This information has been posted in another thread, but it didn't have a very friendly title for the search function.

The LS4 only came from GM paired with the 4T65E-HD with a tranny mounted starter. Due the the Y-block configuration of the LS(x) family of engines, there is almost zero room for an engine mounted starter when using a 142 tooth ring gear (the largest one that will fit within the FWD bellhousing - all other LS engine use a 168 tooth one that is about 2" larger in diameter).

My goal with this starter mount method is for a bolt on solution that retains the LS4 starter and its relative location to minimixe any other required changes in wiring or exhaust.

So here is the special LS4 tranny, starter, and its starter pad:




First order of business was to make a fixture that would located the OEM starter pad based on the bellhousing bolt locations so it could be transferred to the F40:



Then position it next to the F40 to see what all has to be removed:


The vast majority of the upper two bolt bosses need to be trimmed down near flush with the bellhousing flange to make room for the 3/8" thick starter pad. Here the area for the starter mount has been milled flat at the proper elevation and width (the picture does not have the furthest bolt boss milled flat, but it needs to be):


Next fabricate a 3/8" plate that will support the starter:




Test fit to make sure the plate can slide under the starter pad fixture:


The plate will be attached via the bellhousing bolts, so some tabs were cut to size (these will be welded to the plate):


The center stud in this picture is used for the rear support (fabricated from 1/8" steel):


Install the plate, the mount pad fixture, the mounting tabs for the sides and the rear support... then weld the tabs and rear support to the moutning plate and end up with something looking like this:



Finish milling out the notch for the starter gear and body:



Mount F40 tranny to the LS4:


Install starter pad:


Install starter:



Fire In The Hole!!!

[This message has been edited by fieroguru (edited 09-06-2010).]

Awesome news!

Great job. I can't afford to ever do one of these, but it is good that you share the knowledge and method of modification with everyone.

Wow very impressive work. That is a very clean and elegant starter mounting solution. Would you be interested in possibly producing and selling that fabbed bracket for a fee? I would be interested in one if you would be willing to make more of them, as I'm sure others are as well. Let us know.

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88blackchopv8

http://www.foxvalleyfieros.webs.com/

Great write up and photos! Way-ta think outside the box too.

Thanks for the compliments!

For those who have asked if I will make these to sell... maybe.
I have limited free time and normally prefer to make progress on my own projects, but I might consider making a couple to help fund my current project. I am thinking $275 shipped as a fair price. This price should be high enough I do not have to make many, but low enough for most to get it if they want it.

I might even consider selling the bracket with modified F40 so no machining would be involved, but once I buy the tranny, have it shipped to me, do all the work and then ship it to the end user... it starts to get expensive in a hurry.

Very Cool a + for you!

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yellow 88 GT, not stock
white 88 notchie, 4 banger

I agree a very cool idea and write up. I will be attempting to do something similar. but I think I will TIG an aluminum plate for mounting the starter, instead of the mount plate.
Unfortunately I don't have the automatic trans to make a template from.

What flywheel and clutch is used? I didn't read the other thread. Thanks!

quote Originally posted by lou_dias: What flywheel and clutch is used? I didn't read the other thread. Thanks!

My flywheel tips the scale at 14 lbs and is a 3 piece design.
Stock LS4 flex plate is retained for ring gear/starting purposes, then an off the shelf .400" LS(x) crank spacer, and lastly an aluminum flywheel from a LT1/ZF6 corvette. The aluminum flywheel needs the counter weight removed, the crank bolt pattern modified slightly, the outside diameter turned down, the back side cut to clear the ring gear and the pressure plate pattern drilled into it.

Another option is to use an Archie F40 clutch spacer plate for the 2.8/3.1/3.4/4.9 application and turn down a stock LS1 flywheel (about the same thickness as the fiero flywheel) to accept the 142 tooth ring gear, then drill the pressure plate pattern.

Clutches there are bunch of options, but most give you a 9" clutch. I might play around with the 10" one that I think will fit.

When I get home tonight I can upload some pics of the flywheel, but I have not drilled the pressure plate pattern.

[This message has been edited by fieroguru (edited 12-06-2010).]

I already have an Archie 6speed (1st w/2.8 actually)...if the current motor ever blows up, I may have some work for ya.

quote Originally posted by mwhite: I agree a very cool idea and write up. I will be attempting to do something similar. but I think I will TIG an aluminum plate for mounting the starter, instead of the mount plate. Unfortunately I don't have the automatic trans to make a template from.

All you really need is the LS4 starter, a little patience, and the tools to do something similar. I'm hacking up my F40 in a similar way to fieroguru, and don't have the 4t65e either. I've alaready hacked off most of the large protrusion in the way on the trans. Just have to cut/grind some more, and mate it to the block for lining up the starter the same as it is on the automatic, and figuring out where to cut the bell housing out exactly.

Brilliant!

I like the way you think.

Very nice work. I do have a question. The discussion has come up about using the F23 5-speed in another thread as an alternative to the F40 and Getrag 282. Can this mod be applied to the F23 transmission case?

-ryan

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7+ years on this same swap -- NO engine or transmission failures...

Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com

quote Originally posted by Darth Fiero: Very nice work. I do have a question. The discussion has come up about using the F23 5-speed in another thread as an alternative to the F40 and Getrag 282. Can this mod be applied to the F23 transmission case? -ryan

Thanks for the compliment!

From this picture, the starter should go right above the bottom bellhousing bolt. I find it interesting that there is a built up portion of the bellhousing flange right where the starter would mount (atleast the front two bolts).


It would be helpful to have a better picture of this portion of the bellhousing flange, but it looks promising so far.

The nice thing with the 92-94 HTOB Getrag or the F23 would be a stock LS1 flywheel would be really close to the right thickness, just would need to turn it down to accept the smaller ring gear and pressure plate pattern.

[This message has been edited by fieroguru (edited 12-06-2010).]

While I had the F40 seperated from the LS4, I was able to confirm the LS1 flywheel is the proper thickness for a 92-94 Getrag or F23 transmission application. It is just a matter of turning it down to accept the 142 tooth flywheel and drilling the pressure plate pattern. The one I am modifying (billet steel SPEC flywheel) for R&D purposes protrudes .818" from the bellhousing face and has been resurfaced 1 time. This is slightly less protrusion than the stock fiero (.830" was the last one I measured). The LS4 ring gear protrudes .826" from the bellhousing and would probably need to be flush with the face of the flywheel.

[This message has been edited by fieroguru (edited 02-20-2011).]

Couldn't GM's supplier do this for us? (the flywheel)

quote Originally posted by lou_dias: Couldn't GM's supplier do this for us? (the flywheel)

Technically? Yes. Practically? No. I doubt it's a worthwhile market for them to start mass producing them. And you can probably get any good local machine shop to do the necessary work for cheaper anyway.

quote Originally posted by dobey: Technically? Yes. Practically? No. I doubt it's a worthwhile market for them to start mass producing them. And you can probably get any good local machine shop to do the necessary work for cheaper anyway.

@fieroguru
I will probably need to do a clutch job on my F40 within the next year. I have the 1st Archie 6speed+2.8 (now 3.400 franken V6). Would this be a direct swap for the aluminum flywheel+aluminum spacer contraption I'm using now? Would the total weight go down?

Thanks,
Lou

quote Originally posted by lou_dias: @fieroguru I will probably need to do a clutch job on my F40 within the next year. I have the 1st Archie 6speed+2.8 (now 3.400 franken V6). Would this be a direct swap for the aluminum flywheel+aluminum spacer contraption I'm using now? Would the total weight go down? Thanks, Lou

What exactly are you asking? You have a 3.4/F40 and this thread is about the LS4/F40 (and LS4/Getrag). Are you planning to swap to an LS4?

quote Originally posted by fieroguru: What exactly are you asking? You have a 3.4/F40 and this thread is about the LS4/F40 (and LS4/Getrag). Are you planning to swap to an LS4?

I guess I am asking if you can do the same thing for a 3.4...for now...a custom flywheel. Sorry that it's OT.

It seems to me that I need to test this with my LSx adapter plate. Based on what guru has presented thus far, and my own measurements, what guru is doing with this LS4 will work the exact same on the RWD LSx blocks if using the adapter plates I sell.
We haven't collaborated on this, it's just happy coincidence.

quote Originally posted by lou_dias: I guess I am asking if you can do the same thing for a 3.4...for now...a custom flywheel. Sorry that it's OT.

Anything is possible... but I really have no interest in making parts for a 60 degree V6. Just take the one you have and send it into a flywheel shop and tell them to make a new 1 piece flywheel that will reduce the overall weight... be prepared to spend about $600 for it.

Here is the flywheel for the LS4/F40 combo - it weighs 11.2 lbs:

Absolutely beautiful! [tears] Words can not describe [/tears]

My gosh, that probably cost alot!

quote Originally posted by darkhorizon: My gosh, that probably cost alot!

It pays to have AutoCAD, various machining equipment (or free access to it) and the skills to use them. The materials cost was $160.63 for the aluminum, wear strip and ring gear, but this isn't a component you can design and manufacture in an afternoon (I have quite a few hours invested into this flywheel).

Very Impressive! How is the ring gear attached?

quote Originally posted by Brezentski: Very Impressive! How is the ring gear attached?

It is an interference fit between the ring gear and flywheel. After I heated the ring gear up to 500 degrees and put the flywheel in the freezer for 2 hrs it just dropped into place.

Is there *any* chance you would be willing to put together some of these custom parts for other enthusiasts who don't have the facilities or ability? I'm budgeting out a 3800 s/c build right now, but only after looking over the LS4 and realizing I would be unable to build these parts. I *might* be able to pull off the starter mount, but the flywheel is impossible for me.

quote Originally posted by benjamin.long: Is there *any* chance you would be willing to put together some of these custom parts for other enthusiasts who don't have the facilities or ability? I'm budgeting out a 3800 s/c build right now, but only after looking over the LS4 and realizing I would be unable to build these parts. I *might* be able to pull off the starter mount, but the flywheel is impossible for me.

I have very little interest or available time to be a full time vendor or fabricating/selling parts at this time. From time to time I will make parts or perform engine swaps/upgrades for others, but that only happens when the timing is right or I am looking to generate some extra $$$ for my own projects/R&D efforts.

It's such a shame that there is no modifiable OTS flywheel for this application. The engine is inexpensive, plentiful, and made for FWD.

quote Originally posted by benjamin.long: It's such a shame that there is no modifiable OTS flywheel for this application. The engine is inexpensive, plentiful, and made for FWD.

As best I can tell, the 3.9L G6 dual mass flywheel and clutch should fit, and with a relatively stock LS4, should hold up fine. Only problem is that I can't find one cheap, and I don't really want to spend $350+ on a new one to find out it doesn't work.

Do the LS4 and 3.9 V6 have the same crank flange bolt pattern?
Or the Saab 2.8 turbo for that matter?

quote Originally posted by dobey: As best I can tell, the 3.9L G6 dual mass flywheel and clutch should fit, and with a relatively stock LS4, should hold up fine. Only problem is that I can't find one cheap, and I don't really want to spend $350+ on a new one to find out it doesn't work.

Well, I wouldn't be modifying the LS4 for a long time. So if there is a Flywheel/Clutch combo that will handle it I would love to know. I'll look into it as well. Right now I need to head out to the shop and finish stripping down a bent up Formula.

quote Originally posted by dobey: As best I can tell, the 3.9L G6 dual mass flywheel and clutch should fit, and with a relatively stock LS4, should hold up fine. Only problem is that I can't find one cheap, and I don't really want to spend $350+ on a new one to find out it doesn't work.

Joseph Upson has said that the 3.9L flwheel is a torque limiting design. For his turbo 3.9 swap, he ended up pinning it to eliminate the torque limiting feature. His current flywheel is from a RWD 2.8, that came with a 148 tooth ring gear, but that ring gear would not fit inside the tranny, so he turned down the ring gear landing to fit the 142 tooth one.
In the mall, Joseph Upson and some other G6 guys were putting together a group buy for an alumimun 1 piece flwheel that was essentially a copy of the 3.9 flywheel for around $350

The other concern I would have with using the stock G6 flwheel, is it has a raised pressure plate and I am not sure if any of the after market clutch manufacturers will support that application... until they do, you might be stuck running a stock clutch that is probably marginal at best for a stock LS4.

[This message has been edited by fieroguru (edited 04-22-2011).]

quote Originally posted by Will: Do the LS4 and 3.9 V6 have the same crank flange bolt pattern? Or the Saab 2.8 turbo for that matter?

I don't know if the 3.9 has the same bolt circle diameter as the LS4, is my only real worry for it.

The Saab 2.8t flywheel definitely doesn't fit. The High Feature V6 has 8 bolts in a smaller circle. I have one sitting in my garage. I think it might share the bolt circle with the Ecotec though, for the crank flange.