LBZ engine vibration

[tanman_2006]

My lbz has a pretty bad vibration at around 1400 rpm. It does it sitting still on a slow free rev and I can feel it when accelerating loaded and unloaded. Tried to remove the belt and run it like that and couldn't feel a difference. It runs fine so I don't think it is a miss but I could be wrong.

Now what should I check?

 

[CtChevy427]

How are the engine and transmission mounts?

 

[tanman_2006]

Tranny mounts looked good when I changed the oil last weekend. Ill check the engine mounts out. I guess I could chew them up grossing 30k

 

[Mad Maxx]

Usually, the Driver Side Motor Mount is the one that goes.

 

[RI Chevy Silveradoman]

Maybe a bad or misfiring injector?

 

[tanman_2006]

Doesn't sound rough from outside? Shouldn't something that bad throw a code?

 

[btfarm]

Shouldn't something that bad throw a code?

You would think so.

Other than Motor mounts I'm at a loss too.

 

[Max Attitude]

Just fixed my drivers side mount. Pop the hood and have someone watch the motor while you power-brake it... see if it lifts. If its bad you can drill a hole hole through the middle and bolt it like I did. There is a write-up on DuramaxDiesels...where I got the idea from. - http://www.duramaxdiesels.com/forum/showthread.php?t=2976&highlight=motor+mount

Hopefully not your crank going out. - http://www.duramaxdiesels.com/forum/showthread.php?t=23186

 

[tanman_2006]

Haven't gotten a chance to check it out but I will try a power stall and see what gives (besides the tires). The way it feels is like a 6.5 with a bad harmonic balancer. So maybe I have a bad flywheel? I have been having a hell of a time keeping starters around

 

[racedaymechanic]

Sounds to me like you need new Battery Cables:hihi:

 

[tanman_2006]

That cures everything right?! Lol

 

[tanman_2006]

These look all over the place. What should i be seeing, is this something to be worried about?

These readings are off my edge evo on level 3 after hauling hay all day. ECT was 197*

 

[Grendahl]

Those rates look pretty good to me. IIRC the GM spec is +/- 4 in park at idle, and +/- 6 in drive with the truck held stationary by the brakes.

 

[tanman_2006]

That was in park and I had a 7 in there and 3 5's but i guess thats fair for 185K

Now back to motor mounts....

 

[RI Chevy Silveradoman]

The injector rates look real good. No problem there.

 

[3500GMC]

Has any of the Allisons ever 'balooned' a torque converter? Any weights to fly off the flexplate?

 

[tanman_2006]

My local mechanic says that flywheel problems are common on hard working dmax's but i havent seen anyone on the forums with complaints. So either its not a true statement or ya'll arent working them hard enough! lol

 

[RI Chevy Silveradoman]

I haven't heard that at all. Check with someone else.

 

[btfarm]

That's a new one here too. I bet he's repeating the 'ancient' discussion where the very early ZF6 flywheels had some bolts loosening at the crank or maybe the pressure plate. We're talking Allison, not 6 spd manual here.

 

[tanman_2006]

There arent very many dmax's that get beat on in the area but there are a gazzilion cummins. There are alot of cute dmax toys though! lol

I will be pulling the truck in for some much needed R&R today. 3 broken lugs, exhaust is sagging and rattling, and front end needs serviced. Hopefully i get time to add motor mount inspection to my list.

Been hooked to the 12 bale hay trailer for most of the week hauling ~7 loads/ day 20 miles one way. 55 mph in 4th and ~12mpg