Finally got around to mixing and matching parts of the Fiero axle with parts of the Sunfire axle. The Fiero axle will not fit into the Sunfire tripot housing. The axle stubs that the beaing sits on is just slightly larger than the Sunfire housing....as you can sorta see below (Fiero housing on left):



The top of the axle is held on by splines and the diameter of the axles are the same. You can just see the splines of the Fiero axle in the upper left of the photo. So I could pull the top off of one axle and put it on the other. I do think in that case I could use the tripot of the sunfire on the Fiero axle and clear the motor boss.

Apparently, that boss is only used for initial machining of the motor :

quote Originally posted by Will: That's a locating hole for when GM starts to machine the raw casting. It's not necessary for anything we do with the engine.

So I might just grind it off and just use the original Fiero axle. That seems the easiest solution at the moment.

[This message has been edited by Rotmilky (edited 12-17-2020).]

quote Originally posted by Rotmilky: Finally got around to mixing and matching parts of the Fiero axle with parts of the Sunfire axle. The Fiero axle will not fit into the Sunfire tripot housing. The axle stubs that the beaing sits on is just slightly larger than the Sunfire housing....as you can sorta see below (Fiero housing on left): The top of the axle is held on by splines and the diameter of the axles are the same. You can just see the splines of the Fiero axle in the upper left of the photo. So I could pull the top off of one axle and put it on the other. I do think in that case I could use the tripot of the sunfire on the Fiero axle and clear the motor boss. Apparently, that boss is only used for initial machining of the motor : So I might just grind it off and just use the original Fiero axle. That seems the easiest solution at the moment.

The tripod and tulip are a "set" in that they are designed as a product family. It would not be expected that you'd be able to use the Fiero tripod in the Sunfire tulip. However, splines are much more common. If you can install the Sunfire tripod onto the Fiero axle bar, that's the easy way to go. There's a snap-ring retainer, but the tripod should be easy to R&R from the axle bar. Get a high quality boot kit, clean the CV joint thoroughly, reassemble with new grease and it'll be good for another 100k miles.

[This message has been edited by Will (edited 12-22-2020).]

It's nice to see another LS4/F23 swap.

I started mine about 2 years ago. But I've had a lot going on, moved out of state, new house, new job, wife sick, finished another engine swap, rebuilt 1 1/2 boats and I have a 3 year old.

But I'm about the same place you are. I do have 2 LS4's, an F23 and the LS4 4t65e.
I have a flywheel made by LSC. Fieroguru posted their contact info. It was about $400.

Fieroguru's starter mount works great with the f23. I spent more time thinking how to cut the notch from the trans than I did cutting.

Stock axles should work. I clearanced the block and pan. IIRC, I have about 0.160 of an inch clearance. I stopped grinding when I got to the pan gasket. I haven't messed with it since. I figured I could get more if needed but would cross that bridge when needed. The clearance was to the CV boot clamp. Not just the boot.

I won't get back onto this swap until early summer. I live in Florida. I'm taking advantage of the cooler weather(50-75) to work on my boat. The cooler temps make grinding fiberglass better because I can wear long sleeves to keep the itch down. Plus I get extended working time with resin when its cool. I have ac in the garage, so heat isn't a factor for the car.
I do like working with fiberglass. Now I want to make stuff for the fiero.

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SSFiero@Aol.com

quote Originally posted by Rotmilky: I managed to find a LS4 out of a '06 Impala that was largely complete....... Maybe put on a LS3 manifold and timing cover. Dunno exactly...I'll figure that out if we make enough progress to warrant it.

Just an FYI,
And LS4 isn't much different than any other 5.3 engine from the LS family.
It has the 243 casting heads. They are the cathedral port heads. So an LS3 intake will not work. It has rectangular ports. LS1/LS2/LS6 will all work. I'm running the LS6.
Your engine is an '06. It will be a 24 tooth reluctor wheel. You can verify by checking that it is black(24T) or Gray(58T)
This will matter because it will determine what ECM you need to use. Someone with more knowledge can verify what you'll want.
being that it is mostly like any other 5.3 LS series engine, you'll have countless options for aftermarket parts.

I'm looking forward to seeing your progress.

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SSFiero@Aol.com

We've been making steady progress on the Fiero for the past few months, but I've neglected updating the progess. So, the next few posts will try to bring things up to present date.

I think we were working on the fiero axle and comparing with the Sunfire axle. The sunfire cleared the motor, but the Fiero didn't. So, we disassembled the two axles and swapped the transmission end tulips around. The axle diameters and spline counts were the same, so the swap was easy. Now we have an axle that clears the motor without needing to grind anything off.

No major documentation on that part of the project. It was straightforward -- remove the retaining clips on both axles, remove the tri-bearings and swap. The Fiero roller bearings came apart and went everywhere...but we weren't going to reuse them anyway.

I did take one photo of the kids removing the Fiero bearing. It wasn't on all that tight and could have been driven off with a blow from a rubber mallet. But they couldn't get it, so they decided to use a bearing puller.


Replacement boots for the axles seem to be pretty poor compared to the originals. We stole the Sunfire axle boots, which were still in good shape, for the modified Fiero axles.

[This message has been edited by Rotmilky (edited 02-27-2021).]