If You Work On Gen II LTx, Learn From My Mistake

[Dave P.]

Over the years I've R&R'd a zillion harmonic balancers. I used the puller I've used for 40 years on the hub on the LT1, and really struggled. I was under the impression that these hubs are on really tight, so it didn't occur to me that I had the wrong set-up.

I have never seen anyone post that the Gen II LTx is different, but it is. Look at the pic. You have to insert a bolt through the bolt hole in the hub to 'push' on, or you're just pushing against the hub. After I broke the ear off, I called an engine machinist that I use from time to time. It took him a minute to wrap his head around what I was working on, and he nailed it. He thinks he may have a hub in his stuff.

Getting it off with one broken ear was a head-scratcher, but another couple of hours and I got it done with stuff I had in the shop.

Now I know. Remember this if you ever R&R the hub on a LTx.

IMG_4826.jpg

IMG_4828.jpg
This is from the bolt side. I thought I was pushing on the nose of the crank. I wasn't.

[Keith B.]

Re: If You Work On Gen II LTx, Learn From My Mistake

as of seven years ago those where available though the GM parts counter

[Joe L.]

Re: If You Work On Gen II LTx, Learn From My Mistake

Over the years I've R&R'd a zillion harmonic balancers. I used the puller I've used for 40 years on the hub on the LT1, and really struggled. I was under the impression that these hubs are on really tight, so it didn't occur to me that I had the wrong set-up.

I have never seen anyone post that the Gen II LTx is different, but it is. Look at the pic. You have to insert a bolt through the bolt hole in the hub to 'push' on, or you're just pushing against the hub. After I broke the ear off, I called an engine machinist that I use from time to time. It took him a minute to wrap his head around what I was working on, and he nailed it. He thinks he may have a hub in his stuff.

Getting it off with one broken ear was a head-scratcher, but another couple of hours and I got it done with stuff I had in the shop.

Now I know. Remember this if you ever R&R the hub on a LTx.

[ATTACH=CONFIG]121369[/ATTACH]

[ATTACH=CONFIG]121370[/ATTACH]
This is from the bolt side. I thought I was pushing on the nose of the crank. I wasn't.

Dave------


A special puller set is required for the LT1 crankshaft hub. It was Kent-Moore J-39046 (or, equivalent if an equivalent exists).

The last available crankshaft hub for 1992-95 LT1's, GM #12553250, is GM-discontinued. However, there is a replacement available from Dayco. It's their part number FHS1481SS. In some ways I like the Dayco replacement better than the original GM. As you are aware, the GM hub is a cast and machined piece. The Dayco hub looks to be machined from billet steel although I have not seen one "in the flesh".

By the way, the 1996 LT1 and LT4 use a different hub. It was GM #12550097 but it's also GM-discontinued. I do not know how it differs from the above but it appears very similar. The Dayco replacement number is FHXS1481SS.

[Dave P.]

Re: If You Work On Gen II LTx, Learn From My Mistake

Thank you Keith and Joe.

My machinist found a balancer, but the hub wasn't with it, so he concluded he didn't have one. I found the machined hub on both Summit and Hawk. I have a Hawk power steering pulley, but they were really slow on shipping, and they were $60 more than Summit for the same part. Predicted arrival date is next Friday.

I obtained the GM P/N from my fisch to use for online searches. I didn't bother to call my dealer parts guy as I figured it is NLA. Joe confirmed this. Thanks.

Regarding the 1996 hub being different than the 92-95. This is speculation on my part, but based on what I've experienced on the 4.3 V6 which is similar architecture. The 1996 OBD II required a crank-mounted reluctor and sensor to meet the requirement for detecting misfire codes required by OBD II. This reluctor is mounted between the hub and the face of the crank timing drive gear. The hub is .200 shorter to allow for the inclusion of the reluctor ring without changing the stack-up dimension of the hub face. This begins in 96 on the V6, makes sense that it does for the V8 as well.

I read the FSM for hints as to what needed to be done for hub R&R and saw the puller, but didn't pay attention to details. A puller is a puller. My bad.

I'm a little concerned about reinstalling this thing. I own a balancer installer, but it won't setup for this thing. I ordered some Grade 8 threaded rod and some Grade 9 high-strength nuts from McMaster Carr. I'm hoping to be able to McGyver something up with this stuff and bits from my Power Steering pulley installer. We'll see.

Thanks.

[Dave P.]

Re: If You Work On Gen II LTx, Learn From My Mistake

I'm a little concerned about reinstalling this thing. I'm hoping to be able to McGyver something up

The replacement hub was on my porch this morning. I worked on it all day, and most everything is back together. It even ran. I ended up replacing or addressing every possible source of an oil leak other than the rear main seal. Intake, timing cover, oil pan, filter stand, pressure switches, everything. If it leaks again, it's the next guy's problem. I'm done with this leaker. Never, ever, again.

IMG_4832.jpg
Here's the new hub compared to the old. Yes, the Opti comes off with the hub in place. Note the little pip mark at 12:00. This indexes with the arrow on the balancer, and is installed at 12:00 with the #1/#6 pistons at TDC.


IMG_4833.jpg
I had to McGyver an installer tool. I purchased a length of 7/16-20 all thread and some nuts. I drilled a hole in a piece of 1/2" plate. In my fingers is a 4L60/700R4 input drum torrington bearing from my stash. The intent was to minimize friction so I wouldn't strip the all thread or nuts.


IMG_4834.jpg
It fits like it was made for this application.


IMG_4837.jpg
Here's the final set-up. Cost me less than $20 for the McGyver installer. It pressed the hub on effortlessly.

Learn from my mistake.