How to Manual Swap a C10 Truck | 1967-1972 C10 Tremec Install
Some things are just meant to be together. Lennon and McCartney. Peanut butter and jelly. Biscuits and gravy. You get the idea. Well, we think that old trucks and manual transmissions can be added to that list. There’s just something magical about pulling gears in an old truck, whether it’s the OG granny four-speed or a modern overdrive. So with that in mind, when it was time to add an overdrive gear to our ’68 C10 project, we didn’t think twice about making the switch from the TH350 auto that was in the truck to a manual.
C10 Manual Transmission Conversion Kit
Here are the parts we used to complete our C10 manual to automatic conversion:
Tremec TKX LS Swap Kit
Let’s start with the transmission that will be the heart of our Chevy C10 manual to automatic transmission swap. While you could certainly go the vintage route and do a C10 4-speed manual transmission swap using something like an old Muncie or T10, we opted for a more modern Tremec TKX transmission to back up the 5.3 LS engine in our ’68 C10. The addition of an overdriven fifth gear is huge when compared to the TH350 or an archaic Chevy C10 3 speed manual transmission. As a bonus, the internal shift mechanism saved some space and eliminated the need for a finnicky linkage and our C10 TKX swap fit under the stock tunnel.
While some in search of an overdrive manual might consider the more economical T5 transmission LS swap route, we’ve found that even stock, small displacement LS engines make enough power for a T5 to be marginal. The TKX, on the other hand, is rated for up to 600 lb.-ft. of torque, so it’s up to the job even behind hopped up LS engines.
Speedway Motors offers these Tremec Transmission Kits that include everything needed to bolt on up to the engine. That means the flywheel, clutch, throwout bearing, and even the hardware and wiring pigtails. These kits are available as C10 LS swap manual transmission kits as well as TKX manual transmission kits for old school small blocks, so there’s a kit for whatever engine you have in your truck. They’re also available with T56-based Tremec Magnum 6-speeds, but you’ll have to modify the tunnel on your C10 to squeeze one of these between the seats.
TorqLink™ 67-72 C10 Transmission Crossmember
The stock transmission crossmember had long since flown the coop on our C10. If your truck still retains the OG crossmember, it might work for your C10 5-speed swap. But it’s likely going to take some modification to make it all work. The beauty of the Speedway Motors TorqLink™ C10 Transmission Crossmember is that it’s almost infinitely adjustable. That means slotted holes combine with the multiple holes in the truck’s framerails for forward/backward adjustment to accommodate anything from a Powerglide to a T56, but it also means multiple height settings for fine tuning the angle of the engine and transmission to facilitate pinion angle adjustment. They also offer fantastic clearance for tucking the exhaust up into the ‘rails, and they just plain look trick.
Speedway Motors 1967-72 Chevy C10 Hydraulic Clutch Conversion Kit
The transmission kit included all the clutch parts as well as a hydraulic throwout bearing. We’ve used these on countless manual swaps and found them to be extremely slick for packaging manuals into old cars, trucks, and hot rods where space is tight since they forego all the stock z-bar and linkage shenanigans. All that’s needed is a couple lines for feed and bleed and you’re in business.
Of course, the other necessary component is a master cylinder actuated by the clutch pedal to give orders to the bearing. We’ve fabricated brackets and linkage to do this in the past, but this C10 Hydraulic Clutch Converstion Kit makes it easy, with the bracket already fab’d up and powdercoated as well as the linkage and master cylinder. The plate bolts up behind the booster and the hardest part of the install is to drill the holes in the firewall and pedal arm. The finished result is easy, tidy, and the simplest way to actuate the clutch in one of these trucks.
Steel Custom Length Driveshaft Kits
It’s likely that you’re going to need to change the driveshaft along with your transmission swap. These Custom Length Driveshaft Kits kits make it easy to spec exactly what you want in the perfect length for your newly swapped pickup. Note that the Tremec TKX uses the same front yoke as a Ford C6. Also note that while our driveshaft worked out to a 59 1/2" length from the seal surface on the Tremec to the middle of the rear u-joint, your results may vary depending on your engine, motor mount, and rear suspension and axle situation.
To make things easy, we’ve gathered up everything we used for our swap in a C10 Tremec Swap Buildlist with just about everything you’ll need to do the job on your truck.
C10 Manual Transmission Swap Tips
Once you have all the parts in the shop, a 67-72 C10 manual transmission swap is fairly straightforward. The big question with many modern overdrive manual swaps into old cars is the tunnel situation. We’ve all seen big, late model transmissions swapped into old cars with massive tunnel surgery necessary to make room for everything. Cutting and welding sheet metal is one thing, but don’t forget about consoles, seats, carpet, and anything else that might be in the way. That’s one reason we like the Tremec TKX Chevy manual transmissions so much. Unlike the old TKO’s, they are very low profile on the top, making them far more likely to fit where old Saginaws, Muncies, and even 3-speed autos may once have lived. As discussed above, we mocked up a T56 in our C10 and it was going to require some surgery to the tunnel, in particular the area near the rib where the tunnel area transitions into the floor.
Obviously, you’re going to need a shift lever. What you choose will depend on your seat configuration and personal preference. We chose one of the trick Speedway Motors Billet Aluminum Shift Levers, in particular a 16” 30-degree lever to clear our bucket seats and console.
We also learned while swapping our truck that the entire pedal assembly doesn't need to be replaced to add a clutch pedal. The shaft that the brake pedal rotates on is hollow, and the clutch pedal shaft rides inside. This was welcome news to us because we were expecting to wrestle the whole brake pedal assembly and bracket loose from the truck and replacing it. Instead, we just greased up the clutch pedal shaft and slid some bushings into the hollow tube on the brake pedal.
Ok, now that it’s done, what’s our project truck like to drive? In short, our C10 now feels like the truck we were fantasizing about all those years ago when we dragged it home on the trailer. The auto was…fine. But it wasn’t really fun to drive. With the modern Tremec backing up the 430-horse 5.3, the combo feels like the perfect mix of old and new. The long shifter nets slightly long throws, which might not be ideal for blistering times at the dragstrip, but combined with the precise gating of the Tremec shifter it’s the perfect 5-speed manual transmission for Chevy C10 that walks the line between “old truck” and late-model muscle car.
