Check your balencer

I just lost another 6.2 to a bad harmonic balencer. The rubber seperated from the outer ring and the engine busted the crankshaft. This balencer was 2 years old. I had changed it out when i installed this engine. But as with everything else these days it was made in china. I'll be inspecting mine on all three of my trucks often from now on. Or untill i can get fluid dampners for them. I've had this happen in the past and each time i was at higher RPM's. So have a look. I could save your wallet a bit.

How do you check it?

Inspect the rubber between the inner and outer rings. Look for dry rot and cracks. Try moving the outer ring with your fingers. Cracks in the rubber may appear when you move it around by hand. It shouldn't hardly move at all by hand.

It also doesn't hurt to use a paint marker to mark the inner and outer parts of it to easily check it later on to see if it has moved on you.

I've got a paint marking on mine too and have gotten into the habit of checking the balancer every time I change the oil or pickup the grease gun.

Can you guys explain the line drawing a little better for someone who has never checked a balencer before?

The line goes across the inner and out part of the balancer from the inside to the outside edge. When the lines do not line up it is time for another balancer.

As An engine builder, I have a real hard time thinking that a broken crank is from a bad balancer. I have seen several cranks break in the 6.2's but this is caused by the use of a cast crank. Most high end diesels use a forged crank just for this reason but for it to break cause of the balancer I doubt it. I have had engines that the rubber was all but missing and the harmonic ring was flopping all over the place and the crank never suffered any ill effects as a result. It just made a lot of noise. I had a surburban years ago that was a nice clean one owner truck. Driving into Montana on a trip years ago, We were doing 80 with the cruise on and with out any notice there was a big bang and some other horrible sounds. Long story short, got it home and pulled the pan and found the crank broken clean in two just past the #1 and 2 rod before the 2nd main. It did run but it was hurt. I have fixed many like this but thisd was my personal truck and was not hopped up or turning fast at all. Truck was geared with 3.54 and has a .072 over drive. Btw. the dampner was fine and went on the new engine.

Can we get a pic or something?

I second the request for a picture.

The balancer on GM gas Engines will also move hard to time them when this happens

I know the 6.2 uses an externally balanced flywheel. Is the dampener also external, like a small block 400 or a 454? I know having those two with the wrong external parts will cause them to vibrate and beat the bearings out prematurely. Glen

Question-
Checked the TM on harmonic balancer (listed as torsional damper) removal and install, but it's not clear if I have to remove the crankcase cover to do it. Also, a lot of the "how-to's" I've read say you have to pull the radiator and fan shroud to do this.

I really don't think my balancer or pulleys are bad, but I may end up having to drive the truck literally from coast to coast this coming summer (formal school at Lejeune, and then a PCS to Ft. Lewis, WA). I want to avoid any possible breakdown, and figure a $70-80 part is cheaper than a tow and/or a blown crankshaft. Just wondering if someone can offer a little how-to on changing the harmonic balancer and any special tools I might need. Thanks as always!

It is a press fit on the crankshaft. Normall the pulley bolts are removed and those holes are used to pull the balancer. You will need to remove the large center bolt and washer, right in the center of the crank. Be sure to use a puller with a pivot button so you do not mess the threads in the end of the crank. I am lazy and use a 1/2" drive impact wrench to spin the puller bolt. Installation is the reverse, ideally you will use a compression tool to install the balancer, one that threads into the crank and after you make sure your new one is on the key way, tighten the compression nut and waher, or however your tool is set up. I have seen badly damaged balancers from guys beating on them with a hammer. I have also seen guys run the center bolt in to pull the balancer on and gauld the threads inside the crank, great! If you are going to try the center bolt method, be sure to lube the threads so the bolt does not gauld the crank and you wind up with both parts damaged. Glen

Editing to add I have not done this on the CUCVs yet, but every other GM V8 I have done required removal of the raditor, except the 1970 to 1972 Monte Carlos that had that 18" fan shroud. You do not have to remove the timing cover, but I usually do to clean it up and install a new seal. Glen

I had a long talk with a former CUCV mechanic and ASE tech last night, he told me to check mine as a potential cause for it chewing and tossing fan and generator belts all the time, said it could be "walking" on me.

SO of course I start looking for more info, and come here..

the previous engine I had in this truck busted a crank, and I'm sure the guy that did my engine swap reused the balancer..

small price to pay to swap mine out.

I would definitly like to see some pics or how to's by anyone that has swapped one on this engine.


gonna read the manual of course, but if I can get away with not pulling the radiator thats all the better.

REGULATOR said:

I had a long talk with a former CUCV mechanic and ASE tech last night, he told me to check mine as a potential cause for it chewing and tossing fan and generator belts all the time, said it could be "walking" on me.

SO of course I start looking for more info, and come here..

the previous engine I had in this truck busted a crank, and I'm sure the guy that did my engine swap reused the balancer..

small price to pay to swap mine out.

I would definitly like to see some pics or how to's by anyone that has swapped one on this engine.


gonna read the manual of course, but if I can get away with not pulling the radiator thats all the better.

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Yes pics would be good.....since I may be giving this a go for you Regulator!! We may need to invest in a puller kit.... maybye from harbor frieght???



And here we go......

Good luck with these trucks, for the guys that want to take em for long trips, i have to say, man u got guts. These diesels do not have longevity on there side,and they are old , they are a great around town hobby truck, and sure some guys will get the miles out of em, but most will not, the threads are pilling up on problems already. like said in a post in this thread, high end diesels used different parts, they were GM's fast answer to get a diesel out, All i am saying is be prepared,

emr said:

Good luck with these trucks, for the guys that want to take em for long trips, i have to say, man u got guts. These diesels do not have longevity on there side,and they are old , they are a great around town hobby truck, and sure some guys will get the miles out of em, but most will not, the threads are pilling up on problems already. like said in a post in this thread, high end diesels used different parts, they were GM's fast answer to get a diesel out, All i am saying is be prepared,

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I guess I must be the minority having put on 20k+ in 7 months on mine, including two 1700 mile trips the first month I had her. Sure, there are some rotten apples out there, but to say that "most will not" get many miles out of them I believe to be quite incorrect.

aebiv said:

I guess I must be the minority having put on 20k+ in 7 months on mine, including two 1700 mile trips the first month I had her. Sure, there are some rotten apples out there, but to say that "most will not" get many miles out of them I believe to be quite incorrect.

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I agree on this. Same motor that was used in the civilian trucks. Not hot rod diesels for sure... but, you see them all over the place with well over 100,000 miles.

I drive mine 88 miles a day round trip. I have owned 6.2's for 18 years now. With many of them lasting more than 200K. They will torerate alot. But high RPM's just ain't something they can handle. Keep the oil changed and keep them slow and they will give you many years of service. No they were never meant to tow a back hoe on a goose neck trailer. There main intention was fuel savings. And thet they do well. I see if i can post some pics of a cracked balencer today.