Galaxie500XL

iTrader: (1)

All,

The more I read, the more confused I’m getting. I’m putting together a part list for my T56 swap, and am finding conflicting information.

It’s going into my ‘88 L98, 1-piece rear seal 350. Some information implies that engine balance is an issue, other information says otherwise.

Most flywheels I’m finding are for older 2-piece SBC engines, or billet.. I just want a stock type, preferably new/newish.

Where can I find what I’m looking for?

sofakingdom

iTrader: (1)

Parts store.

A stock LT1 flywheel will bolt right up and work on your L98 just like it does on a LT1.

Or, you could go with a high-perf one from any such supplier. "Stock" is the operative concept in any case: if it works on the LT1, it'll work on the L98.

Whatever "information" implies otherwise, isn't "information". It's drivel and diarrhea of the mouth. (keyboard)

TORN

iTrader: (17)

Do you not have the stock LT1 flywheel? It bolts to the 88 block and works fine.

BOTTLEDZ28

iTrader: (9)

If you decide to use a used stock LT1 flywheel, which I advise against due to their age, I would make sure it hasnt been turned multiple times. I had an SLP one years and years and years ago that had apparently been turned too many times and it caused so much trouble for me. I put a new stock one in and my car felt like a million dollars. SLP told me that their flywheels should only be turned once. After that, toss it.

Galaxie500XL

iTrader: (1)

I’ve read similar things about resurfaced LT1 flywheels. So far, I’ve only found no name aftermarket flywheels at the parts stores, and I’m uncertain about the quality of them.

Drew

iTrader: (58)

Could always hit up the local GM dealer, or try GMpartsdirect.com or another online dealer parts counter. GM #10125379 looks to be the part number for the LT1 T56 flywheel, list price is about $400.

TORN

iTrader: (17)

Or EBAY

https://rover.ebay.com/rover/0/0/0?m...2F173296852931

Galaxie500XL

iTrader: (1)

I saw the eBay listing a couple of days ago..

The GM part number is exactly what I was looking for. I’ve spent several hours wading through posts looking for that..thanks!

Tuned Performance

iTrader: (92)

Or RockAuto

Galaxie500XL

iTrader: (1)

Been there, too, but know nothing about the quality of them.

rburrow87

iTrader: (1)

As sofakindom said, a stock LT1 flywheel will bolt up and is balanced the same as any stock 1-piece rear main SBC 305 or 350.


I had some pretty bad vibration problems with the LuK flywheel I got when doing my T56 swap, even after having it and the pressure plate match balanced to the old flexplate to try to fix it. Unfortunately I had already used it a bunch and even resurfaced it before I realized it was probably actually defective (suspecting that the bolt circles weren't all concentric). It was pretty annoying pulling the trans so many times trying to fix it. I'm sure plenty of other people have used them and other brands without issue, but not me unfortunately.

I ended up getting a good used OEM GM flywheel (PN 10125380A N) and it pretty much fixed the vibrations. I snagged it off eBay just under a month ago. At the time there were several listed, but it was only possible to find them when searching for "camaro flywheel" or "lt1 flywheel" or something similar to that because the listings didn't contain the part number even though they had specifically taken pictures of the part number.

I will say that the GM flywheel just seemed higher quality once I had them side by side. The casting was much smoother, the areas where they removed material for balancing seemed cleaner and uniform, the machined surfaces blended into the casting more nicely, etc. Not really sure if any of that is actually a mark of quality or simply something to do with the difference in manufacturing process though.

Galaxie500XL

iTrader: (1)

Exactly the sort of stuff I was looking for...I’d rather spend a couple dollars extra, and do it right the first time.

LT1/TA

The stock Lt1 flywheel will be balanced for any 86 and up Gen 1-2 Sbc.I would buy the Luk brand from Rockauto myself.I have been using one sold from advance auto back in 2014,I believe the brand was Pioneer.I have had good service out of it.

Galaxie500XL

iTrader: (1)

Since I now know the proper part number for the OEM flywheel, I’ll get one of those.

Thinking about the McLeod clutch set..I’m going to be almost exclusively driving this on the street, and have been happy with the McLeod disc currently in the car.

https://www.jegs.com/i/McLeod/673/75...hoCZ_wQAvD_BwE

So, the proper GM flywheel is 10125379?

rburrow87

iTrader: (1)

It does look like the GM part number is 10125379, however the casting number on the flywheel itself may be 10125380.

Here is a picture I took of the number on the flywheel I'm running:

RunawayRadio

iTrader: (2)

I recommend you make sure you balance whatever flywheel you buy against the pressure plate you're removing from your L98. You should be fine with a steel plate, but there is a poorly documented vibration issue specific to the L98/t56 combo that can pop up on your drivetrain after the install. Most don't have an issue but for $100 at a machine shop you can avoid that frustration completely after the swap.

Also, stay away from a pilot bearing and grab a bushing instead. The needle bearings have a bad habit of coming apart on that combo.

Galaxie500XL

iTrader: (1)

I had intended to use a bushing...the needle bearing is a solution to a nonexistent problem...if the bearing fails, it chews up the input shaft, whereas the bushing simply has to be replaced.


I'm assuming it's the same bushing I've been using for my T5? My current bushing is only a couple of years old, but they're so cheap, it would be pretty dumb not to replace it at the same time.


The machine shop suggestion is excellent. There's a few shops around here that should be able to handle that. Do I understand properly you're recommending taking both the L98 and LT1 flywheels to get the shop to match the balance of the original L98 flywheel on the LT1?

rburrow87

iTrader: (1)

Yeah the bushing is so cheap, it's silly to not replace.

I agree. If your current flywheel and pressure plate are vibration free, it would be great insurance to take both your new and old flywheel and pressure plates and have the new ones match balanced. Probably not really needed, but it would be nice to eliminate that as a concern if you can do it.

I imagine McLeod supplies a quality clutch alignment tool. My local clutch shop supplied a USA made plastic alignment tool which worked well enough. I couldn't find it for one of the clutch re-installs when working on the vibration issue and had to get a cheap made in China Dorman one from a local part store to get the job done. It fit very poorly and made it a bear to install the trans. This last time, I purchased a steel RAM Clutch 03-013 alignment tool and it probably fit as well as a real input shaft. Made it a breeze to install the transmission. Basically, just make sure that the portion of the tool that fits in the splines of the clutch disk isn't incredibly sloppy (like the Dorman was) and it should work nicely.

Galaxie500XL

iTrader: (1)

Looking like finding a new GM flywheel may be an issue...GM discontinued them, and many places are now out of stock.

LT1/TA

If you are going to have it checked for balance by a machine shop,just buy one from rockauto.

Galaxie500XL

iTrader: (1)

I may have to do exactly that...I'd though I found a new OEM LT1 flywheel at a dealer in California, but it turned out the flywheel was not in the box...so, back to square one.


The vibration issue appears to be a real thing, because apparently, the 1-piece seal engines utilize balance weights on the flywheel to compensate for the portion of the crank flange that was changed when the rear seal was redesigned.


Unfortunately, no one I've found so far actually mentions whether their flywheel is actually balanced, which is why many have apparently had a vibration issue when using aftermarket flywheels.


I did get confirmation from the local parts counter guy that resurfacing an LT1 flywheel really isn't an option--because of the way the pull type clutch works, the thickness of the flywheel is extremely critical--remove too much material, and slip and chatter become an issue.

Galaxie500XL

iTrader: (1)

Doing a bit more shopping, Mcleod makes a billet steel flywheel, #460350. There's accommodation on the back side of the flywheel for the necessary external weights, which they sell as a kit for $35.00.


It's a $400 flywheel...but that's what the OEM nodular iron flywheel would have cost me. Would I be better off with this on a street car, rather than a nodular iron flywheel that has to be balanced by a machine shop?

LT1/TA

I have never heard of vibration issues on a T56 swap. All 86 and up 350 gen1 and gen2 Lt1
have the same crankshaft,you can look up the part numbers for the crankshafts.
If I am not mistaken the l98 and the lt1 look identical except the lt1 is a little taller.
They are both balanced the same,I know the other member on this thread said he had a vibration problem.He may have just got a bad flywheel or maybe some other circumstance was causing his vibration.
I personally would just buy one from rockauto and not worry about balancing.

Galaxie500XL

iTrader: (1)

Or...this one...which specifically says it's external balance, and only $100.00


https://www.summitracing.com/parts/z...make/chevrolet

Galaxie500XL

iTrader: (1)

You're probably right...I'm probably overthinking the whole thing.


I'm being extremely cautious..with my wife's health issues, I have to make sure whatever I do works right--I don't have a lot of spare time if I don't do it right the first time.

LT1/TA

I looked up a couple of things about the balance being external on the flywheel,but I still believe it will not have any issues because the automatic's flexplate are balanced the same as the l98 and the lt1.They both have the same part number,so I would think if the auto uses the same flexplate then they should be balanced the same.

sofakingdom

iTrader: (1)

Contrary to popular misconception, "internal" and "external" balance DO NOT refer to which side of the oil seal or the crank/flywheel split the balance weight is on. These words refer to the ability to fit adequate crank counterweights between the bottom of the pistons and the crank CL, when the piston is at BDC. The ONLY SBC in which this is not possible in STOCK configuration, is the 400. ALL OTHERS have INTERNAL balance.

These words are so confounded and mutilated when applied to these engines that even some of the aftermarket parts manufacturers have given up, and just to avoid the question when people who don't know what they mean ask about them, call the 86-up internal balance configuration "external".

Balance on ALL 305 & 350 including the LT1 is INTERNAL.

In the 86-up ones, with the rearmost INTERNAL balance weight removed from the crank flange, it is located on the flywheel. Therefore the flywheel is not "neutral" balance. This DOES NOT however make the balance "external".

Best to simply AVOID those words since they are so brutally abused in the marketplace. They will do NOTHING but get you into trouble when applied to this particular engine combination.

The word you should be using instead is STOCK. Ignore those other words and put them out of your vocabulary. If the flywheel you are looking at has the STOCK balance for 86-up 305/350, including the LT1, then it will work for what you are doing.

Galaxie500XL

iTrader: (1)

I agree...it’s gotten to be a confused mess.

The problem is there are no more OEM “stock” LT1 flywheels available, and most of the aftermarket is making (naturally) what the greatest demand is....flywheels for 383 builds.

The problem is most don’t bother actually giving a good description of what they’re making, which is a recipe for problems if the buyer isn’t extremely diligent. The most notable exception I’ve found so far is McLeod.

RunawayRadio

iTrader: (2)

Not really. Granted, there are less now than there were in 1997, but the market is still fairly awash in replacement flywheels that will work for what you're doing. sofakingdom is 100% correct in the terminology, so it's a good idea to throw that all out the door with the wash.

If you're looking for a performance flywheel, there are great aftermarket vendors out there that make steel replacements like mcleod and ACT. Otherwise, an aluminum flywheel from a vendor like fidanza can put some nice pep in the swap. Absolute worst case, if the flywheel will fit your car, the worst that could happen is it's unbalanced and that can be fixed by balancing it against your flex plate at a machine shop.

Galaxie500XL

iTrader: (1)

Looks like everyone has done a great job helping me figure this out..I really appreciate everyone’s help.

One final question.. is there supposed to be a shim on the flywheel?

LT1/TA

No sir.

sofakingdom

iTrader: (1)

True dat. I'm not saying "stock" as in, straight from the GM stealership; rather, stock configuration including balance.

Basically, if a flywheel balances correctly to a STOCK LT1, it'll balance the same to your L98. A GM one or anybody else's.

No shims that I know of.