How do I swap my auto to a manual?
This is a fairly common question on the JBO forums. The actual swap is fairly straightforward, but it's all the little pieces and things that add up that can make it difficult.
For third gen cars, there were really only four transmission options.
1. 3 speed automatic (3T40)
2. 4 speed automatic (4T40E)
3. 5 speed manual, 95-99 (Isuzu-designed)
4. 5 speed manual, 00-05 (Getrag)
The Isuzu and Getrag use different parts.. from the transmission mounts all the way to the shifter assembly. Both have similar upgrades available, and can handle similar amounts of power when built up. Most people won't break the transmission from power, but from bad shifting... so if you're worried about which one is better - don't.
The hardest part of switching from auto to manual (or vice-versa) is swapping over all the parts. The transmission assembly, including the mounts, axles, shift cables, wiring, pedals, etc takes a fair bit of time. You will have to weld in new transmission mount brackets for this swap. You will also have to reflash your existing PCM, or get a manual PCM and replace the automatic PCM.
Here is a list of the parts you'll need for the swap:
- Complete transmission (duh)
- Clutch
- Flywheel
- Clutch pedal assembly
- Gas/brake pedal assembly (from a manual; smaller brake pedal, unless you don't care about the wider brake pedal)
- Clutch master cylinder
- Slave cylinder/throw-out bearing assembly
- Shifter assembly w/ cables
- Axles
- Manual PCM (or reflash)
It is important to note, that because the bellhousing is different between the 2.2L (pushrod) or 2200 engine, the 2.4L Twin Cam (LD9) engine, and the 2.2L Ecotec - the transmission MUST come from the same motor. You cannot use a 2.4L transmission on a 2.2L, unless you swap the bellhousing (which requires the transmission to be disassembled). Get the right transmission to start with, and it's a much easier job.
The easiest way to do this swap is to drop the existing engine and transmission out of your car together. Once they're out, you can separate the transmission from the engine and start putting the manual transmission together. There is plenty of other work to do to the car while the powertrain is out.
The 3- and 4-speed auto transmissions use the same transmission mounting plate. There are four bolts through it. You need to grind off the bottom plate to clear the new transmission. Do this now, while the engine and transmission are out of the car, because it's really hard to do later on when you realize that it doesn't fit properly (learn from MY mistakes!).
Once you drop the engine, take off the starter motor. Turn the crank and undo the three bolts from the flexplate (accessible thru the starter hole) to the torque converter. Once these are out, you can take out the large bolts that hold the transmission to the engine block, and separate the two. The flex plate comes off the crank (six bolts). You need longer bolts for the flywheel, because it is thicker than the flexplate. Once the flywheel is on, you can put the clutch plate, cover, etc together and bolt the manual transmission to the engine.
The next step is to weld in the transmission mount brackets. The rear getrag bracket is available new from GM, and is relatively cheap. The front getrag mount is available from Turbo Tech Racing and is also inexpensive. If you want, you could torch off a set of mounts from a wrecking yard. I do not know if the Isuzu mounts are available from GM anymore. If there's only one thing you get from this FAQ article.. hopefully this is it: MEASURE MEASURE MEASURE. Make sure the mounts are EXACTLY where they need to be. Clamp it, then measure again. Tack weld it, then measure again. Do a test fit, then measure again. Once you're absolutely positive that they're in the right spot, weld them up nice and sturdy.
There's lots of work to do in the interior. Take out the centre console, remove the automatic shifter assembly. Disconnect the park/brake interlock cable. Install the new shifter and feed the cables through the firewall.
The pedals are a special challenge upon themselves. If you want to make it easier on yourself, remove the whole dash. I will not go into those details in this write-up. If you want the smaller brake pedal, you need to remove the stock gas/brake pedals (they're one assembly) and replace them with the manual ones. Then install the clutch pedal. There is a spot above the steering column for the top bolt, but there isn't a hole in the firewall for the clutch master cylinder, so you'll have to drill that. There's a big hole in the middle for the plunger, and two on either side for the bolts. As before, MEASURE MEASURE MEASURE. It doesn't have to be perfect, but it does have to be close. There is a notch in the sheet metal on the engine side if you look closely, that's where you're working. Compare with a friend's car or a wrecked car if you can.
Once you have the pedals installed, you can put the engine back in with the new transmission. Then it's a matter of hooking things up to the right places.
The electronics are another matter.. since the dash harness and engine harness are different between auto and manual cars, you'll either have to swap those or modify them to work. The automatic has a neutral safety switch on the transmission, the manual has a clutch safety switch on the top of the clutch pedal. If you change the entire dash harness (a bit of a pain, but safer to have the switch than to bypass it), then it's just a matter of plug and play. Same goes for the reverse light switch. On an automatic, it's next to the safety switch on the transmission case, but on a manual it's on the back of the case. Also the VSS wire, which is on the passenger side (output shaft) on the auto, but on the driver's side on the manual.
So, it's not exactly a walk in the park, but it's not impossible. Depending on where you get the parts from, it can range up to $2000 or so if you do your own labor, more if you have to pay someone to do it for you.
Obviously, this isn't meant as a "How To" guide.. there's a lot more that I've left out here. But it should give you an idea of what exactly is involved in the procedure.
If you have questions, hit me up in the forums.
Written by John Lenko, with lots of input from the 'Search' button.
