Hi,

I have a completely stock 1984 Trans Am with around 70k miles and the LG-4 right now.

I'm considering buying and building a 383 whenever I get the money (I'm looking for about 250-300 RWHP) and I'd like to know how much torque and how many horsepower the stock drivetrain (700r4-> stock 3.23 WS6 rear end) will take before their lifespans are shortened considerably.

So what are the weak points in that drivetrain, what can I do to fix it, can I fix it myself (I'm a noob at drivetrains and I'm kind of scared of transmissions, but with a shop manual I might be able to figure stuff out), and how much will it cost?

 

250-300rwhp is about 350-400 crank HP. i would say u would need a built 700r4...talk to dana. your trans will have a vette servo, trangsoshift kit, borgwarner hi energy clutches, 10vain pump yadda yadda. a kit should cost u around 900$ or a built trans for 1000-2000$ depending on what u want, u will most likely need a higher stall converter as well that will have to be matched to ur cam and engine and rear gears.

also your rear wont take that. wont last long at all. its prob a 10bolt so that would include moser 28spline axels, raytech installation kit, and a good posi... tracklock, SLP, auburn... and a support gurdle. all in all should run u about 800-1000 that rear should be able to take 400rwhp at a daily basis. id say anything after 350rwhp and ur gona shred ur driveshaft depending on how u drive. before you do anyhting with the engine/drivetrain... get your suspension in track... a low power motor can outrun a high power motor with a good suspension. the engine power is only as good as the platform u build it on

 

The rear end will last a while if you only run street tires with low traction. If the car gets good traction then you will break something. I agree that 28 spline axles will be better, but I believe that the Eaton posi is far better than the Auburn. If you ever rebuilt a rear end that had an Auburn in it then you would understand. I also prefer the DTS or Tom's Differentials installation kit. The Ratech kit has crappy shims and the bearings are not always Timken. If you plan on getting the car to hook up well then you need to forget the stock rear end and look at a Moser or Strange 12 bolt.

 

Those numbers I gave are a little optimistic. I'd like it to make that much power but I'm not sure if I'll actually put that much in it (money and practicallity make it an issue). It's mainly going to be a weekend car, used on the street and autocrossed and it might see the rare drag run.
275- 350 at the crank is probably more realistic for what I'll give it, but should I have it built to take 400hp?

About how much will the setups described run, without cutting corners?
Money's an issue but I'd like to have it done right so it won't break down all the time.

 

it depends on what the car goes through... your stocker just like every other 3rd gen have 20 plus years on them and the rears are never rebuilt most of the time and usually the most neglected part of the car. if you want reliability and better performance, even if its a weekend driver and u want both wheels to spin when u mash the pedal your still looking at a new posi.... so why not just upgrade it?? so u get reliability and if u decide at a later date to throw heads and a cam in it. it wouldnt cost that much more to upgrade it then just replacing worn out parts with stock components. i live under the philosophy of build it once and build it right when its within my budget. i would build it to 400hp. and take out the worries that your gona break it with your engine setup... u'll see how fast u'll want more power and to go faster... HP is an addiction.


ive looked at the moser/strange 12bolts and 9 bolt setups... they are nice but they are over 2 grand! wayyy outa the budget and performance of most 3rd gen owners. if u got the money i would go with the 9bolt. they are stronger than the 12bolt. still u could have a 2,300$ moser 12bolt with an engine thats making 350hp and prob 270 at the wheels and be fine... or spend maybe 1,000$ and have a fully built 10bolt that can handle the hp easily be just as reliable untill u surpass the 400rwhp limit.

also the 12bolt/9bolt/dana60s require more hp to operate... and the 10bolt being a tinier rear allows more hp/tq to get to the wheels.

big gear head... why dont u like the auburn... ive never heard of this... what do u find in the rear when using a auburn posi??? i kno they are cone style clutch and it wears and cant be rebuilt... but the eatons are clutch type, and ive heard that they are weak depending on how many clutches it has... good tho that they can be rebuilt. which eaton do u recomend and why?

 

Auburn-not rebuildable, wears out quickly, fills the rear end with powdered metal, can not handle water burnouts well, chatters more than any other differential that I have ever seen (except the Detroit Locker), powdered metal goes through all of the bearings and is hard to clean out of the axle tubes.

Eaton-rebuildable, tuneable, last MUCH longer, many clutch and spring combinations available, smoother operation, doesn't fill the rear end with metal, no metal going through the bearings.

If you want to build the 7.5 10 bolt then you will need a set of after market 28 spline axles and a 28 spline Eaton posi. You will also need a good installation kit and a quality set of gears. Setting up the gears is very critical. If it isn't done right then you have wasted your money. The pinion depth must be set correctly to within +/- .001 inch and the backlash also must be set to within +/- .001 inch. Bearing preload is also very important. The 10 bolt isn't going to take a large amount of abuse no matter how you build it. The Moser and Strange 12 bolt rear ends are very strong. The 9 inch is over kill and added weight for any car with the stock chassis. The 12 bolt will take the car well into the 9s in the quarter mile.

 

i didnt kno that about the auburn. then again ive never used one. so how long do u think a stock 9bolt ausi rear will hold up to a 480hp/500lb 383 at the crank? and if u could on a low budget upgrade it? u'll prob say the moser or strange 12bolt... but i cant throw 2,400$ out like that when the motors costing 5,000$ and the trans another 300$ would a 10bolt with a eaton posi and 28spline axels and a support gurdle live behind that 383??

 

I've seen rear ends handle power that I never thought they could. I built an 8.2 10 bolt for a '69 Camaro with a 383 and 4 speed. It was lifting the front wheels with slicks and it is still holding up well, although it is in another car now. I've seen the 7.5 hold up pretty well on the street behind some strong engines, but only with street tires. I can't say that the 7.5 would last long with those upgrades, but it would have a much better chance that way. A stock 7.5 just won't handle it. But if you took that $1200 and applied it to the 12 bolt then you would have a rear end that you would never have to worry about. A good 9 bolt will probably last longer than the 7.5 because of the Borg Warner posi that is used in them. It has 4 pinion gears instead of 2, which makes it about 2 times stronger than the 10 bolt.