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OBX Install problems


HB280ZT

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HI All,

 

Been keeping up with all of the OBX threads and I decided to purchase one, plus the bolt and washer kit and the 10mm to 12mm shims for the ring bolts.

 

Well I checked the backlash before taking the unit apart and it was at .006 of backlash, right in the middle, cool! I cleaned everything up and put it all back together just like it came apart and I marked and separated the shims so that there would be no issue when I assembled it.

 

Well I got it all assembled and checked the backlash and it is .002 now, not good. I checked it in several places around the ring gear to see if maybe I got something wrong and it was the same. So now when I read the FSM it tells me to change shims but does not give me an idea of what to change them too, to get the right backlash. I understand the overall length has to stay the same and I need to move the ring gear out from the pinion gear to get the backlash within specs.

 

So if anyone has any suggestions they are greatly appreciated?

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I did not have to change shims but I am going to assume that you need to do the math...

 

Example:

Take .004 off the right shim and add 0.004 to the left one. This will give you more lash...roughly for estimation purposes, ignoring the angles and whatnot..Basically what you take out on one side, you add to the other side or vice versa. But I think you got that part down already.

 

I am not sure what delta shim translates to what delta lash. Depends on tooth angles. I think that's your dilemma right?

 

Here is an unverified statement that I found on the ALWAYS CORRECT internets. :rolleyesg

 

"The backlash will generally change about 0.007" for each 0.010" that the carrier is moved" Ref: http://www.differentials.com/install.html

 

Can anyone confirm this?

 

If that's true, you need to shimmy the carrier over by about 0.006 to go from a 0.002 lash to a 0.006 lash

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Grab a shim and the yellow pages and find your local gear shop. See if they have something close. You can order shims from Nissan but they're just there to take up space so anything close will work. I think MikeC once posted that a 12 bolt Chevy shim works. There should be something at the gear shop that is close enough, and they can probably sell you a shim set or a bunch of different thicknesses so that you can adjust until you get it right.

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Guys,

 

Thanks for the information but I found a solution. For starts when I took everything apart I cleaned and marked the shims just so I would have no problems when I assemble the diff. Well I took it apart again, checked everything and it was still like I took it apart. So I measured the shims again and they were .090 and .086. I then decided to try something and swap the two small shims from side to side and check the backlash. Well the backlash is now .005+ a bit when I checked it so I am within specs, boy was I lucky! So hopefully I will have it in my car tomorrow and on the road to see how it works. Thanks again for the help.

 

HB280ZT

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