I would like to hear from others that had trouble launching their car after installing a Moser 9". I cant cut anything better than a 1.9X 60ft. with E/T streets. Suspension is stock except for lower control arms,relocation brackets, and air bag. The car is an LT-1, M6 with hot cam, intake, exhaust, street twin, 150 shot N2O, and 4.10 gears. Thanks, Ken

 

What is your tire pressure? What rpm are you launching at? I have a 12 bolt and I am leaving at 5500 rpm. You should be able to do better.
Michael

 

Are you getting a lot of wheelhop? I never got any wheel hop with the 10 bolt, but as soon as i installed the 9" the wheel hop went through the roof, which i would assume is because of the all the extra weight. I'm told that the fix for this is relocation brackets and or airbags in the rear springs.

Hope that helps a little.

Eric

 

Thanks for the replys. I have tried tire pressures down to 16psi but the car got real loose at the end of the track at that low. I can not leave at anywhere near that high an RPM. 3000 is as high as I have left. I had real bad wheel hop before the lower control arms and air bag. They solved the wheel hop but I still cant hook like I think I should.

 

Man that seems like alot of air in the rears, I run anywhere from 10.5 to 13 pounds in my hoosiers depending on what the track is doing. You may want to check your pinion angle. If you are using a stock torque arm that will definitely be your problem. I think the torque arm provision for the moser 9 inch will change the pinion angle. Your pinion angle should be somewhere around 1 to 3 degrees negative.

Michael

 

I'm curious about this too. I installed a Moser 9" recently with a mainly stock suspension. Just on the street the car felt loose in the backend when I took it out after the install, I havnt even taken it to the track yet. I have heavy duty Metco lca's, lca brackets, and I just added a BMR adjustable phr. That helped with the side to side alignment and stiffened things up a bit. Everything else is stock except some new ES bushings. I really want to get a body mounted adjustable torque arm to stiffen things up more and to correct the pinion angle. Not to mention I need a new clutch too

 

Have you checked the pinion angle? Appears both the people with problems are using the stock torque arm. The 9-inch drops the centerline of the pinion shaft about 0.75" compared to a 10- or 12-bolt. You need to reset the pinion angle. The 9-inch also typically moves the TA mount point to one side (I think its the drivers side) so that may also contribute to traction problems.

Just a thought.

I'll agree with the tire pressures.... I think I started at 16psi with the QTP's and came down to 12psi. But, just to be clear, I run the 12-bolt.

 

Thanks, everyone. I checked the penion angle and thought it was ok, but I probably messed up. I will go back and check it again. It looks like time for a new TA. Thanks again

 

What did you figure out on the 9" plus stock torque arm regarding the pinion angle? What was your angle?

 

ttt

 

yea, check your pinion angle.. but 16psi is a LOT. i run from 10.5-13 or so..


and YES, its gonna feel really crappy on the top end :-D

 

I just had a similar discussion with Gordon Spohn. The 9" center is slightly offset and not centered under the car like the 10/12 bolts are. In fact, their TA has two mounting positions to compensate for this problem. Using a stock TA may bind the suspension by not being lined up correctly behind the transmission. Even if pinion angle is right you may still have alignment problems. Just a thought. By the way I just installed one of Spohns TAs...Truely a beefy, awesome piece...
--Alan

 

What is it doing when you launch? Spinning, bogging? How does the car react? Does it squat, stay level, or does the rear lift? Etc., etc. A slo-mo video of the launch is a big help, especially if you mark the rear tires with a paint strip so you can see if they are spinning or hooking. What were your 60' before the 9" was installed?

Rich

 

Thats interesting, I didnt know that. I have a Moser 9" that I installed in mine a few months ago and I tried using the stock TA at first. It was a pita to try and reinstall the stocker, it seemed like it didnt fit right and the car felt 'loose' to me in the backend when getting on it. I was looking at replacing it with an aftermarket adjustable one, I think I will go with the Spohn after hearing this.

 

I still run the 10 bolt with future plans for a 9". Anyway I bought the Spohn adjustable TA which uses the trans mount location like the stocker. It comes set to neg. 1 degree of pinion angle and comes with a magnetic angle finder and new polyurethane bushing. Once installed I verified the pinion angle and it was right on 1 degree negative. I've had it in for a few days and the car hooks better with no noticable noise. You get a lot for $295. Plus Gordon and Steve are good guys...
--Alan