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

OptimizePrime

Goblin Guru
The only thing I'm not sure about in going F23 -> F35 is the intermediate shaft, if an LAP would have the block mount for the carrier bearing and how to go from the trans splines to the hub splines.
The Grand Am axles are how you get from the F23 trans splines to the Cobalt hub splines. There's no block mount carrier bearing for the Grand Am passenger side axle but it works and holds ~400whp (so far > knocks on wood). These axles are readily available from a lot of parts stores for like $70 each.... so convenience and cost is at play here also.

If you wanted a carrier bearing you'd have to find some year isuzu shafts. If you figure this out lmk!
 

jayrolls

Well-Known Member
The Grand Am axles are how you get from the F23 trans splines to the Cobalt hub splines. There's no block mount carrier bearing for the Grand Am passenger side axle but it works and holds ~400whp (so far > knocks on wood).

If you wanted a carrier bearing you'd have to find some year isuzu shafts. If you figure this out lmk!
So ideally if I am taking the transmission, axle shafts and hubs from my 2010 which has the F23 and use those instead of the transmission, axle shafts and hubs from my 07, theoretically I should be good?
 

OptimizePrime

Goblin Guru
So ideally if I am taking the transmission, axle shafts and hubs from my 2010 which has the F23 and use those instead of the transmission, axle shafts and hubs from my 07, theoretically I should be good?
Yep, you'll need to get the DF F23 solid motor mounts as well but since you have the F23 hubs you should not have to purchase the Grand Am axles. You're going to a 3.84 FD from a 4.05 so you're kinda pimpin' backwards from the initial intent of the swap but don't let that stop you.
 

jayrolls

Well-Known Member
Yep, you'll need to get the DF F23 solid motor mounts as well but since you have the F23 hubs you should not have to purchase the Grand Am axles. You're going to a 3.84 FD from a 4.05 so you're kinda pimpin' backwards from the initial intent of the swap but don't let that stop you.
I was looking I would pick up a little torque on the low end but maybe I am reading it incorrectly.
 

Rauq

Goblin Guru
Optimize has an LNF which has a different hub and outer spline on the CVs, so the Grand Am axles won't work unless you swap to an LNF hub, knuckle, and lower ball joint.

I believe a 2.2L should have the same outer spline on the CV as an LSJ but I'm not sure the inner CVs are the same between an F23 and an F35. If they're the same inner splines then you may not even need an axle swap, but if that's not the case then I'm not sure what the best solution would be.

Theoretically you'd get better acceleration with a 4.05 than with a 3.84 but we're talking about a 5% difference here, you can accomplish the same difference in final drive by running a tire that's 5% shorter.
 

jayrolls

Well-Known Member
Optimize has an LNF which has a different hub and outer spline on the CVs, so the Grand Am axles won't work unless you swap to an LNF hub, knuckle, and lower ball joint.

I believe a 2.2L should have the same outer spline on the CV as an LSJ but I'm not sure the inner CVs are the same between an F23 and an F35. If they're the same inner splines then you may not even need an axle swap, but if that's not the case then I'm not sure what the best solution would be.

Theoretically you'd get better acceleration with a 4.05 than with a 3.84 but we're talking about a 5% difference here, you can accomplish the same difference in final drive by running a tire that's 5% shorter.
Thank you.
 

Scott #321

Well-Known Member
I believe when I get mine running I will find my 1-2 syncros are in need on replacement in the f35. If that happens I am planning on purchasing a F23 cobalt M86 3.84 and a Saturn Vue MG3 4.41 and swapping the final drive giving me a M86 with a 4.41 final drive. Saturn Vue also uses a half shaft providing for equal length axles but I have yet to work out the details as to whether or not I can make the half shaft work. Will post a write up when and if I can figure this out.
 
I really appreciate the work you put into this walkthrough. I’m in the middle of your guide, but I can’t seem to track down the torque specs for ring gear and bell housing.

Do you happen to remember what they were?
 

Dale E

Well-Known Member
For axles you can always do a mix and match of the CV joints. Folks do it all the time. If you go to an Autozone website you can plug in different cars and look up dimensions of the CV axles and they will have the inner and outer spline counts. Like my HHR hub has 33 splines which is the same as the Cobalt (except for the turbo Which might be a 30 spline?? - I've forgotten a lot of my look ups). My 1991 Chevy Beretta wheel bearing/hub has 33 spline count with a 5 bolt x 100?? My Impala SS has a 33 spline count too. The Fiero guys change the outer CV joints sometimes and still use the Fiero axle and stock inner Splined CV joints.. example here: https://video.search.yahoo.com/search/video?fr=mcafee&ei=UTF-8&p=fiero+cv+axle+change+video&type=E211US370G0#id=1&vid=57e70142d9ebe34e732485039f9b7015&action=click

So do some research and you can come up with a workable solution.

Dale
 
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Scott Geyer

Active Member
I'm at a good point where I believe this can be documented. I'm still trying to figure out how to get the Speedometer to work, so if any you guys have thoughts around this please share! FIXED!

First, why would someone do this?
Well, first is performance. Going from the F35 with Final Drive of 3.82 to the HHR FD which is 4.17 has considerable drivability & torque improvements. The Getrag F23 is known to be able to handle more power than the F35 due to how the shift forks are implemented. F35's are known to break their forks at high torque, low rpm situations. The F23's parts are also more abundant, in the event it does break there are parts available for cheap. That brings me to my second reason, the transmissions are effectively everywhere as they were in a ton of mass produced vehicles. The F35 has become extraordinarily expensive over the past couple of years, going for as much as $1,200 used before shipping to >$3K new. The idea here is that I could take my F35 w/ LSD and swap to the F23 w/ LSD and sell my existing transmission for about the same cost (if not more).

Second, was it worth it?
In summary, I've had about 50miles on the car which includes a dyno session and I can say without a doubt it's made an incredible difference and I'm glad I took the risk. The additional torque due to the FD makes the car feel like it has a lot more power in lower rpms and I don't find myself changing gears as much as the F35 which often felt too low in third and too high of an rpm if I shifted down to second for normal city driving. On the dyno, I put down 350whp and it handled it across many pulls without a sweat. I have yet to sell my F35 w/ LSD and axles so I don't know where I would stand in the netted out cost but it's looking like it'll be close to a couple hundred paid on my part which is totally reasonable.

View attachment 21398

Here's the process:

I used this link to understand the right years and models, off to ebay I went. You'll notice the year on the HHR makes a difference. If you want the 4.17 you want to look for a manual HHR between the years 2005 - 2008. I found a 2008 with 90k miles and thought that was a STEAL.


Delivered
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You could just throw this one with a few minor changes outlined after the LSD part - but if I'm going this far and pulling the engine / trans etc I might as well cough up the money for an LSD and do that also. There are three options for LSD's - one legit LSD, one china LSD, and one insert. The legit LSD is the Quaife ( QDF17B ) which retails for ~$1k, china LSD is the OBX LSD which is ~$450ish which has QC problems and requires additional mods to make it right, and the insert is the Team Green insert. I don't have time for china shyit and the Team Green insert is probably good enough BUT in speaking with Justin at high HP levels it seems to have an issue...so Quaife it is. I found my Quaife NIB on ebay.

I really didn't want to be the one to install the LSD after doing the research, it's not my area of expertise and I just don't have the tools. I called around to everyone in a two hour drive and they either couldn't do it, didn't want to do it, or didn't give me the warm and fuzzies and I might as well do it anyway. For the most part, getting it apart I followed the instructions for the Team Green insert found on youtube


Take your throw out bearing off. Your first mission is to get the cap out, I drilled through mine and then used a little leverage to get the cap and black piece out.
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Notice the snap ring, you'll want to save this. The black plastic part is directly under the cap and easy enough to pull out. You'll want to buy a new cap ( 9120610 )
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Getting that bolt out can be a straight up pain in the ass. In the youtube vid you'll see the dudes using vice grips, I'm not lucky enough to use vice grips and not strip the threads. I hated buying the tool to use just once, but made removing and tightening the bolt a breeze and I can sleep well at night.

Kent Moore Input Shaft Anti-Rotation Tool J-44377
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This is what she looks like with the top half off
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This is where the real fun starts. You can either purchase a bunch of different sized shims and do a bunch of trial and error for the right preload, of you use the shims on your F23 trans which should be close enough. I chose my F23 shims and straight up battled getting the diff bearings off to get to them, you need both sides.

View attachment 21407

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You typically ruin the stock F23 bearings in the process, which is why I had to purchase new bearings. This is the shim you're looking for
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Backside was a total b*tch as there is nothing to get leverage with to remove the bearing.
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As you can see, I did not have a good time but managed to get it out unscathed.
*UPDATE: DON'T DO THIS, BUY THE RIGHT TOOLS SHOWN BELOW!*
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Here is what you need:
KENT MOORE TOOL J-44379 DIFFERENTIAL BEARING PULLER PLATE
KENT MOORE TOOL J-44381 SHIFTER BEARING REMOVER
Total was like $50 from ebay. Well worth the risk / time / effort

Take out your Quaife > insert your shims > press on the bearings > install your ring gear w/ loctite and torque to spec
View attachment 21412

Take out some assembly lube and put it liberally on your bearings and put her back in
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Pick up some anaerobic gasket maker and tighten everything to spec

*** DO NOT FORGET YOUR SPEEDO RING FROM THE STOCK F23 DIFF --- NOT PICTURED HERE! ***
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Tighten your bolt and replace the cap - you're done with the LSD!

You can use the F35 throw out bearing and pipe with slight adjustments to get it to stick through the existing hole
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At this point, you need to install the DF F23 mounting brackets. I had to get different threaded rear mounting bolts compared to the F35, and used stock bolts for the front transmission mount. I don't have a pic of this part

Once you have it all mounted, you could install new axle seals. I strongly suggest you don't if yours look good as the seals were a source of major leaks when I did mine. The first axle seal I tried to use a large socket and tap the seal in, unfortunately I damaged the seal and it didn't sit correctly (hence the leaks). The second seal I went to the big box store and got a PVC fitting, which was the perfect diameter.

You want a 2 x 1 1/4" fitting
View attachment 21417

Just hit the pic limit... more to come
Will our clutch/flywheel and billet shifter work with the F23?
 

Gtstorey

Goblin Guru
If you are considering this you may want to read the first page of this discussion.

"I really didn't want to be the one to install the LSD after doing the research, it's not my area of expertise and I just don't have the tools. I called around to everyone in a two hour drive and they either couldn't do it, didn't want to do it, or didn't give me the warm and fuzzies and I might as well do it anyway. For the most part, getting it apart I followed the instructions for the Team Green insert found on youtube"

[GUIDE] F35 to F23 (with LSD) Transmission Swap | DF Kit Car Forum
 

Scott Geyer

Active Member
If you are considering this you may want to read the first page of this discussion.

"I really didn't want to be the one to install the LSD after doing the research, it's not my area of expertise and I just don't have the tools. I called around to everyone in a two hour drive and they either couldn't do it, didn't want to do it, or didn't give me the warm and fuzzies and I might as well do it anyway. For the most part, getting it apart I followed the instructions for the Team Green insert found on youtube"

[GUIDE] F35 to F23 (with LSD) Transmission Swap | DF Kit Car Forum
 

Rauq

Goblin Guru
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.
 

Scott Geyer

Active 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.
Thanks for the great explanation. I did have one more question. Can the F35 handle up to 425whp?
 
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