Hello all,

After Cam a lot pointed out in my last topic, I found Fiero Rog does not make F23 trans mounts. I have his engine mount (and other parts) to swap my Series III 3800 SC 2004 Grand Prix GTP engine into my 1986 GT.

I decided after I ordered from Fiero Rog to put a F23 out of a 2001 Sunfire in instead of my M17 4 speed that is in the car now.

Can anyone confirm Thelin’s F23 mounts or West Coast Fiero’s F23 mounts will work with Fiero Rog’s engine mount?

If not, what did you all do to make it work?

Thanks again!

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1986 Fiero GT
2.8 V6 4 Speed
176k+ Miles

Reach out to Roger Thelin

https://thelinsells.limitedrun.com/

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-Brian

My 87 GT Poly Suspension Upgrade (all pics) thread
Removing the roof panel
My HUD install thread
Modified stock air canister and base to 3.5 inch for 3800na

Thanks, I have talked to Roger Thelin. He seems to be my best hope so far. I have sent him pictures of my transmission and he identified what brackets of his he thinks will work for it. I just wonder if they have the engine/trans in the same location as Fiero Rog’s.

On a separate note, Thelin is telling me I should be able to use my factory 3.8 SC Grand Prix engine mount by redrilling the two bolt hole locations. Yet again, I wonder if this would keep the engine in the same location or higher/lower, etc.

I am getting ready to pull the car apart so I can see in front of me how it all goes together and the problems that need solving. I plan to drop the cradle by using a come along to lift the back end of the car up in my one bay garage. Hopefully I can keep the car in place and high enough to slide the cradle out from under it to the passenger side where I have room to work on it and keep it all inside. Wish me luck!

[This message has been edited by UP86GT (edited 08-17-2023).]

So I thought I knew what I was going to do, then came across a ‘09 Cobalt XFE F23 in a local junkyard today. This is supposed to have the more desirable 3.63 final drive according to my research vs the 3.94 Cavalier/Sunfire ratio.

Now I will start research on the bellhousing/input shaft swap. (Or possibly look into grinding the shaft as I have seen done on here) Also plan to send Roger Thelin some pics of my new transmission once I have it home, hopefully Tuesday/Wednesday.

I figured if I even thought for a second now that I might want the frankentrans, then now is the time before ordering mounts from Thelin. (Believe it will be different mounts now as majority of trans or at least mounting points will be Ecotec)

[This message has been edited by UP86GT (edited 08-19-2023).]

This topic has been covered numerous times. You will need a 2000-2002 Cavalier trans from a 2200 motor (not ecotec). It is recommended to switch the FDR from a 2009-2010 Cobalt with the 3.63 FDR. It is a better fit for the 3800 torque curve

I have tried several times to deal with Roger Thelin on brackets/mounts for this trans, but he seems unwilling to spend $200 to grab the correct bellhousing F23 to develop brackets. His brackets are for the Ecotec version of the engine/transmission.

I ended up buying the mounts/brackets from WCF and they fit perfectly. Be aware that some people (including myself) ended up having to use customized axles once moving to an F23, since the driver side ended up too short and passenger side too long after the swap, since the trans dimensions are not the same as the Getrag 282. Some people have used Cavalier axles successfully, but I am not sure what year/model of Cavalier

Spec 3+ clutch has been quite good for me for this combo. Make sure to use the correct GM flywheel bolts from 2000 V6 Camaro (brand new) and use correct torque spec.

Thanks for weighing in on this Cam a lot. Figured you are one that has been here and done it.

It seems pretty straightforward to me as far as the trans piecing together. But it always does right? I already have the Cavalier/Sunfire 2.2 non Ecotec on the floor in my garage. That is the transmission that has the matching bellhousing to the Series III 3.8 SC on a stand next to it. Other (Cobalt) transmission is now supposed to be out and waiting for me tomorrow by noon. Yard said they were short on help. This transmission is out of a 2009 Cobalt XFE with the FY1 rpo code. Should have the 3.63 gearing and should be in my possession tomorrow.

Looks like from what I’m reading it “should” be a pretty easy swap to pull my Sunfire bellhousing case half and input shaft and swap it out with the Cobalt pieces. The Cobalt transmission and most all of its internals are used except those two things.

I believe you can swap just the final drive into the Cavalier/Sunfire case but don’t know how involved it is. I like The idea of the Cobalt case because looks like it has better mounting points, especially in the front. I may look into getting a book or video on rebuilding these F23’s

As far as the mounts, I don’t like hearing that! Especially about the axles. I am planning on either taking a chance and trying Thelins mounts he thinks will work for my new combination, or even making my own at this point. May get Thelins and they end up not working how I want and modifying them if need be I guess.

That was really part of my decision on adding the F23 to the swap was I could reuse my axles and placement was supposed to be roughly the same. My car is currently the original M17 4 speed but think my axles should still work. Haven’t gotten to tear down yet.

If I have to make mounts to use stock axles maybe I will try that. Stupid question probably but how do you guys that make your own decide you have the engine/trans positioned level and where you want it? I’m thinking mock up the trans and axles on cradle first, then engine. I am pretty sure of myself that I can design (or redesign Thelins) brackets if need be and have cutting, grinding and welding tools at my disposal. I am sure enough of my welds. Just need to figure out thicknesses and such.

I do think I am going to go with the Spec Stage 3 + clutch at this time. Especially since its one of the only bigger clutches known to clear. Also thanks for the info on the flywheel bolts. I have part numbers saved somewhere but year make model works as well!

Thanks again all!

Hello
I don't believe Roger Thelin's brackets will work, as the mounting points are different on the Ecotec based transmissions. I have asked him repeatedly to obtain a 60 deg transmission, but he seems to be a stuck in his ways ... and just says "all F23 are the same" and they are not. You will see when you receive your Cobalt transmission. They are not even close

I don't know what is involved in switching the FDR (had a local trans shop do it for me), but it is well worth it. The gear ratio for the 2002 cavalier is awful for the 3800. First gear and much of second gear is useless.

Since you are in upper NY State, you can pop over to Niagara Falls Canada and see a small shop that works Fieros. He has several F23 sitting there and can either do the work for your or you can take photos, etc. https://www.facebook.com/gr...user/100003244964981 Nice guy, very enthusiastic, his name is Mitch

I am planning to take a cradle and F23 trans to Olejodad and his son in Michigan. They offered to fab 3800 engine and F23 mounts that will allow me to close the deck lid without cutting into it, even with full stack intercooler. This way they can do a test fit complete with suspension and axles before it goes into the car. So I assume it is possible that by doing this, they can use stock length Fiero axles by positioning the engine to offset the difference between F23 Getrag and 282 Getrag. I am far from an expert and not at all technically savvy- Just sharing what little info I have been able to collect. Maybe reach out to them and see if they can help you as well?

[This message has been edited by cam-a-lot (edited 08-24-2023).]

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