the_blue_rider84

iTrader: (1)

Yeah so I have a Stock rear end in my a4 99 trans am ws6. It turns low 8s in the 1/8. Put some wider tires on and had the tranny beefed up. Now I have that nice grinding sound and loud pops when I turn slow and put it into gear. I know the stock rear is a POS. I am totally clueless as to what to do or search for. I never plan on having more than 500hp. Opinions, prices, how-to's or links please! Thanks so much and I apologize for being iggnorant.

Manic Mechanic

iTrader: (3)

First thing to do would be to have a competent technition verify the source of the problem and give you an estimate to repair what you have. It could be something much simpler like the rear U-joint you know. Then at least if it is the rear axle you will have your cost of repair to consider against the cost to replace. This is important because the replacement bolt-in rear ends for these cars cost a good chunk of change. A larger rear end will go for $2200 to $3000+ depending on options and required mods to fit. If you are considering upgrading you'll need to know what type of ABS your car has. If you have traction control it's 4-channel. If you don't it's 3-channel. Four channel is easyier to build so it cost a little less. For an auto street car around 500 HP a Chevy 12-bolt based rear is great and cost the least overall. The two main manufacturers are Strange Engineering and Moser. As you go up in price and strength you have the Strange S60 based on the Dana 60 and the Ford 9" from Moser and Midwest Chassis. Some bolt right up while others require driveshaft mods and torque arm replacment. The more necessary mods the more it costs to do in time and money. There are many vendors that sell Strange and Moser and several of them are supporting vendors on LS1Tech so pricing and advice are in this forum just look a bit.

You'll want to reuse your stock brakes so specify that and save them, you may need to reuse your caliper brakets or send them in to be installed on the new axle for you. The more axle splines (28, 30, etc.) the side axles have the stronger they are, for your car the starting numbers are more than enough with the built up rears. With a 12-bolt the base package has C-Clip axle retainers, these are ok with disk brakes on the street (see the guy who just drove home on a grenaded diff in Cali) but stepping upto pressed on axle bearings with end plate retainers will provide a far greater safety margin in the case of axle breakage and will be considered mandatory for slicks, high RPM dumps, and running good times at the track legally. The S60 and Ford 9" have no C-clips as standard. These are sometimes refered to as C-Clip eliminators on the 12-bolt.

Since the factory torque arm set-up is just as inadequate as the 7.5" rear if yours is still stock an axle package that brings it all together like Midwest's isn't a bad deal for one stop shopping. Otherwise make sure the torque arm you use and the rear are compatible.

Going to the manufacturers sites and reading through their catalog or descriptions will answer a lot of questions.

Unless you're planning on running slicks at the track the standard sized metric lugs are what you want. Longer or larger lugs are for staying NHRA legal with lower E.T.s and slicks etc.

Differentials are a matter of how much you want to spend. You don't want to consider a spool or a locker for your street car. One of the many limited slip type posi differentials is what you want. With these you usually get what you pay for but even the lower costs units are as good or better than the stock unit just a lot stronger. The higher priced units usually give a slightly better performance under racing conditions or are just a good bit stronger than the competion.

Gear ratio choice is dependent on several things. Engine power and RPM band it is in compared to desired results vs. intended usage. That woud be best decided by descussing it with experienced people so that a good idea of what you need could be advised. Studying the other posts on gear ratios would probably help tremendiously since it comes up a lot. The lower the number is i.e. 3.23, the slower the engine revs vs. car speed and the car will take longer to get going but will be at a slower engine pace once speed is reached so mileage and noise are better. The higher the number i.e. 4.10, means the engine will rev up quicker allowing you to put down more power in the same distance and accelerate quicker but this comes at the cost of a higher engine speed at cruise meaning more noise and higher fuel consumption and engine wear etc. Usually for a street car like yours a compromise between the two extremes is the best overall choice. Consider gear ratios between 3.50 on the low side and 3.90 on the high with 3.73 being the median.

Don't worry about ignorance as it's cureable and that's what we do for each other here. It's stupidity that can't be tolerated LOL.

Vernon

EPP

iTrader: (22)

http://www.exoticperformanceplus.com...html?item=1324
Check out the Moser M9 rear/torque arm combination at the above link. It ships out two days after the order is placed. Bob