TREMEC TKX
Swap Parts & Cost

The TKX is TREMEC's current five-speed manual for the swap and restomod market, and it replaced the long-running TKO-500 and TKO-600. Rated at 600 lb-ft of input torque, roughly 100 pounds, and noticeably more compact than the TKO it supersedes, it exists to solve the specific problem of putting a strong overdrive manual behind an old V8 without cutting the floor to pieces.

Most people arrive at a TKX from one of three directions. Either a T5 has run out of torque capacity and started eating third gear, or a TKO is in the car and the tunnel clearance and shifter position have always been a compromise, or the car still has its original non-overdrive four-speed — a Muncie M20, M21, or M22, or a Super T10 — and the owner is tired of turning 3,200 rpm at 70 mph.

The transmission itself is the easy part. Order it, it shows up, it is a good gearbox. What separates a weekend swap from a six-month project is everything around the transmission: the bellhousing bore and bolt pattern, the clutch disc spline count, whether the release system is hydraulic or mechanical, the crossmember, the driveshaft length, and how the speedometer is going to get a signal. This page is the full list.

Ratios and Shifter Positions — Decide These First

Two configuration choices get locked in when you place the order, and getting them wrong is expensive to undo.

Gear ratios

The TKX is offered with either a 2.87 or a 3.27 first gear, paired with overdrive options of roughly 0.68, 0.72, or 0.81. That gives you real control over how the car drives.

• 3.27 first with a 0.68 overdrive — the widest spread. Short launch gear for a heavy car or a tall rear gear, very tall cruise. Best for a car with 3.73 or 4.10 rear gears that you also want to drive on the highway.
• 2.87 first with a 0.68 overdrive — closer ratios, less of a hole between gears, still a relaxed cruise. Good for a torquey big-block that does not need a short first.
• 0.81 overdrive — a milder top gear. Choose it if your rear gear is already tall (3.08, 3.23) so you do not end up lugging in fifth.

Work the math with your actual rear gear and tire diameter before you order. A 0.68 overdrive behind a 3.08 rear axle puts you at a cruise rpm low enough that the engine will not pull, and no amount of shifting technique fixes a bad final drive combination.

Shifter location

One of the headline features of the TKX is multiple shifter mounting positions in the top cover, which is how it fits factory console and floor openings that a TKO could not. This is not a bolt-in change after the fact on every configuration, so measure your existing floor opening and pick the position that puts the stick where your hand already goes. On a restomod where the original console is staying, this decision matters more than the ratio.

What The TKX Replaces

The automatic-to-manual conversion is the one people underestimate. You are not swapping a transmission, you are converting a drivetrain, and the pedal assembly alone can cost more than you expect. Our comparison of automatic vs manual rebuild cost is worth reading before you commit.

What The Swap Actually Needs

1. Bellhousing

The single most important dimension in this entire swap is the front bearing retainer diameter and the bellhousing's matching bore. The TKX uses a specific retainer OD depending on whether you ordered a GM or Ford input configuration, and the bellhousing bore must match it exactly. A bellhousing that bolts up to the engine but does not center the retainer will chew the input bearing and destroy synchros.

Just as important: measure bellhousing runout before you call the job done. TREMEC's tolerance is tight, and out-of-spec runout is the leading cause of hard shifting and premature bearing failure on a fresh swap. A dial indicator on the magnetic base, engine-mounted, indicating the bellhousing bore is a 30-minute check that saves a transmission. We wrote up the procedure in how to measure and correct bellhousing runout. If runout is out of spec, offset dowel pins move the housing into tolerance.

2. Clutch, flywheel, and pilot bearing

Three things must match your specific TKX input shaft: the disc spline count and diameter, the pilot bearing or bushing bore matching the input shaft nose, and the flywheel bolt pattern and clutch diameter your bellhousing will clear. Order the clutch kit against the transmission part number, not against the engine.

Choose the clutch for how the car will be driven. A high-clamp-force competition disc behind a 600 lb-ft rating sounds correct and makes a street car miserable in traffic, and an aggressive puck disc shock-loads the input shaft on every launch. A good organic or dual-friction street disc with moderate clamp is the right answer for the overwhelming majority of TKX swaps. See our clutch kit buyer's guide for the tradeoffs.

You also need a clutch alignment tool that matches the spline count. A wrong-spline tool centers the disc incorrectly and you will find out when the transmission will not slide the last half inch. Alignment tool guide.

3. Release system: hydraulic throwout vs mechanical linkage

Two paths, and the choice affects cost, pedal feel, and how much fabrication you do.

Mechanical linkage (Z-bar, clutch fork, throwout bearing) is cheaper and, if the car came with it, mostly reuses existing pieces. But the geometry has to work with the new bellhousing and fork position, and on many swaps it does not without modification.

Hydraulic throwout bearing (a concentric slave cylinder that rides on the input shaft retainer) eliminates the fork and linkage entirely, gives a lighter and more consistent pedal, and is what most modern swaps use. It needs a clutch master cylinder, a remote reservoir, and lines run through the firewall. The critical detail: the bearing-to-diaphragm-fingers air gap must be set to spec with shims before final assembly, and it is a measure-twice job because getting it wrong means dropping the transmission back out. Set it too tight and the clutch slips; too loose and it will not fully release.

4. Crossmember and mount

The TKX mount pad sits in a different place than a TH350, a T5, or a Muncie, so plan on a new crossmember. Bolt-in crossmembers exist for the common chassis (early Mustang, F-body, A-body, Tri-Five) from the swap-kit vendors. On anything less common you are either modifying the original or fabricating. Do not skip the driveline angle check: the transmission output should be within a degree or so of parallel to the pinion angle, and the crossmember is what sets it. Our crossmember guide covers the options.

5. Driveshaft

Almost every TKX swap needs driveshaft work. The overall length of the TKX differs from what came out, so the shaft either gets shortened and rebalanced or gets built new. Budget $80 to $180 for shortening and rebalancing an existing steel shaft, or $250 to $600 for a new one. Aluminum and carbon shafts cost considerably more.

Measure with the engine and transmission fully mounted, the crossmember bolted, and the suspension at ride height — not with the car on a lift and the axle hanging. That single mistake produces more wrong-length driveshafts than any other. Confirm the slip yoke spline count and the U-joint series before ordering.

6. Speedometer

Depending on the TKX part number you ordered, you may have a mechanical speedometer drive provision, an electronic speed sensor port, or both. Confirm which one you have before you buy a gauge solution. If you have an electronic output and a mechanical gauge (or the reverse), a signal converter box from a gauge manufacturer bridges the gap for roughly $150 to $300. Cable-driven setups also need the correct driven gear tooth count for your tire diameter and rear gear ratio, or the speedometer will read consistently wrong.

7. The small stuff that stops the job

• Shifter and handle — the TKX ships with a shifter, but offset handles and short-throw options exist if the stick lands in the wrong place.
• Reverse light switch and wiring — the connector will not match your old harness. Plan a pigtail.
• Transmission fluid — roughly 2.6 to 2.8 quarts of the ATF-type fluid TREMEC specifies. Do not fill it with heavy GL-5 hypoid gear oil out of habit; the wrong fluid makes it notchy cold and wears synchros. See manual transmission fluid guide.
• Slip yoke — matched to the TKX output spline count and your U-joint series.
• Clutch master cylinder, reservoir, hose, and firewall adapter if you are going hydraulic.
• Bellhousing dowel pins, offset dowels, and grade-8 hardware — do not reuse tired dowels.
• Tunnel and floor clearance — test-fit before paint. The TKX fits many factory tunnels the TKO would not, but "many" is not "all."

TKX Swap Cost Tiers — 2026

Parts pricing in US dollars for 2026, excluding installation labor unless noted. The bare TKX itself runs roughly $2,900 to $3,600 depending on ratio and configuration, and that is the floor no matter which tier you land in.

Individual line items

The honest budgeting rule for a TKX swap: take the transmission price and roughly double it for a complete, correctly done job. People who budget only for the gearbox are the ones whose cars sit on jack stands for a year waiting for the next paycheck. If you are comparing against a different five- or six-speed, our T56 Magnum cost guide covers the six-speed alternative.

What You Actually Need To Buy (Tools)

Beyond the parts list, here is the tooling that makes the difference between a swap that shifts well and one that comes back apart.

• Transmission jack — a 100-pound gearbox at arm's length over your face is not a bench-press exercise. Our transmission jack buyer's guide covers telescoping vs low-profile. Check price
• Dial indicator with magnetic base for bellhousing runout. Non-negotiable on a swap. Check price
• Offset dowel pin set to correct runout once you have measured it. Check price
• Clutch alignment tool in the correct spline count. Check price
• Angle finder or digital inclinometer for setting driveline angles at the crossmember. Check price
• Fluid transfer pump — the TKX fill plug is on the side and gravity is not your friend. Check price
• Torque wrench that reads accurately in the range of bellhousing and crossmember bolts.

FAQ

How much does a TREMEC TKX swap cost?

The bare transmission is roughly $2,900 to $3,600 in 2026. A budget swap reusing a serviceable bellhousing and clutch with mechanical linkage lands around $4,000 to $5,000 in parts. A typical swap with new bellhousing, clutch, hydraulic throwout, crossmember, and driveshaft work runs $5,500 to $7,500. A complete kit from a swap specialist runs $6,500 to $9,500, plus $1,500 to $3,000 if a shop installs it.

What does the TKX replace?

It replaced the TKO-500 and TKO-600 in TREMEC's lineup, and it is the common upgrade from a T5 that has run out of torque capacity. It is also the usual choice when swapping out a non-overdrive four-speed like a Muncie M20, M21, M22, or a Super T10, because it adds the overdrive gear those boxes never had.

How much torque can a TKX handle?

TREMEC rates it at 600 lb-ft of input torque. That rating assumes a properly aligned bellhousing, a clutch that is not shock-loading the input shaft, and correct fluid. In practice, clutch and driveline abuse breaks more TKX gearsets than raw torque does.

Do I need a new driveshaft?

Almost always. The TKX is a different overall length than nearly everything it replaces. Shortening and rebalancing an existing shaft runs $80 to $180; a new steel shaft runs $250 to $600. Measure with the drivetrain mounted and the suspension at ride height, never with the axle hanging on a lift.

What fluid does a TREMEC TKX take?

TREMEC specifies an ATF-type fluid and sells its own high-performance manual transmission fluid for it. Capacity is roughly 2.6 to 2.8 quarts. Do not fill it with thick GL-5 hypoid gear oil on the assumption that a manual gearbox wants heavy lube — the wrong fluid gives notchy cold shifting and accelerates synchro wear.

Will a TKX fit my factory tunnel?

The TKX was made more compact than the TKO specifically to improve tunnel and floor clearance, and it fits many factory tunnels a TKO would not. It is still not universal. Early Mustangs, A-bodies, and some F-bodies may need minor massaging depending on the shifter position and mount location you choose. Test-fit before paint.

Can I keep my mechanical speedometer?

Depending on the part number you order, the TKX may have a mechanical speedo drive provision, an electronic speed sensor port, or both. Confirm before buying a gauge solution. A signal converter box bridges a mismatch for roughly $150 to $300.

Hydraulic throwout bearing or mechanical linkage?

Hydraulic if you are starting from scratch or the linkage geometry does not work with the new bellhousing — lighter, more consistent pedal, no fork to fight. Mechanical if the car already has good linkage that clears. Either way, if you go hydraulic, shim the bearing air gap to spec before the transmission goes in. That measurement is the difference between a clutch that works and one you pull the transmission back out for.