Then the GM Service Manual says to use another special tool (EN-48034) to install the balancer. On 2004 or later models which have a shim on the balancer snout, the GM Service Manual says you should replace the shim (P/N 12578073) before re-installing the balancer. If I had to do this again, I would probably try to find the special GM puller at a reasonable price (maybe on EBay or ), or I would look around for a larger generic puller that had the same flattened hooks as my Olympia puller. I removed the swivel tip and continued tightening the puller (past the point where it started mangling the exposed tip of the puller screw, and to about the point where I was worried that something else on the puller would break), and finally the balancer started moving! Then the swivel tip on the Harbor Freight puller screw broke before the balancer moved. Luckily, each leg on my Olympia puller has one rounded hook and one flattened hook (much like the special GM puller - check Google Images for pictures of the J-41816 legs to see what I'm describing), and the flattened hook did fit behind the balancer, so I was able to use the legs from my broken Olympia puller and the frame and screw from one of the Harbor Freight pullers to attach to the balancer. The problem is that all of these pullers have rounded hooks on the end of the jaws, and there isn't enough space behind the balancer (in front of the front cover) for the puller hook to fit, so you simply can't hook the puller legs onto the balancer. Unfortunately, none of those pullers fit. So I rented all of the pullers that Advance Auto Parts had available, and purchased this puller kit ( ). I tried using an old Olympia 05-891 4" puller that I already had (I bought it many years ago, I'm not sure where), with a socket over the crank shaft, and a piece of scrap steel over the socket (for the puller screw to push against), but the puller screw broke before the balancer moved. This tool costs about $140 from the official GM Tools Website ( ), so I tried to find another puller that would work. The GM Service Manual says to use a special tool (J-41816) to remove the balancer. I suspect it should be possible to remove this bolt with a breaker bar by using the torque converter bolt trick (described below) to hold the flywheel, but I would recommend using a big impact gun if you have one or can get one. I ended up using this "700 ft-lb" impact gun ( ) to get the bolt out, but even using that gun with my air compressor turned up to 100psi, I had to hammer on the bolt for quite a while (maybe a minute or two) before it broke loose.
Because of the way the impact gun hammers on the bolt, there is no need to hold the flywheel the inertia of the crankshaft and flywheel is enough to hold everything in place. So, I tried using a small (250 ft-lb) impact gun to remove the bolt.
This did not work at all - both the screw driver and pry bar started mangling the flywheel teeth under only moderate torque, and they would twist and slip off the teeth before we were anywhere close to putting enough torque on it to break the bolt loose.
I initially tried jamming both a screw driver and a pry bar in the flywheel, then having my wife try to loosen the bolt with a breaker bar while I held the screw driver and pry bar in place. Note that the 5.3L and 6.0L harmonic balancers are different (and look much easier to remove/install), so this only applies to 4.2L models.
So, I figured I should share my experiences, in the hope that it might save someone else some time, trouble, and money. like using the starter to break the bolt loose). This involved several epic struggles at various stages of the process, and I spent a lot of time searching the web for suggestions to make it easier, but I didn't really find any suggestions that were actually helpful (and didn't involve doing something risky. I just finished removing and re-installing the harmonic balancer on my 2007 4.2L LL8 TrailBlazer (in order to replace the oil pressure regulator in the front cover). Cross-posting an old post of mine from on TrailVoy.