mumzer Posted March 25, 2008 Report Share Posted March 25, 2008 i have an lq9/np149 combo in my truck that is beginning to act flaky. No spectacular failure...when the case is hot...after long freeway drives...it clunks during sharp turns like an old auburn diff without friction modifier. Problem is most pronounced pulling into a parking space. It feels a lot like a front LSD with no friction modifier, but obviosly, it doesnt have one. i took the truck to chevy, who acted clueless, said they couldnt replicate the problem, and didnt know about the factory test procedure to evaluate the viscous coupling. I set them off to find the TSB, and they claim the coupler tests fine. I think they failed to get it warm enough. Am i on the wrong track here with the source of the failure? i am pretty darn sure its a worn out 149, but would love a second opinion. Note - truck has 115k miles and significant towing and snow use. Power levels are near stock with basic bolt ons. Tires are new. diff fluids are new. Quote Link to comment Share on other sites More sharing options...
2004Denali Posted March 25, 2008 Report Share Posted March 25, 2008 If the loaded diameter is reduced by the tire squatting it will rotate at a different speed, causing the diff to constantly slip it's plates to make up the difference. Using more air in the front helps allot. I run 40 psi front and usually 32 psi rear to keep the loaded diameters as close to even as possible. The easiest way to measure is from the top lip of the rim to the ground, minus 1/2 of the rim diameter measured at the lip. That will be the loaded diameter. there was a guy on Denalitrucks.com just the other day that had the same problem, changed his fluid and tire PSI and the noise went away. Might sound wired but just give it a try, you have nothing to lose. Mark Quote Link to comment Share on other sites More sharing options...
mumzer Posted March 25, 2008 Author Report Share Posted March 25, 2008 thanks...i think this may be part of the source of the longterm wear....slip due to tire diameter differences, but at this point the wear and tear is done. I'll try this, but don't think i can undo the damage this way. Quote Link to comment Share on other sites More sharing options...
2004Denali Posted March 25, 2008 Report Share Posted March 25, 2008 it may not be too late. here is the link to the thread over on denalitrucks.com http://www.denalitrucks.com/forum/viewtopic.php?t=10243 Quote Link to comment Share on other sites More sharing options...
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