Incidental info on the F23 swap

The area that covers non-Fiero things going into the Fiero!

Incidental info on the F23 swap

Postby Trinten » Wed Jun 06, 2012 6:18 pm

Please see the F23 Tutorial thread, found here - viewtopic.php?f=8&t=3

While it covers the SBC, it also covers how it would go onto any/most 60 degree engines. Below was the precursor to that thread, a collection of facts and information. Some may find it useful for incidental information, which is the only reason I'm copying it over. EMC209i / L67 covered just about everything major in his thread. It does have useful information for programming the Dakota Digital box, under the "Speedometer" heading

So, let's start with the first question that almost everyone asks:
"What cars do the F23 come out of?"
2000-2002 Pontiac Sunfire or Chevy Cavalier - Only those with the 2200 engine - others use the ecotech pattern. From searching it appears that the vehicle Vin "4" is the one you'd want. The Vin "F" appears to be Ecotec motors.
From 2005 forward (wrong bellhousing, mind you), GM began using brass contact pads on the ends of the shift forks, which is an upgrade from the composite material pads used from 2000-2004. The ideal setup would be a low mile transmission from '00-'02 that's been cracked open to add the brass hardware.

Next is usually "Why should I pick this?" well, Jncomutts Fiero was putting down in the 500 ft/lbs range of torque, and he was doing clutch dumps and everything else, and never managed to break it. He snapped axles more than anything. And then flywheel bolts.

In 2009 and 2010, the Chevy Cobalt offers a better economy gearing behind the 2.2. 3.63 ratio (opt FY1). This means you WILL NEED TO SWAP BELLHOUSINGS!! (that whole ecotec thing, remember?)

It takes 2 quarts of AUTOMATIC transmission fluid. Yes. Automatic. Dexron III or higher. My googling has turned up many people who use the Royal Purple stuff and like it very much, obviously this is personal preference. 2 quarts is "technically" an overfill by 0.2, but there was an article out there about doing that to help with some issues that some F23s experienced. (thanks to Paul and John for the info!! Again!! :) ).

Apparently the bigest obstacle to overcome is the speed sensor, which is a magnetic hall effect sensor. The signal has to be converted from 24,000 PPM signal into 4000ppm for the gauges. Here is a schematic and some information on it:
"Although labeled specifically for the Series II 3800 computer, any computer which can read the newer anolog VSS signal (hall effect) will work, if the output is tuned to 4000ppm." - Ryan's circuit schematic (but I think the PPM conversion has to be done first, not clear if this circuit does that 24K - 4K ppm adjustment).

Sometimes the signal needs to be converted into a 2000ppm for the older PCM's such as the stock Fiero equipment. And interfacing the hall effect VSS sensor. OBD2 computers use them, but the OBD 1 and OBD 1.5 VSS inputs are different. John has tried the Dakota unit, but wasn't able to get it to work.

Quick solution - The OBD 2 computer have a calibrated VSS output that can be used to signal the speedometer. Not only will they read the transmission speed, but will also interface the signal for you. - note from Jncomutt: I simply changed the parameters in the PCM to reflect the different ppm signal from the new trans and the proper signal out to the fiero speedo. The pcm did all the signal conditioning for me.

If you use the Dakota Digital converter instead, here is some information on setting it up:

The instructions suck on the dakota digital... For a 24000 PPM setup all the switches should be in the down position and the VSS wired from the OUT3 position. For the 64000 (assuming the F23 is the same as the F40) I haven't tried to figure it out, but knowing the switches to get a 24000 you should be able to check the instructions for the multiplier values of the switch positions and get it close. Once it is close, then the up/down buttons will fine turn it at speed (use GPS for a known speed and adjust it to match.

Cut the Yellow VSS wire in the center console before the 203.
Connect the YELLOW from the VSS sensor to the INPUT.
Connect the YELLOW going to the 203 to OUT 3.
Connect the POWER (Red)
Connect the GROUND (white)
Switches 1, 2, 3 & 4 are all positioned down.
Then drive the car at a known speed and use the UP/DOWN buttons to set the speedo to the actual road speed.

Once I understood how to work (thanks to the above info from Guru). I did the following:

First thing I did was use one of the "quick presets" to get it closer to where it needed to be -- I used the formula in the directions to find that my output signal had to be .33. one of the quick presets is for .5. So to do this, with Key off, push pin three to "On". While holding down both the up and down buttons, turn key to On.

Did that, confirmed that I was in the ballpark and that it took. So shut the car down, key off, and put it in "Fine Tune" mode. To do this, with key off, hold the "down" button, turn key to on, that puts it in the right setting. I then got on the highway and up to 2500 RPM (my 70 MPH point) and held the "down" button again, and the speedometer gradually dropped to the right speed.

Stock manual Fiero axles work for this.

There are some concerns about the HTOB getting wrecked if you don't put a backstop on your clutch pedal, or find some other metod of reducing the travel/engagement of the master cylinder. Someone else suggested shimming out the Master Cylinder. I'm not sure how/if that's possible, just posting it here for completeness, if that's not possible, someone let me know so I can remove that suggestion!

This is to avoid over extending the HTOB in the f23 which is not cool since the HTOB are not super cheap even for aftermarket but they also dont just go bad either so if you do it right you wont be replacing it any time soon.

Paul isn't terribly worried about the clutch pedal travel, but he does say that it's not a bad idea. He's looking into using a different Master Cylinder that might resolve this concern.

Slave cylinder setup is a bit different, but it seems you can use parts from Rodney Dickman for converting other FWD transaxle transmissions to the Fiero in this application as well. It seems the one pictured might be by Roger Thelin, going by the link information.


Another is transmission mounts. This requires some fabrication - no one (to my knowledge) has ready-to-order mounts (yet).

Here is a picture of what the mounting problem is - there's nothing on the case that allows that stock(?) transmission mount to work/bolt up properly. Thank you to John for the correction!!


You can use stock Getrag shifter cables, BUT you will still need to adapt the hydraulic line/part where the cables hook up to (which is not an easy task) and custom shift cable bracket (which doesn't look to hard). John was pondering making/selling these items.

Alternatively, you can skip modifying it as much by getting custom length cables. There are a few companies out there that do this. I don't recall the name of one of them right now, the other is West Coast Fiero. You just need the right connectors on the ends of the cables, being a cable mount can be made to any specific dimension needed.

You have to adapt the Fiero hydraulic clutch line to the F23's quick disconnect line. Here's info from FieroFiend on how he did it:
The clutch line adapter can be made for free if you have an old 282 slave laying around, all I did was lop the end off where the clutch line screws in smooth it up a bit stick it over the f23 line flare the line and bam, free and easy took maybe 10 minutes. And a pic of another setup.

FieroFiend (on PFF) said he setup his cables like this:
"...Reversing the up down motion at the transmission can be done with one simple cut and re-weld of the steel bracket the ball is attached to. My method simple as it is keeps the stock shift shaft of the f23 oriented the way it was ment to be. All you do it lop the end of the steel ball bracket off and switch the side it pulls and pushes from and weld it back on pretty simple..."

Machined F-body 3800 .840 Flywheel (this one is what I presume is used by the 3800 crowd. Not sure what needs to be done for other engine combinations.)

John said on PFF that most Fiero clutches/pressure plates should work (if I understood correctly), but need to be checked for clearance/grinding. If it grinds, it might be able to resolved with some careful modification of the pressure plate.

Another big chunk of info on clutches from FieroFiend:
The jbody guys are using the 2200 SFI clutch and pressure plate kits with the f23 attached to a 3800 in those. Which should give the trans the stack height it wants to have, since the 2200 flywheel is also the standard .840ish from what Ive gathered after having done mine already using fiero hardware. Which should in theory apply to the stock v6 as well, its worked for multiple people out of the box but should be checked regardless.

Standard 60 degree (Late model GM minivans powered by the 3400 use gear reduction starters with the 60* and 3800 pattern. L67/Emc209i uses this.)
Here's some info on what starters to look for:

Starters for 3400s in the Buick Rendezvous, Chevrolet Venture, Pontiac Aztek and Montana and Oldsmobile Silhouette feature a new solenoid design. With all-wheel-drive, the solenoid in these vehicles can be exposed to the “splash path”, or the area where water is thrown up by the drive wheels. The solenoid now has a vent, which allows any collected moisture to dissipate quickly, ensuring peak starter performance during cold cranking. I found plenty of 2002 Buick Rendezvous starters for around 100 bucks through a junkyard search. Not sure what they cost new.

Picture of the pretty damn meaty looking gears in this thing (thanks to L67 for originally putting it up on PFF).

GM technical specification on the F23: Released 2006
The Getrag F23 is a three-axis conventional transverse 5-speed manual transaxle with fully synchronized reverse gear. It features compact packaging, broad low-torque applications, and reliable operation.

The F23 has two gearsets on each of three parallel shafts – the input shaft, the output shaft, and the intermediate shaft. This three-shaft (also called three-axis) design results in a very short axial length for better packaging. There are three separate shift fork shafts, which hold three shift forks to activate the synchronizer rings for the two gearsets on each of the three gear shafts. The shift forks are activated by a cable system. The clutch release bearing is operated by a concentric slave cylinder that surrounds the input shaft in the clutch housing. A concentric slave cylinder allows more linear clutch feel than an external lever-actuated clutch and release bearing. The input shaft carries the 3rd and 4th gear synchronizer, the intermediate shaft carries the 1st and 2nd gear synchronizer, and the output shaft carries the 5th and reverse gear synchronizer. The aluminum case contains a conventional final drive gearset.

There are sintered bronze double-cone blocker rings on the synchronizers for 1st and 2nd gears, while 3rd and 4th gears use carbon fiber blocker rings, and 5th and Reverse gears use molybdenum on their synchronizers. Carbon and molybdenum are extremely durable friction surfaces that remain stable even under extreme heat.

Gear ratios:
Early F40 F23 282(MG2)
1-3.77 1-3.58 1-3.50
2-2.04 2-2.02 2-2.05
3-1.32 3-1.35 3-1.38
4-.95 4-.98 4-0.94
5-.76 5-.69 5-0.72
Final Drive 3.55 Final Drive 3.94 Final drive 3.61

Thanks to Paul for posting this image up! I put just a link to it here since it's a MASSIVE picture. So feel free download it and open it on your local machine.


4.9 SWAP
88 3.1 V6 Cavalier flywheel is fine. Hower what you need to watch out for is the pressure plate - from John:
"When I checked clearances, I found that the Spec 3 pressure plate rubbed, the S10 pressure plate (common fiero upgrade, 9 11/16, I believe) rubbed, but the unknown cheap fiero specific factory replacement from the 2.8 cleared. Also, my upgraded pressure SuperClamp (9 1/8")from Spec that I installed with my 3+ cleared. I don't really think its the clutch diameter that matters as much as it is the design of the pressure plate, but I didn't really look into it that deeply at the time."
1986 Pontiac Fiero GT, 355 cubic inch small block Chevy putting down 371 HP and 381 ft/lbs torque at the wheels, with more to come!
User avatar
Site Admin
Posts: 513
Joined: Mon Jun 04, 2012 7:02 pm
Location: Charlotte, N.C.

Re: Incidental info on the F23 swap

Postby carolinarigman » Wed Jan 28, 2015 12:48 pm

Hi! how do I contact EMC209i? or L67?
He's got a transaxle I'm interested in.

Thank You
Posts: 3
Joined: Wed Jan 21, 2015 3:27 am
Location: Creedmoor,NC

Re: Incidental info on the F23 swap

Postby Trinten » Tue Mar 03, 2015 8:59 am

Hey! I've got his number, I'll drop him a txt and let him know you're looking to get in touch with him. Sorry for the late response!
1986 Pontiac Fiero GT, 355 cubic inch small block Chevy putting down 371 HP and 381 ft/lbs torque at the wheels, with more to come!
User avatar
Site Admin
Posts: 513
Joined: Mon Jun 04, 2012 7:02 pm
Location: Charlotte, N.C.

Return to Swaps

Users browsing this forum: No registered users and 1 guest