LMM bad vibration

Hello from Australia

I have been a member for ages but not active. Can't remember if I introduced myself before so hi again.

I have a Nissan patrol wagon with 2007 Duramax and built 2006 Allison 6 speed, Billet torque converter, 4" intake, 4" exhaust, edge display. Dsp5 running up to 570hp I think. Currently on 370hp setting.

When I bought the car (already converted) it had a very feint vibration/harshness around 1500 rpm which has gotten a lot worse lately.

Car shakes like a drag car and vibrates the whole car. Insane at 1500 rpm and worse on cold nights than during warm days. Not speed dependent, just rpm so my guess is engine or gearbox.

I have read a heap of threads but none seem to be the same symptoms as what I am experiencing.

Nobody in Australia knows much about these engines, so I need some help please?

It's a transfer vibration definitely but rather than just fix the symptom, I would rather fix the underlying problem.. Or at least know it's not going to cause a major failure at some stage.

Balance rates are all very good. Better than good actually. No codes on the edge display.

I read a few threads about cracked flex plates but they are described as a different sound. The sound is like a resonating vibration sound rather than a clunk, clank or clink, and seems to be coming from under the car, though I expect it can be transferring from anywhere.

I'm not a mechanic, but I'm also not a dummy so any ideas please fire them through and hopefully we can eliminate them one at a time?
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NKlamerus

New member
Jan 31, 2014
186
0
0
I'm not sure what's up with shaking but dang that's a cool setup.

I'm not a huge fan of Nissan but I'd drive that!!!
 

Yellow Jacket

WannaBe Sled Puller
Feb 11, 2009
917
0
16
Waterloo, IA
Watch your balancer as it idles, possibly a cracked crankshaft... I know of one LMM that had a weird cruising vibration, they put all new frontend parts in it, even the whole front diff, tried a couple different sets of tires and wheels and always had a very slight vibration... Had it for over a year, one day it got much worse and crank was busted in half.

Just an idea
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
5,201
363
83
At Da Beach
Mine had a terrible vibration at speed and the truck bucked up and down like a wheel was out of balance, it turned out to be a whacked transfer case. Drain your t case fluid and see of its dark...
 

Tyler_LBZ

Member
Feb 26, 2015
96
0
6
NC
Might sound silly but could it possibly be a motor mount? Since its been swapped into the Nissan maybe what ever was fabbed to make it work didn't hold up.

Does it do it in Park sitting still or only when moving?
 

04BlackSmoker

New member
Apr 8, 2009
37
0
0
Is in in every gear? Mine is doing the same thing for the last year an a half, right at the same rpm that yours is but mine is only doing it in 5th and worse in 6th gear.... Also like you described worse on colder days than warmer days...
 

VinceGU05

duramax lover downunder
May 20, 2011
164
0
0
Melbourne, Australia
Might sound silly but could it possibly be a motor mount? Since its been swapped into the Nissan maybe what ever was fabbed to make it work didn't hold up.

Does it do it in Park sitting still or only when moving?


Not silly. I ripped my trans mount in half. Have to actually take it out to look at it properly unless it is twisted/ badly aligned like mine was.
My mate jay at Australian duramax conversions could rebuild it including remove and refit if it was a crank. Only problem he is in Melbourne.
Yup Heath has great after sales service. Not.
 
Thanks Vince. I've been talking with jay. Might send it down. All three mounts replaced. Vibe can be replicated standing still by putting transfer case in neutral and running up through gears. In sixth gear trans locked it's there. Take off drive belt same. Has to be engine or box. Box was built. Maybe transfer case or adapter shaft, running out of possibles now.


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Brizzy Northside.