Hello all...I am new to the camaro forum and had few questions I was hoping you guys could help me out with. I have a 79 Camaro and it is a one wheel wonder with 28 splines and over 450 hp. Needless to say but the rearend has blown 3 times..Big surprise I know. I was going to go with a eaton posi with a full rebuild kit and 3.73 or 4.11 gears. Its a 4 speed so 3.73 would probably be a little better on driveability. Cost has become an issue so I am looking for a affordable option

I found a posi carrier on e-bay for next to nothing its part ##410408n. Would this be a direct swap? Would I be able to run the gear ratios above? I am going to get a full rebuild kit for the rearend as well as new ring and pinion. Anything else you would reccomend..

Thanks for your before hand

 

Well I found out the rearend will work after do a little internet searching plus it is a 3 series unit that will take the gears I am looking to put in. I can get the ring and pinion for $140, rebuild kit for $130 and I am hoping to score the posi carrier for $150 or less. Now my question is this. $420 for the piece mealI am talking about or I can get a eaton posi with rebuild kit and gears for $630...I am thinking the eaton will take the punishment of 450hp a little better....Any input?

 

You did not say but I assume the car has a 10 bolt unit in it. Considering you have ruined three sets of gears perhaps you need to switch to a 12 bolt differential. If you are racing the car save some headaches and spool it.

 

Well I do take the car to the track occassionally but it is more of a weekend warrior brag and bull kind of car. The only reason the 10 Bolt has blown is b/c of driver input in the corners and the spider gears exploded. Enough to put a tooth through the cover and skipping down the street with sparks and all.

I have friends running up 500 hp on there 10 bolts so I know they can take it if built right. My dilemma is the cash flow. I have 3 cars and a taste for horsepower not a good combo....12 bolt would be ideal but for that much work I can fit a Ford 9" and be done with it. Anybody running 450 hp on a OEM posi carrier in a 10 bolt? I think I have decided to go the Eaton Posi Route with a beefed up cover to keep the housing from flexing plus a full re-build and I will be good for awhile..

With that said does anyone have a 12 bolt unit that will bolt in for cheap? Or know of a good source?

 

I will stir some **** with this post, but, I can't hold it in any more. The 12 bolt is horribly overrated. I have one on my rack right now and after seing how they are cast I will bet anyone that a well built 10 bolt will take more abuse than a 12 any day of the week. Yes, the 12 has larger side bearings and a 3/8 inch larger ring gear, 8 7/8 vs.8 1/2. But, the center housing is the weakest piece of **** I've ever seen. The 10 has more steel cast around the bearing cap bolt boss's, the 12 I'm working on pulled the threads out of the boss's because it flexes more. At least it has 30 spline axles, but, I am upgrading my 8.5 10 bolt to a Detroit Tru Trac, to give me limited slip w/o the clutch packs that fail, and 31 spline axles. This is only a $700 build. The ring gear in the 10 bolt is abit beefier than its 12 bolt counterpart, just not by much. My advise, based on my expierence with my 79 4 spd Z, go with either a 3.08, 3.21, or 3.42. rear gear, use some sort of clutchles L/S for more consistant performance over time, Thorsen or Tru Trac. spend the money and upgrade to 31 spline hardware. You're making enough HP to pull 3.08's easy. I had 3.73's in mine with 255/60's on the rear and I could'nt drive the car on the freeway 70 was about 3200. Pointless since the motor stops producing touque at about 2600. I swaped in a 3.08 and found better ride, fuel milage and performance. I have also droped down to a 235/60 and actually lowered my final drive ratio and now it acts more like a 3.20 range gear. I was cruzin 65 at 2500 and now it's about 2750, definately a noticeable change. To anyone who wants to argue, I have a 28 spline, 4.10 geared, tru trac equiped 8.5 10 bolt under the front of my 3/4 ton Chevy that I've had on the rocks, nothing broke!

 

That is exactly the kind of input that I look for in a forum. Reall world experience and not someone that has read a few articles and threads trying to tell me what the best option is. I know the 10bolt will take it just as well if not better then the 12 bolt but I am trying to play the devils game and pay as little as possible to build a bullet proof set up...Kind of like nasa building a 50 million dollar space shuttle built by the lowest bidder.

Thanks for the real life input. I am going to check into the thorsen and tru-trac setups. One thing I liked about the Eaton Posi is that I found a supplier that provides a master rebuild kit gears and Eaton Posi carrier all for $599. Let me know if you have any good websites for tru-trac an thorsen I would love to take a look at them.

One thing I am curious about is why you were running such a numerically low gear 3.08? I believe that my rear end has that gear in it now by using the spin the drive shaft and count the rotations method. I think I would definately benefit acceleration wise with a 3.73. I ruled out the 4.11 because it is a 4 speed and I dont want to be rowing a boat in traffic...I am running 255/75/15 tires but am wanting to go down to a smaller size as well. Maybe a 245/60/15....What are the pros and cons of a 3.73 vz 3.08. Keep in mind it is a weekend warrior with the occassional trip to the track so gas mileage and hwy driving are not a huge concern....

Thanks in advance....

 

In your case it's not a long distance cruiser, then you could go with 3.55-3.73 gear. It will definately accelerate faster, but, that's all they'll do for you. If you step down to a 245/60R15 you won't use first or fourth gear. I had 255/60R15's on mine and started in second and shifted to fourth at 1600 to 1700 or between 10and 20MPH, but, it was fast up to about 40 then I ran out of motor, it's old and wore out.The main reason I went to a higher gear is that I'm planning a 5 spd. convertion and the trans I picked out has a much lower first gear which puts the final drive ratio at 3.99:1. Basically, it's like having 4.10's, only with the .68 OD I'll be crusing at about 2200 to 2500 at about 70-75MPH. Right in my motors tourque band. In my case I dont' need to go fast straight. I enjoy the long drives. So, to each hisown.