I put a set of richmond 3.73's in my car last summer and broke a tooth off the pinion gear and dont know why.I set the rear up myself and used all the correct tools and pinion depth guage and my backlash is good.I have a 305tpi and run high 13's and a 1.7-1.8 60 ft times.Also its an automatic.Any ideas ?? oh and it broke just after i put on a set of futura ultra z 255 tires they are sick and wont spin to much and just bite the road so i figure its from the stress but i thought they were stronger.

 

possibly the traction. i don;t understand it but the ultra z's are the best tires i've had so far. i pulled my first 1.79 on them

 

Probably not the gears 'fault' it broke. 7.5 inch is small, plus the small case that tends to flex with good torque and good traction. Are you running the support cover and have welded axle tubes? Removed the crush sleeve and installed a solid one? Those things would help. While they say, after the upgrades it can handle 400hp, that is just a guess. In stock form, with only richmond gears, it's probably much less. Good low end torque and good traction(60ft times) are even harder on it.

 

Ok I figured that my rear would not have any problems with my 305 but i did build that 305 pretty nasty.And no i didnt have any of the rearend mods which i guess i should have.I dont think i can blame the gears either i figured the case slightly twisted and let the gears seperate a little. owell.Anyone else have any second ideas thanks.

 

Thats really tough to say. You wouldn't be the first guy to break a 10 bolt in the high 13's, but you wouldn't be the first guy to make a mistake setting up gears without realizing it either. Really no way to tell. You could clean up the gears that are left and run some marking compound on them, recheck the backlash, but it's gonna be hard to tell for sure.

 

did you properly break the gears in? I also have Richmond 3.73's and I know with any gears, there is a break in time period. Getting the gears in and doing burn outs right afterwards would do it.

 

Everyone seems to break gears. My brother is on his 8th set of gears. 96 Trans Am LT1 6 speed with bolt ons.
I cracked the stock 3.42 gears in my 95 Formula rear end with my TPI setup in my 86. We put my rear in his car temporarilly (sp?) and he tore em up casually going down the road.

Try a set of GM Motive gears, they seem pretty durable.

 

I set up the gears right i am almost positive and i checked the blacklash after it broke and it was still pefrect at about 8 like recomended by richmond.And yes i broke them in properly,i casually drove it for about 20 minutes at drifferent speed to let them heat up to tempthen let them fully cool.So i really dont think its something i installed wrong.But good ideas guys,i didnt realize breaking rears like this was this common.

 

Sometimes they last sometimes they don't..

Apparently the big cause for our gears to fail is flex.. the cure a strengthened aluminum cover that torques lightly onto the bearing caps (jegs/summit), welding the axle tubes, and a ratech solid pinion spacer(thunderracing).. While not foolproof those are the three mods that give us the best chances at keeping the rear gears for a while.. if you have already tried this it is time for a twelve bolt! a prayer or two may help also..

currently I have richmond 3.42s and auburn posi and the above mods in my 26 spline behind my LT1 combo.. If it breaks I am upgrading..