[GUIDE] F35 to F23 (with LSD) Transmission Swap

newbtrying

Member
To follow up/confirm, any shifter will work with an F23 swap. You will have to get the newly added F23 shifter cable bracket from DF, though.

The clutch and pressure plate are specific to the flywheel, and the flywheel is specific to the motor. All F35 transmission-equipped motors came with 8 bolt cranks, and all F23 transmission-equipped motors came with 6 bolt cranks, thus different flywheels. But the transmission input shaft splines are the same between F23 and F35, so the transmission doesn't care which clutch is on the engine.

Any shop should be able to do the LSD swap. It's also as straightforward as any other aspect of a Goblin build, aside from three aspects (for me):
  1. It can be difficult to break the intermediate shaft retaining bolt loose. The input shaft will want to spin; I 3d printed a socket adapter so I was able to put a wrench on the input shaft. Piece of cake after that.
  2. The new LSD will need bearings pressed onto it. You will need access to a press, or a shop should be able to do that easy-peasy. If you choose to replace the races in the trans case, it requires some creativity, special tooling, or both. Technically you should replace the case races, but if you're confident the new diff bearings match the old case races, it should work, and other have done this successfully before. I was able to slowly and carefully cut through them, at which point they will just fall out.
  3. The intermediate shaft seal retaining bolt cover is a bear to source. They can be had out of GM Europe, or you can slap something together. I actually 3d printed a replacement cap and RTV'd it into place. I had a catastrophic fluid leak that turned out to be a bad input shaft seal (on a new OEM part!). I thought it might've been my cap, so I ordered a GM replacement, but it turned out that was holding fluid fine, so false alarm there.

DM me plz. Would you be interested in selling me a 3D printed counter gear bearing cap? I'm trying to source all the parts before I dive into this project and this one i'm not finding online.
 

newbtrying

Member
KENT MOORE TOOL J-44379 DIFFERENTIAL BEARING PULLER PLATE
KENT MOORE TOOL J-44381 SHIFTER BEARING REMOVER

I've started this project today and I got to the point where I have the differential out of my F23, have transferred the ring gear to my Quaife LSD and am looking to pull the shims off of my open dif. I'm going to take OP's advice and buy the two tools above to make removing the differential bearings easier, but I figured i'd check if any of you who have done this swap are willing to sell off these tools, assuming you won't use them again.

let me know if any of you are willing to sell the tools listed above. if no replies by tonight, I'll purchase through EBay.

Thanks all.
 

newbtrying

Member
I bought these two tools, so if anybody else is looking to do this in the future, HMU and I'll sell them to the next guy.
 

newbtrying

Member
My F23 LSD installation is complete and successful. I went with OP's advice and used the correct tools to pull the differential bearings, using a hydraulic press (which was beyond easy). Now that everything is sealed back up and the trans is ready to mount, I have a few more questions:

1: Anyone know what size the fluid drain plug is, or where to buy it? My transmission is missing its (circled in red in first photo)
2: Must I use the original slave cylinder? mine is in rough shape. Is there an adaptor or something so I can connect the one that came with my F23 trans?

Thanks all, I wouldn't have done this if it wasn't for your help.

39804


39805



39806
 

Rauq

Goblin Guru
1: Anyone know what size the fluid drain plug is, or where to buy it? My transmission is missing its (circled in red in first photo)
2: Must I use the original slave cylinder? mine is in rough shape. Is there an adaptor or something so I can connect the one that came with my F23 trans?

Thanks all, I wouldn't have done this if it wasn't for your help.
1: I'm pretty sure that's the fill plug? And it's a fancy plug with a built in case vent. It looks like PN 24222255 but I'm not sure that's the right part. I think that's for an auto trans but it might be for the manual trans as well (edit: I've found at least a couple sites that say the 4T45 and the F23 use this vented cap). GM calls the blue circled plug the fill plug and the green circled plug the drain plug, but given that GM and others have advised overfilling to reduce noise and increase durability, I filled through the top port that you circled in red (about 2 qts, or 0.3qts over spec capacity, which is where fluid would spill out of the fill port).
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2: I know OptimizePrime used an F35 slave cylinder with a re-bent line from the slave to the F35 elbow, but I just used an F23 slave cylinder and re-bent the Goblin hardline to the F23 elbow.
 
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OptimizePrime

Goblin Guru
@newbtrying My man! Happy to hear it. Looks great!

I think the F23/F35 throwout bearings (and everything that comes along with it like tubes etc.) are interchangeable. If you have a specific clutch and it came with a TOB definitely use that bearing as opposed to a different one. My phoenix friction F35 clutch came with a TOB so I put it on the F23 with F35 tubes and just carefully massaged them into position so they would work.

Throw some ATF in there and let'er rip!
 

jirwin

Goblin Guru
Where did y'all get "9120610 OR Ford 1311152"? Having trouble finding it. LSD will be here Monday so I'm trying to prepare
 

jirwin

Goblin Guru
I found that too but I was hoping to avoid UK because it'll get here after my LSD. Ford dealer can't get ahold of it because something something certified rebuilder only part. Looks like that's my only option.
40350
 
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Scott #321

Well-Known Member
52 mm end caps are not that uncommon and if you have a local specialty bearing supply company you may be able to pick one up locally.
 

Scott #321

Well-Known Member
We've speculated this would work.
No need to order speciality parts from Europe or spend a fortune on this, just make sure it fits nice and snug as some manufacturers of these types of seals are less precise on QC and you don't want this thing coming out under use.
 

this is actually the correct one
OK so I'm finally back together, I had some trouble with the throw-out bearing/slave spacing and ended up pulling the motor and trans 3 times. :confused:
Made a ton of other changes over the winter and am now re-tuning the car. Ya know the while we are here syndrome, I had it bad. The short-shifter.com linkage works well, Shifts are very tight and short. Sitting Idle it feels a bit too tight and mechanical, but once I'm driving I find I really like it.

EDIT- It looks like they no longer carry it on the website!
 

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