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Hey guys, I recently installed a B4 top shaft in my black pan RC10T SCT conversion and my old B2 so I could run the updated slippers. All was well until last week when I was at the track and the truck's 2.25 Stealth started binding up. I pulled the tranny out and the idler gear was down for the count. So, fast forward to today, I have my replacement idler gear and put the tranny back together and the transmission instatnly binds up while turning by hand. I pulled the top shaft out and the idler and diff rotate freely. Put it back in and instant binding. Just to narrow things down, I happened to have the original top shaft from my B2 in arms reach and threw it in. All three gears rotated nice and smooth. The B4 top shaft looks to be in good nick, it's only a month old with a few packs through it. I was pretty sure this mod was just a direct drop in, am I missing any shims or something?

Thanks to all in advance

Check all the gears in the trans. The teeth in the old gears can get packed with worn teeth causing the mesh to be too tight. An exaxto knife can clean them out.

And you may have had the diff rings fragment off from over tightening causing the first failure.

Thanks guys for the super fast replies. The ball diff was on a pretty fresh rebuild and done correctly, what I did find was most of the stripped teeth from the idler gear gummed up in the top shaft gear and the rest gummed up in the diff gear. Cleaned it all out and the box turns nice and smooth again just like I built it the first time in 94'. Thanks for all the help.

A good wire brush works good for cleaning out the gears too. i do that every time i clean the transmission and i also use it for cleaning the spur and pinion gears when they get dirt in the gears.