12 bolt gear breakage issues....

[ericsz]

Broke another gear saturday at the track thats the 2nd gear in 5 weeks, what could cause this? the first gear that broke had been in the car for over a year it finally let go, it was a Richmond street gear set at .012 lash, I put in another richmond street gear and someone told me to put it in as tight as possible, I installed it at .004 lash. it only lasted 2 weeks. I now have a pro gear installed yesterday at .010 which is what was etched on the side of the gear, I am using a transbrake, first pass was perfect saturday then come into the lanes for rd 2 and heard click click click, i knew it was going so I went out launched the car and then BOOM! it sheered 11 teeth in a row off the ring gear, the wear pattern on the gear was perfectly centered. Now what?? I do have a stock conver on the car and still using the crush sleeve. I also added 100 lbs to the trunk of the car to help it hook, well it hooked it packed the fronts 3 ft in the air and carried them about 25ft, I was tickled until the big boom came, could the weight have caused it?

[TubbedTruck67]

Four thousands lash is too tight IMO. A girdled cover could help, probably something I would invest in if it was me. If you stayed with the same ratio, you did replace ring and pinion right? You didnt just change the ring gear?

[ericsz]

Yes I replaced the ring and pinion.

[aitch o]

i had the same problem with my 12 bolt. broke a couple of gear sets. then i put on the support cover and that was the end of the problem. some folks like the billet bearing caps also, but i just have the factory stock caps with the support cover and it is working fine. usually goes low 1.30s or high 1.20s in the 60' at 3300#.
also, richmond says .008.

[ytnova]

I have a 8.5 ten bolt with a ultimate rear cover and leave flat foot on the brake @3500 with a 3500lb car and a big block to boot, no problems yet. I would look at a solid pinion spacer and a cover with some sort of cap support. It either that or time to go with a 9" or dana 60.

[Craig W.]

The rear cover is the bulk of your problem. Put an aluminum support cover on it and you'll likely put an end to the breakage.

I had the same problem and the cover cured it for me.

I'm also running a solid spacer instead of a crush sleeve. Make setting up a rearend much, much quicker and easier.

[sunsation540]

4 sets of gears in one season and i gave up 750 hp, glide pro tree converter/ brake 4800 3500lbs DANA i hate to work on it,,, the cover and pro gear lasted the longest..

[sunsation540]

DANA!!

[kyleracer]

I had the same problem. I now use 4:10 GM high impact gears and a ultimate pro aluminum cover and axle tube brace kit from LPW (717-394-7432) cost about $275. They are very easy to deal with at LPW. Have used the same gears now for over 400 passes (reset lash a few times) and I drive it on the street in a 3400lb camaro . When I bought my tube chassis car it had a 12 bolt w/4:56's so I bought the same kit for it and it does the 1/4 in 9.2 with a 1.30 60ft with no problems. Just wondering why you would risk blowing up your motor or alot worse if you knew that the gears were going to let go ??

[79 Camaro]

What kind of fluid are you using?? Is it Synthetic?

Were some of the guys on here having problems with the gears or something going out because of the senthetic gear oil??
Or am I dreaming that up??

[race9899]

Solid pinion spacer definitely, Girdle cover good idea, I like the billet cap if not using the girdle. in a Twelve Bolt it is best to run the Backlash a little tight .002 tighter than recommended, try and keep the pattern closer to the inside of the tooth, the pattern will run up the gear under power. Some kind of brace helps as it keeps the the axle housing tubes from flexing the carrier.


I ran a 12 bolt in a super comp car, weighed 2550 lbs. and ran 8.80's 1.20 60'

[Goat Hearder]

I always used .008-010 on a new gear and .010-.012 on a used gear. I forget who makes it but there is a nice solid shim set available . Talk to my parts buddy and post them.