the shift shaft block into the groove of the idler gear first and hold it while the shaft is slid through and rotated into place on the Fifth/Reverse-gear lever. Finally, secure the spring to the shift block and case as shown.
Moving on to assembling the output shaft, place the detent ball and spring into the output shaft. Use a little bit of grease to keep everything in place.
Next, David installs the First/Second-gear synchronizer, inserts, and springs following the same method as previous synchronizer assemblies, and then he fits the blocker rings and outer cone races. A squeeze bottle of ATF is used to soak the friction materials on the blocker rings. This is where you will have found the spiral lock that we removed during disassembly. It's essentially an assembly line aid for manufacturing and isn't needed, so David leaves it out.
The Second gear is installed over the output shaft with a new needle bearing assembly from the M-7000-A kit, followed by the thrust washer and external snap ring to retain everything.
On the opposite side of the First/Second-gear synchronizer assembly this spacer sleeve is refitted from our pile of original parts, followed by a new needle bearing assembly from the M-7000-A kit.
With the spacer sleeve and new needle bearing fitted to the output shaft, the original First gear is slid down in place over them.
To wrap up the tail end of the output shaft, David installs the new tapered bearing and the original Fifth gear and its external snap ring to retain the assembly.
Moving back to the front of the output shaft, a new needle bearing is slid down into place along with its spacer.
David fits the Third gear over the needle bearing next.
The Third gear is followed by the Third/Fourth-gear synchronizer assembly, which is then retained by the external snap ring shown.
Moving over to the shop press David installs the tapered roller bearing to complete the output shaft assembly for this T-5 rebuild. You'll only find this tapered bearing on Cobra- and Ford Performance-spec T-5 transmissions.
Our completed output shaft is now carefully lowered into the main case to continue with our main case component assembly.
The standard T-5 input shaft uses these roller bearings. New ones come in the M-7000-A kit if your T-5 utilizes them. Place them into the end of the input shaft as shown with a little grease to hold them in place.
The Cobra Mustang and Ford Performance T-5s use a tapered roller bearing for the input shaft to output shaft bearing surface. We've already pressed that bearing onto the front of the output shaft earlier; the input shaft, with its new bearing already pressed on, is inserted into the main case.
The input shaft bearing retainer has this oil seal found behind the bearing cup and preload shim. On the standard retainers you can press the seal into place until it seats on the inner lip. For the Cobra-style retainers there is no lip, so you must watch seal placement. In these cases, install the seal flush with the steel retainer sleeve. Temporarily install the retainer with two bolts for now, making note to install with the wide relief toward the bottom to aid in fluid drain.
At the rear of the main case David installs the bearing race for the rear output shaft tapered bearing. It is a light-press fit into the case.
The Fifth-gear drive gear is placed onto the cluster shaft as shown. Apply a light coat of grease to the Fifth-gear blocker ring and seat it on the gear.
Slide the Fifth-gear synchronizer and shift fork over the Fifth-gear drive gear, ensuring the synchronizer taper and fork offset are both facing toward the rear. Secure the synchronizer with its external snap ring. If you haven't installed the new plastic oil slinger/funnel into the end of the countershaft yet, then do so now as well.
On the shift fork casting, line up the retaining pinhole with the shift rail's mating hole and install the roll pin flush to secure the assembly. Use a block of wood to support the assembly as shown.
The top cover with shift forks can be installed at this time. Apply a bead/coating of silicone sealer to the main case surface and let it set up for a few minutes. Start with the forks slightly offset so that the cover is moved in a downward-and-over motion to seat the shift forks onto the synchronizer's grooves properly. Install the two larger shoulder bolts first to locate the cover properly and then install the remaining bolts, torquing the fasteners to 10 lb-ft in an alternating pattern.
Apply thread sealer to the neutral sensing switch and thread it into the T-5's top cover. David opts to not reinstall the small-diameter pin under the switch, essentially disabling the switch.
The M-7000-A rebuild kit includes a new spring steel speedometer drive gear retainer to use. Place the retainer into the hole in the output shaft and slide the speedometer drive gear into place until the retainer catches it. If you need to change your drive gear due to numerically higher rear-axle ratios, now is the perfect time to do it!
David applies silicone sealer to the face of the tailshaft housing and a light coating around the top cover's O-ring opening as well, and then he slides the tailshaft housing over the shift rail and output shaft, leaving about a 1-inch gap between the housing and main case.
The reason for the gap is that the shift rail must pass through the shift block and seated as an assembly. Using assembly grease, David preps the shifter area for the shift block by placing the steel detent ball in the middle position of the rearmost row of detents.
Next, he places the steel ball's spring into the recess in the shift block with more grease and then pushes the spring over the steel detent ball until the shift block is level with the shift rail. While maintaining that position/pressure the shift block is pushed forward onto the rail, while the tailshaft housing is fully seated to the main case.
To secure the shift block to the shift rail a roll pin is installed. The new shifter bushing from the M-7000-A kit is installed into the shift block with a dab of grease at this time as well.
With the transmission complete, all that is left is to measure input shaft endplay and install the correct shim. Once again, using a dial indicator, this time on the output shaft with the trans in a vertical position on the bench and the input shaft facing down, pressure is applied to the input shaft and the dial indicator is read. The shim required will match the measurement taken to effectively create zero endplay. Remove the input shaft bearing retainer and place the appropriate shim behind the bearing race, and then return the bearing retainer to the transmission, securing with all four bolts—this time to 15 lb-ft. Be sure to use sealant on the threads!
And there you have it! A fresh T-5 rebuilt by your own hands that will provide many more years of great service with fresh seals, bearings, and blocking rings. Now drop a quality shifter with shift fork stops built in to prevent over-shifting, and your T-5 will live a happy life!

 

Identifying Your T-5
At first glance you might think that all T-5s are the same, and that is simply not true. Not only do you have different T-5s for different engine applications within the Mustang itself, but you have different T-5s for truck and even GM applications. So, you must be careful of what you're planning to buy, especially if the trans is sitting loose on a workbench, salvage yard grounds, or the buyer doesn't really know what he has.

If the metal case tag is still in place, this will be your best bet to determine what you're looking at. The case tag will ID application, gear ratios, and more. Plus, if the tag is still in place, it's a pretty good indication that the box has never been messed with. Hit the Interwebs for a case tag decoder.
A quick way to determine year of manufacture is to check the main case, top cover, and tailshaft castings for this circular date stamp. This particular example is from 1986 when the T-5 was still a "Borg Warner" product and before Tremec bought the brand. All three pieces should have the same year identification. If the main case is "86" and the tailshaft is "91," then someone has been in it and mixed/matched parts—a solid sign of a previous rebuild/repair.
Early T-5 transmissions used a standard hex-head-style bolt for the Fifth/Reverse gearshift lever pivot pin. This will help to ID early "non-World Class" boxes that used gear oil instead of ATF.
Later World Class T-5 transmissions used this Torx-style bolt for the Fifth/Reverse gearshift lever pivot pin. It also made it harder for Joe or Jane DIY to accidentally remove the bolt thinking it was the case fill location (drain and fill are both located on the passenger side in all applications).
While this difference is internal, we wanted to show you the differences in the three T-5 mainshafts used over the years. From left to right we have the 1993 Cobra and Ford Racing T-5 shaft, the '85-'93 shaft, and the '83-'84 shaft. The Cobra/Ford Racing piece utilizes a caged pocket bearing for the input shaft (note the smaller diameter of the shaft tip), whereas the '85-'93 uses individual roller bearings. The '83-'84 piece is unique in that while it still uses the roller bearings for the input shaft, it does not use the caged needle bearings under the gears like the '85 and ups do, which is why that piece has grooves machined in it for the thicker gear oil used in that transmission.

 

Photography by Mark Houlahan