This is on my 3800 swap. The belt seems to be jumping a rib on the crank pulley. Everywhere else the belt rides fine. A while ago I had replaced the idler [shown in the picture] as it was disfigured with a new one and I thought that had solved the problem. However, I just recently noticed that it obviously hasn't as my belt obviously jumped a rib again a while ago and wore itself down doing so.

The harmonic balancer has been off before so a concern of mine was perhaps I didn't get it fully seated down. However, if that was the case I'm assuming that the belt would be jumping a rib in the opposite direction and not "away" from the engine [plus...the other belt rides fine]. The A/C hasn't been touched and as I mentioned above I replaced the idler shown in the picture. Any new ideas? I'm going to check the idler again to make sure it's fully seated but I can't imagine that I messed that up. Just thought I would post this for any new ideas the forum might have. Thanks!

[This message has been edited by GraterFang (edited 11-12-2011).]

did your original idler have a metal bushing/spacer behind it?
and when you re-mounted the harmonic balancer what method did you use?
and was there a washer behind the balancer before? it's been a little while since I rebuild or worked on a 3800. but jumping a rib on any car can happen when pullies aren't angled correctly (are bent), the belt is TOO BIG, or when you put the belt on you dont make sure it's on fully on all the pullies (I've done this myself in the past).

Means:

Install belt wrong
or
Major problem in pulley alignment

see my cave, serpent belt in general engine section

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

Thanks for the replies!

quote Originally posted by gtxbullet: did your original idler have a metal bushing/spacer behind it?

This is a really good question. It's been about six months at least since I changed out the idler and even longer than that for the harmonic balancer so unfortunately I can't remember. I see your point though and its a good one. Perhaps somebody will chime in on this.

quote Originally posted by gtxbullet: and when you re-mounted the harmonic balancer what method did you use?

I'm not sure what you're looking for here exactly. It's been even longer since I had the harmonic balancer off. I seem to recall that the install was pretty straight-forward though other than getting enough torque on the bolt that holds it all on.

quote Originally posted by gtxbullet: but jumping a rib on any car can happen when pullies aren't angled correctly (are bent), the belt is TOO BIG, or when you put the belt on you dont make sure it's on fully on all the pullies (I've done this myself in the past).

The pullies are not disfigured and as far as I can tell by eye they aren't bent either. The belt is definitely the correct one for the engine and I'm also sure it was installed correctly as I had paid close attention to that then.

Use a metal straight edge on the crank pulley to check alignment of the belt other driven item pulleys (alternator) and the idler pulley. Belt misalignment will eat belts up in short order and cause the belt on the crank pulley to slip a notch in the direction of misalignment.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, ZZP Intercooler, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

I prefer to bolt a piece of angle to the balancer and either use stacked up washers for a pointer to the first groove peak or use a tape measure. Here are some pics (but not 3800 specific).