It's always something. We still had a lack of power and a vibration around 45-55mph so I pulled the cat and cut it open thinking it might be clogged but it was actually burnt out. Put it back together with pipe to the glass pack instead of buying a cat at this time. Took it to a shop to have it re-timed as I'd just paid a friend of a friend who is a mechanic. As I suspected the timing wasn't right. He hadn't been able to turn the distributor far enough so he'd just pulled the wires and moved them around. Now that it's timed properly it runs better but we still have the vibration.

I replaced the outer tie rod ends, pitman arm, and idler arm before the exhaust work even though the vibration didn't feel like it was in the front end and I hadn't been too surprised that it hadn't fixed it. I'm not sure what to suspect at this point. Possibly a wheel or axle bearing? Any thoughts?

 

This is why remote filter delete is the best and only option IMO!

 

Sounds like a hack mechanic and I would not let him touch your truck EVER again!!

 

I think he meant he yanked the distributor, re-clocked it, then moved the wires? That would give you the space needed to adjust. I ran into this same issue after doing the '00 4.3 swap into my '89 S10 Blazer.

When I installed the carb, I had no room to adjust due to the vacuum advance unit hitting the carb. I removed the distributor from the engine, re-clocked the way it faced, then re-installed - had to move plug wires one position around so timing would still be correct.

Brian, you could have a bent driveshaft. Does the vibration show up around 40 MPH? Does it get worse under load? IF that checks out, some other things to look at are a bent flywheel, torque converter issues, or damaged harmonic balancer - all this provided the hub bearings, wheels and tires check out OK.

 

I hope thats what he meant but thats not at all how it reads to me. As I am sure you are aware the distributor is non adjustable in these trucks and the hold down needs to be modified to properly adjust them.

 

Yeah, It ticked me off because anyone who is actually employed as a mechanic knows that's not right and it will never be right that way.

 

Nope, the shop said he had literally moved just the plug wires to different locations Instead of pulling the distributor to re-stab it correctly which is what he had been paid to do. I wanted to pay him a visit:

Brand new tires and didn't notice anything major with the wheels, as well as wasn't told there was an issue with any of them when they mounted the tires. I bought a brand new harmonic balancer when we were putting it together as the old one had a chunk broken out of the neck, which of course was down in the transmission. Had the transmission rebuilt before putting it back in. The fly wheel didn't Look visibly bent when I was putting it on but possibly a slight bend that wasn't detectable by the naked eye? I'm not sure about the balancer but I didn't notice anything that looked suspect while putting it together. Not sure how to check for a bent shaft other than eyeball it for wobble?

I haven't checked the wheel bearings or axle bearings yet. It's been a bit since I drove it and I've slept since then so I don't remember exactly when the vibration shows up or is at it's worse. I was thinking it started around 45-55 and my son says specifically 55. By under a load do you mean pulling something? I haven't tried that as it doesn't have a tow hitch but I could throw a strap on it and pull the van to check I guess.

 

What everyone else said plus... The burned out cat was likely the result of the incorrect timing. I'm kinda surprised it didn't melt and restrict the exhaust. I have filed out the hole for the distributor hold-down bolt to fine-adjust timing a degree or 2, but you would never turn it 60 degrees...

My experience with front-end vibration in the 55-60mph range is that it has always been tires. It is possible that misalignment damaged the tires enough to make them separate, but look first to tires as the cause, if not the root of the problem.

Try rotating tires front-to-rear and see if it changes.

Franco

 

I'm betting the cat was stock equipment based on the shape of everything else but the timing being like that sure wasn't helping anything.

The tires are brand new and even if it were an alignment issue causing wear they haven't had enough miles on them to effect them.

Doesn't really feel like a front end wobble anyway. I don't feel it in the steering wheel like you generally do with front end issues.

I'll get out there at some point and check the wheel and axle bearings next I guess. Can't really afford to replace too much at the moment.

Thanks again

 

Looks Great, love the clean look!