12 bolt gear breaking problems....
 

I have broken 2 gear in the last 5 weeks. This is a 12 bolt 1969 Camaro with Moser Axles, I am using a transbrake and yes they were both street gears, the 1st gear had been in the car right at a year, it let go coming out of the water box, it was set at .012 lash, the one I broke Saturday had .004 lash in it, it lasted 2 weeks. This gear had 11 teeth sheered off of it in a row and they were full teeth taken off, wear marks on the gear show it and the pinion were perfectly in the center of the gear. If you have read my any of my previous posts you know I have been having some hooking problems, I put some spring shackles on the car and also put on a set of 28x10.5-15 instead of the 9 inch tires, I also added 100 lbs in the trunk, let me tell you it was awesome, the car packed the wheels about 3 ft high and carried them about 20 ft, then the next round I put the car in neutral and shut if off to let it coast into the lanes and I heard CLICK CLICK CLICK, i knew it was just a matter of time went out let go of the button and then BOOM! Could the weight have played a part in this??

Re: 12 bolt gear breaking problems....
 

I have seen this happen on a friends D/SA nova and it all went away with a pro gear. Also if you are using a street gear buy a US gear or Richmond they are the only gears I will put in.

Good luck, Mike

Re: 12 bolt gear breaking problems....
 

They were both Richmond Street Gears, so do you think the added weight had any effect on this breakage??

Re: 12 bolt gear breaking problems....
 

It may have but I doubt it, how much does the car weigh and what kind of RPM are you leaving at? .004 is kind of tight on the BL this may have had something to do with it breaking so soon. Also what kind of rear cover do you have the housing could be moving around and that is not going to help.

Re: 12 bolt gear breaking problems....
 

Car weighs 3300 with me in it. When it broke I was launching at 3200 rpm, It just has the stock cover on it.

Re: 12 bolt gear breaking problems....
 

Use billet caps and US GEAR (Strange) Pro gears, and go racing.Joe

Re: 12 bolt gear breaking problems....
 

who makes a good billet cap?

Re: 12 bolt gear breaking problems....
 

I'd go back to.012 and easy out of the water!

Re: 12 bolt gear breaking problems....
 

I used Mark Williams(part #58100) needs minor machining as I remember. I think Moser also makes them. I would spend money on the caps before I spent on the preload covers.

Re: 12 bolt gear breaking problems....
 

Eric,
For sure on the pro gears. I'm 3100 and a 404 with dot tires and using transbrake i made 20 passes and kaboom with the front wheels in the air. Even had the 12 bolt cover from JA that holds bearing caps in place. Teeth are to brittle and will break sooner then later.

Re: 12 bolt gear breaking problems....
 

Do not think you can use a street gear with a trans break, to much stress on the teeth, go right to a pro gear and it should not break. You could get by with a street gear if you were just foot braking.

Good luck

Re: 12 bolt gear breaking problems....
 

Ericsz: I run a stick shift Camaro with a 12 bolt rear end. I can tell you for sure if my 12 bolt stands up to the loads I put on it, a 12 bold will wokk for you too. 7800 rpm starting line launch and so far no trauble. Pro gear is the way to go!

Re: 12 bolt gear breaking problems....
 

Ericsz,
I know a lot of automatics are running Street gears and the RPM?s you are leaving at should be alright, but Pro Gears will take the most abuse because of the softness at which they are harden to. Setting the BL at .012 is too loose for new and .004 is way too tight for new. Try setting them at ..007 and make sure the pinion depth is set correctly to get the pattern favoring the front of the tooth from center. What type of Gear oil are you running? Red Line makes different Shock rated rear end lubes that have always worked great for me. I run a Stick car with Pro Gears (Richmond) and I had great success in setting my rear ends up this way, after a LONG RUN of breakage in trying to find the right set up.
Good Luck??..Don

Re: 12 bolt gear breaking problems....
 

Thanks so much guys, I knew I get some real answers from you guys, I keep hearing people say welp its time for a 9 inch. You guys have proven differently which is why I asked you folks...Thanks a lot!

Re: 12 bolt gear breaking problems....
 

Are you using a solid spacer or a crush sleeve in the pinion? If you have a crush sleeve, switch to a solid spacer with shims.

Re: 12 bolt gear breaking problems....
 

Eric,we finally gave up and did put a nine inch in.But back when we ran a 5.57 gear we never broke any gears.It wasn't until we started running a 6.00 gear and the pinion got so small that every 50 runs or so it would bust one.We set them tight, loose, bought MW caps,T/A cover etc.... Alot of it has to do with weight.We know alot of folks with the lighter class cars that run a twelve bolt and punish the crap out of them and they don't have problems.But when you get over 3100 or 3200 pounds ( our car is @ 3255 in F) they are on the edge,especially with the steep ratios. Buy the way I have a 5 gallon pail of that Redline Shockproof 140w gear oil that never has been opened setting here collecting dust. Anybody give me 50 bucks ?

Re: 12 bolt gear breaking problems....
 

I am in fact using a Crush Sleeve, the car also has a Richmond Mini Spool in it.

Re: 12 bolt gear breaking problems....
 

Eric I've been running a 12 bolt 5:14 Richmond street gears for the past 3 years and have had no problems I run a 68 camaro in G automatic and launch about 2600 rpm. I feel the key to longevity with a 12 bolt is pinion depth. You ensure that both the ring and pinion are getting the most contact when you are dead on this, will make for long life.

Re: 12 bolt gear breaking problems....
 

Get rid of the crush sleeve and use a spacer kit with shims. This will maintain the pinion depth. The shock everytime you drop the clutch will have an effect on the crush sleeve.

Re: 12 bolt gear breaking problems....
 

I used a street gear with a 31 spline axle in a G/SA (3250 lbs) for 15 years with no breakage, same gear set. Leaving on the converter is different than leaving on a trans brake. I have a A/SA with a pro gear because all the other A/SA cars ripped the street gears out within 10 runs on a 2-step or foot braking not even a trans brake.

I really do no think you can use a street gear with a trans brake.... Too much stress to the gear set on the launch. If A/S (leaving @ 7000 plus ) and super stock cars using trans brakes are using a 12 bolt your combo should be fine with a pro-gear with the trans brake. Buying pro gears is lot cheaper than changing the rear to a 9 inch.

J.DeMarzo

Re: 12 bolt gear breaking problems....
 

Even a 9" with a transbrake should use a pro-gear. The shock of the transbrake is hard on parts. Will find the weak link for you. Weight is a factor in all this.

Re: 12 bolt gear breaking problems....
 

Thanks a lot guys, I ordered a TA Performance Cover with some Red Line Hard Launch Gear Lube, hopefully this stuff along with the Pro Gear will take care of the problem! Thanks again!!!

Eric Bowling

Re: 12 bolt gear breaking problems....
 

eric my super stocker weighs 3860 pounds and i use a 12 bolt you definatly need a pro gear i use richmond and then ive got a lpw suport cover and axel braces if you hook hard it will pull the tubes forward putting force on the bearing caps the braces stop this and i have had no problems with breakage

Re: 12 bolt gear breaking problems....
 

Jeff brought up another good point. Axle tubes do need alot of attention. I welded mine with a wire feed welder and thought it would be ok. But it failed. I had a shop replace welds with nickel rod i believe and have not had a problem. Definitly do something proper with the tubes. Brace and or weld. Its better to do it when everything is straight and not messed up by improper welding like i did. A hooking car using a transbrake will tear up a 12 bolt. GUARANTEED.
Jeff

Re: 12 bolt gear breaking problems....
 

Welp I put on the TA Performance Girdle cover on last night along witht the Red line Heavy Shock Proof gear oil, HOpefully this will take care of the problem, thanks again for all your help!

Eric Bowling