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Mammoth ST differential skipping

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Mammoth ST differential skipping

Old 08-06-2006, 11:55 AM
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Default Mammoth ST differential skipping


I recently bought a used mammoth ST off ebay. I heard clicking so I checked it out and it appears that the front/rear metal pinion gears going into the diffs are skipping on the diff gear. The pinions have some play and it appears that shims could be added to decrease that play. Each pinion had one copper shim. The gear teeth appear to be fine so I'm pretty sure it's just a meshing issue that could be solved with the addition of more shims.

Is this a common problem with these trucks?
Where can I get the right size shims?
Does anyone know about how many shims are needed to mesh them nicely?

Old 08-07-2006, 02:14 PM
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Default RE: Mammoth ST differential skipping

The gear skipping in the diffs is a common problem as it is not propper shimmed.(can hear it when u brake hard).Take the diffs out,and lift the insides out.Take the small drive pinion out and install 2 to 3 shims on it(replace with new pinions front and back if the teeth has any wear on them)Remove any other shimms you may find where the outdrives are in side diff housing.Replace the pinion with the new shims .Fit the dogbone drive cup and make sure there is very little movement (the pinion should not move to and fro)Put the diff back in the casing and replace the black top(cap).When the four screws are in and turned in,turn the pinion and feel that it is not to notchy(the pinions is now pushed in to sit deeper in the diff casing to to cover most of the crown gear inside for maxim contact and load)

Do this to the front and back diffs.Hpi shims will help,but get the thin ones.You have to play a around with the shimms the get the perfect mesh without any binding(use some grease after installing on the gears)It will take you about 30mins on each diff.
Old 08-08-2006, 11:37 PM
Henry William French
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Default RE: Mammoth ST differential skipping

Read my review of the XLB which is very similar to the Mammoth in the USER REVIEWS section. Yes I had major diff problems too.

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